ENHANCE THE REPLACEMENT PROCEDURE OF BILLET MILL VERTICAL STAND INCLINED UNIVERSAL SHAFT

MOHAMMED.SAMEER

ABSTRACT

Billet mill vertical stand(BV3) in Light & medium merchant mill are provided with inclined universal shaft to transmit power from bottom to top gear box.

During replacement of universal shaft , difficulties are being faced. While fixing or removing the bottom flange from the bottom gear box. Like insufficient gap between top & bottom gear boxes, inclination of

universal shaft, flange, insufficient closing of universal shaft. This leads to the inordinate delay in replacing the shafts causing the

wastage of resources and human power or machine. In this project the existing procedure for replacement of inclined universal

shaft has been studied and analyzed. The suitable measures are suggested to minimize the difficulties being

faced during fixing of the shaft. Thus delay in replacement of universal shaft can be minimized. The cost saved by following the new method was found by cost benefit

analysis.

INDEX 1. INRODUCTION ABOUT VISAKHAPATNAM STEEL PLANT 2. LAYOUT OF VISAKAPATNAM STEEL PLANT 3. MAJOR UNITS 3.1 RAW MATERIAL HANDLING PLANT 3.2 COKE OVEN 3.3 SINTER PLANT 3.4 CALCINING AND REFRACTORY MATERIAL PLANT 3.5 BLAST FURNACE 3.6 STEEL MELTING SHOP 3.7 LIGHT AND MEDIUM MERCHANT MILL 3.8 MEDIUM MERCHANT AND STRUCTURAL MILL 3.9 WIRE ROD MILL 4. INTRODUCTION ABOUT LMMM 5. BILLET MILL VERTICAL STAND 6. ROLLING THEORY 7. INCLINED UNIVERSAL SHAFT 8. PROBLEM FACED IN EXITING PROCEDURE 9. IMPROVED METHOD 10. COST BENEFIT ANALYSIS 11.CONCLUSION

INTRODUCTION Name of the Company: Rashtriya Ispat Nigam Limited. Company Identification: U27109AP1982G01003404 Number (CN). Date of Incorporation: 18th February 1982 Mode of Incorporation: Incorporated as a Government Company under the provisions of

the Companies Act, 1956 Administrative Ministry: Ministry of Steel Govt. of India. Present Status: A Govt. Company within the meaning of Section -617 of the Share Capital: Authorized Equity Share Capital: Rs.4, 890 Crores Preference Share Capital: Rs.3, 110 Crores --------------------- Total: Rs.8, 000 Crores -------------------- Subscribed, Issued Rs.7, 827.32 Crores and paid up capital Present Share holding. : The entire Share Capital is held By President of India. Address of Registered Office: Rashtriya Ispat Nigam Limited Visakhapatnam Steel Plant Administrative Building Visakhapatnam —530 031

LAYOUT OF VISAKHAPATNAM STEEL PLANT

MAJOR UNITS

RAW MATERIAL HANDLING PLANT: The Raw Material Handling Plant (RMHP) receives the basic raw materials. Required for the steel making process from various sources through

railway wagons and by road. These raw materials are sent to various departments as indicated below: Sinter Plant: Iron Ore Fines, Lime stone (BF), Dolomite, Sand and LD slag. Blast Furnace: Sized Iron Ore, Limestone (BF)/ LD slag, Manganese Lump,

Quartzite and Coke. SMS: Dolomite (SMS), Sized Iron Ore. CRMP: Limestone (SMS), Dolomite (SMS). TPP: Crushed Boiler Coal. COCCP: Imported coking coal (ICC), Medium coking coal (MCC). The Raw Material Handling Plant is divided into two sections Coal

Handling Plant (CHP) and Ore Handling Plant (OHP).

COKE OVEN From the storage yard, the coking coal is sent to foreign material removing section

to remove foreign matter of above 150mm size. Iron traps for ferromagnetic articles and cylindrical screens are provided for this. The crushed and blended coal (74-78% of ñ3mm size) is conveyed to two coal

towers each of 4000 T capacity. Weigh bridges are provided under coal towers to weigh the coal charge. The prepared coal charge in the coal tower is drawn by a charging car on the top of

the batteries and charged into the ovens as per sequence.

SINTER PLANT Sintering is a process of Agglomerating iron ore fines into a porous mass by

incipient fusion caused by combustion within the mass of the ore particles. Sintering being one of them and widely in integrated steel plants. Sinter plant of VSP has the capacity to produce 5.256 MT of sinter per annum,

which will cater for 80 % of Iron bearing feed to Blast furnace. Sinter machine is designed to operate at the rate of 1.2 T/hr/M2 for 330 days in a

year.

CALCINING AND REFRACTORY MATERIAL PLANT

This plant plays a significant role in the manufacturing of liquid steel. The main customer of CRMP is Steel Melting Shop (SMS). CRMP has two units. Calcining Plant Brick Plant Calcining plant produces lime and calcined dolomite, which are used for refining of

hot metal to steel in the converter. This plant has 5 rotary kilns of 325 tons/day capacity. Limestone is procured from Oman & Thailand and Dolomite (SMS grade) from

Madharam mines of VSP. The size of both the raw materials is (25 - 60) mm.

BLAST FURNACE There is a furnace into which, the iron ore and the coke are charged from the top

through conveyors. These conveyors discharge the material at the top of the blast furnace, which is

nearly 33100mm height. In the furnace, the iron ore turns to the metallic molten iron. This molten iron flows from the bottom of the hearth of the furnace. This is carried to the steel melting shop, where this iron is converted into the steel

through oxidation process. Production Capacity – 3.4 MT of Hot Metal per annum.

STEEL MELTING SHOP The liquid steel obtained from LD process is cast into Blooms through Continuous

Casting Machines (Bloom Casters). Steel Melting Shop is divided into two major sections. Converter Shop Continuous Casting Shop

LIGHT AND MEDIUM MERCHANT MILL

Visakhapatnam Steel Plant has three sophisticated Rolling mills. designed to produce 2.656 million tons per annum of finished products. Light and Medium merchant will is designed with the operation floor on a second

elevation, namely +5.0 mts. Facilities: 7 Stand Break-Down Mill 8 Stand Roughing Mill 5 Stand intermediate Mill (2 Strand rolling) 2*4 Stand Finishing Mill (Single Strand rolling) 6 nos. of 4-Stand Continuous Bloom casting machines A Mill of 0.710 MT per annum production capacity.

MEDIUM MERCHANT AND STUCTURAL MILL

The Medium Merchant and Structural Mill (MMSM) is one of the modern rolling mills of Visakhapatnam Steel Plant.

It is the third and last rolling mill as per the rationalized concept. This is a single strand continuous mill having production capacity of 8,

50,000T/year. MILL PROPER: Roughing mill: Roughing mill train consisting of 8 stands. Intermediate mill: Intermediate mill train consists of 6 stands. Finishing mill: Finishing mill train consists of 6 stands.

WIRE ROD MILL

The Wire Rod Mill of VSP is high speed 4 strand No-Twist continuous mill designed to produce 8,50,000 T of wire rod coils.

The mill is designed to produce plain wire rods from 5.5 mm to 12.7 mm dia and Rebar in 8mm, 10mm and 12mm diameter in coil form.

However sizes up to 14mm are being rolled presently. The mill is constructed at an elevated level of +5350mm. Facility• 7 Strand Roughing Mill (4 Strand rolling)• 6 Strand Intermediate Mill (4 Strand rolling)• 4*2 Strand Pre-finishing Mill (Single Strand rolling)• 4*10 Strand Finishing Mill (Single Strand rolling) A Mill of 0.85 MT per annum production capacity.

INTRODUCTION OF LMMM In Light Medium Merchant Mills (LMMM) the blooms of size 320x250mm.

heated to temperatures around 12000c and rolled into different Categories of bars and billet.

MAJOR FACILITIES: Charging grid. Furnace.

The LMMM consisting of Billet mill Bar mill

MILL CONFIGURATION

Billet mill Stand no. 1 2 3 4 5 6 7 Configuration: H H V H V H V

Bar mill Roughing mill: 1 2 3 4 5 6 7 8 Configuration: H H H H H H H H Intermediate mill: 9 10 11 12 13 14 15 16 17 18 Configuration: H H V H H H H V H H Finishing mill: 19/1 20/1 21/1 22/1 19/2 20/2 21/2 22/2 Configuration: V H V H V H V H

LMMM TECHNICAL DATA Billet mill capacity: 1.7 MT/YEAR Bar mill capacity: 8,50,000 T/YEAR

Products:1. Plains(14-36mm), 2. Rebars(14-36mm) Yield: 94% Sp.Fuel consumption: 340 X 1,000 KCAL/T Sp.power consumption: 93.92 KWH Rolling rate: 222 T/HOUR

BILLET MILL VERTICAL STAND

It is used for vertical rolling. it consist of DC motor, horizontal and vertical gear boxes. here the drive from the motor is transmitted to the roll cassette through horizontal

average vertical gear box. MECHANISM OF VERTICAL STAND Electrical drive Gear box Universal shaft arrangement hydraulic arrangement rollers arrangement

TECHNICAL DATA OF VERTICAL STAND(BV-3) Roller diameter=730mm Types of gearing=Helical, Bevel Barrel diameter=730mm Barrel length=1000mm Material of roll bearing=Ni Material of rollers=Alloy Forged Steel Type of drive=Variable frequency drive Number of rotation of roller=0.576m/s ROLLER DATA Life of the roller: 372000 tons set life Discard size (or)scarp size:650 mm Weight of roller:5.07 tons Number of passes: 3 (pass 1,2&3) Diameter of roller:730mm Diameter of passes in roller:570mm Length without bearing:1000mm Length with bearing:3160mm Material of roller: Alloy forged steel

TECHNICAL DATA OF VERTICAL STANDS

BV- 2 BV-3 BV-4

Groove shape Rectangular box shape

Box Rectangular box

DimensionW(mm)

289 224(after reduction)

236

Height(mm)

199 214 156

Area(mm)

53440 44000 33760

TECHNICAL DATA OF VERTICAL STANDS

BV- 2 BV-3 BV-4

ReductionIn %

21.2 17.7 23.3

Roll gap 39 54 12

Nominal Dia. of roller

850 730 730

Working(mm)

694 575 590

StockV(m/s)

0.476 0.576 0.75

ROLLING THEORY In metal working rolling in a metal forming process in which metal stock is passed

through a pair of rolls. Rolling is classified according to the temperature of the metal rolled. There are many types of rolling process. including ring. rolling bending. roll forming. profile rolling . controlled rolling.

TYPE OF ROLLING

Continuous rolling Transverse rolling Shaped rolling(or)Section rolling Ring rolling Power rolling Continuous casting and Hot rolling Thread rolling

SCHEMATRIC DIAGRAM OF FLAT ROLLING

DEFORMATION IN ROLLING Bloom Length(L0)=320mm Bloom Width(B0)=250mm Length of bloom=6.6m Weight of bloom=4092 kg

INCLINED UNIVERSAL SHAFT Inclined universal shaft have been used to transmit power to the vertical stands

present in the billet mill. Length of shaft(closed)=4540mm Diameter of the shaft=310mm Diameter of the flange=350mm Torque rating for spindle=3085KN.m Material of shaft=Cast iron

REASONS FOR REMOVAL OF INCLIND UNIVERSAL SHAFT FLANGE BOLTS

Inclined shaft failure. Bevel gear box failure. During the maintenance of the top gear box.

EXISTING PROCEDURE FOR REPLACEMENT OF INCLIND UNIVERSAL SHAFT REMOVAL: Hold the inclined the shaft at top using chain pulley block and sling. Open the bottom flange stud nuts and disengage the bottom flange from bevel

gear box hub. Hold the shaft with crane. Open the shaft top flange studs. Gradually lower the chain pulley block and takeout the shaft with crane.

FIXING:

Hold &lift the new/revisioned inclined shaft with EOT crane. Positing the shaft above the bevel gear box and hold it with CPB from top. Fix the top flange to the top gear box. Positing the inclined shaft bottom flange near to bevel gear box hub studs with

max pull to know the gap between the bottom flange & studs. Gas cut the studs for the required minimum gap by trial & error method. Slide the inclined shaft into the studs by lowering the chain pulley block and fix

the nuts.

PROBLEMS FACED IN EXISTING PROCEDURE:

Take more time in doing the job. Gas cutting of the bottom flange studs leading to the reduction in strength. Welding has to be done to ensure the proper locking which will lead to vibrations

of bottom gear box. EFFECTS OF TIME DELAY IN REPLACEMENT: Less effective utilization of manpower. Decrease in production and productivity. Increase in the physical labor. OBSERVATIONS: During fixing the universal shaft flange is fouling with bottom gear box studs due to

less gap between flange & studs.

It is due to The universal shaft is not closed fully. The bevel gear box has been in lifted condition compared to drawing

parameters to keep it in aligns with motor.

IMPROVE METHOD

Ensure that the inclined universal shaft is in completely closed condition as per the drawing(4540mm).

Arrest the universal shaft in closed condition using either maxpull or turnbuckle.

position the shaft above the bevel gear box and hold it with CPB from top. Fix the top top flange to the gear box. Position the inclined shaft bottom flange near to bevel gear box hub studs with

maxpull. Slide the inclined shaft into the studs by lowering the chain pulley block and fix

the nuts.

ANALSIS:

Distance between the shaft top flange and bottom gear box studs=4550mm Shaft length with existing procedure=4575mm Clearance=4550-4575 =-25mm Shaft length with improved procedure=4540mm Clearance=4550-4540 =10mm

BENEFITS OF MODIFICATION: Effective utilization of man power. Time saved on doing the work. Increase of employee morale. Increase in production and productivity. Improved safety in doing the job.

COST BENEFIT ANALYSIS:

PRODUCTION COST: Cost of production delay in billet mill/hr=1200000 approx Number of occurrences per annum=2 Time required to replace the shaft during existing method=6hr Time required to replace the shaft with improved method=4hr Time saved/occasion=2hr Saving due to improved method=4hr Saving= Rs 4800000/annum

MAN POWER COST:

Cost of man power/hr= Rs 140 approx Time saved by modified method=2hr Number of persons=6 Man power cost=Cost of man power/hr x number of persons x number of hours =140 x 6 x 2 =Rs 1680 Total man power cost = Number of incidents x man power cost =2 x 1680 =Rs 3360/annum.

TOTAL COST SAVED: Total cost saved=Production saving +Total man power cost =4800000 + 3360 =Rs 4803360/annum

CONCLUSION

In this project it is learnt that while replacing lengthy of this kind.

the design parameters are important to be considering and using suitable tackles.

such a shaft can be replaced with in scheduled time and subsequently.

production delay can be minimized.

The suitable measures are suggested to minimize the difficulties being faced during fixing of the shaft.

Thus delay in replacement of universal shaft can be minimized.

The cost saved by following the new method was found by cost benefit analysis.

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