IS 11592:2000

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Indian StandardSELECTION AND DESIGN OF BELT CONVEYORS —

CODE OF PRACTICE

( First Revision)

ICS 53.040.10

@ BIS 2000

BUREAU OF INDIAN STANDARDSMANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARC

NEW DELHI 110002

October 2000 Price Group 15

Bulk Conveying, Elevating, Hoisting, Aerial Ropeways and Related Equipment Sectional Committee, ME 06

FOREWORD

This Indian Standard (First Revision) was adopted by the Bureau of Indian Standards, after the draft finalizedby the Bulk Conveying, Elevating, Hoisting, Aerial Ropeways and Related Equipment Sectional Committeehad been approved by the Mechanical Engineering Divisional Council.

Belt conveyors play an important role in the key sectors of the economy such as mines, steel plants, thermalpower stations etc. Accordingly, the design of the belt conveyors has to take care of various parameters. Thisstandard has been prepared to help the engineers and technocrats and industry for making use of uniformpractice for selection and design of belt conveyors in India.

This standard was first published in 1985 and has been revised to bring it in line with 1S0 5048 which has sincebeen revised. In addition, the reference of Indian standards referred in the standard is also being up-dated.Further the errors noted during the implementation of the standards are also being corrected.

This standard has basically covered the conveyor system using belts from 300 mm to 2000 mm belt widthsconforming to IS 1891 (Part 1) : 1994 ‘Conveyor and elevator textile belting : Part 1 General purpose belting~ourth revision)’. At present belts of width upto 3000 mm are also being used in Indian industries. Thisstandard can be made applicable to belts of all widths subject to availability of technical data.

In the preparation of this standard assistance has been derived from the following:

1S0 5048:1989

1S0 5049 (Part 1) :1994

1S0 5293:1981

ISO/TR 10357:1989

DIN 22101:1979

BS 2890:1973

BS 5934:1980

Continuous mechanical handling equipment — Belt conveyors with carryingidlers — Calculations of operating power and tensile forces

Mobile equipment for continuous handling of bulk materials — Part 1: Rulesfor design of steel structures

Conveyor belts — Formula for transition distance on three equal length idlerrolls .

Conveyor belts — Formula for transition distance on three equal length idlerrollers (new method)

Continuous mechanical handling equipment; belt conveyors for bulk materials:bases for calculation and design

Troughed belt conveyors

Method for calculation of operating power and tensile forces in belt conveyorswith carrying idlers on continuous mechanical handling equipment

For the purpose of deciding whether a particular requirement of this standard is compiled with, the final value,observed or calculated, expressing the result of a test or analysis, shall be rounded off in accordance withIS 2: 1960 ‘Rules for rounding off numerical values (revised)’. The number of significant places retained in therounded off value should be same as that of the specified value in this standard.

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IS 11592:2000

Indian Standard

SELECTION AND DESIGN OF BELT CONVEYORS —CODE OF PRACTICE

( First Revision)

1 SCOPE

1.1 This standard provides guidance for selection anddesign pt-actices to be adopted for belt conveyors.

1.2 This standard applies to stationary and shiftableand/or expendable conveyors handling loose bulk ma-terial and such material, which behave as solids+Forguidance, classification and properties of such mate-rial are covered in IS 8730.

1.3 This standard covers the conveyors with belt widthsranging from 300 mm to 2000 mm as currently invogue in conformity with relevant Indian Standardsbut excluding special purpose conveyors.

NOTES

1 Conveyors, not covered under this scope and special purpose

conveyors, for example, feeders, package conveyors, etc. will be

covered in a separate standard.

2 This standard also covers the conveyors using steel cord belting.

3 Special i-equiremen~ for conveyors for use in underground coat

mines are also covered by this standard,

4 This standard does not include certain data on steel cord

conveyors and conveyors for underground mines where relevant

Indian Sr~ndards are available.

1.4 Attention is drawn to the many varied factors whichinfluence the driving force on,the drive pulley and whichmake it extremely difficult to redirect the power re-quirement exactly. This Indian Standard is intended togive a simple method of conveyor design calculation.Consequently it is limited in terms of precision but issufficient in the majority of cases. Many factors are nottaken into account in the fortnulae but details are pro-vided on their nature and their effect. In simple cases,which are the most frequent, it is possible to progresseasily from the calculation of power requirements tothose of the necessary and the real tensions in the belt,which are critical in the selection of the belt and in thedesign of the mechanical equipment. However, certainconveyors present more complicated problems, for ex-ample those with multiple drives, or with an undulat-ing profile in vertical elevation. For these calculations,which are not covered in this Indian Standard, it isadvisable to consult a competent expert.

1.5 The recommendations given in this standard shallbe applied both to individual conveyor, as well asconveyor systems consisting of more than oneconveyor. Care shall however be taken to apply clausespertaining to system requirements.

1.6 This code covers the belt running on idler rollersonly and not on slideslbeds.

1.7 This standard applies for only smooth surfacedbelt.

1.8 This standard excludes the installations usinghorizontal curves

2 REFERENCES

2.1 The Indian Standards listed in Annex A containprovisions which through reference in this text, con-stitute provision of this standard. At the time of pub-lication, the editions indicated were valid. All stan-dards are subject to revision, and parties to agreementsbased on this standard are-encouraged to investigatethe possibility of applying the most recent editions ofthe standards indicated in Annex A.

3 TERMINOLOGY, SYMBOLS AND UNITS

3.1 For the purpose of this standard, the terms anddefinitions given in IS 4240 shall apply.

3.2 Symbols and Units

Symbols and their units used in this standard for cal-culations are summarized in Table 1.

4 TYPE OF CONVEYORS

4.1 The conveyors are troughed and flat, both hori-zontal and/or inclined or declined with or withoutcurvatures in vertical plane.

4.2 Troughed conveyor is that in which the belt formsa trough on the carrying side while restinglrunningover idler rolls which are either in set of 5-rolls/3-rollsor 2-rools. The troughing angle adopted shatl con-form to IS 8598 and shall be selected from the follow-ing values: 15°, 20°, 25°, 30°, 35°, 40°, 45°.

NOTE—The troughed angle of 15° is applicable for 2-roll belt

conveyors only.

4.2.1 For return idlers, the troughing angle of 0°, 10°,or 15°, shall preferably be adopted.

4.3 Flat belt conveyor is that in which the belt runsflat on the carrying side, over an idler or a set ofidlers.

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1

IS 11592:2000

Table 1 Symbols and Units

(C/auses 3.2,8 .5.1.3,8.11.3.1 urrd8.1 1.3.2.)

S lSymbols Description

No.

(1) (2) (3)

1. A

2. Al

3. B

4. B,

5. c

6. C,

7. D

8. E

9. E,

10. F.

11. F,

12. Fd

13. Fd

14. F

15. Fq-m16. F,

17. GLr2

(4wk2)

18. H

19. H,

20, K

21. K.

22. K,

23. K,

24. K,

25. K,

26, L

27. L,

28, m

29. N:

30. N,

31. No

32. PA

33. P“p

34. PM

35. PM,

36. Q

37. R<

38. R,

39. R,

40, R

41. R,,

42. R~

43. Rv

44. Rw

45. R=

46. Rbc47. R&

48. R,,

Cross-sectional area of load on belt

Area ofcontact between belt and belt cleaner

Belt width

Bearing life factor

Conveyor capacity

Coefficient depending upon trough angle

Pulley diameter

Belt modulus

Belt specific modulus

Force available for acceleration of the total equi-

valent mass

Bracking force

Force required for deceleration

Additional force required for deceleration

Equivalent force on each idler bearing

Modified equivalent force on each idler bearing

Total vertical.force on central idler roll

Moment of inertia of drive system

Unit

(4)

m’mz

m—

rih—

m

kNlm—

N

N

N

N

N

N

N

N.ms2

Lift of conveyor between loading end and dis- m

charge end

Height of material on belt at discharge pulley m

Slope factor —

Scraping factor N/m

Application factor for idler —

Lump factor —

Service factor —

Speed factor —

Conveyor length (distance between cerrtres) m

Length of installation equipped with tilted idler m

Total equivalent mass kg

Rated motor speed rev/rein

Drive pulley speed revlmin

Normal strength of belt N/m

Absorbed power kW

Operating power requirement on drive pulley kW

Motor output power (shaft) kW

Installed motor output power kW

Volumetric conveyor capacity m’ls

Radius (minimum) of curve m

Pulley bearing resistance not to be calculated for N

drive pulley

Resistance due to idler tilting N

Main resistances N

Resistance due to friction at discharge plough N

Secondary resistances N

Vectorial sum of the two belt tensions acting on N

the pulley and of the forces due to the mass of

the revolving parts.ofthe pulley

Wrap resistance between belt and pulley N

Inertial and frictional resistance at the loading N

point and in the acceleration area between the

handled material and.the belt

Frictional resistance due to the belt cleanersN

Resistance due to friction between handled N

material and skirt plates

Slope resistance N

Table 1 (Con~inued)

S1 Symbols Description

No.

(1) (2)

49. R

50. R:

51. R,p,

52. R,p,

53. s

54. SF

55. T,

56, T,

57. Tm

58. T*

59. Tti60. T,

61. Tm

62. T,m

63. T,m,n

64. T,,

65. Tcm

67. T

68. v

69. ~

70. Vw

71. x, Y

72. Z

73. b

74. b,

75. d

76. e

77. f78. g

79. h,, hz

80. i

81.1,,12

82. la

83. I*

84. mB85. m,

86. md

87. m.

88. m,

89. m,

90. m,

91. n,

92. P

(3)

Special resistance

Frictional resistance between handled material

and the skirt plate in acceleration area

Special main resistances

Special secondary resistances

Maximum allowable belt sag

Safety factor

Peripheral force on the drive pulleys

Tension at the curvefor both starting and

running condition

Maximum recommended belt tension

Average belt tension at the pulley

Minimum belt tension to limit belt sag

Maximum belt tension under normal operating

conditions

Maximum operating belt tension

Maximum peripheral force

Minimum slack side tension

Belt tension in startirrghrrking condition

Tension at the curve when belt is partially

loaded up to beginning of curve

Maximum belt tension when belt is partially

loaded up to beginning of curve

Induced belt~dge stress in ~itions

Belt speed

Handled material conveying speed component

in the direction of belt motian

Load factor

Coordinatesof curves

Distance between working, point and tangent

point on curves

Width ofmatenal on belt

lnterskirt plate width

Shafi diameter inside bearing

Base for natural logarithm (a constant)

Arititicial friction coefficient

Acceleration due to gravity

Ordinates for trajectory of material

Angle of tilt of the idler axis with respect to a

plane perpendicular to the longitudinal axis of

the belt

Dkances from point of separation to the points

situated on the tangent line from which ordi-

nates are to be drawn

Acceleration length at loading area

Length of installation equipped with skirt plates

excluding (see SI No. 82)

Mass ofbelt per metre

Mass of revolving idler parts along the carrying

side of the conveyor per metre

Mass of material that can be safely discharged

on the next chute or hopper

Mass ofhandlcd material on conveyor per metre

Equivalent mass for drive system per metre

length of conveyor

Mass of revolving parts of pulleys per metre

length of conveyor

Mass ofrevolving idler parts along the return

side of the conv.eyrrrper metre

Number of trippers

Pressure between belt cleaner and belt

Unit

(4)

N

N

N

N

—

N

kNlm

kN/m

N/m

N/m

N/m

N/m

N/m

N/m

N/m

Nlm

N/m

N/mm

M/s

Or/s

—m

m

m

m

m

2.718

Appr—

9:806

rdsz

m

degree

m

m

m

kgfm

kglm

kg

kg/m

k~m

kg/m

—N/m2

—

2

Table 1 (Concluded)

S1 Symbols Description Unit

No,

(1) (2)

93. Pc

94. P,

95. P,

96. t,

97. 1

98, (6

99. 1,

100. 1/

101. f“,

102 1,

!03. /m

104. x

!05. y

106. ff

107. D

108. 6

(3)

Pitch of carrier idler or idler spacing on carrying

side of the conveyor

Pitch of return idler or idler spacing on return

side of conveyor

Ratiomf starting motor torque and full load

torque

Radius of discharge pulley +0.025m (this

0.025 m represents the approximate thickness

of belt)

Belt thickness

Time taken to accelemte the load

Deceleration time

Reduced deceleration time

Time required by motor to accelerate the con-

veyor

Length of the centre idler

Maximum permissible slopping time or maxi-

mum permissible coasting time

Transition distance

Vertical distance the belt edge rises or lowers

during transition

Numerical coefficient, being a fimction ofcon-

veyor length

Factor for extra power for trippers

Slope angle of the conveyor from horizontal

line in the moving direction

I 09. rf,q, Power transmission efficiencies for positive.-

110. q

Ill. e

112. r

113. A

114, p

I 15. !.+,

116. P,

117. /l*

118. ~,

119. &

120, p

121. @

122. qJ

123. B

124. 0

125, b

126. S

and regenerative power respectively

Drive efficiency

Angle from vertical at which material will

leave the belt

Troughing angle of return idlers

Angle between side axis of the troughed canying

idlers and horizontal troughing angle

Coefficient of friction between drive pulley

and belt

Coefficient of friction between carrying idlers

and bell

Coetlicient of friction between material and belt

Coefficient of friction between material and

skirt plates

Coefficient of friction between belt and belt

cleaner

Acceleration coetlcient

Bulk density of material

Angle of wrap

Surcharge angle

Belt width

Surcharge angle

Edge margin, that is unusable width of the belt

Total cross-sectional area of the material

S, = Upper section

S, = Lower section

(4)

m

m

—

m

m

s

s

s

s

m

s

m

m

—

—

degree

—

—degree

degree

degree

——

—

—tlm]

radian

degree

m

degree

m

5 SELECTION

Table 2 lists the features of troughed and flat belt con-veyors and shall help in selecting the type of belt con-veyor.

6 LAYOUT

.6.1 For a single conveyor the centre-to-centre distance

IS 11592:2000

between head and tail pulley and lift of conveyors isfixed to suit feed and discharge requirements. How-ever, points mentioned in 6.3 shall be considered herealso to the extent applicable.

6.2 For system layout, the following data is required toproceed further:

a)

b)

c)

d)

e)

f)

g)h)

Site plan with suitable contour drawings;

Over/under surface interferences, namely, exist-ing and proposed roads, drains, rails, rivers,transmission lines, buildings, structures, etc;

Grade deviations;

Material flow diagram and flow rates;

Details of receiving point(s), discharge/distri-bution point(s);

Material characteristics including size analysis;

Climatic data and site condition; and

Specific requirement for tensioning arrangement,if any.

Table 2 Features of Belt Conveyors

(Clause 5)

Troughed Belt Flat Belt

Conveyors Conveyors

Higher capacity requirements Lower capacity requirements

High speed requirements Low speed requirements

Large lump size of material with Relatively higher angle of repose

or without intermediate discharge of conveyed material, limited

with trippers Iumpssize of conveyed material,

intermediate discharge with

ploughs, distributor plates

With or without vertical curvature Without vertical curvature

Suitable for inclimtion or decli- Maximum inclination allowed is

nation in accordance with IS 8730 6°. Declination undesirable

6.2.1 In case of shiftable conveyors, in addition to datacovered in 6.2, the following data is also required:

a)

b)

c)

d)

e)

o

!3)

Layout of working face;

Difference in levels between the head and tailends;

Whether future extensions are required or not.If so,the proposed level of the head end or tailend to be altered;

Type of shiftin~

Location of discharge conveyors in case of pivotoperation;

Type of tripper/transfer feeder movement(whether crawler mounted or rail mounted);and

Maximum allowable ground pressure.

6.2.2 For layout of system of conveyors andlor indi-vidual conveyor in underground (mining) installations,points such as compact drive head, flame proofmotors, fire retarding belting and safety precautions

3

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IS 11592:2000

against fire in all other equipment especially fluid cou-pling and other electrical items shall be duly takencare off.

6.3 Based on the above data, the conveyor system islaid out, taking following points into consideration:

a)

b)

c)

d)

e)

Keeping allowable inclination within per-missible limit (see IS 8730);

Keeping conveyor lengths (including allowancefor belt elongation) within reasonable limits soas not to exceed the likely RMBT (recommen-ded maximum belt tension) for selected typeof conveyor belting;

Keeping minimum overhead clearances belowthe conveyors according to the site require-ments while crossing road, water ways andrailways and maintaining minimum clearancesin accordance with the statutory requirements;

Keeping all transfer points in line withdirection of flow, maintaining a minimumtransfer point height and avoiding reversal ofdirection of flow of material unless absolutelynecessary due to site constraints; and

Coasting time of a conveyor shall be taken intoconsideration to avoid build-up of material. Incase, it is unavoidable, suitable means ofcoasting corrections at transfer point shall beconsidered. Use of surge hopper shall beconsidered if coasting time cannot be corrected.

6.4 Typical layouts of conveyors are shown in Fig.lAto lJ.

7 CONVEYOR DESIGN PROCEDURE

7.1 Once the configuration and layout of a conveyoris finalized the following design steps are taken forsizing the conveyor.

7.1.1 Wherever multiple choices are specified, theworst condition applicable shall be considered for thedesign of the conveyor system.

7.2 The known maximum lump size of the materialcan be found from Table 3 taking into account theclassification of material as given in 7.3.1.*

7.3 Size of Material

7.3.1 Material shall be classed as ‘sized’ and ‘unsized’based on the material as follows:

a) Unsized — 30 percent by mass of all materialless than one-sixth maximum lump size.

50 percent by mass of all material less thanone-third maximum lump size.

75 percent by mass of all material less thanone-half maximum lump size.

90 percent by mass of all material less thantwo-third maximum lump size.

b) Sized — Material not falling within the abovegrading.

Table 3 Maximum Lumps Sizes inRelation -to Belt Width

(Clause 7.2)All dimensions in millimetres.

Width of Belt Maximum Lump SizeAccording to

1s 1891 (Pa’t 1, ~(Standard Widths Uniform Size Unsized

Underlined) (Maximum Dimensions)

X-N 75 100

4QQ 75 100450 75 125

m 100 150

6(!!2 125 200

m 125 230750 180 300

8.(!Q 180 330900 200 380

260 4301 050 280 460

360 5301 350 380 660

380 6801 500 410 750

410 800

460 900

500 1020NOTE — The exact determination of maximum lump size

also requires consideration of troughing angle, belt speed or

abrasiveness and other material characteristics.

7.3.2 Lump Size

Lump size indicates the longest single dimension of larg.est lump. This shall not be cont%sedwith crusher settingor screen openings as these limit only one dimension.

7.4 Ascertain speed factor as sum of lump size factor(see Table 4), air borne factor (see Table 4) andabrasiveness factor (see Table 5) and select belt speed(see Table6).

7.5 If the conveyor is inclined/declined, select a safeangle of inclination/declination for the particularmaterial (also see IS 8730 and 8.1.2). Determine theangle of surcharge according to the nature of thematerial (see IS 8730).

7.6 From the selected belt speed, angle of inclinatiorddeclination and angle of surcharge for the material,determine belt width and troughing angle for therequired capacity of the conveyor from Tables 7, 8,9,10andll,

7.7 Use the larger of the belt width as determinedby 7.2 and 7.6 and rework if the belt width require-ment from 7.2 is lower than that required by 7.6.

7.8 Consider the type of supporting idlers and theirspacing [see 8.8 for selection and IS 4776 (Part 1) forspacing].

4

IS 11592:2000

Skirt Boards on Intermediate Loading HoppersHinged to Clear Load from End Hopper

DRIVE ENO

Fig. 1A Horizontal or Inclined Conveyor — Loaded at one end and discharged at other end may also beloaded at intermediate points through fixed or movable spouts

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/’*

/-+&Q y..... ~~-.”.~”’ ,“s,,,:.,.,..+ ““:”””s;’”-9-&q#J-

U 1

DRIVE END

Fig. 1B Horizontal Conveyor — Discharges at intermediate points through fixed trippers or at end

DRIVE END

Fig. 1C Inclined Conveyor — will carry up varyingslopes which depend upon the nature of material is

loaded in usual way and discharges over head pulley

ORIVE END

Fig. 1D Inclined or retarding conveyor for loweringmaterial gently down slopes similar to those used

in stvle in Fia. 1C convevor. Mav be combined withot;er arrangements a;d whe; in operation the

drive acts as a brake

CONVEXCURVE

I

DRIVE END

Fig. 1E Combination Inclined and Horizontal Conveyor — The horizontal run can be discharged at headend or at any intermediate point by means of fixed or movable trippers. The bend in carrying run can be

made over an idler pulley, but the method shown is preferable

5

IS 11592:2000

RADIUS OF CURVEDEPENDING UPON TENSIONOF BELT AT CURVE

DRIVE END

Fig. 1F Simplest method for conveying horizontally and up an incline where belt tension is not excessive. Theradius or curved section must be ample to prevent belt, loaded or empty, lifting from carriers, maximum

inclines depend upon nature of material handled and method of loading

Fig. 1G This arrangement combining two conveyor units is often necessary where limited space and high belttension make the sweeping curve impracticable

LOADING POINT

w w LOADING POIN.T

w

Fig. 1H For conveying on both upper and return belt often used with flat belt for packages

CARRYING SA TRAINING IDLER

T h—’ 15 To 20 ~3To ~fi

+3104—4= \30 ——————i

TAIL END RETURN SA TRAINING IOLER ORIVE END

Fig. lJ

All dimensions in millimetres.

Idlers spacing for belt conveyor

6

IS 11592:2000

7.9 Calculate the resistances (tensions) for all condi-tions including empty belt, loaded belt, liftidrop andother accessories.

7.10 From the tension requirement, determine the ab-sorbed power.

7.11 Select type of drive and determine slack side ten-sions.

7.12 Find out the minimum recommended belt ten-sions for limiting belt sag to 0.5 to 2 percent of thedistance between adjacent idlers on the carrying side.This sag in no case shall exceed br$yond2 percent.

Table 4 Lump Size Factor

(Clause 7.4)

Material Lump Size Lump Air

Size Borne

Factor Factor

Ftne Grain < 10mm o 4

m Dust

Granular <25 mm I o

Sized and Quantity of largest lump is 2 0

Unsized <20 percent of maximum

permissible lump size (forthe selected belt width)

Sized Quantity of largest lump is 3 0

<60 percent of maximum

permissible lump size (forthe selected belt width)

Unsized Largest lump does not 4 0

exceed maximum per-

missible lump size (for the

selected belt width)

Sized Largest lump does not 4 0

exceed maximum per-missible lump size (for the

selected bett width)

Table 5 Abrasiveness Factor

(Clause 7.4)

Abrasive- Type of Material ‘Abrasi-

ness veness

Factor

Non Free flowing materials, such as cereal 1

Abrasive grains, wood, chips, wood pulp, fullersearth, flue dust, soda lime, char, loam

sand, ground gravel.

Mildly Materials, such as aggregate, run-of- 2

Abrasive bank sand and gravel, slate, coal, salt,sand stohe.

Abrasive Materials, such as slag, spar, limestone 3concentrates, pellets.

Very Iron ores, taconite, jaspar, heavy 4

Abrasive minerals, flint rock, glass crdlet,

granite, traprock, pyrites, sinter, coke.

7.13 Calculate slope tension and return side frictiontensions.

7.14 Depending upon conveyor configuration, that isinclination/decli nationregeneration, location of drive,compute the minimum required slack side tension.

Table 6 Maximum Recommended BeltSpeeds (m/s)

(Clauses 7.4,8 .1.3,8.2.2 and 8.3.3)

600 to 750 to 950 to 1200

650 800 1050 to2000

\SpeedFactor I

7.15 Compare slack side tension values obtainedfrom 7.11 and 7.14 and use higher of the two valuesto calculate maximum operating tension. Also calcu-late maximum starting tension.

7.16 Multiply maximum operating tension by the mini-mum safety factor with reference to type of belt, jointsand take-up, etc.

7.17 Select a belt having breaking strength in excessof value obtained from 7.16. -Check this result withrecommended maximum and minimum and maximumbelt widthhtumbers of plies for troughing and sup-porting the load.

7.18 Tentatively decide belt specification includingcover thickness grade and construction.

7.19 Check adequacy of belt for starting and breakingtension calculated in 7.15.

7.20 Finalise belt selection.

7.21 Determine drive power considering transmissionlosses after selecting machinery between drive pulleyand source of power. Consideration shall be given hereto limiting requirements of starting tensions and cor-responding minimum acceleration time requirements.

7.22 Determine the various pulley sizes namely, drivepulley, head pulley, tail Tttlley, snub pulley, take-uppulley, etc. Due considerations shall be given torecommendations made in IS 1891 (Part 1) whilemaking the selection for pulley sizes.

7.22.1 Basis for selection of pulley sizes for PVC beh-ing (see IS 3181) for underground use are as follows:

PVC Tensile Strength Minimum PulleyBelt (Minimum) Diameters forType Satisfactory Flexing

~~Longi- Trans- Drive Driven Lowtudinal verse Pulley Pulley Tension(kN/m (kN/m mm mm PulleyWidth) Width) mm

3 580 245 450 350 2504 700 265 500 400 3005 875 280 650 550 4006 1140 350 800 700 5508 1400 350 900 700 550

—

7

IS 11592:2000

Table 7 Maximum Section of the Handled Material in mz for Triple Roller TroguhedBelts According to Fig. 2 with Equal Length Carrying Idlers

(Clauses 7.6,8 .3.2,8.4.3,8.4.3.2 and 8.4.5)

I.J-lFIG. 2 MAXIMUM SECTION B OF HANDLED “MATERIAL FOR TRIPLE ROLLER TROUGHED BELT

Belt Surcharge Trough AngleWidth Angle

mm 20° 25” 30° 35° 40” 45”

500 0° 0.009 8 0.0120 0.0139 0.0157 0.0173 0.0186

I0° 0.014 2 0.016 2 0.0180 0.0196 0.0210 0.022020” 0.018 7 0.020 6 0.0222 0.0236 0.0247 0.0256

30° 0.023 4 0.025 2 0.0266 0.0278 0.0287 0.0293

)50 o’ 0.018 4 0.022 4 0.0260 0.0294 0.0322 0.034710“ 0.026 2 0.029 9 0.0332 0.0362 0.0386 0.0407

20° 0.034 2 0.037 7 0.0406 0.0433 0.0453 0.0469

30° 0.042 7 0.045 9 0.0484 0.0507 0.0523 0.0534

ioo (r 0.027 9 0.0344 0.0402 0.0454 0.0500 0.0540

Io“ 0.040 5 0.046 6 0.0518 0.0564 0.0603 0.0636

20” 0.053 5 0.059 1 0.0638 0.0678 0.071 0.0736

30° 0.067 1 0.072 2 0.0763 0.0798 0.0822 0.0840

1 000 0° 0.047 8 0.0582 0.0677 0.0763 0.0838 0.0898

10° 0.067 4 0.077 I 0.0857 0.0933 0.0998 0.105

20° 0.087 6 0.096 6 0.104 0.111 0.116 0.120

30” 0.109 0.117 0.134 0.129 0.134 0.136

1200 0° 0.070 0 0.085 3 0.0992 0.112 0.123 0.132

10° 0.098 8 0.113 0.126 0.137 0.146 0.154

20° 0.129 0.142 0.153 0.163 0.171 0.176

30° 0.160 0.172 0.182 0.190 0.196 0.200

I 400 0° 0.098 0 0. I 20 0.139 0.1-57 0.171 0.184

10° 0.138 0.158 0.175 0.191 0.204 0.214

20° 0.179 0.197 0.2)3 0,220 0.237 0.245

30° 0.221 0.238 0.253 0.264 0.272 0.277

I 600 0° 0.130 0.159 0.185 0.208 0.228 0.244

1o“ 0.182 0.209 0.233 0.253 0.270 0.283

20° 0.236 0.261 0.282 0.300 0.314 0.324

30° 0.293 0.3 I 5 0.334 0.349 0.360 0.366

I 800 0° 0.167 0.203 0.237 0.266 0.292 0.313

I 0° 0.233 0.268 0.298 0.324 0.346 0.363

20” 0.302 0.334 0.361 0.384 0.401 0.414

30° 0.374 0.403 0.427 0.446 0.460 0.468

2000 0° 0.207 0.253 0.294 0.331 0.362 0.388

10° 0.290 0.332 0.370 0.403 0.429 0.450

20” 0.376 0.4 I 5 0.448 0.476 0.490 0.514

30° 0.465 0.501 0.530 0.554 0.571 0.581

I8

IS 11592:2000

Table 7 — Concluded

I Belt -. . .

Width

mm

2 2001)

2.10011

2 600’J

2 800’)

Surcharge I rougn .4ngle

Angle

0°

10“

20°

30”

0°

1o“

20”30°

0°Io“20”30°

0°10°20”30°

— 20”

0.257

0.357

0.461

0.569

0.3030.4230.5470.677

0.360

0.502

0.648

0.801

0.413

0.578

0.749

0.928

25°

0.311

0.408

0.508

0.613

0.368

0.484

0.604

0.729

0.439

0.575

0.716

0.863

0.505

0.663

0.827

0.998

30°

0.363

0.455

0.549

0.649

0.428

0.539

0.653

0.772

0.510

0.640

0.774

0.914

0.585

0.737

0.894

1.063

35°

0.4~8

0.494

0.584

0.677

0.482

0.586

0.694

0.806

0.573

0.695

0.822

0.953

0.660

0.803

0.950

1.104

40”

0.446

0.527

0.610

0.697

0.528

0.625

0.725

0.830

0.628

0.741

0.859

0.982

0.721

0.885

0.993

1.137

45° -

0.478

0.552

0.629

0.710

0.566

0.656

0.748

0.845

0.672

0.777

0.885

0.999

0.774

0.897

1.025

1.158

I NOTE — Suitable adjustment maybe made in case of other values of surcharge angle and troughing angle.

II Indicates sizes generally not available in the c&ntry and meant for information only.

7.23 Finalized drive power considering transmissionlosses after selecting machinery between drive pulleyand the source of power.

7.24 Finalise the drive element’s specification like cou-pling, belt/chain drive, gear box.

7.25 Determine drive shaft diameter and other termi-nal shaftings.

7.26 Select proper bearings for the duty conditionsand service life.

7.27 Consider location and type of take-up and findout the amount of take-up tension and the take-upmovement.

7.28 Calculate coasting time of individual conveyorsand correct the coasting times for the conveyor system.

7.29 Consider if hold back and brake are requiredsimultaneously or one will be sufficient. Determinethe type and location of hold bacldbrake.

7.30 Calculate the braking force and torque required.

8 DESIGN ASPECTS

8.1 Characteristics of Material Affecting ConveyorDesign

8.1.1 The proper design of a belt conveyor/conveyorsystem is greatly influenced by the characteristics ofthe material to be handled. Generally, the material isclassified as shown in IS 8730.

8.1.2 Care shall be taken for the inclination of aninclined/declined conveyor, carrying lumps ofmaterial, as these are likely to slide down, wherever

possible. Actual inclination of the conveyor shall notexceed the maximum allowable value (see IS 873.0).In case of declination, the angle of declination shallnot exceed 12° in any case.

8,1.3 Table 6 shows the maximum recommended beltspeeds for different sizes of belts based on speed fac-tor (speed factor -= lump size factor + abrasivenessfactor). For systems with ploughs and trippers, lowerspeeds of belt shall be adopted.

8.1.4 Physical Condition of Material

Care shall be taken to analyse the physical conditionof the material to be conveyed which are classified asfollows:

a) Oily .or liable to react with rubber products,

.b) High temperature,

c) Non-abrasive,

d) Mildly abrasive,

e) Abrasive,

f) Very abrasive,

g) Sharp abrasive,

h) Easily degradable,

j) Mildly corrosive,

k) Highly corrosive,

m) Explosive or creating harmful dust,

n) Very dusty,

p) Inflammable,

q) Hydroscopic, and

r) Sticky.

9

IS 11592:2000

Table 8 Maximum Section B of the Handled Material in mz for Two Equal Idler Troughed BeltsAccording to Fig. 3 and for Flat Belts According to Fig. 4

(Clauses 7.6,8 .3.2,8.4.3,8.4.3.2 and 8.4.5)

--t

—

I

FIG. 3 MAXIMUM SECTION B OF HANDLED MATERIAL FIG. 4 MAXIMUM SECTION B OF HANDLED

FORTwo EQUAL IDLER TROUGHEDBELT MATERIAL FORFLAT 13ELT

Belt Width

mm

300

400

500

650

800

I 000

I 200

1400

1600

Surcharge

Angle

o“10°20”

30”

o“

1o“

20”

30°

0°1o“

20”

30°

0°1o“

20°

30°

0°1o“

20”

30°

0°

10°

20”

30°

o“

Io“

20”

30°

0°

1o“

20”

30”

0°

10°

20°

30°

Two Idler Troughed Belts

Trough Angle

15“ 20” 25°

. — —

. — —— — —— . .

0.0059 0.0077 0.0092

0.0085 0.0102 0.01150.0112 0.0127 0.0138

0.0140 0.0154 0.0163

0.0100 0.0129 0.0154

0.0143 0.0170 0.0192

0.0188 0.0212 0.0232

0.0235 0.0257 0.0273

0.0179 0.0231 0.02740.0257 0.0304 0.03420.0337 0.0380 0.04130.0421 0.0459 0.0486

0.0277 0.0360 0.04290.0399 0.0473 0.05360.0524 0.0594 0.06470.0656 0.0718 0.0763

0.0449 0.0579 0.06900.0644 0.0765 0.08620.0846 0.0956 0.1040.106 0.116 0.123

0.0663 0.085-1 0.1020.0950 0.112 0.1270.125 0.140 0.1530.156 0.170 0.181

— — —— — —— — —— — —

— — —. — —— — —

— — —

Flat Belt

—0.00.14“0.00290.0044

—

0.00280.00570.0087

—

0.00470.00940.0145

0.00830.01690.0259

—

0.01300.02650.0406

—

0.02100.04270.0653

—

0.030-80.06260.0958

—

0.04250.08640.132

—

0.05600.1140.175

NOTE — Suitable adj ustments maybe made in case of other values of surcharge angle and troughing angle.

10

IS 11592:2000

Table 9 Slope Factor K

(Clauses 7.6,8 .3.2,8.4.4 and Fig. 5)

Conveyor Slope Conveyor slope Conveyor Slope

Inclination, Factor K Inclination, Factor K Inclination, Factor K

Degrees Degreea Degrees

2 1.00 25 0.68

4 0.99 16 0.89 26 0.66

6 0.98 18 0.85 27 0.64

8 0.97 20 0.81 28 0.61

Lo 0.95 21-22 0.78-0.76 29 0.59

12 0.93 23 0.73 30 0.56

14 0.91 24 0.71

1.1.0

xE“~

~ ~.9

UJLo

d

0.8

0.70° 5° 10° 15° -2{

SLOPE ANGLE,6—

FIG. 5 FACTOR K AS A FUNCTION OF 8 FOR ASCENDING CONVEYOR

8.1.4.1 Selection of various components of the con-veyor system shall be made taking the relevant physi-cal conditions of material into account.

8.1.5 Flowability, Abrasion and Other MiscellaneousCharacteristics of Materials

“8.1.5.1Based on size, ‘shape, angle of repose and angleof surcharge, the flowability of bulk materials is givenin IS 8730.

8.1.5.2 Due consideration shall be given to abrasionand other miscellaneous characteristics of material inselection of belts. These properties of material areclassified in IS 8730.

8.2 Belt Speed

8.2.1 Belt speed depends on the following factors:

a)

b)

c)

d)

e)

f)

Capacity required and belt ~idth;

Loading and unloading conditions;

Size, shapes, flowability and other characteri-stics of the material conveyed,

Belt construction;

Inclination of belt conveyor, and

Idler construction and diameter.

8.2.2 Belt speed shall be selected from the recommen-dation given in Table 6. Higher belt speeds may beconsidered under special design conditions.

11

—

IS 11592:2000

Table 10 Maximum Cap-city of a Belt Conveyor in tonnedhour

(Clauses 7.6,8 .3.2,8.3,3 and 8.4.5)

Capacity based on:

Bulk density of material, p = 1.0 t/m3

Belt speed v= l.orn/s

Slope factor K= 1.00

Belt Surcharge ‘hiple Equal Roll Roller ‘Ikoughed Belt, .lkmrgh Angle

Width Angle

mm 20° 25° 30° 35° 40° 45”0° 35 43 50 56 62 67

500 10° 51 58 65 -70 75 79

20° 67 74 80 85 89 92So 84 90 96 100 103 105

0° 56 80 93 106 116 125

650 10° 94 107 119 130 139 146

20° 123 135

6 153

146 156 163 169

30° 165 174 182 188 192

0° 100 123 144 163 180 194

800 10° 145 168 186 203 217 229

20° 192 212 229 244 255 265

30° 241 260 274 287 296 302

0° 172 209 243 274 301 323

1000 10° 242 277 308 336 359 378

20° 315 348 374 399 417 432

30° 392 421 446 464 482 489

0° 252 307 357 403 443 475] 20(3 10° 355 407 453 493 525 554

20° 464 511 551 587 615 633

30” 576 619 655 684 705 720

o“ 352 432 500 565 615 662

1400 10° 497 569 630 687 734 770

20° 644 709 767 792 853 882

30” 795 857 911 950 979 997

0° 468 572 666 749 820 878

1600 10° 655 752 839 911 972 1019

20° 849 939 1015 1080 1130 1166

30° 1054 1 134 1202 1256 1296 1 317

0“ 601 731 853 957 1051 1127

1800 10° 839 965 1073 I 166 1245 1307

2W 1087 1202 1299 1382 1443 1490

30” 1346 1451 1537 1605 1656 1685

0° 745 911 1058 1191 1303 1397

2000 1o“ 1044 1195 1332 1451 1544 1620

20° 1359 1494 1613 1713 1793 1850

30” 1674 1803 1908 1994 2055 2091——

N(JKE— Suitable adjustments maybe made in case of other values of surcharge angle and troughing angle.

12

IS 11592:2000

Table 11 Maximum Capacity of a Belt Conveyor in tonnes/hours

(Clauses 7.6,8 .3.2,8.3.3 and 8.4.5)

Capacity based on:

Bulk density of material, p= 1.0t/m3Belt speed V= l.Om/s

Slope factor K= 1.00

Belt Width Surcharge Two Idler Troughed Belts Flat Belts

mm Angle Trough Angle

15“ 20” 25°0° . — . —

300 Io“ — — — 5.020° — — — 10.530” . — — 15.8

0° 21 27 33 —

400 I0° 30 36 41 10.020” 40 45 49 .20.530° 50 55 58 31

0° 36 46 55 .

500 10° 53 61 69 1720° 67 76 83 3430° 84 92 98 52

0° 64 83 98 --

650 10“ 96 109 123 3020” 121 137 148 6030° 151 165 175 93

o“ 99 129 I54 —

800 10” 143 171 193 4720” 188 214 233 9530° 236 258 274 146

0° 161 208 248 —

1000 10° 232 275 310 7520” 304 344 374 15430° 381 417 443 235

0° 238 306 367 —

I 200 1o“ 342 403 457 11120° 450 504 551 22530° 561 612 651 345

0° — . — —

I 400 10° — — — 15320” — — — 31130° — — . 475

0° — — . —

1 600 10° — — — 20120° — — — 410

30° — . — 630

—

NOTE — Suitable adjustments may be made in case of other values of surcharge angle and troughing angle.

13

IS 11592:2000

8.2.3 Higher belt speeds may be adopted after takinginto consideration the resultant effect arising out ofi

a)

b)

c)

d)

creation of turbulence at loading points andacceleration in cover wear;

encouraging of low density material to becomeair borne;

increase in product size degradation; and

reduction in life of chutes and transfer devices.

8.2.3.1 It is important also to check the adequacy ofthe type of belting, its joining and safety devices forthe conveyors.

8.2.4 Extreme care shall be exercised while selectingspeed, as lower speed will make the installation costlybut on the other hand a higher speed is likely to createproblems of spillage, dust generation and loss of tinepowdery materials.

8.3 Widths of Belt

8.3.1 The width of belt is predominantly governed bytwo factors, the lump size of the material conveyedand the capacity requirements of the conveyor.

8.3.2 Tables 7, 8, 9, 10 and 11 give cross-sectionalarea, slope factor and carrying capacity respectivelyof belt conveyors.

8.3.3 The width of belt for the capacity requirementcan be read off from Tables 10 and 11, This shall,however be checked for minimum belt width fromTable 6 for given lump size factor. The greater of thetwo values shall be adopted.

8.3.4 The standard width of belts in millimetres asspecified in IS 1891 (Part 1) are as follows:

300, 400, 500, 600, 650, 800, 1000, 1200,1400, 1600, 1800 and 2000.

8.4 Capacity of Belt Conveyor

8.4.1 The capacity of a belt conveyor isprimarily by the following three factors:

determined

a)

b)

c)

Cross-section ofload on the belt — The cross-sectional load on the belt will vary with thewidth of belt, the type of carrying idlers usedwhich determines the amount of troughinggiven to the belt, and the nature of the materialbeing handled, which determines the quantityaf material that can be safely loaded on to agiven cross-section;

Speed of belt; and

Slope factor.

8.4.2 General formula for calculation of the capacityof all types of belt conveyors shall be as follows:

C=3600p A VK, Max ... (1)

8.4.3 Figures 2 to 4 show -the most usual troughsections for which the cross-sectional area. A of thematerial is given in Tables 7 and 8 which are calculatedon a belt width, tilled with material, of width b (below2000 mm):

b = 0.9 B -0.05 ... (2)

8.4.3.1 For belts of width greater then 2000 mm,

b= B- O.25 ... (3)

8.4.3.2 Tables 7 and 8 indicate cross-sectional areafrom materials having surcharge angles of 0°, 10°,20° and 30°. The choice of right surcharge angledepends on the conveyed material and the distance ithas to travel. For normally flowing material, surchargeangle of 20° shall generally be chosen as standardvalue. Easily flowing or almost fluid materials, how-ever attain surcharge angle of less than 20° and maydrop down to OO. Surcharge angle higher than20° occur only for materials featuring a very highinternal friction.

8.4.4 The slope factor, K, in equation [1) takes intoaccount the decrease of the section of the handed-ma-terial on the belt when a gradient is involved. Table 9read with Fig. 5 gives values of K, the slope factor, fordifferent inclinations of a conveyor.

8.4.5 Tables 10 and 11 give the belt conveyor capaci-ties for horizontal conveyors, that is, K= 1.0 based onthe load cross-section as given in Tables 7 and 8 for amaterial of bulk density of 1.0 t/m, and “beltspeed of1.0 mfs. To calculate the capacity of a specific con-veyor, the corresponding value given in Table 10 andTable 11 shall be-multiplied by the actual bulk densityof the material, the belt speed and the slope factor.

8.4.5.1 To take surges and unevenness in loadingoperations into account, the capacity of belt conveyorcalculated according to 8.4.5 shall be generally limitedto 90 percent. In case of conveyors with belt widthsup to 600 mm, the capacity shall be reduced to75 percent.

8.5 Driving Force and Power Calculation

8.5.1 Peripheral Force Required on the DrivingPulley(s).

8.5.1.1 The required peripheral force, TEon the driv-ing pulley(s) ofa belt conveyor is obtained by addingup all the resistances,

TE= R + R, + R,Pi+ R,Pz+ Rs~ ... (4)

=f. L.g. [mC+m, +(2m~+mG)cosi$J+R,+ R,Pl+ R,Pl+ R~~ ... (5)

= ixf. L. g.. [m, + m, + (2m, + mG)cos 6]+mG. H.g+R,Pl+R,Pz ... (6)

14

where

T~ = driving force on the driving pulleys in N;

R = main resistances in N comprising of

i) rotational resistance of the carryingand return idlers due to the frictionin idler bearings and seals, and

ii) belt advancement resistance, result-ing from the impression of the idlersin the belt, the recurrent flexing ofthe belt and of the material;

R, = secondary resistances in N comprising ofl

i)

ii)

iii)

iv)

the inertial and frictional resistances

due to the acceleration of the materialat the loading area,

resistance due to the friction on theside walls of the skirt board at theloading area,

pulley bearing ~esistance with theexception of the driving pulleybearings, and

the resistance due to wrapping of thebelt on the pulleys;

R,o, = special main resistances in N comprising

i)

ii)

drag resistance due to forward tilt ofthe idler in the direction of movementof the belt, and

resistance due to friction against chuteflaps or skirt plates, when these arepresent over the fill length of the-bel$

R,Pz= special secondary resistance in Ncomprising ofi

i)

ii)

iii)

iv)

v)

resistance due to friction with belt andpulley cleaners,

resistance due to friction with thechute flaps or skirt plates, whenpresent over a part of the conveyorlength,

resistance due to inverting the returnstrand to the belt,

resistance due to discharge ploughs,and

resistance due to tripers;

RS~ = slope resistance in N, that is, the resistancedue to lifting or lowering the material on in-clined conveyors; and

= m=.H.g ... (7)

NOTE — H is taken as positive for ascending installation

and negative for descending installation.

J = artificial coefficient of ftiction, dimension-less comprising of rolling resistance of theidlers along the carrying and return

.

.

NOTES

IS 11592:2000

sides of belt and the belt advancementresistance;

0.020, is a basic value for normally alignedbelt conveyors; and

0.012, is a basic value for down hillconveyors requiring a brake-motor.

1 Underfavorable conditionssuch as fixed and properly aligned

installations with easily rolling idlers and low internal ffiction

material j’may be as low as 0.016 (basic value of 0.020 reduced

by 20 percent) and for unfavorable conditions such as poorly

aligned belt conveyors with badly rolling idlers andhigh internal

friction material,j’may be as high as 0:030 (basic value of 0.020

increased by 50 percent). The basic value 0.020 conforms to

majority of cases.

2 The basic value, 0.020 ofJis only applicable to installations

used at around 70 to 110 percent of their nominal capacity,

conveying products with an average internal friction coefficient,

equipped with three-roll carrying idlers for the upper side of the

belt, a 30° side troughing angle, belt speeda of about 5 mk,

surrounding temperatures of about 20”C and 108 to 159 mm

diameter carrying idlers with labyrinth grease seals, together with

idler spacing of 1 to 1.5 m for the carrying aide of the belt and of

around 3 m for the return side of the belt.

3 The value,j may, increase above the value 0.020 range up to

0.030 in the following cases:

a) for handled materials with a high internal friction

coetlicienta;

b) for troughing angle of over 30°;

c) for belt speeds of over 5 nr/s;

d) for carrying idler diameters lower than the above mentiond,

e) for surrounding temperatures of less than 20”C;

f) fora decrease of the belt tension;

g) for flexible carcass belts and those with thick and flexible

covers;

h) for poorly aligned installations;

j) when operating conditions are dusty and wet and/or sticky;

k) for idler spacing of markedly more than 1.5 m for the

carrying side upper atrand of the belt and 3 m for the return

side (lower strand]of the”belt.

4 The artificial friction coefflcient,~ may decrease under the basic

value of O.020 if the conditions stated in Note 3 are reversed.

5 When the installation is running under no-load conditions, the

value of~ can be either lower or higher than under full-load

operating conditions, depending on the mass of the moving parts

and on the conveyor belt tension. Downhill conveyors which

require to be braked by brake-motor, shall, w-a safety measure,

be calculated with a value lower by 40 percent than used for the

calculation of driven belt conveyors. The result of this is a basic

value off= 0.012.

6 Value of~may increase above the value of O.030 under certain

adverse conditions and/or type installation as for example in case

of underground mines.

a’) = numerical coefficient, being a function ofconveyor length L (see Fig. 6)

Total resistance without slope resistance andwithout special resistance=

Main resistance

1) For conveyom with centre distances less than 80 m,the value of ~

is unsure, as indicated by the batched area of Fig. 6. Where the smaller

secondary resistances and the greater values arepossible especially

for short high speed feed conveyors of large capacities.

15

IS 11592:2000

R~~.—R

5.0

I

4.5

64.0

5qg 3.6u.

boU

3.0

2.5

2.0

1.5

1.1

1.05

1.010 20 30 50 100 200 1000 5000 m

CONVEYOR LENGTH (DISTANCE BETWEEN CENTRES),L

FIG. 6 VALUES OF COEFFICIENTCXAS FUNCTIONOF CONVEYOR LENGTH L

... (8)

m= = mass per metre, of handled material inkglm

= 1000 rQ/V ...(9)

where

Q =volumetric conveyor capacity inm3/s;

=AVK; and ...(10)

H = lift of the conveyor between the dischargearea in m. In case a belt tripper is used Hshall include .Iift of the tripper also.

8.5.1.2 Equation (6) is generally use for determiningthe driving force Tw If the conveyor slope is less than18°, the factor cos 8 in equations (5) and (6) shall beomitted. Equation (5) is applicable for all conveyorlengths. However equation (6) can be used for approxi-mate calculations for conveyors length more than 80 m.

8.5.1.3 Calculation for secondary resistance, R, (forsymbols, see Table 1)

where

R, =

.

R&, =

16

intertial and frictional resistance at theloading point and in the acceleration areabetween the handled material and the beltin N

Q.lOOO. p.(V-VJ ... (12)

frictional resistance between handledmaterial and the skirt plates in theacceleration area in N

= p2.Q2.1000p.g.1,

...(13)

RW = wrap resistance between belt and pulley,

in N (not to be calculated for drive pulleys)

‘B[’40+001”a+‘-for fabric carcass belt

,(14)

‘2B[200+00’”a:...(15)

for steel cord beltNOTE —The values of wrap resistance Rw shall generally be

calculated in accordance with formulae (14) and (15), Forguidance. following table gives the values of wrap resistance

Locaticul of Degrze of Wrap Wrap Resistance?’Ldley of Belt N

Tigb[ side 150° to 240° 230

Slack side 150° to 240° 175

All other pulleys — 140

pulley bearing resistance (not to bc!cal-culated for driving pulleys) in N

0.005~ Rv ..D

.(16)

acceleration length at loading area m

v? - v;

‘&PI, Min ...(17)

coefficient of friction between material andbelt

0.5 to 0.7

coefficient of friction between material andskirt plates

0.5 to 0.7

8.5.1,4 Calculation for special main and secondaryresistances. R,Pland RSP1

R,v=—

—

where

RI =

=

=

R,k =

.—

special resistances in N

(R$,l+-R~P2) ...(18)(Ri + R,, + R,=+ R> ...(19)

resistance due to idler tilting

g. c, KOL,(ma + nl~) cos 5 sin i ... (20)in case of carrying idlers equipped withthree equal length rollers.

g . P#i (fn~)cos ~ cos 6 sin i ... (21)in case of return idlers equipped with tworollers.

resistance due to friction between handledmaterial and skirt plates in N

wz.Q2.1OOOp.g.1,~

V2b~... (22)

IS 11592:2000

R~C= frictional resistance due to belt cleanersin N

= A,p. p, ...(23)NOTE — The frictional resistance due to belt cleaners. Rb, shall

be calculated in accordance with formula (23). For guidance, a

value between 360 and 530 N/m length of each scraper may be

resistance due to friction at the dischargeplough in N

B.K= ...(24)0.4 trough factor up to 30° trough

0.5 trough factor above 30° and up to 45°trough

coefficient of friction between carryingidlers and belts

0.3 to 0.4

coefficient of friction between material andskirt plates

0.5 to 0.7

0.6 to 0.7 between belt and belt cleaner

Pressure between belt cleaner and belt

= 3 (10)4 to 105N/mz

K, = scraping factor in N/m

= normally 1500 N/m

8.5.2 The formulae given in 8.5.1 for the calculationof the peripheral force at the driving pulley tire suit-able only for uniformly and continuously loaded in-stallations. For belt conveyors running over roughground with slope changes or only sloping in the downhill direction, for which partial loading of the belt isfrequently the case, the computing of the peripheralforce shall be carried out for different operating con-ditions, for example:

a)

b)

c)

d)

empty conveyor;

fully loaded throughout;

loaded on some sections of the conveyor with arising, level or slightly dropping run whereeach section requires positive force to move it,and empty on the remaining sections whichwould be regenerative if loaded; and

loaded on regenerative sections and empty onsections with a rising, level or slightlydescending run.

8.3.2.1 The highest peripheral force on the driving pul-ley, whether positive or negative, found in this mannershall be used for the design of the driving system.

8.5.3 Belt Conveyor Operating Power Requirements

8.5.3.1 The power required at the driving pulley(s) ofa belt conveyor shall be:

PDP= ~ kw1000 ... (25)

17

IS 11592:2000

TE v + (Rwd ‘Rbd)v ~,PA=—

1000 1000... (26)

after taking drive pulleys loss into acount

where

RWd= Wrap resistance between belt and pulleyfor drive pulley and is to be calculated asgiven for RW,and

R,, = Pulley bearing resistance for drive pulleyand is to be calculated as given for R~.

8.5.3.2 The motor output power (shaft) shall be:

(27)

for conveyors requiring Tositive power

= PAqz for regenerative conveyors ... (28)

NOTES

1 Efficiency of various transmission elements shall be taken into

accounl while adopting the values ofq,.Forguidance,Table12may be referred.However where necessary, the actual eftlciency

may be taken into account.

2 While deciding on the motor power to be adopted, consideration

shall be given to the actual likely condition of usage of installation.

3 rJ,= 1.otoo.95.

8.5.3.3 Additional power required due to tripper

a)

b)

c)

d)

If a belt conveyor has n, number of trippers-thepower requirement shall be:

Pa=~(l+ntp)+ ‘R”;;;: ‘v ‘w ... (29)

where

~-= factor for extra power for each tripper andshall be taken from Table 13 or Table 14 asthe case may be.

Table 13gives the values of factor~for a tripperwhich is either fixed or separately driven andTable 14 is for belt propelled trippers and isrestricted to those lengths and slopes wherethese are applicable.

The lift of the tripper shall be included in theconveyor lift (H).

The peripheral force required on the drivingpulleys for a belt conveyor with ‘n,’numbers oftrippers shall be 7’~(1 + @)N and furthercalculations shall be based on this force only.

8.5.4 Belt Forces

8.5.4.1 The tensiIe forces on the belt, being differentat different point on belt of the conveyor, depend upon:

a)

b)

c)

the path of the conveyor;

the number and arrangement of the drivingpulleys;

the characteristics of the driving and brakingsystems;

Table 12 Efficiency for Various‘Ikansmission Units

[Clause 8.5.3.2 (Note 1)]

~pe of Drive Percentage

Etllciency

Enclosed gear units —

Single reduction heticatlstraight cut Up to 98

Double reduction helical/straight cut Up to 96

Triplereduction helicaf/straight cut up to 94Spiral bevel/helical/worm gear Use manufac-

turers’ ratingDouble reduction up to 96Triple reduction up to 94Chain drives — Totally enclosed and oil lubricated Up to 98V-Belt drives 95Tooth belt drives 95-98

Fluid drives Use manufac-turer’s rating

NOTES

1 The percentage given for gear units are based upon wellventilated boxes tilled with the manufacturer’s recommended

lubricants.

2 Multiply together appropriate percentage for each reduction from

prime mover to head pulley to obtain overall efficiency of

transmission.

d) the type, location and arrangement of the belttensioning devices; and

e) the load case of the installation: starting,nominal rating, braking, stopped either at noload or completely or partially loaded.

8.5.4.2 The tensile forces exerted on the belt shall besuch that, at any rating, the peripheral forces appliedto all the driving pulleys are transmitted to the belt byfriction without slipping and the belt sag between thesupporting idlers does not exceed a safe limit.

8.5.4.3 Transmission of the peripheral force at thedrivirrg pulley(s)

For the transmission of a peripheral force for TEfrom a driving pulley to the belt the minimum tensileforce Tz~inon the return belt shall be calculated fromthe formula:

.,.. ” 1

(30)

2 l~sg— ... (31)ep~- 1

where

T=E max

P“

18

Maximum peripheral force, in N, oftenoccurs when starting up or when brakingthe completely loaded conveyor. Forguidance, with ratio of TEand TEmmmay

be taken from Table 15 depending uponthe characteristics of selected drive.

the coefficient of friction between thedriving pulley and the belt and -can bedetermined from Table 16.

-IS 11592:2000

Table 13 Factor /3 for Extra Power Required for Separately Driven ‘Mpper

[Clauses 8.5.3.3 (a) and 8.5.3.3 (b)]—

Conveyor Tripper Slope

Lengthm 0° 19.50 6“ -10° 11”-15° 16°-20°

5 — — — “0.27 0.23

10 — — 0.29 0.24 0.19

Is — . 0.20 0.17 0.15

20 — 0.21 0,17 0.14 0.12

30 — 0.19 0.11 0.10 0.08

45 — 0.15 0.10 0.08 0.08

60 —- 0.11 0.08 0.08 0.08

75 — 0.11 0.08 0.08 0.08

90 0.11 0.10 0:08 0.08 0.08

120 0.09 0.09 0.08 0.08 0.08

i50 0.08 0.08 0.08 0.07 0.07

180 0.07 0.07 0.07 0.07 0.07

210 007 0,07 0.07 0.07 0.07

250 0.07 0.07 0.07 0.07 0.07

300 0.07 0.07 0.07 0.07 0.07

6(X3 0.07 0.07 0.07 — 0.07

1000 0.07 0.07 0.07 — 0.06

Table 14 Factor ~ for Extra Power Required for Belt Propelled ‘IYippers

[Clauses 8.5.3.3 (a) und 8.5.3.3 (b)]

—

=57m

5

10

15

20

30

45

60

75

90

120

I 50

180

210

250

0°

—

—

—

—

—

.—

—

—

019

0.14

0.13

0.11

0.11

0,10

1“-5”

—

—

—

0.40

0.32

0.27

0.21

0.19

0.17

0.13

0.12

0.10

0.10

—

Tripper Slope

-

—

0.54

0.36

0.30

0.21

0.18

0.15

0.14

0.12

0.10

0.10

—

—

—

11°-150

0.52

0.46

0.30

0.23

0.17

0.15

0.12

0.11

0.10

.—

—

—

—

—

16°-20°

0.44

0.35

0.25

0.19

0.14

0.13

0.11

0.10

0.09

—

—

—

—

—

19

IS 11592:2000

8.5.4.4 Minimum tensile force to limit the belt sag

The minimum tensile force Tn,iflwhich shall be exertedon the belt to limit the amount of belt sag between thetwo sets of idlers shall be:

~ ~~(m~+mG)gmm for carrying side ... (32)

8S ‘

> ~m~.g——, for return side

8S... (33)

where

s = maximum allowable belt sag

= 0.005 to 0.02.

Values lower than these never be reached at any pointon the installation. The maximum allowable beltsag [(S = hla),d~], is generally fixed at between 0.005and 0.02

8.5.4.5 Variation of the tensile forces and maximumterrsileforce on the belt

The necessary tensile force and its alteration alongthe conveying length shall he determined for each loadcase as a function of the number, the arrangement andcharacteristics of the driving and braking devices, andaccording to the type and location of the tensioningdevices, by suitably adding to or subtracting from theminimum forces exerted on the belt the motion resis-tances, the forces due to the weight of the belt and theconveyed products, and the peripheral forces appliedto oil the driving pulleys. The minimum necessarytensile force is fixed either by the ability of transmit-ting the peripheral force at a driving pulley or by thelimitation of belt sag. This highest value of the neces-sary tensile force for a given load case is generallymaintained with all the other load cases even if theydo not require it, as normally it is not reasonable andnot practicable to produce different take-up forces withdifferent load cases. The maximum tensile force T~m,exerted on the belt which has to be used for the choiceand the dimensioning of the belt can not be indicated

T,

Table 15 Values of Drive Coefficient&

(Clause 8.5.4.3)

sl Type of Drive

No.

O Three phase squirrel cage motor with pin

bush coupling and.direct on line start

ii) Three phase squirrel cage motor with fluid

coupling and direct on the line start

iii) Three phase squirrel cage motor with

special fluidcouplingwithdelayedchamberfitting

iv) Three phase squirrel cage motor with

special fluid coupling with delayed chamber

with panel and scoop control

v) Three phase squirrel cage motor with flexi-

ble coupling and start/delta start, slip-ring

motor with slip gear startinrz control

Drive

Coefficient

1.8. to 2.2

1.5tol.6

1.2tol.5

1.2

1.2

by a formula which is universally valid. It is only in thesimple cases, which, however, occur relativelyoften, that is, in the case of horizontal conveying orwith a small gradient, and ifthere is a single drivingpulley, and if low braking forces for stopping the plantare required, that the maximum tensile force appliedto the belt can be calculated, approximately, by usingformula (34) (see Fig. 7):

...(34)

NOTE — The coefficient takes into account the fact that

the peripheral force should be higher when starting the

plant up then when at its nominal rating. According to the

drive characteristics, the coefficient is between 1.2 and 2.2

8.6 Belt Specification

8.6.1 A conveyor belt consists of two elements, thecarcass and the cover. The carcass is the reinforcingmember and may be of either textile reinforcements orsteel cords and supplies the tensile strength and thebody to the belt to hold the shape. In case of textile

@ ANGLE OF WRAP

TE

FIG. 7 TENSILE FORCES EXERTED ON“BELT

20

IS 11592:2000

Table 16 Friction Coefficient Between Driving Pulley and Rubber Belting

\

Pulley Leg Smooth Bare

Rim Steel

OperatingPulley

Conditions

Dry condition operation [ 0.35,00.4

Clean wet condition

I

o.I(water) operation

Operation under wet 0.5 to 0.1

and dirty (clay or loam

conditions)

Operation under very

I

0,05wei and dirty condition

(Clause 8.5.4.3)

RubberLaggingwithHerringbonePatternedGrooves

0.4 to 0.45

0.35

0.25 to 0.3

0.23

reinforcement, the carcass is normally buildup of pliesof textile fabric. The strength of fabric and the number ofplies in the carcass of the belt maybe varied together tosuit the strength requirements. However, the strength ofcarcass has a practical limit. If the belt is too tough,troughing and training the belt will be very difilcult.Thereftrre, the belt with lesser number of plies with stron-ger fabric is generally preferred because it is more flex-ible both in troughing and going round the terminal pul-leys. The steel cord beking is used to meet the conditionof small elongation and good troughbility in conjunc-tion with higher operating tensile forces. PVC belting isgenerally selected for underground mining applicationswhere fire hazard exists.

8.6.2 Selection of Belt Carcass

8,6.2.1 Tensile forces calculated in accordance withformula (34) (see 8.5.4.5) is then used in selection ofbelt carcass based on full thickness tensile strength(FTTS) (belt type).

8.6.2.2 Full thickness tensile strength (FTTS) method

The value of tensile forces (see 8.6.2.1) multiplied byfactor of safety gives the required value of fullthickness tensile strength of the required belt. The fullthickness tensile strength of belt tixes the ‘Type’ ofbelt to be selected. The factor of safety may vary from9 to 12.5 in case of textile belts and 7 to 10 in case ofsteel cord belts depending upon the application, typeof belt joint, type oftakb-up device and type of startingfor convertors. For general guidance a factor of safetyof 10 is normally used for textile belts with vulcanizedjoints and on a conveyor with gravity take-up and 7 forsteel cord belting.

8.6.2.3 After the selection, the selected carcass shallhe checked for the following two constraints:

a) Adequate ‘body’ to support the load of thematerial carried for the specific width of the belt.This may be checked from manufacturers’recommendatory tables providing either mini-

PulyurethaneLaggingwith.Herringbone

PatternedGrooves

0.35 to 0.4

0.35

0.2

0.2

b)

Caramic LaggingwithHerringbonePatternedGrooves

0.4 to 0.45

0.35 to 0.4

0.35

0.3

PVC Belt Type

0.25 tO 0.35

0.15 to 0.30

Less than 0.25

0.15

mum number of plies for adequate load supportor maximum width for adequate load support forvarious types/constructions as also impact load-ing.

Adequate flexibility to trough on the specifiedangle of idlers.-Thismay be checked h-n manu-facturers’ recommendatory tables pro-vialingmaximum number of plies for adequate troughmgor minimum width for adequate troughing forvarious types/constructions.

8.6.2.4 The selected belting carcass shall besubsequently cross-checked for compatibility with thevertical curves occurring on the conveyor (see 8.9).

8.6.3 Selection of Cover

8.6.3.1 The properties needed for the cover of belt in-clude resistance to cutting, gauging, tearing, abrasion,aging, moisture absorption and in some conditions tooils, chemical and heat.

8.6.3.2 The grade and thickness of top cover of beltdepend upon a number of conditions, the mostimportant of which are:

a)b)

c)d)e)

og)h)

abrasive qualities of the material being handled.loading cycle, that is, the frequency with whichthe belt receives the load.lump size of the material.loading and unloading conditions.temperature of the material to be handled.chemical activity of the material.contamination of the material with oils,fire resistant cover needed or not.

8.6.3.3 The back cover thickness of a belt is generally1,0 to 3.0 mm for textile rubber belts and 0.8 to1.2 mm for PVC belts. In case of steel cord belts, backcover thickness is minimum 4.0 mm and range up to fillthickness of face cover.

8.6.3.4 Care shall be taken for the determination of backcover thickness for belts on tandem drives and other

21

1s 115Y2 : 2(NMJ

other special applications, where there is consider-able wear and tear in the back side of the belt. In suchcases the back cover thickness may be increased to3 mm and above as maybe necessary.

8.6.3.5 The cover grade is determined by characteris-tics of the material handled. The recommendedvalues of rubber cover grade selection are given in

IS 1891 (Part 1).

8.6.4 Standardization of Belt Constructions

Where belting specifications are being selected for anumber of conveyors in a plant it is worthwhile toconsider .standardization of carcass and covers for aparticular width of belting. This is to be looked into.in terms of expected life and inventory. It may be notedhere that the adequacy of belting constructions withrespect to actual service conditions that exist on eachindividual installation should be ensured whilststandardizing.

8.7 Pulleys

8.7.1 Based on percentage tensile force (ratio betweenthe working tensile force and maximum allowable ten-sile force of the selected belt), diameters of pulleysshall be selected from the recommended values givenin IS 1891 (Part 1) and shall conform to IS 8531.

8.7.2 The drive pulleys may be lagged, wherever nec-essary, to increase the coefficient of friction betweenthe belt and the drive pulley.

8.7.3 The lagging thickness shall vary between 6 to12 mm and the durometer hardness on head pulleyshall be 55 to 65 Shore A scale, whilst on the snuband bend pulley shall be 35 to 45 Shore A scale. Thesofter rubber tends to resist the build up and allowingof solid objects to get embedded in the rubber ratherthan damage the belt.

8.7.4 In case of steel cord belting and PVC belting,special consideration shall be made in selection ofpulley diameters and lagging, its type, thickness,material and application.

.8.8 Idlers

8.8.1 General Types of Idlers

8.8.1.1 There are two basic type of belt conveyor idlers:

a) Carrying idlers which support the loaded runof the conveyor belt; and

b) Return idlers which support empty return runof the conveyor belt.

8.8.1.2 Carrying idlers

a) General configurations — Carrying idlers canhave three types of general configurations:

1) Five/three roll throughing idlers for

22

2)

3)

troughed belts (see Fig. 2) consisting offour/two outer rolls, which are inclinedupward and a ‘horizontal central roll.

Two roll throughing idlers for troughedbelts (see Fig. 3) consisting of two identicalidler rolls, inclined upward 10 facilitate thebelt to from a trough.

Horizontal carrying idler for supporting flatloaded belts (see Fig. 4) consisting of asingle horizontal idler roll positionedbetween brackets which attach directly tothe conveyor frame.

b) Type of carrying idlers

1)

2)

3)

4)

5)

6)

The most commonly used type to carryingidlers consists of three in line idler rolls ofequal length. For a given width of belt, rollinclination and surcharge angle of thematerial, the three equal length rolltroughing idler forms the belt into the besttroughed shape to carry a maximum loadcross-section.

Troughing idler arrangement having arelatively long horizontal roll and two shortupward inclined rolls does not form a givenbelt into a trough for maximum load cross-section but is useful under certainconditions, for instance where conveyor’sload must be spread for manual inspection,picking up or sorting. The inclined end rollsturn up the belt edges to prevent or greatlyminimize spillage.

In an offset troughing idler, the inclinedrolls (two numbers on both the sides) andthe horizontal roll are located in twodifferent vertical planes.

Catenary type — Troughing idler consistsof a flexible catenary member on whichintegral small diameter rolls or multiple rollassembly is mounted. The rolls can bemoulded either in the flexible member,which rotates as an assembly in fixedbearings at the ends of the catenary memberor in the individual rolls which may rotateon bearings supported by the flexiblecatenary member.

Garland type — This type of idlers aresuspended from stringers by suitablesuspension methods. This type of idlersconsist of rolls connected in between withflexible links and can be used for both oncarrying and return side.

Impact cushioned idlers — Impact typeidlers having rolls made of resilientmaterial, are used at loading points wherethe-lump size and the weight of the handled

7)

8)

material may seriously damage the belt, ifthe belt was rigidly supported. The mostfrequently used type of impact idlersconsists of a three roll assembly, each rollbeing made of spaced resilient discs. Similarimpact idlers are made to support flat loadedbelts also. For moderate impact absorption,idler rolls are covered with a thick layer oftough rubber. In case the impact at the feedand exceed-s 50 Nm, impact idlers shallinvariably be used. The impact resistanceIhat a belt can withstand without anydamage can be obtained from the beltmanufacturer. Where garland type carryingidlers are used, garland impact idlers,connected in between with flexible links,shall be used as impact idlers.

Transition idlers — Transition typetroughing idlers are used adjacent to thehead and tail pulleys on wide,.high tension,low stretch belts, supported on 20° or abovetroughing idlers. With these idlers theloaded belt is properly supported near thehead and tail pulleys without excessivestretch of the belt edges. The transitionidlers are designed with concentrator (end)rolls and long centre rolls, to suit thetroughed belt contour between the lastregular troughing idler end the adjacentpulley. In case of adjustable transition idlers,the end rolls are adjustable. Troughingangle of transition idlers shall be kept as10°, 15°, 20°, 25°, and 30°.

Trahing idlers — Training idlers are usedto train or align the belt to a central positionsince conveyor belts tend to displacetransversely. In case of transverse beltdisplacement, both troughing idlers and flatcarrying idlers can -beso arranged that theyautomatically move the belt to its centralposition on the idlers. For this purpose thetroughing or flat belt carrying idlers, asunits, are pivotally mounted, with the pivotaxis approximately vertical. The threegeneral methods of pivotally mounting theidlers are as follows:

i) Small approximately vertical rolls, oneither end of the carrying idler, aremounted so that when the belt dikplacesa little, contact of these rolls w[th thebelt will cause the idler to pivot.

ii) Rotary discs are provided at the outerends of the inclined rolls, so that whenthe under surface of the slightly

iii)

IS 11592:2000

displaced belt engages the discs, theidler assembly will pivot. Wheregarland idlers are used there is nonecessity to use the training idlers.

Fixed guide idler rollers, consisting ofa roll on a vertical or nearly verticalaxis, sometimes are used to restrain aconveyor belt from transversedisplacement, such fixed idlers shall beused with great care for unusualcircumstances, as insurance againstpossible damage to the belt, fromappreciable transverse displacementsbecause continuous contact with fixedguide rollers of the belt edge greatlyaccelerates the belt edge wear and mayruin or appreciably reduce the normallife of a costly belt.

8.8.1.3 Return idlers

Return idlers are of three general types to performvarious functions:

a)

b)

c)

Normal return idlers — These idlers are usedto support the flat return belt and consists of along single roll, fitted at each end with amounted bracket. Idler roll length, bracket,design and mounting hold spacing shall allowfor adequate transverse belt movement withoutpermitting the belt edges to come in contactwith any stationary part of the conveyor w itsframe.

Training return idlers — These idlers are usedto train and align the return run of the belt andcan be mounted to train or align the return beltin a manner similar to the tra:ning idlersspecified in 8.8.l.2(b)(8).

Self-cleaning return idlers — The idlers areused to clean the belt carrying sticky materialwhich adhere to the belt. The sticky materialcan be abrasive thereby causing high wear rateor the material may buildup and adhere to thereturn idlers causing misalignment of the belt.Several types of self cleaning return idler rollsare available. For very sticky material metal-cage, rubber disc, or double covered helicallyshaped self-cleaning return idlers are used. Discrolls, helical and metal-cage idlers present onlyvery narrow surfaces for adhesion and thusreduce the tendency to build up.

8.8.2 Idler Specification

The carrying and return run idlers shall conform toIS -8598.

23

IS 11592:2000

8.8.3 Tilting ofldler

8.8.3.1 Angle of tilt shall be provided on the side roll-ers if specified by the purchaser.

8.8.3.2-The angle of tilt on side rollers of idlers shallbe .in the direction of belt run for the unidirectionalconveyors and it shall be ‘zero’ degree for reversiblebelt conveyor.

8.8.3.3 Angle of tilt on side rollers of idlers shall beassmall aspossible (generally 2°)andinanycase, itshall not be more than 3°.

8.8.4 Idler Spacing

8.8.4.1 Carrying idler spacing

The following points shall be considered carefullywhile determining the idler spacing for carrying idlersof a belt conveyor:

a)

b)

c)

d)

Increased idler spacing increases the belt sagand hence the power loss due to friction isgreater.

Very low belt sag means higher belt tensionsand therefore, cost of the belt is high.

The practical upper limit of belt sag is 2 percentof the idler spacing after which the forcerequired to pull the load increases steeply,However, for all practical cases, the belt sagshall be limited to 0.5 to 2.0 percent of the idlerspacing.

The belt tensions, especially for a long centreconveyor, very considerably along the lengthof the conveyor, which means different idlerspacings are required to limit the belt sag to afixed value. Proper care shall be taken todetermine the idler spacings for suchconveyors. The idler spacings in the carryingside (PC)and in the return side (P,) of the beltcan be determined from the equations (32) and(33).for graduated idler spacings by deciding asafe maximum allowable belt sag (S); andfinding other terms of the equations. Forexample, in a long centre conveyor, withuniform slope, there can be three sections, thefirst might be one-tenth of the conveyor length(independent of loading section) with acarrying idler spacing of 100 percent of theaverage, the secbnd section of three-tenth ofconveyor length at 85 percent of averagespacing, and the remaining three-fifth ofconveyor length at 125 percent of averagespacing. The maximum spacing shall be soselected as to ensure that the belt do-esnot looseits troughed shape. If the slope of the conveyorvaries, the idler spacing shall be arranged tosuit the belt tensions at various points.

Idlers at the feed point of the conveyor shall-beclosely spaced to avoid higher belt sag due toimpact of load.

To determine the idler spacing towards or atthe head, the following factors other than thelimiting belt sag shall be considered:

1)

2)

3)

There shall be no side spill of the materialas the belt flattens out in going from thelast troughing idlers on to the head pulley.

The load shall not change its cross-sectionbetween idlers that is the edges of the beltshall not flatten down.

The load on each idler shall not exceed theload rating value.

In normal circumstances, conveyors arrangedwith the pitch as indicated in Table 17 may befound to be suitable.

8.8.4.2 The spacings of carrying as well as return idlersfor belt widths of 1200 or more as given in Table 17shall be checked for the idler load capacities.

8.8.4.3 A set of self aligning idler shall be provided atdrive end and return end of conveyor and at an inter-val of 15 m on the carrying run wherever feasible and30 m at the return run. In case or short convertors, atleast one set of self-aligning idlers shall be providedat the carrying and return run. In case of steel cordbelting, the distance of self-aligning idlers on carry-ing run may be reduced to 10 m.

8.8.4.4 Calculation of transition distance

The distance between the terminal pulley and theadjacent fully troughed idler set at either at the heador tail end of a conveyor, .is known as transitiondistance. This spacing shall not be short so that theedges of the belt are stretched too much as the beltloses its tmughed shape and flatterns down the rim ofthe pulley. The transition distance, therefore, shall besuch as to limit the edge tension to a maximum of 130percent of maximum rated belt tension and preventbuckling of centre portion of belt. In addition,occurrence of zero or negative tensions in the centreof the belts also shall be avoided when the belt tensionis low such as occurring at tail end of some conveyors.To minimize this stretch, usually the pin of theterminal pulley is set in line with the tops of thehorizontal rolls of the troughing idlers. Alternatelythe rim of terminal pulley may be set at a line locatedat one-third of the depth of troughed section .of theconveyor. The transition distance shall be calculatedfrom the following formula:

[1)“2x = o.707y 2

AT... (35) I

24

IS 11592:2000

Table 17 Recommended Idler Spacing

[Clauses 8.8.4.l(g) and 8.8.4.2]

Alldimensionsin rnillimetres.

Belt Width Troughed Belt Ftat Belt Return Idler Sets

Carrying Idler Sets for Materials of Bulk Trotrghed and Flat Belt

Density (t/m3)

0.40 to 1.20 1.20 to 2.80

Recommended Spacings

300400500

I 500 1200

650 1000

8001000 1200 1000

3000

1200I 4001600 t 000 1000 75018002000

where

Y =

E=

AT =

B sinA— when pulley is in line with ...(36)

3top centre idler roller

B sinA— when pulley is elevated

4.5...(37)

by one-third of the trough depth above theline of the centre idler roller

the elastic modulus measured at themaximum rated belt tension (RMBT) inN/inn and is provided by the manufacturer

the induced belt edge stress in thetransition in N/mm and is selected fromTable 18 in relation to the ratio of belttension at the transition to maximum ratedbelt tension. An alternative method ofcalculating AT is given in Annex F.

8.8.4.5 Special consideration for spacing the idlersut head end

The distance from the head pulley to the nearesttroughing idler shall not be more than the spacing ofthe idler which is considered proper for the load onthe belt and tension on the belt.

8.8.4.6 Special considerations for spacing the idlersat loading point

The following points shall be considered while decid-ing the idler spacing at the loading point:

a) The distance between tail pulley and the first

b)

c)

d)

e)

f)

@

25

fully troughed idler shall be in accordancewith 8.8.4.4.

The rim of the tail pulley shall be in accordancewith 8.8.4.4 so as to aviod the belt gettingdamaged due to liftrng and rubbing against theloading chute or skirt boards.

The first fully troughed idler is generally setabout 150 mm behind the end of the loadingchute or wherever the material first strikes thebelt so that neither the idler is hurt by the impactof the material, nor any darnage is done to thebelt where it is backed up by the idler.

The spacing of first few idlers under the skirtboard shall be made closer, generally 0.33 to0.75 of normal idler spacing to prevent the beltfrom sagging away from the boards or therubber guard strip.

Rubber covered idlers or alternatively mountingthe idler stand on rubber ‘filler blocks shall beconsidered if the impact of the material is severeat the feed point. Provision of impact shall beconsidered.

When idler spacing is graduated, the idlers justahead of the loading point shall be set closerthan the average spacing so that the belt takesthe load of the material away from the skirtboards without abrupt change of load cross-section.

In case of a long conveyor having a continuousloading zone for almost entire length of theconveyor, for example, when fed by mobileplough feeder or by mobile reclaimer provision

.—

IS 11592:2000

of impact table in the feeding machine isrecommended in place of providing conti-nuously closed spaced cushioned idlers for theentire length of the travel. The receivingconveyorshallhave normally spaced troughingidlers without any skirt.

8.8.4.7 Idler spacing on curves (convex or concave)

Following points shall be taken into consideration:

a)

b)

The spacing of the idlers on concave curvesshailbenormal spacing, andfor convex curves,it shall be 40 to 50 percent of the normalspacing of the idlers or if the spacing is variable,the spacing on that part of the length ofconveyor.

The number of idler spacings shall not be lessthan three for any type of curves.

Table 18 Induced Belt Edge Stress

(Clause 8.8.4.4)

Ratio of Belt Tension at ATlkansition to Maximum Rated

Belt Tension

(TJ

1.0 ;.30Tm

0.9 0.35Tm

0.8 0.45Tm

0.7 0.55Tm

0.6 to 0.3 o.60Tm

0.2 0.40T~

0,1 0.20T=

0.05 O.lOT~

8.8.5 [dler Selection

8.8.5.1 It is extremely important to select proper idlersas they considerably influence the performance of abelt conveyor. The selection of idler is governed bymany factors, namely, the type of service, loading,surrounding conditions, the characteristics of thematerial handled, the belt speed, etc.

8.8.5.2 Typical methods for selection of idler basedon a particular service conditions of a belt conveyorare given in Annexes B, C and D for guidance. Anymethod of selection of idler may be used for arrivingat suitable idler sizes.

8.8.5.3 Annex E gives the method for calculation ofidler bearing load.

8.9 Curves in Belt Conveyors

8.9.1 There are two kinds of curves in belt conveyors:

a) Convex curves, where the components of belt

b)

tension act downwards or against the beltsupports; and

Concave curves, where components .of belttension act upward tending to lift the beh offits supports.

8.9.2 Convex Curves

8.9.2.1 The transition of the belt from inclined tohorizontal or less inclined maybe done with help of aturning pulley or a group (minimum three sets) oftroughed idlers. The belt shall not be bent with theaid of a turning pulley where the belt speed is highenough to cause the load to leave the belt by anappreciable distance (see 8.13.3 on dischargetrajectories). However, even if the beh speed is nothigh, the later method shall generally be adopted.

8.9.2.2 The minimum radius of the curves shall notbe less than 12 times the width of belt for practicalpurposes where troughing idlers of 30° troughingangle or less are used. However, two factors, as fol-lows, shall be considered in design to ensure that thepath of the belt follows a satisfactory radius:

a)

b)

Overstress of belt edges

B.Esin AMinimum radius, ‘C =

4.5(Tm– ~)m ...(38)

Luck of tension at belt centre

B.Esin A mMinimum radius, ‘c =

9(L – 4.5)...(39)

NOTES

1 TCwill be checkedfor all load conditions.

2 Racths to be checked forallload conditions and maximum radius

to be adopted.

8.9.2.3 Belt modulus ‘E’ required by formulae (38)and (39) is a product of specific modulus for the ma-terial of belt carcass and rated tensile strength. Forcalculation, values of specific modulus, E,, can betaken from Annex G.

E = Es x Rated Tensile Strength ...(40)

8.9..2.4 Idler spacing shall be in accordancewith 8.8.3.7.

8.9.3 Concave Curves

8.9.3.1 When the belt curves upwards from horizontalto an incline section or from an inclined section ofthe belt to a more inclined section, the freeIy saggingbelt forms a curve that composes part of a catenary.

8.9.3.2 The minimum radius shall be such that thebelt will not lift off the carrying or return idlers evenunder worst condition when the belt is fully Ioaded upto the start of the curve and empty thereafter.

26

IS 11592:2000

ENT

1AN

—

All dimensions in mil]imetres.

FIG.%RADIUS OF CURVATUREFOR CONVACE CURVE

8.9.3.3 The radius of the curve is proportional to thebelt tension but inversely proportional to the mass ofbelt per metre.

8.9.3.4 The minimum radius, RC,of the curve is rec-ommended as 45 metres for practical purposes. How-ever following three factors shall be considered indesign to ensure that the path of the belt follows asatisfactory radius:

a) Lift off

Minimum radius for empty belt,

T .B.l 000R,= c metres

9.8 mB

Minimum radius for loaded belt,

... (41)

RC=TC.B.l000 meme~

9.8 (m~ + m~ )... (42)

Minimum radius for partially loaded belt(loaded up to beginning of curve),

Rc=T,mmB.1000

9.8 m~... (43)

Tc,mJX=T,~AX‘&’ [m. + m, cos ~ - [Rs + R,,, +R,P21 ... (44)

[R, + R,,, + R,,,] shall be caluclated for distancein which belt is empty and shall excludethe length of cruve.

T,,,,,X shall be worked out from equations (33)and (5) considering the belt is onlypartially loaded.

.b) Overstress at centre of belt

13.EsinAMinimum radius ‘C =

9 (Tm-~) ‘etres ““”’45)

POINT

wzx

c) Lack of tension at belt edge

B.EsinAMinimum radius Rc =

4.5 (~ -4.5)metres ... (46)

8.9.3.5 Belt modulus ‘E’ required for formulae (45)and (46) can be calculated with the help of equation(40) and Annex G.

8.9.3.6 The empty belt may be held from rising toofar by the use of one or more hold-down pulleys sethigh enough to clear load when the belt is on thecarriers.

8.9.3.7 Table 19 read with Fig. 8 gives typical valuesfor ordinates with 8 = 20°.

8.10 Drive Selection

8.10.1 Basis of Selection

8.10.1.1 The fundamental equation for a belt conveyordrive is given by equation (30) -in 8.5.4.3. For mostefficient drive, the ratio of maximum tensile force,T,, and the minimum tensile force, T2,that is the slack-side tensile force in the belt, should be as high aspossible.

8.10.1.2 Table 20 gives the value of ratios of forces7’1,T2 minimum and T~ for different arcs of contacton driving pulley(s).

8.10.1.3 For the selection of type of drive, minimumnumber of pulleys and least flexing of the belt consis-tent with the lowest practical belt tension is preferred.

8.10.2 Types and Selection of Drives

8.10.2.1 Single, unsnubbed, bare/lagged pulley drive

The simplest drive arrangement consists of one steelpulley connected to the source of power, having beltwrapped around it on an arc of 180°. This can be usedfor low capacity, short centre conveyors handling

27

IS 11592:2000

non-abrasive material. The pulley may be lagged toincrease the coefficient of friction and avoid pulleywear for abrasive materials.

8.10.2.2 Snubbed, bardlagged pulley drive

The ratio of maximum belt tension to effective belttension for the drive is decreased by snubbing,the beltat head pulley which may be bare or lagged. The arcof contact is increased from 180° to 210° and canfurther be increased to 260° by providing snub/drivepulley. In majority of normal medium to large capacitybelt conveyors, handling mild abrasive to fairlyabrasive materials, 210° snub pulley drive with headpulley lagged with hard rubber is adopted.

8.10.2.3 Tandem drive

Where the belt tensile fo~ces are very high and it jsnecessary to increase the angle of arc of contact,tandem drives are used. The tandem pulleys are bothdriven and share the load resulting in a lower effectivetension for a given power transmitted. The tandemdrive with arc of contact from 300° to 440° or morecan function with one or two motors. The location ofsuch drive is usually determined by the physicalrequirements of the plant and its accessibility.

8.10.2.4 Drive pulleys with twin drive

For belt conveyors, use of twin drive pulleys can beconsidered as given in Annex H.

8.10.3 Drive motors

8.10.3.1 At the start of the belt, the tension is normaltension plus additional tension to overcome the iner-tia of the load. This increased starting tension is det-rimental to the belt specially for long conveyors andit is necessary to design the drive system to suit thestrength of the selected belt. Except in short and lowspeed conveyor, the belt tension during the start willtend to be as much as the drive capable of exertingand in cases of repeated over-ioading, the belt mayfail due to fatigue.

8.10.3.2 Safety factor at starting and brakingcondition

Safety factor for the belts when calculated in accor-dance with the following formula shall not fall belowsix in case of textile fabric belt and below five in caseof steel cord belt when the conveyors are starting upor braking:

N~.BsF=—

T.,

SB,. (47)

8.10.3.3 Belt manufacturers commonly rate conveyorbelts so that they are able to withstand the frequentextra loads that occur in starting. Also drive factors,

1or T2/T~allow for some extra tension before

eP$ – 1

slipping would occur between pulley and belt. Acorrectly designed drive will allow maximumallowable tension force of the belt until the belt hasbeen brought to its running speed. It shall be ensuredthat the drive system including drive motor, coupling,gear box, pulley and chain drive, etc, does not exerteven at the starting condition, any more tensile forcethan the recommended transient capacity of the belt.

8.10.3.4 The above applies to normal duty conveyorswith single or dual drive provided with controlled startof motor (that is fluid coupling, centrifugal hydraulicslip, eddy current, clutch) by use of devices for speedand acceleration control.

8.10.3.5 To avoid these undesirable aspects it isnecessary to limit the torque developed during startup,and extend the acceleration period as reasonably longas possible, and this is achieved by accelerationcontrol. The acceleration control can be provided byusing a dc motor as the prime mover, but the motorand associated switchgear are both large andexpensive. A most effective means of control is tointerpose a hydraulic coupling or torque converterbetween the electric motor and input shaft of the driveunit’s reduction gear. This allows the compact, highspeed, ac motor to be employed, whilst providing, thedesired acceleration control. It is important, however,to ensure that on multi-motor dual drives that allelectric motors and hydraulic couplings have the sametorque and speed characteristics respectively, and thatthe speed differential between the drive pulleys iswithin the slip characteristics of motors and couplings.When selecting hydraulic couplings it shall beremembered that the slip characteristics can bemodified by adjusting the volume of oil in the workingcircuit. Two basic forms are available. In one type the-oil filling can only be adjusted with the unit stationaryand remains constant thereafter. In the other type thefilling may be adjusted during operation so that boththe rate of filling and the final quantity can be varied.The first type is very widely adopted for conveyordrives up to approximately 110 kW but it is obviousthat the latter type gives a wider range of adjustmentand is amenable to external control. It is commonlyselected in multi-motor installations where individualpowers of 75 kW and larger are used. The rate at whichthis slack belt is accumulated and, therefore, the rateat which the take-up unit has to be designed to operateis directly proportional to the rate to acceleration, sothe longer and more controlled the acceleration thesmoother and lower the rate of take-up.

28

—

IS 11592:2000

Table 19 Value of Ordinates for Convace Curve

(Clause 8.9.3.7)

L)is- Radius of Curve (RJ in metreskmce —t’I’OM 50 65 80 95 110 125 140 165 180 210 240 270 300 330‘r~n-

360

genthint inmetres

1.5 0.022

3 0.090

4,5 0.202

6 0.361

7.5 0.565

9 0.816

105

1~

13.5

15

16.5

lx

19.5

21

22.5

24

25.5

27

28.5

30

31.5

33

34.5

36

.37.5

39

40.5

42

43.5

45

46.5

4x

49.5

51

52.5

54

55.5

57

58.5

60

61.5

63

64,5

66

67.5

0.017

0.069

().155

0.277

0.434

0.626

0.853

1.117

0.014

0.056

0.126

0.225

0.352

().507

0.692

0.905

1.147

1.418

0.011

0.047

0.106

0.189

0.296

().427

0.582

().760

0.964

1.191

1.443

1.720

0,0100,0400.092

0.163

0,255

0.363

0.502

0.656

0.831

1,027

1.244

1.482

1.742

2.023

0.009

0.036

0.081

0.144

0.225

0.324

0.441

0.577

0.731

0.903

1.093

1.305

1.530

1.776

2.041

2.325

0.008

0,032

0,092

0.128

0.201

0.289

0.394

0.515

0.652

0.805

0.957

1.161

1.364

1.589

1.819

2.072

2.341

2.628

0.006

0.027

0.061

0,109

0.170

0.245

0.334

0.436

0.553

0.683

0.827

0.984

1.156

1,341

1.541

1.754

1.982

2.224

2.480

2.750

0.006

0.025

0.056

0.100

0.156

0.255

0.306

0.400

0.506

0.626

0.757

0.902

1.059

1.229

1.411

1.607

1.815

2.036

2.270

2.517

2.777

3.050

0.005

0.02 t

0,048

0,085

0.133

0.192

0.262

0.343

0.434

0.336

0.649

0.772

0.907

1.052

1.208

1.375

1.553

1.742

1.942

2.153

2.375

2.609

2.853

3.108

3.375

3.653

0.00460 .00410.00370.00340.003 1

0.018 0.016 0.015 0.013 0.012

0.042 0.037 0.033 0.030 0.028

0.075 0.066 0.060 0.054 0.050

0.117 0.104 0.093 0.085 0.078

0:168 0.150 0.135 0.122 0.112

0.229 0.204 0,183 0.167 0.153

0.300 0.266 0.240 0.218 0.200

0.379 0.337 0.303 0.276 0.253

0.469 0.416 0.375 0.341 0.312

0.567 0.504 0.454 0.412 0.378

0.675 0.600 0.540 0.491 0.450

0.793 0.705 0.634 0.576 0.528

0.920 0.817 0.735 0.668 0.613

1.057 0.939 0.844 0.767 0.703

1.203 1.068 0,961 0.873 0,800

1.358 1.206 1.085 0.986 0.904

1.523 1.353 1.217 1.106 1,013

1.698 1.508 1.356 1.232 1.129

1.882 1.671 1.503 1.366 1.252

2.076 1.843 1.658 1.506 1.380

2.279 2.024 1.820 1.654 1.515

2.492 2.213 1.990 1.808 1.656

2.715 2.410 2.167 1,969 1.804

2.947 2.616 2.352 2.137 1.958

3.189 2.831 2.545 2.312 2.118

3.441 3.054 2.746 2.494 .2.285

3.703 3.286 2.954 2.683 2.458

3.975 3.527 3.170 2.879 2.637

4.256 3.776 3.394 3.082 2.823

4.034 3.625 3.292 3,015

4.300 3.864 3.509 3.214

4.567 4.111 3.733 3.419

4.860 4.366 3.964 3.630

4.629 4.202 3,848

4.900 4.448 4.073

5.178 4.700 4.303

5.464 4.960 4.541

5.226 4.784

5.500 5.035

5.292

5.555

5.825

6.101

6.384

.—

29

IS 11592:2000

Table 20 Arc of Contact and Ratio of Tensions

(Based on ~ = 0,25 for bare pulley and 0,35 for lagged-pulley)

(Clause 8.10.1.2)

Arc of Ratio T1/T2 Ratio TJz’E Ratio T1/TECon&act on

DrivingBare

Pulley degreeLagged Bare Lagged Bare Lagged

p[llley pulley pulley pulley pulley pulley

180 2.19 3.00 0.85 0.50 1.85 1.50

I90 2.29 3.19 0.78 0.46 1.78 1.46

200 2.39 3.39 0.72 0.42 1.72 1.42

210 2.50 3.61 0.67 0.38 1.67 1.38

220 2.61 3.83 0.62 0.35 1,62 1.35

230 2.73 4.13 0.58 0.32 1.58 1.32

240 2.85 4.33 0.54 0.30 1.54 1.30

360 4.80 9.02 0.26 0.13 1.26 1.13

380 5.25 10.19 0.23 0.11 1.23 1.11

400 5.72 11.51 0.21 0.09 1.21 1.09

420 6.25 13.00 0.19 0.08 1.19 1.08

440 6.90 15.29 0.17 0.07 1.17 1.07

460 7.67 1.5.90 0.15 0.063 1.15 1.063

480 8.15 19.21 0.14 0.055 1,14 1.055

500 8.86 21.21 0.13 0.050 1.13 1.05

600 13.71 39.06 0.08 0.030 1.08 1.03

Type ofDrive I

2Plain

Snubbed

do

do

Snubbed

do

do

Tandem

do

do

--i

do

Tandem

do

-i

do

Tandem

do I

8.11 Coasting

8.11.1 Coasting Time

It is important to note that the drives of a conveyorsystem which consists of more than one belt conveyorin which at least one belt feeds on to another, have tobe interconnected electrically so that if one conveyor isstopped for any reason, the one feeding on to it muststop. If Lhephysical properties of conveyor are suchthat it would coast for a longer time than the one on towhich it feeds there will be pile up of material at thetransfer point. In general, in any conveyor system withmore than one conveyors, the length of the decelerationcycle of any successive conveyor calculated inaccordance with 8.11.4, shall be at least equal to orgreater than that of the preceding one. Therefore

.,. (48)

8.11.1.1 For conveyors with belts conforming toIS 1891 (Part 2) carrying hot material, this aspect takesspecial importance as otherwise belt is liable to bedamaged by burning.

8.11.2 Hold-back and 13rake.~

8.11.2.1 Hold-back arrangement and/or brake shall

be provided on conveyors which tend to reverse thedirection of run when power is off or under very heavyoverload.

8.11.2.2 Any conveyor requiring greater power to liftthe load than the power required to move the belt andthe load horizontally, shall be provided with hold-backor brake arrangement.

8.11.2.3 A regenerative downhill conveyor does notneed a hold-back, but it shall be equipped with anautomatic brake capable of bringing the fully loadedconveyor to rest within a reasonable time, when poweris off.

8.11.3 Acceleration Time

8.11.3.1 Acceleration time for the load of a conveyor

The time taken to accelerate the load on any conveyoris given by (for symbols see Table 1).

(mc+m, +2mB+mG+mp)L.V.la =T~–~

... (49)

where

T~ = 1.5 T~ for steel cord belts; and

= 1.6 T~ for tensile fabric belts.

30

8.11.3.2 Time taken by the motor to accelerate theconveyor

The time which the drive motor needs to accelerate

the conveyor assuming the components treated as hol-low cylinders is given by (for symbols see Table 1):

vtm=.me~—

F.... (50)

where

m=,q

m=

F,, =

P, =

(mC+ m, + 2m, + mti+ m, +m.JLkg ...(51)

(1

(GD)2 2nN 2

4L “ 60V... (52)

(qp\x PM- PA).looo

v...(53)

ralio of average starting motor torque andfull load motor torque depending upontype of coupling to and starting of motor(see also 8.5.4.3)

NOTE — The GLY value in the above equation shall be

cumulative value of all the equivalent GD2 of motor, reducer, drive

pulley, coupling and drive pulley in Nm all referred to the motorshaft axis.

‘Z-w+w$a=]+JH,.L. } –

(For Motor) (for H,S. Coupting) (ForGear Box)

(For S.S, Coupling) (For Drive Pulley)

8.11.3.3 The allowable time taken for the motor toaccelerate the loaded belt has to be greater than orequal to the minimum acceleration time to stay withinthe maximum allowable belt tension, while startingthe conveyor fully loaded that it tm2 ta.

8.11.4 Deceleration Time

8.11.4.1 By equating the kinetic energy of a conveyorto the power absorbed, the time, t~in seconds to bringLheconveyor to ~est from its running speed of V m/swith usual notations is given by:

v’td = meq

1OOOPA... (55)

8.11.4.2 The resisting frictional retarding force is:

<I ‘YE newtons ... (56)

8.11.4.3 If the deceleration time, td, is to be reducedto “t’d”since the total retarding force is inversely

proportional to the decelerationbraking force, Fad,required is:

~ = PA.1000 t~–t: newtonsad

V“t;

IS 11592:2000

time, additional

... (57)

8.11.4.4 If the brake is connected to the drive pulleyshaft, the drive pulley is required to transmit to thebelt a braking force equal to:

PA.l OOO td–tj meq –mi.Lnewtons

v“td” ‘eq

8.11.4.5 The difference in the values of

... (58)

8.11.4.3and 8.11.4.4 is the braking force required to deceler-ate the drive and drive pulley and is not transmittedto the belt.

8.11.5 Braking or Deceleration Forces

8.11.5.1 The braking force required for any conveyoris the algebraic sum of inertia force, frictionalr~sistance force, and gravity material load forces,inclined or declined. The frictional resistance forcesand gravity forces, if any, are equal to T~,the effectivedriving force.

8.11.5.2 The braking force is given:

a) In case of horizontal, inclined or declined andnon-regenerative belt conveyors, by

F~ = me~v

— – T~ newtons1

. . . (59)max

b) In case of regenerative decline belt conveyorsby

Fb = m~v

— + T~ newtonst

...(60)max

8.12 Take-Up

8.12.1 Functions

Main functions of take-up are:

a)

b)

c)

d)

ensuring adequate tension of the belt leavingthe drive pulley so as to aviod any slipping ofthe belt;

permanently ensuring adequate belt tension atthe loading point and at any other point of theconveyor to keep the troughed belt in shapeand limit belt sag between carrying idlers;

compensating for operating belt lengthvariation due to physical factors (instantaneoustensions, permanent elongation, outsidetemperature, temperature of conveyed material,dampness, etc); and

making available, if needed, an adequate extra

.—

31

IS 11592:2000

length of belt to enable rejoining withouthaving to add an extra piece of belt.

8.12.2 Types

8.12.2.1 Two types of take-up generally used are:

a) fixed take-up devices that are adjustedperiodically, and

b) automatic take-up devices (constant load type).

8.12.2.2 Fixed take-up devicc,s

In this type of take-up devices, the take,up pulley re-mains fixed between successive periodic adjustments.Take-ups of this type generally used are;

a)

b)

Screw take-up — In this system the adjustmentis manually effected by means of two screwsacting upon the pulley bearings and which aretightened simultaneously or successively. Thescrew is normally of non-expendable type andsliding surfaces are suitably protected againstingress of dirt. In this system, the appliedtension is not fully determinable. This generallyleads to excessive tension of belt (when tensionis insufficient, belt slips and quickly deterio-rates). This excessive tension is unavoidableand shall be taken into account when deter-mining the size of the belt, designing themechanical components and calculating theadjustments. For this reason, these devices areused only in case of short conveyors of up to60 m lengths and under light duty cyclecondition.

Wnck take-up — In this system, thetension isadjusted by means of a mechanical motorizeddevice which does not automatically compen-sate for belt length variations. A tensionindicator may be included between winch andpulley. This system also requires carefulchecking of tension and leads to excessive belttension in order to aviod too frequent take-ups.However, it may be used for long conveyorsand under heavy duty conditions provided thatthese conveyors are equipped with belts havingvery low elongation coefficient under the effectof load and over a long period, for example,steel cord belts which are used almostexclusively.

8.12.2.3 Automatic take-up

In this system, take-up pulley is mounted on slides oron a trolley and travels freely while a constant ten-sion is automatically maintained to ensure normalconveyor operation in all cases. The most frequentlyused type is gravity weight operated take-up device.Hydraulic, pneumatic or electrical take-up devices ofvarious types are also used. All types of automatic take-

up devices shall include a system for adjusting belttension. Automatic take-up has following features:

a) It is self-adjusting and automatic.

b) Greater take-up movement is possible.

c) It is suitable for horizontal .or verticalinstallation.

d) It is prefemed for long centre conveyors.

e) It can be located at drive end (preferred for lowtensions).

f) In case of underground mines, provision of loopat drive end maybe made to cater for take-up andsmall extension of belt conveyor lengths.

8.12.2.4 Winch take-up (automatic)

Winch take-up device can also be used as automatictake-up arrangement when automatic tension regulation(ATR, by employing load cells, electronic sensingdevices etc) is provided to signal for the winch motorto run in one direction or reverse for specific number ofturns or to stop as governed by predetermined values ofbelt tensions for any particular installation. This is“highlyrecommended for long centres high capacity beltconveyors since it fetches-lessspace (horizontalhertic~)and also do not unnecessarily put the belt always inheavy tension as imparted by the constant counterweights necessary for operation at maximum designload in a gravity take-up. The heavy tension is gravitytype-up arrangements continues to exist in the belt evenwhen it is not running.

8.12.3 Selection of Take-Up

The choice of take-up and their location has to bedecided depending on the configuration and length ofthe conveyor and available space. But acceleration andbraking of conveyors have certain effects on the take-up. These have to be taken into account while decidingthe location of take-up. For guidance effect ofacceleration and braking on counterweight take-up isgiven in Table 21.

8.12.3.1 Typical take-ups are shown in Fig. 9 to 12.

8.12.4 Take-Up Weight

After having decided the location of take-up, the belttension at this location, the take-up weight can be cal-culated as follows:

Take-up weight mechanical advantage = belttension at point of take-up – weight of take-uppulley and its frame + friction force of take-upcarriage rope, sheave, etc ...(61)

8.12.5 Take-Up Movement

8.12.5.1 It consists of two parts:

a) Allowance for belt elongation, and

b) Allowance for contingenciesand factor of safety.,

32

IS 11592:2000

Table 21 Effect of Acceleration or Braking-on Counter Weight Take-Up[Ql,w,oo Q 19 ‘l\Iubuwoc Q. ~~.~)

Conveyor Preferred Take-Up Acceleration Effect Braking EffectGeometry Location

Horizontal head drive Following drive on return None Tends to Iitl counterweight.side of belt Brakes not usually large

enough to cause trotible.

[ncline, head drive Following drive on return Little or none Little or noneside of belt

Decline, tail drive At or near head Tends to Iitl counterweight if Nonedeclination is low

Decline then horizontal At or neti head Critical — iitls countemveight Noneportion, tail drive and feeds slack to foot of

inclinel)

Combination of incline, and Following head or low point Little or none Critical when stopping withdecline, head drive in return run decline loaded — Lifts

counterweight and slack runsto foot of decline’)

Combination of incline and Following head or point in Critical — Iitts counterweight Little or nonedecline, tail drive return run and feeds slack to foot of

decline

I)Such take-up problems ~an be handled by a very heavy single counterweight, a double counterweight. by tail-end bmkes, or head

and tail driving.

—

b)

c)

d)

e)

f)

.!3

h)

J

Belt jointing system;

Belt carcass determining the elastic and perma-nent stretch values which shall be provided bythe manufacturer;

Ratio of operating tension to the maximum al-lowed tension;

Starting up system and magnitude of resultingdynamic force on the belt;

Position of take-up device;

Possibility, when take-up device has reachedthe end of its adjustment length, of its beingbrought back to its former position by cuttingand rejoining the belt;

Weather conditions in which the installation isoperated (wide temperature deviations betweenday and night); and

Influence on some types of belts of the physi-cal characteristics of conveyed materials (heator excessive moisture content) especially if cov-ers are not carefully checked and maintainedperiodically.

8.12.5.3 Take-up movement may be worked out as fol-lows:

a)

b)

c)

Delermine the belt elongation according tomanufacturers recommendations,

Check the operating tensions at critical pointsthrough the circuit. Calculate average belt ten-sion throughout the circuit with belt startingwhen fully loaded.

The average tension with conveyor empty andstopped.

33

d) Determine the load facto~

~ _ Value at 8.12.5.3(b) – Value at 8.12.5.3(c)LF - x

Belt rating

Total length of belt ... (62)

e) Actual belt = v~~x Belt elongation atelongation reference lead ... (63)

t) Allowance for contingency and safety=0.300 m+ 0.5 percent of belt

length in mm ... (64)

g) Belt reserve for splicing. It shall be equal to al-lowance for one minimum splice length.

8.12.5,4 Where take-up movement worked out is verylarge, it maybe necessary to reduce the take-up move-ment or make use of combination of gravity and winchtake-up or use more than one gravity take-up. In any ease,the values of take-up shall be not less than the valuesspecified in Table 1of IS 4776 (Part 1).These values areapplicable to underground installations also using beltsconformingtoIS318 1[seeIS4776 (F&t2)].

8.13 Conveyor Loading and Discharge

8.13.1 For a successful belt conveyor installation, it isabsolutely necessary that the conveyor belt be loadedproperly and discharged properly. The requirements ofloading and discharge are so important that they needvery careful consideration while planning the layoutand detailing of the loacling/unloading facilities. Be-sides contributing to a good performance of the con-veyor without spillage, a properly designed loadingand discharge system would add considerably to thebelt conveyor life.

.. .

IS 11592:2000

TAKE UP BY HYELECTRIC GRAVIOR MECHANICALAS SHOWN

CARRYING S1OE

‘Di?AULICTY WEIGHTMET HOD .

BELT FROM DRIVING PULLEY

TAKE-UP PULLEY- —-.

~.ADJUSTMENT

9ELT TRAVEL -BEND P’uLLEY

.. .——

FIG. 9 TYPCIAL LooP TAKE-UP DEVICE

BEND PULLEYS BELT

TAKE-UP PULLEYENT —

u

/ADJUSTMENT

,

II

OPERATING SCREW

@PEcTIoN PLATFORM

FIG. 11 TYPICAL SCREW OPERATED‘FIG. 10 TYPKAL GRAVITY WEIGHT OPERATED TAKE-UP AT TAIL END OF CONVEYOR

TAKE-UP AT INTERMEDIATEPOINT OF CONVEYOR

I I

+&_..+!~-._.-

IIb

-–

T.-l..-1 TAKE-UP

/RXLEY

fj

1

FIG. 12 TYPICAL GRAvlTY WEIGHT OPERATEDTAKE-UP TAIL END OF CONVEYOR

34

need very careful consideration while planning thelayout and detailing of the loadingh-mloading facili-ties. Besides contributing to a good performance ofthe conveyor without spillage, a properly designedloading and discharge system would add considerablyto the belt conveyor life.

8.13.2 Conveyor Loading

8.13.2.1 Some of the main considerations for properloading of the material and transfer of the material onto the belt conveyor are as follows:

a)

b)

c)

cl)

e)

f)

~)

h)

j)

k)

m)

n)

P)q)

1Placing of material centrally on the belt.

Avoiding too frequent surging of loads.

Material velocity being in the direction of belttravel and as close to the velocity of the belt aspossible.

Loading of the lumps near the centre and ridinga cushion of fines.

Keeping the loading in case of transversetransfer as near to 90° as possible.

Avoiding horizontal angularity of transfergreater than 90°

Providing a suitable skirt plate extending alongthe sides of the belt serving to confine the loadwhile it is in a state of agitation before it settlesdown into a quite moving stream.

Feeding the sloping conveyors where the sizeof lump or absence of fines would indicatedanger of lumps rolling specially for downhillconveyors.

Inclining the loading chute both forwards andoutwards.

Keeping the width of the chutes generally notgreater than two-thirds the width of thereceiving belt, inside width being 2.5 to 3 timesthe largest dimensions of uniformly sizedlumps.

Providing the back or bottom plates of the chutesin a manner so that the material preferable isguided from the back of the chute to the belt. Incase of fines and lumps, it may be necessary toprovide a grizzly so that the screened fines mayreceive the lumps over them.

Provision of stone boxes for heavy, abrasive andlumpy material so that the impact is absorbedby the stone boxes where the blow of theabrasive material is taken on the retainedmaterial at that point.

Keeping the transfer heights to the minimum.

providing minimum angle of slope. Keepingin conformity with the static angle of repose ofthe material, it should preferably be about 20°to 30° higher than the static angle of repose of

IS 11592:2000

the material. The slope shall be fixed based onthe properties of the material such as moisturecontents, stickiness, flowability etc.

r) Avoiding direct impact of the material on tothe roller and the bottom most back portion ofthe chute being minimum 150 mm away fromthe idler.

8.13.2.2 Skirt board

To retain the material on the belt after h leaves the

loading chute and until it reaches belt speed, skirt

boards are necessary. These skirt boards are usuallyan extension of the sides of the loading chute. Thelength of skirt board is generally between 0.6 m to1.0 m for every 0.5 mk speed of belt depending onthe loading conditions but in any case not less than1.6 m in length. The skirt board preferably shouldterminate above an idler rather than between the idlers.The skirt boards are normally covered with rubberstrips of adjustable type both at the back and at thesides being provided with suitable shape forcentralizing the material on the belt. At times, the skirtboards are provided with rubber screen, that is, rubberflapper to minimize the dusting due to air turbulence.

8.13.3 Conveyor Discharge

8.13.3.1 The material can be discharged-from the beltconveyor in different ways to achieve the variousdesired results. The discharge can be accomplishedeither at the end of the conveyor or at a definite pointor points in between which can extend along side thebelt conveyor, either on one or both sides, at a pointor for a considerable distance. The flexibility ofdischrage arrangement of belt conveyor facilities itsuse in the maximum fill of long bins and the erectionof large and various shaped storage piles.

8.13.3.2 The simplest arrangement of discharge froma conveyor belt is by material passing over an endpulley and falling on to a pile or onto the other con-veyor through a suitable loading chute. A fork in thedischarge chute with a gate or flapper can permit thematerial to flow either in one or in both directions asdesired.

8.13.3.3 If several specific points of discharge are re-quired, the fixed trippers may be provided. Moveabletrippers, if provided, can discharge intermittently eitheron one or both sides of the belt conveyor. Sometimes,ploughs can also be used for discharging the materialeither on one or both sides at intermediate locations.

8.13.3.4 A carefully designed discharge chute isnecessary for successful operation as besides meetingthe operational requirements of discharging orapportioning the-material in to the various directions.It can also eliminate collection of the material adhering

35

IS 11592:2000

to the belt, avoidance of spilled material and

controlling of dusty or dry powdary and fine material.

8.13.3.5 The following are some cfthe main featuresfor designing a good discharge chute:

a)

b)

c)

d)

e)

f-)

9

The upper end of the discharge chute shallenclose the cleaning device and catch materialcleaned from the belt if necessary by employinga separate dribble chute,

Calculate the trajectory of the material andensure that material falling from the end of thedischaEge pulley falls on the back plate of theloading chute.

Provision of removable of liners in case ofabrasive material.

Providing sliding surface at an angle of about20° to 30° higher than the static angle of repose.

Avoiding abrupt changes of direction in thechute to eliminate material build up andplugging.

Provision of rock boxes in the discharge chute;where necessary, for abrasive, lumpy and heavymaterial.

Providing cross-sectional area of 4 times, theload cross-section and minimum three lumps.

8.13.4 Trajectory of Material

8.13.4.1 The path or the trajectory of the materialafter it leaves the belt is a parabola when the materialis discharged over the head pulley, and is determinedby two considerations:

a) Thepoint where the material leaves the belt. Thisis the point at which the centrifugal force on thematerial acting radially outward is balanced by[he gravitational force or its component in theradial direction as the case may be.

b) The direcriorr in which the material moves atthe instant it leaves the belt.

8.13.4.2 Practical determination of the trajectory isexplained in Annex J.

NOTES

1 In drawing the belt running into the pulley, care shall be taken

for the actual slope of the centre portion of the belt. Actual slope

is often greater than that is assumed for the following reasons:

a) The rim of the head pulley is sometimes set above the line

along the rims of the carriers centml rolls.

b) There is always some sag in the belt which causes an increase

in actual slope,

2 The effect of air resistance being negligible in most of the ca$es,

is not taken into account in determining the trajectory.

3 The trajectory obtained as discussed here locates the bottom of

the stream of material.

8.13.5 Typical arrangements of loading and dischargechutes are shown in Fig. 1.

8.14 Structura}s

8.14.1 General

While designing the structural, due attention shallbe given to the provisions laid down in IS 7155 (-ineight parts). In addition, the following main pointsshall also be taken into consideration:

a)

b)

c)

d)

e)

The design of the structural members, besidestaking care of the surge loading, shall also takeinto account the likely loads coming on accountof any spillages due to failure of protective/coasting devices.

A maintenance walkway of:800 mm minimumwidth along the run of the conveyor in a galleryshall be provided. If specified by the purchaser,and additional walkway on the other side mayalso be provided. In case of double conveyors,side walkways (see Fig. 12) may be providedon two sides cf conveyors in addition to thecentral walkway, if required by purchaser.

Walkwary runner — Size of the selection shallbe adequate to satisfy strength and deflection.

Toe guard — Toe guard shall be providedaround all openings on floor and also on sidesof conveyor gallery walkway as a safetymeasure. The toe guard shall have a minimumdepth of 65 mm and a thickness of minimum6 mm. Gallery walkway supporting angle shallbe considered-as toe guard provided dimensionlimitation as shown in Fig. 12 is satisfied.

Hand rail — Hand rails shall fu”lfil thefollowing requirements:

1)

2)

3)

4)

5)

f) The walkway along the inclined conveyor shall

Hand rails shall be provided around allopenings. It shall also be provided on oneside of walkway in conveyor gallery havingslope more than 7°.

The hand rails, either single or double (asindicated in Fig. 13) shall be provided.However in case of belt height more than1 m from floor level, double handrails, thatis, one at top and other at half way heightfrom floor, shall “beprovided.

The hand railing shall be supported eitherfrom conveyor stand/post or from inde-pendent support. For conveyor standlposthavrng more than 3 m spacing, the railingshall have independent supports.

The section for hand railing shall be ofgalvanized pipe of 32 mm nominal boreunless specifically required by purchaser.

The hand rail post shall be 32 NB (A)galvanized piW or minimum ISA 65 x 65 x 6galvanized unless specified otherwise.

36

IS 11592:2000

WALKWAY RUNNER

DETAIL Y

/ SIOE WALKWAY (OPTIONAL)TO BE PROVIDED IFSPECIFIEO BY PURCHASER

FiG. 13 ARRANGEMENT JNDOUBLE CONVEYORS AND THEIR DESIGN APPROACH

g)

h)

-i)

k)

be provided with anti-skid surface and shall bedesigned for a single moving load of 300 daNor a live load of 250 dapa whichever is larger.Use of gratings or chequered plates or precastconci-ete slabs with their top surface leftunfinished may be considered for providinganti-skid surface. In case of conveyor install-ations with more than 10° inclination, steppedwalkways without any intermediate landingsshall be provided. However in case of gratings,provision of gallery seal plates shall beconsidered in structural design.

For corrosive and open atmospheric conditionsof working, due consideration shall be givento 3.8.2 to 3.8.4 of IS 800 and 6.3 and 6.4 ofIS 6521 (Part 1) in the design of structuralcomponents.

Supporting of gallery frames on the trestlesusing roller supports shall be prefer~d. Suitableprecautions shall be taken to protect the rollerguides/slotted holes/guides etc, from accumu-lation of dust or material carried through theconveyor. Such installations shall be regularlyinspected for their proper operation.

Where conveyor gallery frames have to be

connected to junction houses or otherbuildings, it is desirable that such connectionsbe made so that the gallery frames are free tomove in the longitudinal direction.

Wherever conveyor has to run in an under-ground tunnel, a clear walkway space of 1000mm shall be provided along the length ofconveyor on either side. For conveyors used inunderground mines, this clear space shall be

37

not less than 1 m along the length of conveyoron either side from any structure of theconveyor. In case of double conveyors, a centralwalkway of minimum 1000 mm width shallbe provided ensuring that at least 800 mm isavailable at drive or head pulley end. Inaddition, at head or tail end a clear walkwayspace of not less than 1 m on either side shallbe provided.

m) The drive end structure shall be made

n)

P)

sufficiently rigid to prevent any vibration andshall be provided with sufficient maintenancespace all around, which shall not be less than800 mm to the nearest obstacle. The design ofstructure shall be in accordance with 8.14.8.

Transfer homes shall be so designed so as toprovide sufficient head room for removal ofheaviest parts and lifting of the belt to enablechanging of the conveyor belting. Whereverprovision has to be left in the transfer towerfor keeping a heavy equipment forming a partof the conveyor such as pulley, motor gearbox,the structural shall be designed to take care ofthe concentrated load in addition to thedistributed load of 350 dapa.

All structural design shall conform to relatedIndian Standards such as IS 800, IS 875 (infive parts), IS 7155 (in eight parts), etc takinginto account the various environmentalconditions including earthquake and windforces.

8.14.2 Structural Design

8.14.2.1 Whenever designing the structure for con-veyors, the total of following three load _groups shall

Is

be

11592:2000

taken into account:

a) Main loads,

b) Additional loads, and

c) Special loads.

8.14.2.2 The main loads comprise of all the perma-nent loads which occur when the equipment is usedunder normal operating conditions as specified by thepurchaser. The main components of main loads are:

a)

b)

c)

Dead loads — These are load forces of all fixedand movable construction parts, always presentin operation of mechanical and electrical plantsas well as of the support structure.

Useful loads — The effective load carried onthe conveyor is considered which is determinedfrom designed output in m3/h. The followingpoints are considered while deciding thedesigned output:

1)

2)

3)

4)

Where the belt load is limited by automaticdevices, the load on the conveyor will beassumed to be that which results from theoutput thus limited.

Where there is no output limiter, the designoutput is that resulting from the maximumcross-sectional area of material conveyedon the conveyor multiplied by the conveyingspeed. Unless otherwise specified in theagreement, the cross-sectional area shall bedetermined assuming a surcharge angLeof20°. Figures 2 to 4 show the maximumsections of product conveyed as a functionof surcharge angle and for the trough anglefor different conveyor design.

Where the design output resultingfrom 8.14.2.2 (b) (1) or 8.14.2.2 (b) (2) onupward units is lower than that of down-ward units, the downward units may havethe same output as the upward units.

Dynamic loadfactor — In order to take intoaccount the dynamic loads which, could beapplied to the conveyor, the load ascalculated above together with weight ofbelt shall be multiplied by factor 1.1. Fortrippers and other movable equipments, thefactor shall be 1.5.

Incrustation — The degree of incrustation (dirtaccumulation) depends on the specific materialand the operating conditions prevailing ineachgiven case. For guidance, a load of 10 percentof the theoretical effective load calculatedaccording to 8.14.2.2(b) shall be taken intoaccount as the load on the conveyor devicesdue to dirt accumulation. The actual values candeviate to either higher or lower values. For

38

d)

e)

f)

g)

h)

storage yard appliances, the values aregenerally lower while for reclaimers, they areto be taken as minimum values.

Forces at conveying elements for the usefulload — Belt tensions shall be ‘taken intoconsideration for the calculation as far as theyhave an affect on the structure,

Permanent dynamic effects — Followingpoints shall be considered under this head:

1)

2)

In general the dynamic effect of the fallingmasses at the transfer points, the rotatingparts of machinery .etc, shall be consideredas acting locally.

The inertia force due to acceleration andbraking, of moving structural parts, liketripper and shuttle conveyor, shall be takeninto account. These can be neglected forappliances working outdoors if the accele-ration or deceleration is less than or equalto 0.2 rn/s2.

Inclination of the conveyor—The effect ofinclination of conveyors shall be taken intoaccount for design of structures. The incli-nations shall be according to appropriateconveyor layout.

Loads on gang ways, #atforms and ~oof—Loads on these structures shall be consideredas given below:

1)

2)

3)

4)

5)

Live loads, only for the design of claddingroof truss, purlins shall be according toIS 875 (in five partsj.

Live loads to be considered for gallery framework design shall be in accordancewith 8.14.l(f). For the design of gallerywalkway, platform, etc, member, theworst combination shall be considered asindicated in 8.14.l(f).

The platform members shall be suitablydesigned for live load of 2500 Pa (uni-formly divided load) or 3000 N whicheveris worst.

The stairs shall be designed for a singlemoving load of 1000 N and the railingsand the guards shall be able to withstand ahorizontal load of 300 N.

When higher loads are to be sup-ported temporarily. under 8.14.2.2(g)(l)to 8.14.2.2 (g)(4) above, the sizing of themember shall be done accordingly.

While designing the trestles supporting theconveyor gantry, 80 percent of live loadconsidered for walkway under (g) shall betaken.

8.14.2.3 Additional loads

These are loads that may occur intermittently duringoperation or the equipment or when the equipment isnot working. Those loads either replace certain mainloads or are loaded to the main loads. The maincomponents of additional loads are:

a)

b)

c)

d)

Snow and ice load — The loads due to snowand ice shall be considered as in case ofincrustation load [see 8.14.2.2 (c)]. In case, thecustomer does not prescribe load values due toparticular climatic conditions, snow and iceload need not be included.

Temperature load — Temperature effects needonly be considered in special cases, forexample, when using materials with verydifferent expansion coefficients within the samecomponent. Alternatively, the temperatureeffects may be taken care of by providingsuitable connection details to permitmovements due to thermal effects such asslotted holes etc.

Spillage load — During the operation of beltconveyor or at the time of repair/replacementof belts, the material on the belt is spilled on tothe conveyor structure. The structure shall,therefore, take into account loading due to thiseffect. A load of 1 kPa may be considered.

Non-permanent dynamic effect — The mainforces due to the “acceleration and braking ofmoving parts such as traveling tripper, paddlefeeders etc. occurring less than 2 x 104 timesduring the life time of the appliances shall bechecked as additional load. As additional loads,they may be disregarded if their effect is lessthan that of the wind forces during the

operation. If the main forces are such that theyhave to be taken into account, the wind effectsshall be disregarded.

8.14.2.4 Special loads

These comprise the loads which shall not occur duringand outside the operation of the equipment but theoccurrence of which is not to be excluded. The maincomponents of special loads are:

a)

b)

Clogging of chutes—The weight of theclogging is to be calculated using a load whichis equivalent to the capacity of the chute inquestion, with due reference to the slope angle.The material normally within the chute maybe deducted. The actual bulk weight must betaken for calculation.

Loads due to earthquakes—As far as thedelivery contract contains data concerning theeffects due to earthquakes, these loads have to

c)

d)

e)

f)

g)

h)

39

IS 11592:2000

be considered in the calculation as specialloads. While calculating load, reference maybe made to IS 1893.

Bujfer eflects-For equipment like tripper,paddle feeders etc, having speeds belowO.7 m.k,no account shall be taken of-buffer effects. Forspeeds in excess of 0.7 m/s, account must betaken of the reaction on the structure bycollision with buffer, when buffering is notmade impossible by special devices. It shall beassumed that the buffers are capable ofabsorbing the kinetic energy of the machinewith operating load upto a certain fraction ofthe rated traveling speed VT— this fraction isfixed at minimum 0.7 VT. The resulting loadson the structure shall be calculated in terms ofthe retardation imparted to the machinery bythe buffer in use.

Wind load—Wind loads on the structure of theconveyor installation shall be calculated takinginto consideration the recommendation madein IS 875 (in five parts). The lattice girderssupporting the conveyor shall be suitably bracedat top and botton chord levels to transmit thewind load to the end portals connected to thetrestles.

Conveyor installations transporting ~nematerials like sulphur, fine chemicals, ores, andcoal with high percentage of fines, require acontinuous hood over the conveyor. This hoodis also required where protection from mois ure

Jcontamination is required and where ustcontrol equipment are provided as essentialrequirement. Due consideration shall be givento these loads in design of structures forconveyors.

Foundation for conveyors structures shall besuitably designed and constructed so that it doesnot settle. Due consideration shall given to theaction of deformation in structures due tosettlement of foundation, if settlement can notbe avoided.

In case of galleries, temperature expansionjoints shall be introduced at intervals ofapproximately 180 m to divide galleries in toblocks. In each block, one four-legged rigidsupport guaranteeing stability of structure inlongitudinal direction shall be provided. Thisshall also take care of all longitudinal forcesforeseen in the given block.

Other loads, if any, for the provision offollowing:

1) Water pipe line for dust suppression, plantcleaning or fire fighting etc.

IS 11592:2000

2) Dust extraction/ventillation ducting.

3) Electric cables and cable racks.

j) In case of conveyors exceeding 250 m in length,

crossovers sha!l be provided from ground to

ground with cat ladder or from side walkway

to otherside walkway andlor central walkway

at a spacing not exceeding 180 m.

S.14.2.5 Skid mounting used in open-cast andunderground mines, in case of shiftable conveyor isshown in Fig. 14.

8.14.3 Vibration

It’no resonance is to occur in adjoining structures andbuildings, then the amplitude of vibration of thefoundation shall not exceed the values specified inFig. 15. The design of foundations and structuressupporting heavy machineries such as crushers,screens and vibrating feeders shall be in accordancewith IS 2974 (Part 1) or IS 2974 (Part 3) or IS 2974(Part 4).

8.14.4 Design Considerations for Stringer and StandSupporting Intermediate Portion of Conveyor

8.14.4.1 Figure 16 gives the general layout ofintermediate portion of conveyor for the purpose ofidentification of loads.

8.14.4.2 Design of stringer

The design of stringer shall be carried out consideringthe stringer as either a simply supported beam or acontinuous beam as the case may be. The followingloads shall be considered for the design of stringer:

a)

b)

c)

A concentrated load consisting of materialconveyed considering normal capacity ofconveyor, weight of belt and weight of carryingidler unit.

A uniformity distributed load consisting ofweight of decking plate, belt top cover, belt sidecover and weight of stringer itselfi and

A concentrated load consisting of weight of beltand weight of return idler rinit.

8.14.4.3 De$gn of stand or post

Stand/Post shall be designed considering endconditions provided, namely, both ends hinged or oneend hinged and other end fixed etc. The load to beconsidered for the design of stand or postshall includeweight of stand unit and weight of cabled in additionto the loads specified in 8.14.4.2(a), 8.14.4.2(b)and 8.14.4.2(c).

8.14.4.4 Supporting stools

Typical arrangement is shown in Fig. 17 for supportingstools between conveyor galleries bottom and top ofstool.

8.14.5 Limiting Deflection

Deflection for various structural members supportingconveyor structure shall not exceed the followinglimits:

a)

b)

c)

d)

Conveyor gantrylbridge ~325

Trestle supporting grmtry/tower Heightin the transverse direction 1000

Stringer supporting conveyor mstructural member directly 900supporting in the tripper

Member supporting the tripper ~325

8.14.6 Camber shall be provided for span greater than20 m. It shall be either zero or positive to neutralizethe deflection due to dead load only.

8.14.7 Cladding for Galleries/Tower Structure

In view of the economy in structural members/foundations, easy availability and ease in working,faster speed, easy repairs, the material shall be eitherof “G I sheets or aluminium sheets, Provision oftranslucent sheets at intervals shall also-be consideredfor natural lighting inside galleries during daytime.

8.14.8 Design of Head and Tail Frame

8.14.8.1 Head and tail frames shall, preferably, bedesigned as braced portal frame. Following loads shallbe considered for the design:

a)

b)

c)

d)

e)

Maximum belt tension,

Dead load of head or tail pulley together withthe belt being supported by head or tail pulley.

In order to take into account the dynamic effect,the above loads as calculated in 8.14.8 .l(a)and 8.14.8.l(b) shall be multiplied by 1.25.

Self weight.

Additional loads, both live and dead load, frommaintenance platform and/or drive unit if

supported from frame.

8.14.8.2 In addition, suitable cross-bracing connecting

the frames (as shown in Fig. 17) shall be provided toreduce the effect of vibration.

9 ACCESSORIES

9.1 General

The various accessories required for a conveyor couldbe briefly stated as follows:

a)

b)

Drive elements like motors, gear boxes, chain

and chain drives, flexible and fluid couplings,clutches and brakes;

Trippers both belt driven and motorised, fixedand moving;

40

CARRYINGROLLER

, \1

ll\

/A\

2.5

1.25

0.50

g 0.050

0.0125

0.0050

0.0025

1S 11592:2000

STRINGER

r

GARLANO~YPEIDLERS

r

HI

RAILFOR SHIFTING HOLLOWSLEEPER/THE CONVEYOR

FIG. 14 SHIFTABLE CONVEYOR IN OPEN-CAST MINE

F-eHtNw?’A I I I I 1111

I 1 I IN .

I I I I 1~

N I I I I IIIJ

\ RETURNROLLEi

100 200 500 1000 2000 5000 10000

FREQUENCY (f) IN CPM

NOTES

1 Resonance in the neighboring structures will be negligible if the amptitude of vibration is less than 0.20 mm.

2 For foundations of rotary type of machines of low frequency (O to 300 c/rein), it is possible to state that if no resonance is to occur in

adjoining buildings and structures, then the amplitudes of vibrations of a foundation shall not exceed 0.30 mm.

FIG, 15 LIMITING AMPT]TUDE FOR VERTICAL VIBRATION

41

. . .

IS 11592:2000

BELT SIDE COVER

Q /WilONAL III

PITCH FOR IDLERSIN METRES

1AIm I

DECKING PLAT-E 1

r(OpTIONAL)

@NO OR POST

MATERIAL

\ F’T

~TURN IDLER UNIT

ROLLER

r BELT TOP COVER

CABLES r[OPTIONAL)

r(OPTIONAL)

A-A B-B

NOTE — Belt top cover and belt side cover maybe replaced by semi-circular type belt cover in one piece.

FtG. 16 GENERAL LAYOUT FOR INTERMED1ATE-PORTIONOF CONVEYOR STRUCTURE

c)

d)

e)

8

g)h)

Ploughs;

Special lowering chute for example, spiral, bin-lowering rock ladders and telescopic chutes;

Belt cleaners both internal and external;

Hold-backs;

Control gears;

Protective.devices for example, emergency stopswitches and cable, overload switches, over loaddevices, belt slip, chute plugging, take-upmovement; belt sway overspeed tripping, etc;

Decking plates; and

Skirt plates.j)k)

9.2 Motor Selection

9.2.1 General

9.2.1.1 The motor for belt conveyor drive shall be

selected considering various factors such as startingtorque, pull-out torque, starting current (for selectionof cables considering voltage drop during startingconveyor drive), speed/torque characteristics of load,type of coupling used and following electricalparameters effecting motor design:

a)

b)

c)

d)

e)

o

.!0h)

Rated voltage and frequency;

Variation in voltage, frequency and combinedvoltage and frequency variation;

Construction, for example, type of mounting;

Class of insulation;

Ambient temperature;

Speed;

Type or enclosure and degree of prtection;

Direction of rotation;

—..—

42

IS 11592:2000

FIG. 17 TYPICAL DETAILS OF HEAD AND TAIL FRAMES

j) Location of terminal box looking from driveend shaft;

k) Short circuit load of terminal box;

rn) Number of cables and size of cables for cableterminal box;

n) Type of starting;

p) Vibration limit; and

q) Type of earthing and number of earthingterminals.

9.2.1.2 Motor shall have continuous ratio at least equalto the power required by the conveyor divided by theefficiency of the drive unit.

9.2.1.3 For downhill regenerative conveyors, the motorrating shall be at least equal to the power required

multiplied by the drive efficiency of the motor. Themotor shall be capable of giving higher torque thanrequired at steady-state of operating condition underworst permissible conditions of voltage and frequencyvatiation, The starting time of the conveyor shall not ~exceed locked motor withstand time of the motor. Incase of low starting torque requirements, whereacceleration time is more than thermal withstand time,suitable protection like locked rotor relay and speedmonitoring device shall be provided to the drive.

9.2.1.4 In general, squirrel cage three-phasealternating current induction motors are the simplest,most economical and minimum maintenance driveunits for conveyors coupled with fluid couplings.

9.2.1.5 Motor acceleration time, t~, shall be within

43

Is 11592:2000

the thermal characteristics of the motor, that is, the

motor shall withstand the starting current for that

period. Otherwise the motor shall be specially

designed.

9.2.2 Selection

9.2.2,1 For conveyors of small capacities up to drivepower of 40 kW, squirrel cage induction motor withdirect on line start-shall be used. Motorised head pulleyup to 10 kW can be used.

9.2.2.2 For medium length conveyor of mediumcupacit y up to drive power of 150 kW to ensure torque

control of drive, the following type of drives be used:

a)

b)

c)

d)

Slip-ring induction motor with resistancestarting; or

Squirrel cage motor with controlled eddy-current coupling; or

uc motors with static power amplifiers; or

Squirrel cage motor with scoop controlled fluid

coupling or traction type fluid coupling.

9.2.2.3 For long conveyors of heavy capacity, forstabilizing the desired value of load torque of drivingmotor, not only during starting but also during normaloperation of the conveyor, the following electric drivesare recommended:

a) Squirrel cage motors with controlled electro-magnetic (eddy-current) couplings; or

b) -Squirrel cage motors with thyristor frequencyconverters with sufficient overload capacity; or

c) Squirrel cage motor with scoop controlled fluidcoupling or traction type fluid coupling; .or

d) Slip-ring motor with resistance start.

9.2.2.4 When high voltage motors are used, the ratingfor motor is not the criteria for type of starting. Methodof starting shall be determined by the systemparameters.

9.2.2.5 For selection of motor and its starting methods,consideration shall be given to the type of couplingselected (see 9.2.2.3) and drive requirements.

9.2.2.6 The geatbox shall be selected to suit the drivesystem (see 9.2.2.3 to 9.2.2.5) and the requirementsof 9.3.

9.3 Speed Reducers

9.3.1 Selection of the type of speed reducers can bedetermined by preference cost, power limitations,space limitations and drive location.

9.3.2 The gearbox shall be enclosed type running inan oil bath to give quietness of operation and savingof power.

9.3.3 Stepless or in-xtage reduction may be accom-plished satisfactorily by means of a V-belt drive inportable and very small capacity installations so thatadditional advantage of changing the speed ratio tomeet different capacity requirements of the conveyorsare obtained.

9.3.4 For drive motor of power requirements up to30 kW, worm reducers may also be considered.

9.3.5 For drive motor of above 30 kW, helical gearbox shall be preferred.

9.3.6 The gear box shall be rated with the followingminimum service factor for electric drives, inaccordance with IS 7403.

Duration of Service Service Factor

2 hours per day 0.9

8 hours per day 1.1

12 hours per day 1.25

24 hours per day 1.5

9.3.6.1 The rating of the gearbox shall not be less thanthe rating of the installed motor.

9.3.7 The selection of gear type, that is, spur, wormand helical, shall be done trddng into considerationvarious aspects such as layout, torque, elfeciency,economics, etc.

9.4 Couplings

9.4.1 The use of flexible couplings shall be preferredup to 30 kW and may also be considered for smallconveyors requiring less than 50 kW.

9.4.2 Fluid couplings shall preferably be used whenconveyor power requirement exceeds 30kW. For slip-ring induction motors requiring power up to630 kW, flexible coupling maybe used.

9.4.3 The choice between an allowable slip typecoupling, for example, fluid coupling, and a solidcoupling, for example, pin-bush coupling, shall alwaysbe considered for any conveyor requiring higher motorpower than 30 kW. Fluid coupling provide followingadvantages:

a)

b)

c)

Smooth acceleration of belt thereby reducingT.Emiix9

Quicker acceleration of motor reducing itsheating during its starting; and

Reduction in oversizing of cables for motors tocompensate terminal voltage drop duTin.gstarting.

9.5 Ladders and Spiral Chutes

9.5.1 Ladders and spiral chutes are used to lower loads

44

vertically by gravity. They retard the rate at which theload descends and prevent its landing with an impact.

9.5.2 Ladder chute for bulk material is a vertical squarepipe, the inside of which holds alternately spacedshelves. The material being lowered is held up byfailing from shelf to she\f. The layer of materialcovering the shelves protects”them against rapid wear,

9.5.3 When a fragile load (such as coke, coal, coalbriquettes) has to be lowered from a great height(within a hopper, for instance), special devices likepartitions, with rubber diaphragms or spiral chutesmay be used to arrest the material degradation.

9.5.4 A bulk or unit load lowered along a spiral chuteSIides down the spiral surface and reaches the lower

level without impact. A spiral chute is a trough which

IOIIL)WSa helix secured around a vertical column orsuspended rod, sometimes mounted within a vertical

pipe of large diameter. The chute may have arectangular, rounded or oblique-angled cross-sectiondepending on the shape generated. The spiral chuteshave the property of automatically keeping the speedof the load within definite limits.

9.6 Ploughs

9.6.1 Ploughs are used to discharge/divert free flowingond non-abrasive materials which can be carried witha little or no troughing, from belt conveyors. Ploughcan be used on belt troughed with idler rolls inclinedat 20°. A flat steel plate or closed pitched one pieceidler roller of a span more than the belt width may beused under the troughed belt where it flattens todischarge/directldivide the material flow.

9.6.2 Ploughs are used in places where it isinconvenient or impossible to install a tripper. Ploughsare cheaper than trippers and takes-up less head room.Fixed trippers are better in performance than ploughs.

9.6.3 The plough m:iy be fixed or traveling. Themovable plough can be operated manually or by rope-h~iulagesystem,

9.6.4 Several ploughs can be incorporated along onebelt conveyor and can be arranged to dischargematerial to either or both sides of the beltsimultaneously. When not in use the blades can beraised to clear the material on the belt.

9.6.5 The blades can be constructed of timber or steelplate, the conveyor belt being flattended by means ofmovable platform of timber, steel plate or rollers. Thesingle discharge type shall be arranged at an angle to

the belt when discharging at one side and when it isdesired to discharge the material to both sidessimultaneously, the blade can be arranged in ‘V’ form,the angle being determined by the speed of the belt.

IS 11592:2000

9.6.6 With any construction, a chute or guard shall beprovided at each discharge point to prevent scatteredmaterial from collecting under the upper run andfouling the idlers or else falling on the return belt.

9.7 IMppers

9.7.1 Trippers are devices used to discharge bulkmaterials from a belt conveyor at points upstream fromthe head pulley. Essentially, trippers consist of a framesupporting two idling pulleys, one above and forwardof the other. The conveyor belt passes over and aroundthe upper pulley and around and under the bwerpulley. The belt usually inclines to the upper pulleyand may run horizontal or it may then incline againfrom the lower pulley. By this construction materialis discharged to a chute as the belt wraps around theupper pulley. The chute can be arranged to catch anddivert the discharged material in any desired dkection(see Fig, 18).

9.7.2 Trippers can be stationary (fixed) or movable.Stationary trippers are used where the discharge ofmaterial is to occur at a specific location. More ‘thanone stationary tripper may be used on a belt conveyor.Trippers shall have dimensions as given in IS 14386.

9.7.3 All trippers absorb a certain amount of powerfrom conveyor belt drive. This is because belt flexesover the tripper pulleys and also the material is to beraised to sufficient height to allow for necessary chutehead room.

9.7.4 Movable trippers can be moved by a cable andwinch by the belt itself, or by an electric motormounted on the tripper.

9.8 Belt ‘llmner

The cleaning of a belt handling wet, sticky, corrosiveor freezing materials is always difficult and very rarelyis all the material removed before the carrying surfacecomes in contact with the return idlers. The consequentbuild up of material cmthese idlers causes a reductionin the belt life ‘and the return idler life. This damagecan be greatly reduced by the use of turn-over conveyorbelt system. The belt at both ends of the return strandis turned, each being in the same direction giving a360° twist. This results in the carrying surface of thebelt never being in contact with any of the carrying.orreturn idlers, the only contact being with the snubbingpulley causing a reverse bend in the belt.

9.9 Belt Cleaner

9.9.1 It is necessary to clean the belt when snub pulleysor bend pulleys or tandem drive pulleys make contactwith the dirty side of the belt on the return run. Thisis especially the case when handling materials whichare likely to pack on the belt, such as sticky and wet

45

—-—

TYPICALTRAVELLINGTRIPPERThe discharge chutes may be as below and are shown in direction arrow ‘B’

One-way chute for one sidedischerge (left hand)

R---”u

Orw-way chute for cme side discharge (right hand)R-#,I

../’

Two-wav chute for dischargeeimultaneou;ly

to both sides

W-./.Two-way chute with flap valve for discharge to one

Two-way chute with flap valve for discharge to one Three-way chute with flap vah.e for

side (left side) or alternatively forwardside right hand or alternatively forward discharge to both alternatively forward

R-.I

-./’

Two-way chuta with flap valws for discharge to either sidealternatively or to both sides simultaneously

R“R-qv,,6

.-/’

Three-way chute with two flap valves for dkcharge toeither sides alternatively, both sides simultanaousiy or

alternatively forward.

u

..Nco0

FIG. 18 TRIPPERS

i

IS 11592:2000

m~terials, or those that are likely to have damp, greasy

or oily patches which eventually rot the belt.

9.9.2 There are three main types of external automatic

belt cleaners:

a) a rotary brush,

b) thecou’nterweighted wiper, and

c) the spring-loaded wiper.

9.9.2.1 In addition, internal belt cleaners of V-typeshall be used neartai lpu]leytoprevent material fromgetting between the pulle_yand belt as it wraps roundthe tail pulley. These V-type_plough cleaners shall beadjusted to float on the return belt without exertingundue load on belt surface. These can also be made ofadjustable counterweighted type. Their use isrecommended even on short conveyor lengths andwhere ful I length decking is provided from the feed tothe discharge end as a safety measure.

9.9.3 The ~otary brush is fitted with a drive pulleyand is rotated in opposite direction from it by a shortcentre roller chain drive. A cantilevered weighted armis attached to the brush for facing it to the belt, whilstat the same time, preventing jamming and unnecessarywear on the bristles. The speed of the tip of the bristlesfor brushes 200 to 300 mm in diameter shall generallybe:

Dry materials 2.0 to 3.0 mls

Damp materials 5.0 to 7.5 rnls

Wet and sticky materials 6.0 to 7.5 lnh

9.9.3.1 The brush shall be mounted so that it can beadjusted toward the belt to compensate for wear onthe tips of bristles and in such a way that the drive tothe bmsh is not affected.

9.9.4 Because of high speed, brushes are short-lived.The most effective as well as mast economic type ofbelt cleaning apparatus is the spring-loaded type beltwiper. Dry or very wet materials are easiest to remove.

9.9.4.1 When particularly gummy materials withtendency to cling to the belt and solidfy, are

encountered, it is recommended to use water spraydirected against the -return belt about 500 mm aheadof the cleaner. It is also beneficial to have a very finespray directed against the belt just before it passesunder the loading point; as this will tend to keep thematerial from adhering. Usually a small amount ofwater will suffice. As the cleaner is specially effectivein removing water, there is little danger ofobjectionable dribble.

9.9.4.2 Where cleaning is of primary importance, twocleaners may be provided so that one can be removedat any time for servicing. In any case, arrange pulleysat the discharge end to allow ample room for cleaningequipment including dribble chute of flume.

9.9.4.3 The blades of the spring type cleaner shallengage the belt only where it is straight, never on aptdley. One cleaner shall generally have at least300 mm of straight belt, two cleaners not less than750 mm.

9.9.5 It is sometimes necessary to use steel scrapperson the rims of snub pulleys. Tripper pulleys anddeflector pulleys that engage the carrying side of belt,in order to prevent accumulation of material, may hurtthe surface of the belt or cause it to run out of line.The blade shall be located so that the scrapings canbe disposed of.

10 SAFETY AND STATUTORYREQUIREMENTS

The conveyor shall conform to all the statutoryrequirements. In addition, the conveyor shall also takeinto account all the statutory requirements asmentioned in IS 7155 (in eight parts). Any additionalsafety requirements to the extent specified by thepurchaser shall also be taken into account.

11 PAINTING

The complete conveyor system and the conveyor shallbe provided with suitable painting both primary andfinished to suit the environmental conditions inaccordance with requirements of the purchaser.

47

—

IS 11592:2000

1SNo.

800:1984

875

(Part 1) :1987

(Part 2) :1987(Part 3) :1987(Part 4) :1987(Part 5) :1987

1891(Part 1) :1994

(Part 2) :1993(Part 3) :1988

(Part 4) :1978(Part 5) :1993

1893:1975

2974

(Part 1) :1982

(Part 3) :1992

(Part 4) :1979

3181:1992

4240:1984

ANNEX A

(Clause 2)

LIST OF REFERRED INDIAN STANDARDS

Title

Code of practice for general cons-truction in steel (second revision)Code of practice for design loads(other than earthquake) for buildingsand structures:Dead loads—Unit weights of build-ing material and stored materials(second revision)Imposed loads (second revision)Wind loads (second revision)Snow loads (second revision)Special loads and load combinations(second revision)Conveyor and elevator textile belting:General purpose belting (fourthrevision)Heat resistant belting (thiti revision)Oil resistant belting (secondrevision)Hygenic belting (first revision)Fire resistant belting for surfaceapplicationCriteria for earthquake resistantdesign of structures (fourrh revision)Code of practice for design andconstruction of machine foundations:Foundation for reciprocating typemachines (second revision)Foundatio-ns for rotary typemachines (medium and highfrequency) (second revision)Foundations for rotary typemachines of law frequency (firstrevision)Conveyor belt — Fire resistantconveyor belting for undergroundand such other hazardous appli-cations ~ourth revision)Glossary of conveyor terms anddefinitions @t tzwision)

IS No.

4776(Part 1): 1977

(Part 2): 1977

6521 (Part 1) :1972

7155

(Part 1): 1986(Part 2): 1986

(Part 3): 1986

(Part 4): 1990

(Part 5): 1990

(Part 6): 1990

(Part 7): 1990

(Part 8): 1994

7403:1974

8531:1986

8598:1987

8730:1997

14386:1996

7’Me

Specification for troughed conveyors:Troughed”belt conveyors for surfaceinstallation .(/irst revision)Troughed belt conveyors for under-ground installationCode of practice for design of towercranes: Part 1 Static and railmountedCode of recommended practice forconveyor safety:General information (first revision)General safety requirements (firstrevision)-Belt conveyor and feeders (firstrevision)Vibrating convey orlfeeder (firstrevision)Apron conveyorlapron feeder (firstrevision)Selection, training and supervisionof operators (first revision)Inspection and maintenance (firstrevision)Flight conveyor (scraper conveyor)(first revision)Code of practice for selection ofstandard worm and helical gearboxesSpecification for pulleys for beltconveyors (/irst revision)Specification for idlers and idler setsfor belt conveyors @st revision)Classification and codification ofbulk materials for continuousmaterial handling equipment (firs/revision)Belt conveyor — Traveling tripper— Motorised — For belt widths650 mm to 1600 mm —Dimensions

48

IS 11592:2000

ANNEX B

(Clause 8.8.5.2)

FIRST METHOD FOR IDLER SELECTION

B-1 IDLER CLASSIFICATION

The idlers are classified into six numbers series as

given in Table 22.

B-2 IDLER SEL-ECTIOiV

B-2.1 Select required duty along Y,, axis of square I

(see Fig. 19), then move horizontally to meet line

representating maintenance condition applicable.

From this point move vertically again to meet the

curves signifying effect of stoppage on the system.From this point move horizontally to meet Yzaxis.This will represent reference point A.

B-2.2 Select density of material to be “handled alongthe axis Yqof square 11 (see Fig. 19) and movehorizontally to meet the lines representing required

belt width. From this point move vertically up or downto join the lines representing conveyor speed desired.

33-2.3 From this point of intersection proceedhorizontally to meet axis YJ. This will representreference point B. Join point A and B. The segment ofthe selection bar through which line AB passes, willindicate the series of idler conveyor most suitable foruse.

B-2.4 The dotted line drawn on the chart as an exampleillustrates the selection of.suitable idler far followingduty:

a)

b)

c)

d)

e)

o

16 hlday continuous duty;

Used under normal conditions and normalmaintenance;

System accepting occasional stc3ppage asnormal;

Conveying trap rock with 1790 kg/m3 density;

On belt width 6$0 mm; and

Moving at 1.0 ds speed.

Table 22 Idler Classification

(Clause B-1)

Idler Roller Bearing Type Belt Width Maximum Belt Suitable forSeries Diameter Speed, m/s

I 63.5 to 101.6 Ball 300-800 2.5 Fine material with small lumps-Non-abrasive, intermittent duty.

[1 88.9 to 139.7 Ball 400-1000 4.0 Fine material, small sized lumps, slightlyabrasive, continuous duty.

111 101,6to 139.7 Ball 500-1200 4.0 Unsizes medium lumps, mixed with tinesized small lumps, moderately abrasive,

continuous duty.

Iv 127 to 139.7 Ilall/roller/taper 500- I 400 4.0 Unsized, large lumps, mixed with small sized

roller medium lumps moderately abrasive

contimrous duty.

v 139.710219.1 Ball/roller/taper 800-2000 5.0 Large size lumps, highly abrasive, critical

roller duty.

VI 168.3 t0219.l Ball/roller/taper 1600-2000 4.0 Large capacity conveyor with lumps.roller

49

..goc

WIo

NORMAL OCCASIONAL UNS HEOULEO STOPS NOTSTOPPAGE ACCEPTABLE

?ACCEPTABLE PROCESS UPSET

/kHIGHEST RELIABILITYSTOPPAGE CATASTROPHIC

OCCASIONAL STOPPA6EOFNOC0NSE12UENCE

7BAO CONDITIONS

~l? MAtNTEt4At4CX

,..0

4 L7 SALT720 WHEAT GRAINS

D COAL

v~

SAW DUST

WWO CHIPS

CHARCOAL

DRY ASHES

LIME STONE

WE.

CONCIRON

40 SULPHUR100 SLAG1250 PHOSPHATE ROCKS

{--

) =OIJ??3ARY SANDO EARTH, CLAY

3 TRAP ROCK

ET SAND

;RETi

ORES

JD COPPER ORES

I 174 32WII Cl BORINGS

SQUARE 11Y/.

NOTES

1 Select required duty along Y, axis of square I, then move horizontally to meet line representing maintenance condition applicable from this point move vertically again to meet the curves signifying effect ofstoppage on the system. From this point move horizontally to meet Y1axis. This will represent reference point A.

2 Select density of material to be handled along the axis Y. of square II and move Irorizmstallyto meet the lines representing required bolt width. From this point move vertically up or down to joint the lines

representing conveyor speed desired.

3 From this point of intersection proceett horizontally to meet axis Y,. This will represent reference point B. Join point A and B. The segment of the selection bar through lineAB passes, will indicate the series of

idler conveyor most suitable for use..

FIG. 19 SELECTION OF IDLERS

.i

IS 11592:2000

ANNEX C

(Clause 8.8.5.2)

SECOND METHOD OF IDLER SELECTION

C-1 IDLER CLASSIFICATION c-2 I-DLER SELECTION

Idlers are classified in four series as given in Idler spacing for troughed belts and flat belts are

Table 23. selected as shown in Fig. 20 and 21 respectively.

Table 23 Idler Classification

(Clause C-1)

Series Bearing Type Shaft Dia RoB Dia B-elt Width Application Rangeat Bearing (mm) (mm)

(mm)

Light Deep groove ball bearing 20 63.5,76.1,88.9, 300-800 For intermittent operation, rela-

101.6 tively low capacities and forlight weight materials oflimited lump size.

Medium Deep groove ball b&dring 20 88.9, 101.6, 108, 400- I 200 For intermittent operation, medium

114.3, 120, 127, capacities and for moderate

133, 139.7 weight, semi-abrasive materials

containing lumps larger andheavier than those handled bylight duty series idlers, or for

continuous operation when

handling light weight, finematerials.

Heavy duty Roller/taper roller/ball 25 101.6, 108, 500~ I 600 For continuous operation, high

114.3, 120, 127, capacities and for heavier

133, )52.4 weight, abrasive materialswhere the size of lump is

limited by belt width.

Extra heavy Roller/taper rollerlball 25-30 139.7, 152.4 to 800-2000 For continuous operation, highestduty 219,1 capacities and for the heaviest

and coarsest materials.

—

51

—

IS 11592:2000

1500

1350

1200

1050

E\

~ 900

n-

d

s 600wA

\

~ 4503 \aw 300

150

0.500 0.750 1.000 1.250 L500 1.750

FIG. 20 TROUGHED BELT IDLER SPACING

1500135012001050

900

750

600

b50

300$

20’

sA

z 150y 135~ 120

: 105

w 90

75

60

L5

30

15

)ELT WIDTH AND IDLER SERIES

3.000

2.500

2.000

1.750

1.500 ~

1.250 gwz

1.000 ~-=

0.750 ;

mw

0.500 dz3

0.375 {x

0.250

0.150

FIG. 21 FLAT BELT IDLER SPACING

52

-

IS 11592:2000

ANNEX D

(Clause 8.8.5.2)

THIRD METHOD FOR IDLER SELECTION

D-1 CLASSIFICATION OF IDLERS

The idlers are classified into five series numbers asgiven in Table 24 based upon roll diameters andhewing sizes. The bearings may be either deep groovedball or taper roller bearings with shaft diameter asshown in Table 24.

Table 24 Classification-Idler Series Number

(clause D-1)

Ail dimensions in md]imetres.

Idler Roll Dia Shaft Dia at MaximumSeries Bearing Belt

Number Width

I 63.5 tO 127 17 650

II lt)l.6to 127 20 1200

111 127. 133, 139.7 20 or 22 1600

Iv 139.7, 152.4, 159 250130 1600

v 152.4,159 25,30 or 40 2000

V1 168.3, 219.1 30 or 40 2000

D-2 BASIS FOR SELECTION OF IDLERS

D-2.1 This selection of idler series depends on threeconditions:

a) Type of service;

b) Characteristics of material to be handled; and

c) Belt speed.

‘D-2.2 ~pe of Service

The severity of conditions under which the idlers willbe used, is the prime consideration for the selectionof idlers. This includes the hours of operation perday and overall life expected from the installation.In temporary installation such as dam constructionor quarrying, life may be a few years while forpermanent installations, several decades of life maybe expected.

D-2.3 Type of Material Handled

The weight of material on belt effects the load andspacing of idlers and therefore has a direct bearing onidler selection. The material lump size modifies thedirect effect of weight by introduction of an impactfactor. In case of return idlers, only weight carried byidlers is that of belt itself.

D-2.4 Belt Speed

Belt speed is an important factor in idler serJice lifeand therefore governs its selection. It determines therotational speed of idler based upon the diameter ofthe roll. Belt speed also has a direct bearing on wearlife of idler roll surface, particularly for the returnidlers.

D-3 METHOD FOR SELECTION OF IDLER

SERIES

D-3.1 Table 25 gives the service factor ‘A’representingthe type of service of.conveyor installation, Table 26and “Table 27 give the service factors ‘B’ and ‘C’applicable for troughing and return idlers respectively,representing the effect of material handled. Theproduct of service factors ‘A’ and ‘B’ ( ‘A’ and ‘C’ forreturn idlers) gives application factor used in theselection of idler series number.

Table 25 Service Factor ‘A’

(Clause D-3.1)

~pe of Service Factor ‘A’

Intermittent operation-(less than 6 hours per day) 6

Return idlers 6

Troughing idlers — Portable or temporary installations 6

Seasonat operation for stockpiling 12

Conveying materials with bulk density over 1920 kg/m3 15

One shift operation—(6 to 9 hours per day)

Return idlers 9

Troughing idlers — Classified material 9

up to 1280 kg/m3

Classified materiat 12

up to 1920 kg/m3

Classified material over 15

1920 kg/m3

Unclassified material, limited by belt widths only 15

Two shift operation—(10 to 16 hours per day)

Return idlers 12

Troughing idlers — Classified material up to 121600 kg/m3

Classified material over 15

1600 kg/m3

Unclassified materiat, limited by belt width only 15

Continuous operation<over 16 hours per day)

All materials 15

53

—

IS 11592:2000

Table 26 Service Factor ‘B’

(Clause D-3. 1)

Maxi- Bulk Density of Material, kg/m3

mumLump 800 1200 1600 2000 2400 2800 3200

Size

mm

100 24 36 48 60 72 84 96

150 32 48 64 80 96 112 128

’200 40 60 80 100 120 140 160

250 48 72 96 120 144 168 192

300 56 84 112 140 168 196 224

350 64 96 12/? 160 192 224 256

400 72 108 144 180 216 252 288

450 80 120 260 200 240 280 320

D-3.2 Figures 22 and 23 depict the relationshfi

between app~ication factor and belt speed for troughingand return idlers. These curves are used for selectionof idler series number for troughing and return idlersrespectively.

D-3.3 The application factor (see D-3.1) when plotted,tigainst the selected belt speed for installation inFig. 22 and Fig. 23 gives the best suited idler seriesnumber for troughing and return idlers respectivelyof the particular installation.

D-3.4 Example

Type of service 8 h/day one shift

Type of material Crushed stone,1600 kg/m3

Maximum lump size 100 mm

Belt speed 1.75 m/s

Belt width selected 800 mm

Table 27 Service Factor ‘C’

(Clause D-3.1)

Belt Width Bulk Density of Material, kg/m3

mm

up to I 200 1 200to2000 Above 2000

300 2.3 2.8 2.9

400 2.8 3.5 3.6

500 3.5 4,5 4.6

630 4.6 6.2 6.8

800 6.6 8.0 9.2

1000 10.2 10.19 13.0

1200 13.6 14.2 16.6

1400 16.1 17.7 20.0

1600 18.0 21.8 22.6

1800 20.3 24.3 25.7

—

D-3.4.1 For Troughing Idler Selection

From Table 25 Factor A = 12

From Table 26 Factor B =48

Therefore, trough-ing idler application Ax B= 12x48=576factor

D-3.4.1.1 From Fig. 20, for a belt speed of 1.75 m/s andan application factor of 576 a series II idler is selected.

D-3.4.2 For Return Idler Selection

From Table 25 Factor A = 9

From Table 27 Factor C = 8

Application factor Ax C=9 X8=72for return idlers

D-3.4.2.1 From Fig. 23 for a belt speed of 1.75 m/s andan application factor of 72, a series II idler is indicated.

54

IS 11592:2000

5.0

4.5

.L.O

3.5

$ 3.0E

: 2.5

\’ \

—a-u-l

~ 2.0wm

1.5

1.0

\

0.5 ~

o500 1000 1500 2000 2500 3000

APPLICATION FACTOR (FOR TROUGHING IDLE-RS)

FIG. 22 SELECTJON CHART FOR TROUGHING IDLER (FOR BELT WIDTH UP TO 1500 mm)

5.0

4.5

4.0

3.5

s 3.0Ea: 2.5

&m~ 2.0w03

1.5

Lo

0.5

0

-t-h--m, ‘r,, I “\ I I, \ — I \

111\ \

lr- \“

1,

100 200 300 400 500 600

FIG. 23 SELECTION CHART FOR RETURN IDLER (FOR BELT WIDTH THROUGH 1500 mm)

55

—

IS 11592:2000

ANNEX E

(Clause 8.8.5.3)

CALCULATIONS FOR EQUIVALENT LOAD ON IDLER BEARINGS FORTHREE EQUAL ROLL TROUGHED IDLER SET

E-1 The load on central idler-roll is the summation ofloads due to weight of material and weight of belt andis given by (for symbols see Table 1)

‘=[:’’1G:”p;+[+mBg”pc)newt0nE-2 The equivalent force on each bearing of the idleris given by:

Feq=~. &Ki2

... (66)

where Ki is the application factor for the idlers as givenin Table 28.

E-3 The modified equivalent force on each bearingconsidering the life of bearing is given by:

Feqm =~fjKiBf ... (67)

where B~is the bearing life factor. The value B[ basedon 60000 working hours at the required belt speedmay be obtained from bearing manufacturers.

NOTE — The above is typical method of calculation and there

Type of Factor Operating Conditions Service/Speed/Lump Factor

Service fhctor (Ks.) Hours of operation LrP to 6 0.7

6 to 10 1.0

10to 16 1.3

16t024 1.7

Service fwtor (Kv) Belt SpCd, I1tiS .Upto 1.0 0.8

1.0 to 2.0 0.9

2.0 to 3.0 1.0

3,0 to 4.0 1.1

4.0 to 5.0 1.2

Lump factor (K.) Maximum lump Unclassified Oto 100 1.0dimension in material 100to 150 1.3mm

150 to 20U 1.7

200 to 250 2.0

250 to 300 2.3

300 to 350 2.7

350 to 400 3.0

400 to 450 3.3

450 to 500 3.7

500 to 550 4.0

550 to 600 4.3

Classified material Oto 100 1.3

100 to 150 1.6

150 to 200 2.0

200 to 250 2.3

250 to 300 2.7

can be orher methods as w~lL

Table 28 Application Factor Ki

(Clause E-2)

Factor K,= K, K,,. K,

56

IS 11592:2000

ANNEX F

(Clause 8.8.4.4)

ALTERNATIVE METHOD OF CALCULATION OF INDUCED BELT EDGE TENSION, AT

F-1 ]nduced belt edge tension is the ratio of maximum F-3 Value of AT given in Table 29 will ensure that:belt edge tension and the maximum rated belt tension,

a)T,,,.The induced belt edge tension may be more thanlnaximum rated belt tension during peak belt loadingsin short time non-steady operating condition duringstw-ting and stopping the conveyor belt.

F-2 Based on the recommendation of the manu- b)

Iacturer. the maximum belt edge tension under steadyoperating condition is selected. The value of AT is F-4 A

edge tension does not exceed either in steadyoperating conditions or in the temporary non-steady conditions from the maximumrecommended tension of the belt or belt jointin the steady condition by the ratio selected.

tension in the belt centre remains adequate andalways positive to prevent belt buckling.

hgiher value of AT may be fixed, if agreed byLaken from Table 29 (interpolating if necessary) the belt manufacturer, for the maximum transition

distance. If agreed by the manufacturer, the value ofagainst the ratio of average belt tension at transition10 maximum rated belt tension with the assumption maximum belt edge tension may be taken as twice the’

that the gap (or overlap) between the rollers (idlers) maximum rated belt tension in case of textile beltsand 2.7 times the maximum rated belt tension in case

conforms to IS 8598. of steel cord belts for belt edge tension in short timenon-steady operating condition.

.-...’

Table 29 Values of AT

(Clauses F-2 and F-3)

hlaximwn Belt Edge 1.3T., 1.45T~ 1.6Tm 1.8Tm 2Tm 2.3Tm 2.7Tm‘rension F 130% 145% 160% 180% 200% 230% 270%

Ratio of Average Criterion

Belt Tension at ATTransition to T

1.5T,,, — — — 0.45 Tm 0.75 Tm 1.2 Tm 1.8 Tm

1.4T,,, — . 0.3 T~ 0.6 T~ 0,9 T~ 1.35 T~ 1.95 Tm

I .3r,,, . 0,25Tm 0.45 Tm 0.75 Tm 1.05 Tm 1.5 T~ 2.1 T~

1.2T,,, 0.15 T,, 0.4 T~ 0.6 T,. 0.9 T~ 1.2 Tm 1.65 Tm 2.25 TmMaximum belt edge

l.l T,n 0,3 T,. 0.55 Tm 0.75 Tm 1.05 Tmtensioo F percent

1:35 Tm 1.8 Tm 2.4 T~

1.OT,,, 0,45 Tn, 0.7 Tm 0.9 Tm 1.2 Tm 1.5 Tm 1.95 Tm 2.55 Tm

0.9T,,, 0.6 T,,l 0.85 Tm 1.05 Tm 1.35 Tm 1.65 Tm 2,1 Tm 2.7 Tm

0.8 T,l, 0.75 T,,, 1 T,,, 1.2 T,. 1.5 Tm 1.8 Tm 2.25 Tm 2.4 Tm

0,7 T,,, 0.9 T,,l t.15 Tm 1.35 Tm 1.65 Tm 1.95 Tm 2.1 Tm 2.1 Tm

0.6T),, 1.05 T,n 1.3 Tm 1.5 Tm 1.8 Tm 1.8 Tm 1.8 Tm 1.8 Tm

t).5Tn, 1.2 T,,, t.45 Tm 1.5 Tm 1.5 Tm 1.5 Tm 1.5 Tm 1.5 Tm

0.4 T,,No belt centre

1.2 T,,, 1.2 Tm 1.2 Tm 1.2 Tm 1.2 Tm 1.2 Tm 1,2 Tm

0.3T,,, 0.9 T,,, 0.9 Tm 0,9 Tm 0.9 Tm 0.9 Tmbuckling

0.9 Tm 0.9 Tm

0.2T,,, 0.6 T,,, 0.6 T~ 0.6 T~ 0,6 T~ 0.6 T~ 0.6 T~ 0.6 T~

0, I T,,, 0.3 T,,, 0.3 T,,, 0.3 T~ 0.3 T~ 0.3 T,n 0.3 T., 0.3 T,,,

0.05T~ 0.15 T,,, 0.15 T~ 0.15 T~ 0.15 Tn 0.15 T~ 0.15 T~ 0.15 Tn

—

57

-

IS 11592:2000

ANNEX G

(Clauses 8.9.2.3 and 8.9.3.5)

SPECIFIC MODULUS FOR BELT MATERIALS

G-1 For the calculation of belt modulus, the values for specific modulus for different types of material of belts

are given below:

Curcass Construction Range(Longitudinal Direction)

Cotton 7-1o

Polyamide 5-7

Polyester 10-20

Nylon/Nylon 6-8

Rayon 10-14

Steel cord 30-50

ANNEX H

(Clause 8.10.2.4)

SELECTION OF DRIVE PULLEYS WITH TWIN DRIVE

H-1 Drive pulleys with twin drive consists of twopulleys of identical overall diameters each beingindependently driven.

H-2 The driving motors shall be of the same type andhave the same torque/speed characteristics, as alsoshall be of the case with fluid couplings, when theseare fitted.

H-3 In practice, the two drives will not share equally,there being a small difference in power due to thecontraction of the belt in drive head causing thesecondary pulley to revolve at a lower speed than theprimary pulley. The difference in speed will be afunction of the belt tensions related to the stretchcharacteristics of the belt and is normally well withinthe slip characteristics of either the electric motors orfluid couplings (when these are fitted).

TypicalValue

9

7

16

6.5

12

50

H-4 With this type of drive, the distance between thetwo drive pulleys is not fixed as in the case of gearedtandem drive and the extent of separation is notcritical, although practical considerations such asmounting and housing usually make it convenient tohave the two drive units reasonably close together. Thescope of having a greater length of belt between thetwo drive pulleys, than is possible with geared tandemdrive, makes for greater flexibility in absorbing theeffect of belt contraction or creep. Also the greaterflexibility of layout of dual drives normally makes itpossible to reeve the belt in such a way that.the non-carrying or clean side of the belt is in contact withboth drive pulleys, thus eliminating the liklihood ofdifficulty due to material built-up on the face of thepulleys. In dual, drive units should be arranged, sothat both drive pulleys drive on the clear side of belt.

..—

58

IS 11592:2000

ANNEX J

(Clause 8.13.4.2)

DETERMINATION OF TRAJECTORY OF MATERIAL LEAVIN.G THE BELT

J-1 For design of discharge openings and receiving

chutes, it is necessary to know the trajectory of material

leaving lhe head pulley in a conveyor system.Trajectory of material is fixed by the angle of

separation of material from the belt and the verticalordinates from the tangent line drawn at the point ofseparation on head pulley.

J-2 DETERMINATION OF POINT OFSEPARATION

J-2.1 The angle of separation, that is, the angle fromvertical at which malerial will leave the belt as it

travels over discharge pulley is calculated from thefollowin~ formula:

V*cOse=— ... (68)

-g”rP

J-2.2 For guidance, a graphical representationfor determination of angle of separation is given inFig. 24.

J-3 DETERMINATION OF ORDINATES

J-3.1 The length of vertical ordinates h,, h2, ........from point at equal intervals placed on tangent linedrawn at the point of separation are calculated fromthe following formula:

r I I 1 1 1 I [

1-0.50”

I

‘“’’l-t+1.00F

m

/

3.00

1.8 1.6 1.4 1.2 1.0 0.8 0.6 0

ANGLE ~ DEG

PULLEYDIAMETER— METRES

—

FIG. 24 ANGLE OF SEPARATIONFORBELTS

59

IS 11592:2000

... (69)

J-3.2 For guidance the value of ordinates,, hz, ...........in metres with 1= 0.50 m per 1.0 m/s of belt speed aregiven below:

h, h2 113 h4 h5

0.012 0.049 0.110 0.196 0.306

116 h, h8 h9 h 10

0.441 0.600 0.784 0.993 1.226

h II h12

h13

h“ hlj14

1.483 1.765 2.071 2.402 2.757

J-4 GRAPHICAL REPRESENTATION OFTRAJECTORY OF MATERIAL

J-4.1 The graphical representation of trajectory ofmaterial indicates the actual path which will befollowed by the material after it leaves the discharge

pulley. The trajectory of the material depends uponthe configuration of the belt conveyor and isgraphically represented in the manner laid downin J-2.2 and J-4.3.

J-4.2 For Ascending and Horizontal Belts

If cos 61<1 (see J-2.1) then the tangent line shall bedrawn at the point of separation (see Fig. 25). Ifcos 0 = 1, the tangent line shall be drawn in thedirection of belt travel (see Fig. 25).

J-4.3 For Descending Belts

If cos Et<1 and angle of separation is more than angleof inclination, 5, of the conveyor belt then the tangentline is drawn at the point of separation (see Fig. 25).If cos .(3 2 1 and is less than or equal to angle ofinclination, 6, of conveyor belt, the tangent line shall

be drawn in the direction of belt travel (see Fig. 25).

J-5 For drawing the trajectory of top of the stream ofmaterial of height HI, the radius rPin formula (68) isreplaced by (rP+ Hi ) and velocity V by :

v(rP+H1)

‘P

60

.1S 11592:2000

BELT

CASE 1,

HORIZONTAL BELT

x

CASE 2HORIZONTAL BELT

~.,,-.

CASE 5 \Cose<l ande>6t)~sc EN131NG BELT

CASE 3ASCENDING BELT

k-’13’

/“x

T“P

CASE 4ASCENDING BELT

CASE 6

Cose>l and e<6 \

DESCENDING BELT

Fi~. 25 TRAJECTORY OF MATERIAL

6:

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fT

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Amendments Issued Since Publication

Amend No. Date of Issue Text Affected

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