ENGINEERING / INSTALLATION & TROUBLE … · COMPOUNDING OF RUBBER CONTENTS ... CHEMICAL RESISTANCE...

CCOOMMPPOOUUNNDDIINNGG OOFF RRUUBBBBEERR

CONTENTS Compounding of Rubber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47-48

Effects of Oil on Rubber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

Chemical Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .50

Physical Testing-Rubber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51

Effect of Heat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

Fabric Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53-54

Fabric Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

Foreign Fabrics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

More About Textiles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

Adhesions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

Conveyor Belt Grades . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

Conveyor Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60-61

Elevator Belt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62-64

Engineering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65-66

Raw Material Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .67

Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .68

Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .69

Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .70

Training . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .71

Training Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .72

Loading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .73-74

Load Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .75

Transition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .76-77

Pulley Diameter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .78

Squaring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .79

Vulcanizing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .80-82

Step Lengths . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .83

Cure Rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .84-85

Trouble Shooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .86-88

EENNGGIINNEEEERRIINNGG // IINNSSTTAALLLLAATTIIOONN && TTRROOUUBBLLEE SSHHOOOOTTIINNGG

Montgomery, Alabama USA1•800•633•1470 • FAX 334•271•3194

www.pricerubber.com

47


Carbon black is the most commonly used ingredient in allblack rubber recipes, because it reinforces rubber to make it tougher and moreabrasion and crack (fatigue) resistant. Carbon is chosen from a wide range of sizes andgrades to suit the end product. Carbon is heavy (Sp. gr. 1.6).

Clays are used extensively in rubber to improve serviceability, modify elongation, hardness, stiffness and specific gravity. Generally, they are cheap but heavy (Sp. gr. 2.6) andmust be used in limited quantities, not to impede tensile strength, tear resistance or resistance toabrasion.

Oils and waxes are considered extenders. They are chosen to improve processability, asmoother product and to decrease cost, as most oils are cheaper than rubbers.

Coloring, antioxidants, accelerators and vulcanizing agents are chosen to suit the intendeduse of the finished product.

Probably No Other Industry Uses as Great aVariety of Materials as Rubber.

Compounding of Rubber is much like a bakery . . . the recipe is designed to suit theintended end use of the product.

The rubber (elastomer) is chosen for abrasion, resistance to heat or oils, cold weather flexingor resistance to sunlight, ozone or electrical fields. Oftentimes, two or more rubbers are blended to gain the natural advantages of each. But these rubbers are not serviceable by themselves, and must be blended with fillers, oils, plasticizers,waxes, coloring agents and vulcanizing chemicals.

COMMON

ELASTOMERS + COMMON

+ COMMONFILLERSOILS

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EEFFFFEECCTTSS OOFF OOIILL OONN RRUUBBBBEERR

Rubbers Sp. GrButyl .92EPDM .86 Hypalon 1.10 Mineral 1.04 Natural .92 Neoprene 1.23 Nitrile 1.00 Polybutadiene .94Syn. Natural .92 SBR .94 Silicone .98 Thiokol 1.27

Fillers Sp. Gr. AI. Hydrate 2.42 Barytes 4.45 Ca. Carbonate 2.70 C. Black 1.80 Clays 2.60 Graphite 2.25 Kaolin 2.60 Lime 2.20 Mg. Carbonate 2.22 Mica 2.95 Soapstone 2.72 Talc 2.72 Titanium Di. 3.93

Processing Sp.Gr. Aids

Carnauba Wax .99 DOP Oil .98 Factice 1.06 Mineral Oil .84 Pine Oil .93 Tall Oil .98 Parafin Wax .90 Petrolatum .84 Pine Tar 1.08 Rosin 1.08

Vulcanizers Sp.Gr. Mg. Oxide 3.32 Sulfur 2.07 Zn Oxide 5.57

Chosento suit the finished product

Accelerator Activators to assist accelerators

Age-Resistors to retard deterioration from oxygen, heat, light, ozone

Miscellaneousretarders, colors, blowing aids, abrasives, dusting agents, odorants

Fillerscarbons and clays

Softeners for mixing, tack, elasticity

Processing Aidsoils, plasticisersand waxes

Vulcanizing AgentsSuch as Sulfur for crosslinking

Acceleratorsto hasten cure

Miscellaneous Sp.Gr. Am. Bicarbonate 1.58 Asbestos 2.47 Coal Tar 1.18 Cork .80 Cotton Flock 1.25 Gelatin 1.27 Rubber Dust 1.20 Iron Oxide 5.14 Lead 11.34 Lignin 1.30 Mg. Carbonate 2.22 Castor Oil .96 Cotton Seed Oil .92 Palm Oil .88 Pumice 2.35 Shellac 1.10 Sodium

Bicarbonate 2.20 Stearic Acid .85 Urea 1.34 Whiting 2.62 Wood Flour 1.25 Zinc Stearate. 1.05

AirOperatedRam

Like a bakery, thousands ofrecipes are written aroundhundreds of ingredients, eachintended to contributesomething to the finishedproduct.

Rubber can be made soft orhard, flexible or rigid, elasticor tough, alive or dead-liquid, sponge, almost anycolor and resistant to sunlight,electrical current, sub-zerotemperature, heat, and manychemicals and oils.

Rubber serves everywhere man goes!

Naturalor

SyntheticRubber

DropDischarge Door

MixingRotors

LoadingHopper


48Back to Contents Next Page

Petroleum

Wheat

Corn

EEFFFFEECCTTSS OOFF OOIILL OONN RRUUBBBBEERR

49

Both Neoprene and Nitrile rubbers may be blended in almost any degree with other rubbersto achieve the desired level of oil resistance.

Generally, oils, fats and greases will cause rubbers to swell,become tender and soften. To retard this action, rubbers arecombined with other elements. The two most commonly used oilresistant rubbers are Neoprene (chloroprene) and Nitrile(acrylonitrile).

Cl

CH2 = C - CH = CH2 (Chloroprene)

Neoprene: Has an occasional Chlorine atom on themolecular chain, which stabilizes the rubber against attack ofpetroleum based products better than most common rubbers.Though effective against animal and vegetable fats, Nitrile is evenbetter and generally more cost effective.

H

(Acrylonitrile) C = C

H C = N

Nitrile: Has an atom of Nitrogen on the molecular chain that retards attack of oils, particularly animal and vegetable.

Soybeans

Pine and Fir (Conifers) oils and resins are handled by Nitrilerubbers in moderate blends with other rubbers.


PPHHYYSSIICCAALL TTEESSTTIINNGG -- RRUUBBBBEERRCCHHEEMMIICCAALL RREESSIISSTTAANNCCEE OOFF RRUUBBBBEERRSS

Most rubber compounds will resist moderate concentrations of alkaline materials (bases).However, Resorcinol-Formaldehyde-Latex (RFL)fabric treatments may be destroyed by hydroxide solutions.

Specific applications may be laboratorychecked for the best rubberrecommendation.

Ask for assistance in choosing the mostsuitable rubber for specialcircumstances.

Alkaline - A base is thehydroxide (OH)

14.0of a metal.

13.0

12.0 + water

11.0EPDM

10.0 Dry ChemicalsNitrile

9.0 Salts A salt is a metalSBR combined with an

Natural8.0 Alcohols acid radical.

Pure Water pH 7.0 Neutral

SBR

Natural 6.0 Mild Acids

Neoprene 5.0 Organic Solvents + an active metal

EPDM

Butyl 4.0 Moderate Acids

Hypalon 3.0

2.0

1.0

pH Scale

Chemical alterations of rubber depend uponchemical concentration, temperature andavailability of water or other solvents to carryreactions forward.

Acid - A hydrogen compound whose water solution containshydrogen ions. Free hydrogen ion concentrations in strong acidswill attack most rubber compounds. In conveying, many materialswill combine with atmospheric moisture to form these acids.

s

s


Tensile is a measure of force required to break a material. In rubber, generally a dumbbell sample with a 1/4” x 1/4” cross section (neck) is broken and pounds per square inch are calculated.

Elongation is the “stretch” of a material at break, expressed as a percent of the relaxed original.

Modulus is a measure of force required to stretch a materiala particular amount. In rubber, generally a sample is stretched 300% and the necessary force (pounds per square inch) is calculated.

Durometer is a measure of hardness, measured with a plunger and read on a gauge. A rubber band might read 35, a tire tread about 60 and ashoe heel about 70 durometer.

Modulus of Elasticity is the same as modulus, but some-times offered as a mathematical (calculated) expression of theforces in a composite material, such asconveyor belt, as it “curves” upor down a troughed conveyorsystem. The figures far exceedany force the belt wouldwithstand in actual use, andthey serve no practical applica-tion in conveyor belt design, other than to compare one setof numbers with another.

Abrasion is wear from scuffing. Pico Abrasion is a method of measuring the wear of rubber by scraping a sample with keen knife blades and weighing the sample at the end of a specified time. The higher the number, the less material is abraded away, and the more abrasion resistant the sample is believed to be. No claim is made for validity.

Dumbbell

OriginalLength

1''

4''

Modulus at300%Elongation

Tensile meas-ured at break

s

s

s

PPHHYYSSIICCAALL TTEESSTTIINNGG -- RRUUBBBBEERR


FFAABBRRIICC SSPPEECCIIFFIICCAATTIIOONNSS

Belt fabrics are used

at 1/10th of break

strength because

elongation makes

them unusable

above that rating.

52

EEFFFFEECCTT OOFF HHEEAATT


Weight Tensile Count GaugeFabric Grams per Ozs. per kg Pounds Ends Ends Thdths. Thdths.No. Sq. Mtr. Sq. yd. per cm. per inch per cm. per inch mm inches

75 426 12.6 140 x 105 785 x 585 18.5 x 6.9 47 x 17.5 .584 .023

90 541 16.0 193 x 113 1080 x 630 12.5 x 3.9 31 x 10 .781 .031

110 609 18.0 215 x 132 1200 x 740 13.8 x 4.7 35 x 12 .838 .033

125 704 20.8 241 x 94 1350 x 525 10.2 x 5.1 26 x 13 .939 .037

150 863 25.5 268 x 161 1500 x 900 10.2 x 5.9 26 x 15 1.245 .049

200 971 28.7 360 x 164 2010 x 916 9.3 x 4.3 23.5 x 11 1.321 .052

250 1194 35.3 447 x 157 2500 x 875 15.7 x 5.3 4 0 x 13.5 1.626 .064

300 1330 39.3 555 x 157 3100 x 875 18.1 x 5.3 46 x 13.5 1.651 .065

Multi-Ply (Plain Weave) Polyester/Nylon

EP100 355 10.5 125 x 63 700 x 353 11.8 x 6.7 30 x 17 .53 .021

EP125 430 12.7 165 x 65 924 x 364 19.7 x 6.5 5.0 x 16.5 .70 .028

EP160 560 16.5 210 x 80 1176 x 448 10.0 x 4.5 25.5 x 11.5 .90 .035

EP200 690 20.4 250 x 1001 1400 x 560 9.4 x 3.9 24 x 10 1.05 .041

EP250 860 25.4 310 x 100 1736 x 560 8.3 x 3.9 21 x 10 1.21 .047

Fabric Styles:

Polyester

EP FabricsPolyester/Nylon

s

s


53

M u l t i - P l y / S t r a i g h t Wa r p / P o l y e s t e r o r P o l y e s t e r - N y l o n


FFAABBRRIICC TTEESSTTIINNGG

Conveyor Belt fabrics usually are cataloged according to intended use strengths... a 110 lb. fabric isintended to be used at working tensions not greater than 110 lbs. per inch of width, per ply. Customarily,such 110 lb. fabric will have a breaking strength of 10 x allowable working tension (AWT), but sometimesa 7: 1 or even less “safety factor” is used.

This 10: 1 limit of AWT to ultimate breaking strength is felt necessary to avoid excessive stretch and“necking down” of the fabric at loads greater than 1/10th of break. While the fabric will not break until aload of 10 x the AWT is applied to it, it will begin to change shape severely (neck down) and the fibers orstrands will begin to elongate or slip... the fabric gets weaker and weaker as it grows longer and longer.Though break may not occur for quite awhile, the product will be stretched far beyond practical use longbefore it breaks... maybe even 300% to 400% of the original length.

Weight of a fabric generally is per square yard, 36'' x 36'', though sometimes a 42'' x 36'',measure is used.

Gauge is overall thickness of fabric usually in thousandths of an inch.

Tensile is the ultimate breaking strength of a fabric, per inch of width, either lengthwise (warp) or crosswise (weft). This tensile can be calculated by multiplying the number of yarns per inch by the tensile of each yarn. Or, it may be measured by either the Ravel Method or the Grab Method.

54



In the Ravel Method, a strip of fabric 1-1/4” wide x 6” long is raveled at the edges by removing a fewstrands until the test strip is 1” wide. These longer cross strands (weft) are expected to provide a moreaccurate measurement than a strip that is 1” x 6”. Jaws 2” wide are used to make this test.

In the Grab Method, a strip 4” wide x 6” long is pulled with 1” jaws, but a slightly higher reading isexpected than in the ravel method because of the outside strands that add some to the fabric tensile.Either method is used to test fabric, either lengthwise or crosswise.

Count is the number of strands per inch of width, either warp (lengthwise) or weft (crosswise).

Conveyor Belt Fabrics are available in a wide variety of materials, woven into many different stylesfrom many combinations of twists and plies. Today, most such fabrics are made from Polyester or Nylon,or some combination of the two. Lighter fabrics are sometimes made from Cotton or other synthetics.

FFAABBRRIICC TTEESSTTIINNGG


MMOORREE AABBOOUUTT TTEEXXTTIILLEESS

Since Conveyor Belt is an “international product,” it is necessary to compare the fabric ratingsused in various areas of the world. Direct comparison of fabrics by number is misleading becausethe figures are not uniform, one area to another, and do not indicate equal strengths of the fabrics.Allowable Working Tension (AWT) is approximately 33-1/3% of Asian (NN) numbers, andapproximately 70% of European (EP) numbers, compared with American numbers.

Foreigners coat their fabrics with a layer of rubber before tensile tests are made, but do notspecify the thickness nor the type of rubber used. Figures represent the strength of the fabric in thefinished belt, after having been down-graded by 25% from exposure to heat during vulcanization.

However Asian belt fabrics are downgraded to 75% of these calculated strengths when built intoa multiple belt carcass. Asians and Europeans rate the fabric in the finished belt. A three ply beltmade from NN-300 (a 140 lb. fabric) is rated at 105 lbs. per ply in the finished belt. This compareswith the EP160 designation in Europe, and with 110 in America.

American fabrics are measured in pounds per inch and are considered the same strength whenplaced in a belt. The belt carcass is a simple multiple of the number of plies times the fabricweight, with no adjustment made for rubber layers or for heat degradation.

Designated generally as “EP” fabrics, European fabrics are made from Polyester and Nylon.Asians use “NN” to suggest Nylon-Nylon construction of warp and filler. In addition, Asiansreduce fabric strengths by up to 50% in belts subjected to temperatures of 180 deg. C (356 deg. F).American fabrics are not down-graded in this heat range.

Asian European* American*

Fabric AWT Fabric AWT Fabric AWTNumber Lbs. / In. Number Lbs. / In. Number Lbs. / In.

100% 75%NN-100 46 34NN-120 56 42NN-125 58 44NN-150 70 52NN-160 78 58 60 60NN-200 93 75 EP 100 70 75 75NN-250 116 87 EP 125 90 90 90NN-300 140 105 EP 160 110 110 110NN-350 163 122NN-400 186 139 EP 200 140

150 150NN-500 234 175 EP 250 175NN-600 280 210 200 200

250 250300 300

*See page 51 for complete specifications.

56

FFOORREEIIGGNN FFAABBRRIICCSS VVSS.. AAMMEERRIICCAANN


MMOORREE AABBOOUUTT TTEEXXTTIILLEESS

57

Denier is a unit of weight of a yarn. 9,000 meters weighing one gram is one denier, or 15 denier yarnweighs 15 grams per 9,000 meters (.529 ounces per 29,520 feet or 5.59 miles).

Carding arranges fibers into a loose rope called a sliver. Many slivers may be drawn together to form athin strand called a roving. This roving is twisted on a spinning frame to form yarn.

Yarn may be formed from blended fibers at carding, from blended slivers when drawn together, orfrom blended rovings as the yarn is spun.

Plies are formed by twisting two or more yarns together. Spools of yarns are placed in a rack called acreel and wound onto a larger spool called a beam that is placed on the loom to be fed off as the warp(lengthwise) strands of the fabric.

Weft/(crosswise) yarns are wound on shuttles and passed through the warp yarns as the loomharness raises and lowers various warp yarns to form the fabric weave.

Plain weaves are formed by passing the weft strand over and under each warp strand.

Twill weaves are formed by passing the weft strand over and under 2,3 or 4 warp yarns, with each rowbeginning slightly to the right or left of the previous row.

Here are some common industrial fabric weaves.

STRAIGHTWARP

CROWFOOT

PLAINWEAVE

TWILLWEAVE


CCOONNVVEEYYOORR BBEELLTT GGRRAADDEESSAADDHHEESSIIOONNSS

The Scott Tester is widely used to measure and record theforce necessary to separate two surfaces, usually in poundsper inch of width. This information is critical in decidingupon the quality of a product, and the expected life inactual use.

In conveyor belting, common SBR (StyreneButadieneRubbers) are compounded to yield an adhesion betweencovers and plies in the 60 to 70 lb. range, while Nitriles,EPDM, Coal stocks and Chlorobutyl will measure somewhatless.

Natural rubber compounds, high grade truck tread stocksand specially treated fabrics can produce test figures as highas 150 to 200 lbs. per inch of width, measured on the ScottTester.

Industrial hoses usually are made with lower adhesions, asare OEM tires, where tests as low as 24lbs. per inch ofwidth may be considered adequate. As a rule, thicker rubbercompounds will produce higher adhesions, both between therubbers and between rubber and metal, fabric, or plastic.Thin rubber layers do not test as well.

58

Adhesion is firm or steady contact between two surfaces. In rubber, generally it applies to the “grab”of rubber to rubber or rubber to metal, fabric, plastics or other components of a finished product.

Because most synthetic fabrics are slick and will not stick to most rubber compounds, it is necessary totreat these fabrics with a “go-between.”

RFL (Resorcinol-Formaldehyde-Latex) is the most commonly used treatment for rubber to fabricadhesions, but sometimes other coatings such as special resins or isocyanates must be used. This RFLcoating is applied at the fabric mill, where the fabric is dried and heat set at the same time.

Heat Setting of fabric is done in the 325 to 375 degree F. range while under tension. Such heatingcan shrink Nylon and Polyesters as much as 15% from woven dimensions, both width and length. Thisheat shrink must be considered throughout the manufacturing process.


The RMA (Rubber Manufacturer’s Association) established specifications for conveyor belt gradesseveral decades ago. Though many of the early members of that association are no longer manufacturingbelting, those standards have been passed along with suitable changes to accommodate more “modern”raw materials presently used in belt work.

Only commonly used belts in general industrial applications are graded as to rubber (generally SBR,natural or a combination), though the carcass fabrics are essentially the same when covered by specialtyrubbers such as Neoprene, Nitrile or Chlorobutyl. The standards for the three grades of general purposebelts were:

Because Cotton was the basic carcass material when these standards were established, adhesions weremore difficult at the time. Today, with synthetic fabrics and RFL treatments, average adhesions wouldbe in the 60 to 70 lb. range on most general purpose belts.

Though cover tensile specifications have been clouded by the introduction of more “modern” rubbers,such as EBR (Polybutadiene), there is little justification for relaxing the tensiles first prescribed, otherthan to reserve for the manufacturer the freedom of using lesser rubbers without criticism.

continues to recognize these original specifications, and publishes complete details ofall components. The comparative grades of belts common in the general industry are shown on theReference Chart contained in this engineering guide, with currently marketed trade names of various beltsin each of these three categories. Other specialty belts are listed as well, with original RMA classificationsand trade names, but specifications never have been as clear as with Grades #1, #2, and #3.

The Consumer is urged to insist upon details on any belt product purchased, so that the grade may bedetermined, and the suitability of the product for the intended application may be judged.

RMA Original Specifications RMA 1994 Specifications

RMA Grade #1 - Cover tensiles of 3500 to 4000 Ibs.Adhesion between components of 20 to 24 Ibs.

RMA Grade #2 - Cover tensiles of 2500 to 3000 Ibs.Adhesion between components of 16 to 19 Ibs.

RMA Grade #3 - Cover tensiles of 800 to 1000 Ibs. Adhesion between components of 12 to 15 Ibs.

RMA Grade #1 - Cover tensiles of 2500 Ibs. 400% elongation.

RMA Grade #2 - Cover tensiles of 2000 Ibs. 400% elongation.

RMA Grade #3 - No specifications.

CCOONNVVEEYYOORR BBEELLTT GGRRAADDEESS


AANNDD TTEERRMMIINNOOLLOOGGYY

Supply as many details (?) as you can.The factory can match and suggest specifi-cations for the balance of the conveyordesign figures.

Discharge incenter of belt, indirection oftravel.Fall ?____feet.

Loadingimpact area

Transition(trough forming)

Troughing Idlers

area. Degree? ______.

Tail pulleySize? _____inches.

Mechanical or hydraulic takeup

Return Idlers

(?) _______ (?) _______ (?) ________

Loading chute

60

Computer generated conveyor design figures are available from the factory 1•800•633•1470. With a few basic design numbers, the correct belt can be suggested immediately.

Width x Length x Speed(inches) (C:C feet) (feet per minute)Belt must Almost limitless, Usually 350 to 600 fpm.trough com- properly designed. Sometimes much faster.pletely to betrainable.

CCOONNVVEEYYOORR DDEESSIIGGNN


Type of DrivePulley Plain (?) Lagged (?)

Deg. of Wrap 180 (?) __________ 180 (?) _________Snubbed 210 (?) __________ 210 (?) _________Tandem 420 (?) __________ 420 (?) _________

Transition area where Head pulleytrough flattens out Size ? _____inches.

Lift ? _______feet

Size ? ______inches.

Size ? ______inches. Gravity TakeupTo accommo-date thermalexpansion and

Size ? _____inches. prevent drivepulley slippage.

Weight ? ______lbs.Center to Center

(?) _______ (?) _______ (?) _______ (?) ________

AANNDD TTEERRMMIINNOOLLOOGGYY

61

Material Wt. x Lift ä Horsepower Carcass Strength

(lbs./cu. ft.) (feet)A high user of The most “energy Maximum available Carcass musthorsepower hungry” conveyor horsepower must be accommodate theon heavy feature! considered in choice maximum horsepowermaterials of belt. or load possible.


EELLEEVVAATTOORR BBEELLTT

Belts used for bucket elevator service do not have the samerequirements as those on conveyors.

In Elevator Service, the strength of the belt to support theweight of the bucket and the material being conveyed, as wellas to handle the available horsepower is easily calculated. Sincethe weight of the buckets is essentially the same on both sidesof the leg, the weight of the material is the difference.

The critical factors of elevator belting are the bucketprojection (how far it sticks out at the lip) and the tug of thebucket bolts on the belt carcass... the ability of the carcass tohold the bolts and not allow the bolt heads to wallow out thebolt holes and pull through the belt, dropping the load ortearing the belt at this weakened area.

Buckets are spaced apart on the elevator belt when they areloaded by digging in the boot. Usually they are turned faster andthrow the load away from the elevator at the top. Grain andother light, free flowing materials are handled in this way.

When large, lumpy materials must be elevated, the bucketsare spaced closer together and filled with a chute. Belt speedsare slower than with “digging” elevators.

The type, size, weight, capacity, spacing and projection of thebucket are critical in determining the correct belt for carryingthe load and holding the buckets. The number and size of thebolt and bolt head are important, too.

The elevator application and design help determine thetype of belt to use, the strength of the carcass, and the coversnecessary to protect the carcass from the materials beingelevated.

Elevator BootBuckets Dig to Load

Bucket

BucketProjection

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The selection of a suitable elevatorbelt depends upon many factors. Thefactory can help with the proper choice.Get all information shown below forfactory help.

See page for standard buckethole punching.

Splicing of elevator belts should bedone with the buckets mounted andthe belt drawn tight. Vulcanized splicesrun the smoothest, but mechanicaljoints will serve well if properly done.

Material elevated:Weight? __________________Size? ____________________Temp.? __________________

Number ofBuckets? ____________________Belt Speed? __________________Leg Height? __________________Horsepower?__________________Pulley Sizes? __________________Bucket Spacing? ______________Type of Bucket? ______________Bucket Weight? ______________Punching Pattern? ____________Number of Bolts? ______________Bolt Size? ____________________Type of Splice?________________


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Loading Chute

Splices

Lap - Butt - Clamp -thin belt heavy belt thin belt

Plate fasteners - Vulcanized -thin belt any belt


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Standard Elevator Bucket Punching

5 x 4 P-1 2 3-3/16 9/3 1/46 x 4 P-1 2 4-3/8 9/32 1/46 x 5 P-1 2 4-3/8 9/32 1/47 x 4 P-2 3 2-11/16 9/32 1/48 x 4 P-2 3 3-1/16 9/32 1/49 x 4 P-2 3 3-5/8 9/32 1/47 x 4-1/2 P-2 3 2-11/16 9/32 1/47 x 5 P-2 3 2-11/16 9/32 1/48 x 5 P-2 3 3-1/16 9/32 1/49 x 5 P-2 3 3-5/8 9/32 1/4

10 x 5 P-2 3 4-1/8 9/32 1/410 x 5-1/2 P-2 3 4-1/8 9/32 1/4

8 x 6 P-2 3 3-1/16 9/32 1/49 x 6 P-2 3 3-5/8 9/32 1/4

10 x 6 P-2 3 4-1/8 9/32 1/410 x 7 P-2 3 4-1/8 9/32 1/411 x 5 P-3 4 3 9/32 1/412 x 5 P-3 4 3-3/8 9/32 1/411 x 6 P-3 4 3 9/32 1/412 x 6 P-3 4 3-3/8 9/32 1/411 x 7 P-3 4 3 11/32 5/1612 x 7 P-3 4 3-3/8 11/32 5/1614 x 5 P-4 5 3 9/32 1/414 x 6 P-4 5 3 9/32 1/415 x 6 P-4 5 3-1/4 9/32 1/414 x 7 P-4 5 3 11/32 5/1615 x 7 P-4 5 3-1/4 11/32 5/1616 x 5 P-5 6 2-7/8 9/32 1/416 x 6 P-5 6 2-7/8 9/32 1/418 x 6 P-5 6 3-1/8 9/32 1/420 x 6 P-5 6 3-1/2 9/32 1/416 x 7 P-5 6 2-7/8 11/32 5/1618 x 7 P-5 6 3-1/8 11/32 5/1620 x 7 P-5 6 3-1/2 11/32 5/16

8 P-7 5 3 9/32 1/49 P-7 5 3 9/32 1/4

10 P-7 5 3-1/2 11/32 5/1611 P-7 5 4 11/32 5/1612 P-7 5 4-1/2 11/32 5/1613 P-8 7 3-1/2 11/32 5/1614 P-8 7 4 11/32 5/1615 P-8 7 4 11/32 5/1616 P-8 7 4-1/2 11/32 5/1618 P-8 7 5 11/32 5/1620 P-9 9 4 11/32 5/16

BucketSize

PunchStyle

No. ofHoles

HoleCenters

Hole BoltSize Size

0 0

P - 10 0 0

P - 2

0 0 0 0 0

P - 40 0 0 0 0 0

P - 50

00

0 0

P - 70

00

0 0

00

P - 80

00

00

00

00

P - 9

0 0 0 0

P - 3

1"

1"

1"

Material WeightsMaterial Lbs. / Cu. Ft.

Wood Chips 20Coke 30Corn 45Rice 45Soybeans 45Wheat 50Coal 50Clay 75Bauxite 80Salt 95Limestone 95Cement 100Sand 100Granite 100Gravel 110Phosphate 110Slag 110Copper Ore 140

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Conveyor Lift (feet) per 100' ofIncline Conveyor length (C:C)

5 8.717-1/2 13.05

10 17.3612-1/2 21.6415 25.8817-1/2 30.0720 34.2022-1/2 38.2725 42.2627-1/2 46.1730 50.0032-1/2 53.7335 57.36

Examples:

A 350 ft. C:C Conveyor on a 17-1/2 degree incline would have a total lift of 105.25feet (3.5 x 30.07).

A 203 ft. C:C Conveyor on a 20 degree inclinewould have a total lift of 69.43 feet (2.03 x 34.20).

or, a 69.43 lift on a C:C Conveyor 203 feet long would indicate an incline of 20 degrees(69.43/2.03), read from chart.

Engineering Help!

Properly chosen, most belts will give long andtrouble-free service, even in severe applications.The choice of the best elastomers and suitablecarcass fabrics, plied together for adequate strengthand flexibility can be assured through properengineering.

Calculating Lift from Degrees of Incline Calculating Belt Weight.375 lbs. per sq. ft. per 1/16” thickness.

Calculating Feet per RollFeet = D2 - d2

15.3T D is outside diameter of roll (in inches). d is core diameter (in inches). T is belt thickness (in inches).

Calculating Belt ThicknessCover Thickness + Carcass GaugeBelt Thickness

Calculating Roll Diameter .325 √T x L

T is Belt Thickness (in inches) L is Belt Lengths (in feet)


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BELT CALCULATOR

ROLL CALCULATOR

Conveyor Belt Calculatorsare just the tool for complete conveyor design. Easyto use, these little “gems” will “check you out” formost jobs. Call 1•800•633•1470 to receive your’sFREE and for instant computer help on designproblems.


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Carcass AWT* 150 180 225 220 270 330 360 440 550 300 450 600 800 1000

No. of Plies 2 2 3 2 3 3 4 4 5 2 3 3 4 5

Fabric Wt. 75# 90# 75# 110# 90# 110# 90# 110# 110# 150# 150# 200# 200# 200#

*Allowable Working Tension per inch of belt carcass width.

Min. Pulley Diameter

80% Tension 14 15 16 16 17 18 19 20 26 18 22 24 30 48

60% Tension 12 13 14 14 15 16 17 18 24 16 20 20 24 42

Min. Width for Troughing

20° Idlers 14 18 24 24 24 24 27 30 30 24 30 36 42 48

35° Idlers 18 20 24 24 24 24 27 30 36 24 30 36 42 48

45° Idlers 18 24 30 30 30 30 33 36 42 30 36 42 48 54

Max. Bucket Projection Grain 5 6 7 6 7.5 9 9.5 10 11 9 10 12 18 20Industrial 4 4.5 5 6 7 8 8.5 9 10 8 9 11 16 18

Flexco Fasteners

Plate 140 140 140 140 190 190 BR10 BR10 BR10 190 BR10 BR10 BR14 *VULC.

Hinge R2 R2 R5 R2 R5 R5 R5 R5 R51⁄2 R5 R5 R51⁄2 R6 RAR8*Vulcanize

Max. Take-up Travel Fasteners Vulcanized

Screw 1-1/2% 4% Gravity 2% 2-1/2% + 2 ft.

Cube Ft. Wt. Max. Width for Load Support Under 40 lb. 36 42 54 48 54 60 66 72 84 54 60 72 84 9641 to 80 lb. 30 36 42 36 48 54 57 60 72 48 60 60 72 84 81 to 120 lb. 30 36 42 36 42 48 54 60 72 42 54 60 72 84Over 120 lb. - - 36 30 36 42 46 54 60 36 48 54 60 72

Belt Modulus Per Inch of Width

X 1000 10.4 14.4 15.7 16 21.6 24 28.8 32 40 20 30 40.2 53.6 67

Belt Carcass Data

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31

32

33

35

36

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38

61

76

93

95

Tensile Elongation Modulus Durometer Specific Compounds (psi) (%) (300%) (hardness) Gravity

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

- CHLOROBUTYL - BLACK 1900 650 950 65 1.14 400º Hot Material

- TAN NATURAL 2400 775 400 46 1.22 Non-Marking

- RMA GRADE I 3050 580 1500 64 1.14 Cut and Gouge Resistant

- RMA GRADE II/X-TRA 2400 640 1100 60 1.14 General Purpose SBR

- HIGH TEMPº/SBR 2700 580 1300 63 1.14 300º Heat Resistant

- MOR 2400 600 1100 62 1.15 Moderately Oil Resistant

- HYFLEX 3000 630 1300 65 1.14 High Flexibility Abrasion Resistant

- LOW TEMPERATURE 2590 560 1300 63 1.14-80º F. Polar Bear

- MSHA/ABRASION 2100 525 1000 65 1.25 ABOVE and BELOW Ground Service

- MSHA/SBR #28-53/9 1800 540 1000 66 1.38 Underground Mine Service

- MSHA/NITRILE #28-58/10 2000 500 1100 65 1.35 Coal Prep & Grain

- MSHA/CLIMATIC #28-53/8 1600 450 1150 70 1.37 High Altitude & Ulta-Violet Resistant

- WASTE TREATMENT 2200 510 1100 62 1.16 Municipal Disposal Service

- ALUMINA 3000 550 1300 65 1.17 Desiccation Resistant

- NITRILE - BLACK 1600 500 1150 62 1.25 350º Hot Asphalt

- CHLOROBUTYL - WHITE 1600 520 1020 65 1.36 400º Hot Material

- GRADE II / BELTMASTER 2400 640 1100 60 1.14General Purpose SBR

- PRC GRADE II / X-PORT 2400 640 1100 60 1.14General Purpose SBR


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New conveyor belt should be stored upright in the factory package until used, preferably on a drysurface. Block it safely so it can’t accidentally roll or tip over. Do not lay on its side or lean against a wall!Keep belting out of direct sunlight or where ozone is present as it will deteriorate exposed rubber overtime. Belts should not be stored in excessively wet places or in areas where oils, acids, and other chemicalsare present. Motor-control rooms, welding shops, and other places where ozone is generated should like-wise be avoided.

Excessive temperature variations should also be avoided and can have an adverse effect on a belt overtime. Low temperatures or prolonged storage can harden or stiffen the compounds. If installed in thisstiffened state, the belt may not train well until it adjusts or “warms up” to the system.

During longer periods of storage, heavier rolls weighing more than 10,000 lbs. should be placed in anA-Frame or if left standing, rotated a quarter turn every three months to avoid “flat spots” from its ownweight.

Do Not Lay on End!

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Factory packaging is designed to protect your conveyor belt during normal shipping and handling.When your belt arrives, be careful unloading it. Don’t drop or handle it roughly as this could break thepackaging and cause the belt to telescope. Once “scoped” it is nearly impossible to re-roll.

Do not roll the slab. If there is no other way to move the belt, then roll it in the direction the belt iswound. Rolling in the opposite direction can cause it to loosen and telescope.

The optimum way to move a belt is to slip a sturdy hoisting bar through the center core. Then, lift thebelt with a spreader bar with chains or strong cables. Protect the belt edges against rubbing by using aspreader bar that is wide enough or with wood planks/old belting next to chains or cables.

SpreaderBar

Core Bar

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Mount roll of belting on a suitable core bar for unrolling and threading on to the conveyor system.Conveyor belting is normally rolled at the factory with the carrying side out. Consequently, whenmounting the roll the belt must lead off the top of the roll if it is being pulled onto the troughing idlersbut off the bottom of the roll if it is being pulled on to the return side.

In certain cases, where head room does not permit maneuvering of a roll, the belt may have to bepulled off the roll and “reefed”. Extreme care should be exercised to see that the loops have large bends toavoid kinking or undue strain on the belt, and no weight should ever be placed on the belt when in thisposition or the belt can be lain on a turn table with a vertical spindle. The belt will make a 90º twist as itis spun off. In this procedure, care must be exercised to avoid excessive abrasion to the belt edges.

No Weight ToBe Placed On Top

Keep Bends Large ToPrevent Breaking Carcass

Belt Reefing

Spindle Method

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Training of a conveyor belt is the process of adjusting idlers, pulleys, and loading conditions in amanner which will correct any tendency of the belt to run other than centrally. Once installed on theconveyor, problems of design, manufacture, erection, and other abnormalities become apparent. All toooften these conditions are considered “belt problems”.

If designed, manufactured, slit and cut properly, the belt will “go where directed” by the conveyorsystem as designed and built. The conveyor belt serves as an indicator and should be so regarded. Rarelyis a belt at fault and is more likely reacting to a structural defect or maladjustment to the system.

alleviates this condition since all products are made to width, not slit from a slabwhere “camber” can occur.

When all portions of a belt run off through a part of the conveyor length, the cause is probably in thealignment or leveling of the conveyor structure, idlers, or pulleys in that area. If one or more portions ofthe belt run off at all points along the conveyor, the cause is more likely the belt itself, in the splice or inthe loading of the belt. When loaded off-center, the center of gravity of the load tends to find the centerof the troughing idlers, thus leading the belt off its lightly loaded edge.

IT IS IMPORTANT TO REALIZE THAT BELT TRACKING IS A SYSTEM PROBLEMAND SHOULD BE APPROACHED FROM A SYSTEMS POINT OF VIEW!

Effects of Off-Center Loading

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THE BASIC PRIMARY RULE WHEN TRACKING A CONVEYOR BELT IS SIMPLE:

THE BELT MOVES TOWARD THAT END OF THE

ROLL/IDLER IT CONTACTS FIRST!

Initial installation of conveyor equipment should ensure proper alignment of all pulleys, troughingand return idlers, i.e., and should be placed at right angles to the direction of belt travel, leveled andcentered on a straight line.

The best procedure in starting the training sequence is to start with the return run and work toward the tail pulley:

1 Move from idler to idler in direction of belt travel.

2 Shift only one idler at a time. Shifting subsequent idlers may cause over correction.

3 Make slight adjustments rather than extreme ones.

4 Wait for at least 2 or 3 revolutions before making further adjustments.

5 Try never to adjust pulleys for belt training.

6 Apply the “Handle Bar” method to each of these indicators. This will help ensure early centering of the belt on the tail pulley so that it can be centrally loaded.

If the empty belt troughs readily, not erratic, training should be complete. Should the belt tend towardstiffness and erratic running, place some load onto the belt. The added weight will help control the beltand aid during “Break-In”.

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Transverse Stiffness Correct Troughing

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Receiving material off center will cause the belt to move sideways after loading as the center of theload seeks the lowest point in the troughing idlers. This can be corrected by proper chute arrangementprovided, of course, that the belt is centered as it enters the loading point.

The loading point of any conveyor is nearly always the critical point, the life determining point of thebelt. Here the conveyor receives its major abrasion, and practically all of its impact. The “ideal condition”is to have the material pass from chute to belt at the same speed and direction of travel as the belt with aminimum amount of impact.

The width of the receiving end of the loading chute should be great enough to accept material lyingon the extreme edge of the preceding belt or feeder, and its position determined by the trajectory of thematerial coming into it. At no place should the chute be less than twice the size of the largest lumps, iffines are present, and 3-1/2 times the size of lumps, if uniform. The discharge width of the chute thusdetermined should not exceed about 2/3 of the receiving belts width.

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Simple Conveyor Loading Points


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The slope of the chute is determined by the nature of the material, its entering velocity and length ofthe chute. This value varies with each particular installation, but about 35 degrees has been foundsatisfactory for most dry industrial materials such as rock and coal. An attempt to approach the above“ideal condition” should be made continually by adjusting the chute arrangement. Optimum loading andtransferring through chutes still requires considerable experimental adjustment in the field.

Skirt boards should be used to further center and settle the load as it leaves the loading point. Thesteel structure of the chute and skirts never should be placed closer to the surface of the belt than 1''.This distance to be made increasing in the direction of belt travel to free any material trapped betweenthe belt surface and the skirt. Skirt boards are usually 4 or 5 times the belt width in length, but may varyconsiderably due to belt speed, type of material and lump size.

BA C

1'' Minimum Increasing in direction of travel

Usually4 to 5 x Belt

Width

Variable Variable VariableIdler Idler IdlerAngle Angle Angle

Skirtboardrubber heldin compression

Skirtboardrubber heldin compression

Skirtboardrubber Backup Plate

Backup PlateBackup Plate

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Sample Skir tboard Arrangements

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20º

Most conveyor belts carrying “free flowing” materials operate over troughed idlers. The troughingangle of these idlers will usually vary from 20 to 45 degrees... and beyond. The trough-angle affects thebelt by creating a line along which the belt is constantly flexed. The greater the trough angle, thegreater the flexing action. When the belt is fully loaded, the portion of the load (X) directly over theidler junction gap forces the belt to flex to a shorter radius. The heavier the load, the smaller the radiusthrough which the belt must flex. Further, at higher troughing angles (like 45 degrees), gravitational forceis exerted on the portion of the belt in contact with the wing idler. All these forces are trying to pull thatbelt down into that idler junction gap.

Consequently, consideration must be given to designing the belt with sufficient transverse rigidity andflex life so that for a given idler angle and load weight, premature belt failure will not occur. This is doneby designing the belt with sufficient transverse stiffness to “bridge” the idler junction gap with asatisfactory radius.

This specification is detailed in the “load support” engineering section, page 64. The load supportnumber refers to the maximum width possible for a given belt construction at a given troughing anglecarrying material of a specific density.

Single-plied belt constructions do well on idler sets up to and including 35 degrees. Plied constructionsare generally thicker for a given belt tension rating, and therefore, appear to perform better on 45 degreetroughing idler sets.

Differential in Radius Between Idlers Proper Bridging of Idler Junction

45º

Improper Bridging of Idler Junction


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Transition distance is defined as the distance from the center line of the first fully troughed idler sys-tem to the center line of either the head or tail pulley. The geometry of the situation, causes the edge ofthe belt to be stretched since it is following the hypotenuse of a right triangle. The distance from thepulley to the top of the wing roll is greater than the distance from the pulley to the center roll of thetroughing set. If the transition distance is too short, the edge of the belt can be over-stretched. This willadversely affect the load support and belt life. A good rule of thumb regarding transition distance is:

20-27 degree troughing systems - - - times belt width.

35 degree troughing systems - - - - - times belt width.

45 degree troughing systems - - - - - times belt width.

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Transition distance is defined as the distance from the center line of the first fully troughed idler system tothe center line of either the head or tail pulley. The geometry of the situation, causes the edge of the belt tobe stretched since it is following the hypotenuse of a right triangle. The distance from the pulley to the topof the wing roll is greater than the distance from the pulley to the center roll of the troughing set. If thetransition distance is too short, the edge of the belt can be over-stretched. This will adversely affect the loadsupport and belt life. A good rule of thumb regarding transition distance is:

Belt Width x 3 x 4 x 5

20º35º

45º

20º45º

35ºTroughing Idlers

Belt Edge

Tangent to

Top of Pulley

Trough

Transition for 100% AWT with Belt Centered on Tangent

THE TRANSITION DISTANCES SHOWN WILL ACCOMMODATE VIRTUALLY ALLBELT CONSTRUCTIONS, INCLUDING CABLE BELTS. MOST BELTS,

PROPERLY INSTALLED, WILL GIVE MANY YEARS OF . . .

TROUBLE – FREE SERVICE!

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45º35º 20º

If a particular conveyor system has shorter transition distances than those above, there aremodifications to the system that can help reduce the stress on the belt:

Elevate the terminal pulley in the system relative to its heightverses the center roll of the troughing idlers in the system.

Remove first high angle idler in the transition area and use a variable angle troughing idler, “adjust” it to support the belt without added stress.

A

B

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This differential in distance creates higher tensions in the edge of the belt than the center of the belt, which can create belt problems.

The most common of these problems are:

If transition is too short at the head pulley: Idler junction gap failure.Splice failure (from the outside in). Belt folding up in the center and folding over on itself.

If transition is too short at the tail pulley: Splice failure (from the center out). Premature wear or failure in the center of the belt.


The smallest pulley diameter the belt will encounter in the conveyor system is a primary considerationin selecting the proper conveyor belt. When a belt travels around a pulley, the outer plies of the carcasstraverse a greater distance than the inner plies. It is important that as the belt wraps around that pulley,under tension, the stress in the belt is below the fatigue limit of the bond between the belt components.Over stressing the belt, particularly the bond between the individual plies and the skim, can result in plyseparation and premature belt failure... especially, at the belt splices.

In some applications, due to system limitations, smaller than recommended pulleys may be used. Thiswill affect the service life of the belt and will result in more frequent splice replacements. A given beltconstruction has a characteristic “flexibility” in the lengthwise direction.

In most applications where a mechanical fastener is used to splice the belt, the minimum recommendedpulley diameter for the fastener will be the limiting factor. This by virtue of the fact that rubber and fabricis more flexible than metal. Also, it should be noted that if a conveyor system utilizes a wing typeterminal pulley, that pulley should be 25% greater in diameter than the minimum pulley diameternormally recommended.

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Accurate squaring of the belt ends prior to lacing is essential to correct belt tracking and helpsdistribute stress evenly throughout the joint. It is important to note that belt ends are not necessarilysquare when they are shipped. Further, the width-wise fabric wales are not necessarily square to the belt’slongitudinal axis. These cannot be used as guides to cut the belt ends.

TO PROPERLY SQUARE THE BELT ENDS, USE THE CENTER LINE METHOD.

To establish the belt center line, start near the belt end as shown. Measure the belt width at five pointsapproximately 10” apart. Divide each measurement in two and mark the center points.

Using these five “center points” draw the resultant “average” center line. Next, using a carpenter squareor “T” square, draw a “cut line” across the width of the belt near the belt end as shown. It is also a goodidea to mark several right angle reference lines across the belt surface for use as guidelines later on.

Using the “cut line” as the guide, cut off the end of the belt with a razor knife. Make sure that the cutis clean and vertical. This operation should then be repeated on the other end of the belt. *Keep in mindthat the final belt length may need to include an allowance for such things as diagonal splice, skive taperlength, skive overlap, fastener extension, etc. . . . depending upon what kind of splice is being performed.

BELT CENTERLINE.

MARKING OFCUT-LINE AND OTHER RIGHT ANGLE GUIDE LINES.


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TEN BEST PRACTICES

On a properly engineered, well maintained conveyor system, a vulcanized splice performed correctly should last for many years and in some cases last the life of the belt. Utilizing and understanding these TEN BEST PRACTICES in conveyor belt splicing is the best way to assure the success andperformance of your splice.

1.) PROCESS CONTROL OF VULCANIZING TEMPERATURE TIME, AND PRESSURE IS CRITICAL.

Thermocouples provide precise temperature monitoring at the platen-belt interface. Thermostats on many vulcanizers do not indicate the actual temperature. Without precise monitoring, the temperaturecan fluctuate drastically, resulting in a splice that is either “over or under cured”. Either condition will limit the life of the splice. Top splicers will use such thermocouples to monitor and gather cure temperature data. A record of this data can then be supplied to to assure that the curing process was performed properly.

2.) USE PROPER KNIVES AND SKIVING TECNIQUES TO AVOID NICKING OF FABRIC PLIES.

Nicking the adjacent fabric plies with a knife effectively reduces the tension rating of the belt carcassbecause the tension members (warp cords) are disabled if they are cut or nicked. Use quality tools such as single-ply knives designed specially for this procedure.

3.) PERFORM MINIMAL BUFFING OF THE EXPOSED FABRIC PLIES.

The fabric plies of all belts are coated with RFL (resorcinol-formaldehyde-latex) or other special coatings to enhance the adhesion of the rubber to the fabric. These dip coats should not be buffed off when preparing the belt splice or reduced ply and cover adhesion will result. If residual rubber must be buffed off after stripping down the step, it must be done carefully so that the buffer wheel does not actually touch the fabric. Severe overbuffing will reduce belt strength and integrity by damaging both the warp and fill cords. Buffer wheel should not exceed 2000 RPM.

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ALLOW CEMENTS TO DRY COMPLETELY BEFORE ASSEMBLING AND CURING THE SPLICE.

When a belt splice is assembled and cured before the cement has had sufficient time to dry, the heat from the vulcanizer will cause the solvents and carriers in the cement to vaporize and form bubbles. If the surface area of these “ply or cover blows” is large enough, the strength of the splice is severely limited. Ply separations can also occur when cements and solvents are not allowed to come up to room

temperature after removal from cold storage because of water condensation occurs on cold surfaces. Additionally, try not to accelerate the drying process by using heat guns or hair dryers that can cause a “skin” to form on the surface of still wet cements. Space heaters can be used to accelerate the drying time provided safety is not compromised in any way.

5.) AVOID OVERPRODDING THE FABRIC WHEN LIFTING THE PLIES.

Use the right tools and methods to assure that the fabric plies are not damaged when they are lifted. Prodding tools should have smooth, rounded corners. Do not use screwdrivers!

6.) USE SPECIFIED STEP AND FINGER LENGTHS.

When step lengths are shortened by more than an inch or two to accommodate vulcanizers that are not large enough for the job, splice strength and integrity is severely reduced. It is recommended to cure the splice in one heat, but if the vulcanizer is too short to cure the splice then multiple heats can be used as long as the fill-in strips are completely cured in a single heat. See pages 83-84 for splice dimensions/recommended cure rates or contact Technical Support for further informtion &

WORK CLEAN TO HELP ASSURE A CLEAN ASSEMBLY.

Experience has shown that almost anything can end up inside a vulcanized splice from sand, rocks, trash, even work gloves left on the inside of failed splices. For these reasons, the splicing work area must be clean and protected. Tents, awnings, tarps, or temporary plywood walls and ceilings should be used depending on the particular circumstances or where conditions allow. These added measures will help avoid contamination in the splice.

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guidelines: 1•800•633•1470.


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NEVER USE CEMENTS OR TIE GUMS THAT ARE OUT OF DATE.

Universal Splice Materials are manufactured to the highest standards. Part of this quality control comes from our custom mixing division, . There, materials are produced and recorded by date, and then refrigerated to ensure maximum freshness and longevity. Splice materials should never be stored in sunlight, hot-humid conditions or left in a prolonged state at room temperature. When unused materials reach life limits, dispose of properly in accordance with federal, state, and local ordinances.

USE CORRECTLY SPECIFIED GUMS & CEMENTS.

For best adhesions and splice longevity, conveyor belts should be spliced with our Universal Splice Materials. The same compounds and stocks used in the production of our belt lines are supplied to our customers to assure complete compatibility and highest performance. Even with ourmaterials, care must be observed to ensure that the correct gums and cements are used. For complete cross reference/splice recommendations, please refer to page or call Technical Support: 1•800•633•1470.

ALIGN THE SPLICE SQUARELY AND PROPERLY.

Splices that are not aligned cause many problems! Tracking and training problems can frequently be traced back to splices that are not square. Additionally, splices that are out of square do not distribute the tension load evenly across the splice, which can cause premature splice and belt failure.

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When the “TEN BEST PRACTICES” in conveyor belt splicing previously referenced are incorporated into your S.O.P. and the system is properly engineered and well-maintained, a dependable, long splice life can be achieved.

PLIED BELTING VULCANIZED SPLICE DIMENSIONSStep Fill-In Overall Splice ''Outer''

Belt No. of Length Length Length (in) Ply JointStyle Plies (Inches) (Inches) w/o bias angle Type

2-180 2 6 4 10 Butt2-220 2 8 4 12 Butt2-250 2 10 4 14 Butt2-400 2 15 4 19 Butt2-500 2 18 4 22 Butt2-600 2 20 4 24 Butt3-330 3 8 4 20 Butt3-375 3 10 4 24 Butt3-450 3 12 4 28 Butt3-600 3 15 4 34 Butt3-750 3 18 4 40 Butt3-900 3 20 4 44 Butt4-440 4 8 4 28 Butt4-500 4 10 4 34 Butt4-600 4 12 4 40 Butt4-800 4 15 4 49 Butt4-1000 4 18 4 58 Butt4-1200 4 20 4 64 Butt5-550 5 8 4 36 Butt5-750 5 12 4 52 Butt5-1000 5 15 4 64 Butt5-1250 5 18 4 76 Butt5-1500 5 20 4 84 Butt


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Because most conveyor belt splicing is done on the job, portable, electrically-heated, vulcanizers areused. Curing time depends on belt thickness, rubber compound, and type of vulcanizer being used. Thefollowing chart of curing times can be used for either splice or repair work:

CURING TIME FOR CONVEYOR BELTING

GRADE I & II NITRILE OR NEOPRENE BUTYL (EPDM)

(IN MINUTES AT 287 deg. f) (IN MINUTES AT 287 deg. f) (IN MINUTES AT 287 deg. f)

Thickness of Belt 1 Heated 2 Heated 1 Heated 2 Heated 2 Heatedor Repair Depth Platen Platens Platen Platens Platens

3/16'' and less 34 23 50 37 451/4'' 38 24 52 37 465/16'' 42 26 53 40 473/8'' – 26 – 42 48

7/16'' Use 2- 27 Use 2- 43 481/2'' platen 28 platen 45 49

9/16'' press 29 press 47 505/8'' above 30 above 48 51

11/16'' 5/16'' 31 5/16'' 49 523/4'' – 32 – 50 52

Over 3/4'': Add 2 minutes for each 1/16” of additional thickness. *This curing schedule is intended for portable

vulcanizers under average field conditions. For Belt Repair Shops having permanent repair presses in heated

buildings, the time can be reduced 5 minutes from the schedule shown for Natural or SBR.

CURING TIME FOR BELT JOINT

Thickness of Belt Vulcanizer with Vulcanizer with Vulcanizer with Vulcanizer with2 Heated Platens 1 Heated Platen 2 Heated Platens 1 Heated Platen

3/16'' and under 18 24 37 501/4'' 19 26 39 525/16'' 20 28 40 533/8'' 21 31 42 577/16'' 22 31 43 571/2'' 24 31 45 579/16'' 26 31 47 575/8'' 27 31 48 57

11/16'' 28 31 49 573/4'' 29 31 50 57

Generally, vulcanizers are heated to 287 degrees F. After vulcanizer is clamped on the belt, platen tem-perature will drop. Let it return to 287 degrees before initiating recommended cure cycle. The curingtemperature (287 F.) must be maintained throughout time of vulcanization. If it drops, allow more curingtime; if it rises, a shorter time will do:

SBR/NATURAL RUBBER OIL PROOFLength of Heat - Minutes


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UNDERCURING / OVERCURING

Undercured rubber is soft and lacks resilience. To test: Press end of prodding tool into rubber. Ifindentation remains, rubber is probably undercured and additional time in vulcanizer is needed.Overcuring, up to a degree, is indicated by too much hardness as compared with rest of belt rubber.Extreme overcuring can cause softening (known as reversion) which becomes worse if further curing isattempted.

OVERLAPPING HEATS

When vulcanizer platens will not cover entire splice, two or more heats or “cooks” are necessary. Eachheat should overlap preceeding one about 1-1/2”. A common practice is to cure top cover fill-in first, thenproceed in overlapping steps toward bottom cover fill-in.

COOLING SPLICE

Rubber compounds lose tensile strength at temperatures used during vulcanizing. Therefore, allow beltsplice to cool to normal air temperature before maximum belt tension is applied. This is important whenoperating tensions are 80 to 100 percent of maximum permissible tensions.

BLOW-UPS / BLISTERS

A blow-up or blister that appears when platens are removed is caused by moisture in the belt or bytrapped air in new material. Moisture may be water that was in the belt carcass, or in the solvents beingused in cleaning off skimcoat rubber. To prevent blow-ups, allow vulcanizer platens to cool below steamtemperature (212 degrees at sea level) before releasing platen pressure. If a blow-up or blister does occur,repair work must be done in affected area. Simply reapplying vulcanizing heat and pressure will notremedy the condition as cement and tie gum already have been fully “cooked” and further curing willnot cause them to adhere.


TTRROOUUBBLLEE SSHHOOOOTTIINNGG

PROBLEM CAUSE: in order of probable occurrence.

Conveyor runs to one side at given point on structure.

Particular section of belt runs to one side at all points on conveyor.

Belt runs to one side for long distance or entire length of conveyor.

Belt runs off at tail pulley.

Belt runs off at head pulley.

Belt slip.

Belt slip on starting.

Excessive belt stretch.

Grooving, gouging or stripping of top cover.

Excessive top cover wear, uniform around belt.

Severe pulley cover wear.

Longitudinal grooving or cracking of bottom cover.

Covers harden or crack.

Cover swells in spots or streaks.

Belt breaks at or behind fasteners; fasteners pull out.

Vulcanized splice separation.

Excessive edge wear, broken edges.

Transverse breaks at belt edge.

Short breaks in carcass parallel to belt edge, star breaks in carcass.

Ply separation.

Carcass fatigue at idler junction.

Cover blisters or sand blisters.

Belt cupping- new belt.

Belt cupping - old belt (was OK when new).

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6 7

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39 10 1

34 31 33

18 25 26

29 30 23

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33 10 1 3

13 14 15 16

4 10 9 33

24 22 12 23

8 10 40 7

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34 33 31 10 4

19 20 10 8 36

38 30 12 17 25

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41 42 43 12 32 35

4 9 10 17 11 27

25 26 27 28 29 36



Idlers or pulleys out-of-square with center line of belt: readjust idlers in affected area.

Conveyor frame or structure crooked: straighten in affected area.

Idler stands not centered on belt: readjust idlers in affected area.

Sticking idlers: free idlers and improve maintenance and lubrication.

Buildup of material on idlers: remove accumulation; improve maintenance, install scraper or other cleaning devices.

Belt not joined squarely: remove affected splice and resplice.

Bowed belt: for new belt this condition should disappear during break-in; in rare instances belt must be straightened or replaced; check storage and handling of belt rolls.

Off-center loading or poor loading: adjust chute to place load on center of belt; discharge material in direction of belt travel at or near belt speed.Slippage on drive pulley: increase tension thru screw take up or add counterweight; lag drive pulley; increase arc of contact.

Material spillage and buildup: improve loading and transfer conditions; install cleaning devices; improve maintenance.

Bolt heads protruding above lagging: tighten bolts; replace lagging; use vulcanized-on lagging.

Tension too high: increase speed, same tonnage; reduce tonnage, same speed; reduce friction with better maintenance and replacement of damaged idlers; decrease tension by increasing arc of contactor go to lagged pulley; reduce Counterwight to minimum amount.

Skirt boards improperly adjusted or of wrong material: adjust skirt board supports to minimum 1” between metal and belt with gap increasing in direction of belt travel; use skirt board rubber (NOT OLD BELT)!Belt spanking down under load impact: install cushion idlers.

Material hanging up in or under chute: improve loading to reduce spillage; install baffles; widen chute.Impact of material on belt: reduce impact by improving chute design; install impact idlers.

Material trapped between belt and pulley: install plows or scrapers on return run ahead of tail pulley.

Belt edges folding up on structure: same corrections as for 1, 2, 3; install limit switches; provide more clearance.Dirty, stuck, or misaligned return rolls: remove accumulations; install cleaning devices, use self-cleaning return rolls, improve maintenance and lubrication.Cover quality too low: replace with belt of heavier cover gauge or higher quality rubber.

Spilled oil or grease, over-lubrication of idlers: improve housekeeping; reduce quantity of grease used; check grease seals.Wrong type of fastener, fastener too tight or too loose: use proper fastener and splice technique; set up schedule for regular fastener inspection.


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Fastener plates too long for pulley size: replace with smaller fastener; increase pulley size.

Improper transition between troughed belt and terminal pulleys: adjust transition in accordance

with engineering, pages 74-75 .

Severe convex (hump) vertical curve: decrease idler spacing in curve; increase curve radius.

Excessive forward tilt of trough rolls: reduce forward tilt of idlers to no more than 2 degrees from

vertical.

Excess gap between idler rolls: replace idlers; replace with heavier belt.

Insufficient transverse stiffness: replace with the proper belt.

Pulleys too small: use larger diameter pulleys.

Counterweight too light: add counterweight or increase screw take-up tension to value determined

from calculations.

Counterweight too heavy: lighten counterweight to value required by calculations.

Pulley lagging worn: replace pulley lagging.

Insufficient traction between belt and pulley: lag drive pulley; increase belt wrap; install belt

cleaning devices.

System underbelted: recalculate belt tensions and select proper belt.

36. Excessive sag between idlers causing load to work and shuffle on belt as it passes over idlers:

increase tension if unnecessarily low; reduce idler spacing.

Improper storage or handling: refer to pages 66-67 for proper storage and handling instructions.

Belt improperly spliced: resplice using proper method as recommended by .

Belt running off-center around the tail pulley and through the loading area: install training idlers

on the return run prior to tail pulley.

Belt hitting structure: install training idlers on carrying and return run.

Improper belt installation causing apparent excessive belt stretch: pull belt through counterweight

with a tension equal to at least empty running tension; run belt in with mechanical fasteners.

Improper initial positioning of counterweight in its carriage causing apparent excessive belt stretch:

contact for recommended initial position.

Insufficient counterweight travel: contact for recommended minimum distances.

Structure not level: level structure in affected area.

Cover cuts or very small cover away from carcass: make spot repair with vulcanizer or self-curing repair material.

Excessive cover gauge ratio: use a belt with a lower gauge ratio and/or a thicker carcass. 46

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