CONTENTS

❖ INTRODUCTION ❖ EQUIPMENTS IN PICKLING LINE NO. 1 ❖ EQUIPMENTS IN PICKLING LINE NO. 2 ❖ EQUIPMENTS IN REGENERATION PLANT ❖ EQUIPMENTS IN TANDEM MILL ❖ EQUIPMENTS IN REVERSING MILL ❖ EQUIPMENTS IN ANNELING FURNACE ❖ EQUIPMENTS IN SKIN PASSING MILL ❖ EQUIPMENTS IN ELECTROLYTIC TINNING SECTION ❖ EQUIPMENTS IN CONTINUOUS GALVANIZING LINE

Continuous Pickling Line No. 1

(A)ENTRY SECTION:

1. COIL RAMP : Coils are brought by crane and placed on the coil ramp .Coil ramp is provided with three coils stops which are operated by compressed air through hand operated levers. Side guides on the coil ramp are adjusted manually to the coil width +100 mm. 2. COIL ADJUSTING DVICE: The coil adjusting device is equipped with two parallel adjustable guide plates and 2 carrying rollers. They serve to bring the coil to the center line and for tightening the outer laps of the coil. Hydraulically operated coil ejector feeds the coil to the uncoiler supporting rolls. After centering the coil on the coil adjusting device, coil strap is cut and the head end of the coil is straightened with the help of a wooden block for easy feeding into uncoiler. 3. UNCOILER, SCALE BREAKER AND LEVELLER: This unit comprises of following equipments:- i) Supporting Rolls(2) are driven electrically. These are used to support the coil after it is ejected from coil positioner and to lift to the center-line of the uncoiler mandrel. Supporting rolls are raised and lowered hydraulically. ii) SCALE BREAKRS: In order to facilitate pickling in the pickling tanks, the cracking of scale becomes essential, upper layers of scale on hot rolled strip consist of Fe2O3 and Fe3O4 which act very slowly with sulphuric acid. After upper layers of the scale are cracked, sulphuric acid penetrates to the inner oxide layer of FeO. iii) UNCOILER PINCH ROLLS: Head end of the strip is straightened and fed into the pinch rolls by electrically operating the supporting rolls. 4. CROP SHEAR: Entry crop shear serves for cropping the coil ends of the strip for subsequent welding. The shear has one steady top knife and one mobile bottom knife and is driven by a three phase A.C. motor.

Continuous Pickling Line No. 2.

Introduction: Continuous pickling line has been erected under the 1.8 million ton expansion program for pickling of hot rolled coils before these are cold rolled. Important technical data of the line is given below.

Capacity - 468000 tons per year Max. strip width - 1350 mm Min. strip width - 560 mm Strip thickness -1.6 -4.00 mm Coil wt. before pickling - 12- 5 tons max Inside coil dia on entry side- 710 mm Outside coil dia on exit side- 1550 mm Coil Wt. after pickling - 15 tons(max) Speed of entry section(max)- 300 meters/min Speed of pickling section(max)- 120 metres/min Speed of delivery section(max)- 150 metres/min

Equipments and their operation.

5. COIL RAMP : Coils are brought by crane and placed on the coil ramp .Coil ramp is provided wit three coils stops which are operated by compressed air through hand operated levers. Side guides on the coil ramp are adjusted manually to the coil width +100 mm.

6. COIL ADJUSTING DVICE: The coil adjusting device is equipped with two parallel adjustable guide plates and 2 carrying rollers. They serve to bring the coil to the center line and for tightening the outer laps of the coil. Hydraulically operated coil ejector feeds the coil to the uncoiler supporting rolls. After centering the coil on the coil adjusting device, coil strap is cut and the head end of the coil is straightened with the help of a wooden block for easy feeding into uncoiler.

7. UNCOILER, SCALE BREAKER AND LEVELLER: This unit comprises of following equipments:- i) Supporting Rolls(2) are driven electrically. These are used to support the coil after it is ejected from coil positioner and to lift to the center-line of the uncoiler mandrel. Supporting rolls are raised and lowered hydraulically. ii) SCALE BREAKRS: In order to facilitate pickling in the pickling tanks, the cracking of scale becomes essential, upper layers of scale on hot rolled strip consist of Fe2O3 and Fe3O4 which act very slowly with sulphuric acid. After upper layers of the scale are cracked, sulphuric acid penetrates to the inner oxide layer of FeO. iii) UNCOILER PINCH ROLLS: Head end of the strip is straightened and fed into the pinch rolls by electrically operating the supporting rolls.

8. CROP SHEAR: Entry crop shear serves for cropping the coil ends of the strip for subsequent welding. The shear has one steady top knife and one mobile bottom knife and is driven by a three phase A.C. motor.

9. WELDING MACHINE: It is basically hydraulically operated machine and is equipped with a compact hydraulic power system.

Operating sequence of the welding machine

I) after the tail end of hthe strip is sqared by the crop shear, it is run past the welder center. II) The spacer bar down button is operated and this causes the upset platen to move approximately 6mm. towards the stationary platen and sets the proper dimensions for die cleaning and strip loading. It also causes thespacer bar to move down between the welder die and clean them. III) The desired step of the spacer bar is previously selected by means of the space bar selector switch. At the end of the space bar stroke, the space bar move upward and it stops in the selected loading position. IV) The exit die blow off push button is operated to blow off the foreign material prior to clamping the strip. V) The operator no backs up the tail end of the strip to the welder and loops the strip with the exit pinch roll. The push button is released after strip is centered. VI) The exit clamp button is operated to clamp the tail end. VII) The head end of the next strip is sqared by the crop shear prior to clamping the strip. VIII) The operator runs the head end of the strip against the spacer bar by using the uncoiler control and operates the entry loop push button. IX) The entry clamp push button is operated to clamp the head end of the strip. X) The selector switch is turned to weld position and the weld thumb button located at the end of the manual operating handle is operated. It initiates the starting ignition contactor which applies secondary voltage to initiate flashing. The strip is brought together by moving the manual operating handle forward and then the flashing start. Forward movement of the handle is continued at a rate suitable to maintain flashing for a shot standing period. When handle reaches full forwarded position, limit switch is operated which start the automatic flashing cycle. Flashing is fully automatic. XI) After that the welded strip is unclamped automatically and is moved to flash trimmer.

10. CROSS-CUT FLASH TRIMMER:- the trimmer is hydraulically operated machine and is mounted as close to center line of the weld as possible, so that it may receive the welded joint with the minimum loss of time. It is designed to remove the upset of the flash from both the sides of a welded continuous strip of the steel in a single stroke across the strip. The trimmer automatically adjust s the single stroke across the strip. The trimmer automatically adjusts the cutting tools of the different strip gauges through the action of clamping ram.

11. SCALE WASHER: the scale loosened in the scale breaker is sprayed off by the series of top and bottom sprays. Water from wet looping pit is sprayed by a pump. Wash water goes back to wet looping pit trough scale pit wher lose scale collected.

12. PINCH ROLL UNIT II: this pinch roll pulls the strip from he wet looping pit via a deflector roll through scale breaker and spraying device and convey it to actual pickling bath. Design of this unit is same as that of pinch roll unit no. 1. both rolls are of 350 mm dia and 1800mm. barrel length.

PICKLING SECTION

GENERAL DESCRIPTION: the strip is treated in the pickling tank having the following internal dimensions.

Length = 100,000 mm
Width = 1950 mm
Height = 1650 mm

Pickling line is sub-divided into four chambers of identical length. It is made of welded steel construction and provided with 6mm thick rubber at inside and protected by acid proof painting at the outside. In addition pickling line is equipped with 250 mm thick acid proof ceramic lining. The covers of the tank are also protected with 6mm. thick inside rubber lining and an acid proof painting outside.

EXIT SIDE OF THE PICKLING LINE.

Exit side comprises of following units.

1. PINCH ROLL UNIT-III: Pinch roll-iii pulls the strip through the pickling line and convey it into dry looping pit. A strip guide table with lateral guides is provided before these pinch rolls for proper strip alignment . they have a crowned dia of 350 mm with a barrel length of 2000mm.

2. DRY LOOPING PIT: dry looping pit act as a strip bank for regular strip flow to the delivery side. When delivery side of the line is down for changing coils pickling line should always be in running condition at slower speed so that over pickled patches are not formed on the strip.

3. DELIVERY SET: it comprises of one deflector roll and two flanged discs. Discs are adjusted to the strip width for feeding the strip in the center of the line.

4. PINCH ROLL UNIT IV: pinch roll iv serve for conveying the head end of each strip from the exit crop shear to pinch rolls of the side trimmer and to hold it in the subdividing shear during the cutting process so that it does not run back into dry looping pit by its own weight. Pinch rool are of 300 mm dia with 1800 mm barrel length.

5. EXIT CROP SHEAR: this shear is used for cutting the strip at the weld or at any other point for making the individual coils.

6. SIDE TRIMMER: the side trimmer serves for trimming the strip to a certain final dimension.

7. SCRAP CHOPPER:the blads are mounted on the knife shafts and can be adjusted to the strip width required for jogging respective jogging switch. Pinch rolls on the entry side of the side trimmer convey the strip to the side trimmer knives.

8. OILING MACHINE: coil is strapped on the first coil stop and is then rolled over to the coil conveyor. .

9. UPCOILER: the pickled , trimmed and oiled strip is aligned to the center of the unit by lateral guide and is then guide to pinch roll . pinch roll convey the strip to the bending rolls which bends the strip beyond its elastic limit.strip after bend forms a ring and then rises to the supporting rolls. Carrying rolls are driven forms a ring and take over the turning of the coil to be wound.

Upcoiler speed: 60m/min. max Speed of supporting rollers: 76.1 r.p.m max Speed of pinch rolls 95.8 r.p.m max Speed of bottom bending rolls: 95.8 r.p.m max Speed of top bending rolls: 73. r.p.m max

10. COIL RAMP: coil is strapped on the first coil stop and is then rolled over to the coil conveyor.

REGENERATION PLANT

Increase in the salt content of the pickling tank reduces the rate of the pickling and if salt is allowed to increase beyond certain limits, it reduces the pickling rate and results in the formation of monohydrate which result in the chocking of pipe-lines. The separation of salt is achieved by crystallization. Details of various equipment is given below:

1. ABSORPTION TANK: this is rubber lined steel tank which just acts as a buffer for the solution to be sucked into primary cooler. 2. PRIMARY COOLER: it is a rubber lined mild steel vessel which sucks the acid from the absorption tank due to vacuum inside it. At top it is connected to the condenser which in turn is connected to a steam ejector which keeps the primary cooler under vacuum. because of this vacuum, the acid gets cooled to a temp of about 40(c. the primary cooler is connected to the crystallizer from the bottom.

3. 4-STAGE CRYSTALLIZER: crystallizer is a rubber lined steel shell divided into four chambers. Cooling takes place in steps in four chambers due to vacuum maintained inside the chambers. The acid flow from one chamber to the other by over flow due to suction and due to the increased vacuum in the subsequent chambers. The acid is agitated by bubbling of air. It produces a large number of nuclei so that the number of small crystals increases. Agitation also provides a better opportunity for the crystals to grow uniformly and lastly it prevent seting of crystals thus keep them in the form of slurry. The slurry of the salt and acid from chamber no. 4 is pumped to buffer tank with the help of stainless steel centrifugal pump.

4. BUFFER TANK: it is a rubber lined steel shell with conical bottom and delivers the slurry to the centrifuge.

5. MIXING TANK: mother liquor flows to the mixing tank where concentrated acid is mixed to bring up the concentration.

6. ACID STORAGE TANK: two storage tanks each of 40 m3 capacity are provided for the storage of concentrated acid.

MILL EQUIPMENT

A) ENTRY SIDE:

1. COIL CONVEYOR: it is nonreversible plate type conveyor on which pickled coils are placed by means of crane.

Length - 10.2 m Conveyor speed- 7.6m/min Capacity- 5 coils of 15 tons each

2. COIL RAMP: Coils are brought by crane and placed on the coil ramp .Coil ramp is provided wit three coils stops which are operated by compressed air through hand operated levers. Side guides on the coil ramp are adjusted manually to the coil width +100 mm.

3. UNCOILER BOX: the coil can be rolled into the uncoiler box by hydraulically lowering the coil positioner. This can only be done when the side plates are moved apart. The strip guide table is then moved backward and the roller basket is moved forward. Ther are lateral disc mounted which can be hydralically displaced individually or together to align the coil exactly to the rolling center.

4. 3 ROLLER PINCH ROLL UNIT/ STAIGHTENING MACHINE:the loosened strip from the strip holding device falls on to the bottom straightening driven rollers.

5. STRIP GUIDE ROLLER: it guide the strip from the uncoiling box to the stand-1.

Roller dia – 300 mm Opening widt of lateral disc- 1525mm(max)

6. LATERAL STRIP GUIDE: it can adjusted through geared motor to various strip width.

B. MILL STAND

1. ENTRY GUIDES: there are 5 entry guide for 5 mill stands which can be set to the respective strip width. Top part of the wiper box presses against the bottom press lining pneumatically. When the head end of the strip is gripped by stand 1, the entry guide in the front of it is closed thus giving the required tension.

2. Rolls: Work rolls back up rolls

Diameter (max)mm - 585(600mm for stand-1) 1420 Diameter(min)mm- 540 1295 Barrel length- 1420 1420 Weight(kg) 4.5 t 25.5 t

The work rolls are cooled from either side and bottom back ups only on exit side by a network of cooling pipes. Ther are separate pipes for cooling and lubrication of strip being rolled. Stand no-5 is provided with strip drying arrangemen to blow off the emulsion from the strip before coiling.

C. DELIVERY GUIDE EQUIPMENTS

1. TENSION REEL: the strip is threaded into all the 5 rotating at threading speed and then led on to the expanded reel of the coiler via a deflector roll. After a few laps have been wound over the reel, the belt wrapper encircling the reel is retracted backwards. At the end of coiling the reel is collapsed and coil is stripped off by the transfer car. 2. COIL STRIPPER: inner strip windings, sticking to the drum and small strip sleeves which cannot be gripped by the coil lifting device can be pushed out of the drum by the removing plate that can be hydraulically displaced. Ther are two stripper plates one for 450 mm drum and the other for 510mm drum.

3. BELT WRAPPER: it is hydraulically moved towards the expanded reel running with threading speed.

4. COIL TRANSFER CAR: it transfer the coil from the drum to the conveyor.

5. COIL CONVEYOR : coil conveyor has a capacity of 5 coils of 15 tons each.

6. WEIGHING M/C

REVERSING MILLS

A four-high reversing mill consists of a single stand with reels located on the either side o the mill. Steel is passed back and forth till the required thickness is obtained. In CRM of RSP we have two reversing mills. Both are four-high mils.1700mm reversing mill is used for rolling sheet gauge coils from 0.5 to 2.00 mm thickness. 1200mm reversing mill is used for rolling of the tin plate coils and black plate coils, it is of .30mm,.40mm&.50mm

TECHNICAL DATA OF REVERSING MILLS:

CR-I CR-II

1. Maximum strip width 1540mm 1040mm 2. Minimum strip width 630mm 600mm 3. Initial thickness 2-4mm 2-3mm 4. Finished thickness 0.5-2.5mm 0.5-1.00mm 5. Maximum coil weight 16 tons 10 tons 6. Back up roll dia 1390mm 1390mm 7. Work roll dia 460mm 460mm 8. Barrel length 700mm 1200mm 9. Maximum rolling speed 500m/min 720m/min 10. Diameter of reel 610mm 510mm

EQUIPMENTS

COIL RAMP: Coils are brought by crane and placed on the coil ramp. Coil ramp is provided wit three coils stops which are operated by compressed air through

hand operated levers.

COIL CENTRING DEVICE AND UNCOILER: The coil adjusting device is equipped with two parallel adjustable guide plates and 2 carrying rollers. They serve to bring the coil to the center line and for tightening the outer laps of the coil. Hydraulically operated coil ejector feeds the coil to the uncoiler supporting rolls. After centering the coil on the coil adjusting device, coil strap is cut and the head end of the coil is straightened with the help of a wooden block for easy feeding into uncoiler.

PINCH ROLL UNIT/ STAIGHTENING MACHINE:the loosened strip from the strip holding device falls on to the bottom straightening driven rollers.

SCREW DOWN DEVICE: the screw device serve the purpose of setting gap as desired.

EMICRON: this is a automatic thickness measuring device which is very useful for continuous rolling mills. This device works on the basis of comparison.

REEL AND COIL DISPLACING DEVICE, COIL RAMP

EMULSION SYSTEM: in cold reduction of steel only few energy is spent in reduction process rest are consumed by internal and external friction. This beside causing the waste of energy, the heat produced effects the equipment used for cold reduction. Complete elimination of friction is not possible but substantial reduction in external fricton may be effected by lubricating the surface involved. The unavoidable generation of heat requires its quick dissipation to cool the equipment.

EMULSION CLEANING SYSTEM: the used emulsion carries all th scale and rust which is carried over strip.this has to cleaned befor recirculation.
The deficit oil and water are added to maintain the percentage of oil volume.
The emulsion that is sprayed at the mill get collected below in the tank, from where it flows to another tank, known as emulsion tank. After filtration, the emulsion I cooled by emulsion coolers. There are two cooler for this purpose, both bare parallel.the filtrate and cooled emulsion then flows to the emulsion main.

FUME EXHAUST SYSTEM: fumne exhaust system consists of exhauster, fume suction caps, oil separator and the chimney .

DEGREASING

It is vital that all trace of rolling lubricant and coolants should be removed prior to annealing and tinning since surface contamination by these materials or their decomposition products precludes satisfactory tinning.

EQUIPMENTS AND THEIR OPERATION

COIL RAMP: : Coils are brought by crane and placed on the coil ramp .Coil ramp is provided wit three coils stops which are operated by compressed air through hand operated levers.

DISPLACEBALE COIL BUGGY: before actuation of ythe last coil stop, the coil buggy is moved into receiving position by merans of displacing cylinder and lifting cylinder is acutated so that the carrying plate stops at the height of coil ramp. Coil buggy is operated from hydraulic control desk.

UNCOLING MACHINE: the coil can be rolled into the uncoiler box by hydraulically lowering the coil positioner. This can only be done when the side plates are moved apart. The strip guide table is then moved backward and the roller basket is moved forward. Ther are lateral disc mounted which can be hydralically displaced individually or together to align the coil exactly to the rolling center.

ENTRY CROP SHEAR: Entry crop shear serves for cropping the coil ends of the strip for subsequent welding. The shear has one steady top knife and one mobile bottom knife and is driven by a three phase A.C. motor.

WELDING MACHINE: It is basically hydraulically operated machine and is equipped with a compact hydraulic power system.

PRELIMINARY SCRUBBER: the function of the preliminary scrubber is to roughly degrease the strip by acid of detergent solution and the driven scrubber rolls. The strip is cleaned by spraying an alkaline solution at 85-90°c .

ELECTROLYTIC CLEANING CELL: in the electrolytic cell strip is guided through the grid alternately arranged as anode and cathode and the grease residue are dissolved in the solution, 2-3% solution of sodium ortho-silicate at 80-90°c is used for the purpose. Three leach separator are provided in the line which separate out the dirt etc. by centrifugal pumps.

FINISHING SCRUBBER: the design and function of the finishing scrubber is same as preliminary scrubber. Finishing scrubber is covered with nylon fiber instead of high speed steel wire as in primilary scrubber.

HOT RINSE TANK: the strip running through the hot rinse tank is rinsed with hot water and later squeezed by the squeezr rolls at the exit. The two dipping rolls hold down the strip to the desird depth.
HOT AIR DRIER: Hot air is blown on top and bottom strip surface to dry out the strip. Air is heated in hot air drier by superheated steam(at about 180°c and 10 atm pressure).

PINCH ROLL UNIT: the pinch roll unit pulls the strip through the rinse tanks and conveys it to the looping pit. Pinch rolls are 500mm dia. And 1250mm long.

STRIP GUIDE AND TENSION ROLL UNIT: the strip leaving the looping pit is first drawn over the strip guide rollers to the disc guides. The strip is then guided to the top tension roller and is pressed against the same by top pressure rollr. Tension rolls are rigidly mounted in the housing and are individually driven. By looping angle of the strip they cause a back tension , which is necessary for coiling.

UPCOILER: strip is aligned to the center of the unit by lateral guide and is then guide to pinch roll . pinch roll convey the strip to the bending rolls which bends the strip beyond its elastic limit. strip after bend forms a ring and then rises to the supporting rolls. Carrying rolls are driven forms a ring and take over the turning of the coil to be wound.

STACK ANNEALING

Stack annealing is still the most common and convenient method of annealing and major portion of cold rolled coils are still annealed in this furnace.

TECHNICAL DATA:

OLD SECTION: NEW SECTION:

1. Capacity 265,000 tons/yr 185,000 tons/yr 2. No. of furnace 32 16 3. No. of bases 96 56 4. Ratio of furnace to base 1:3 1:3.5 5. No. of cooling hoods 48+2 24 6. No. of inner covers 96 56 7. Max. of charging height 3600mm 4000mm 8. No. of burner per furnace 12 12 9. Base fan 7.5 kw 12kw 10. Cooling hood fan 6 kw 6.2 kw 11. Furnace air blower 2.5 kw 2.5 kw 12. No. of flue gas chimney 8 4 13. Pressure of mixed gas at furnace 300mm w.g. 300mm w.g. 14. Wt. of furnace 17 tons 20 tons 15. Type of seal used sand rubber

ANNEALING EQUIPMENTS:

1. ANNEALING BASES: these are the supports for the material to be annealed and are provided with the inlet and the outlet for the protective atmosphere, the thermocouples and a circulation fan at the center. The gap between the lined with insulation bricks. The coils are separated by convector plates. These help in proper circulation of protective atmosphere and increase the rate of heating by convection.

2. PROTECTIVE HOOD: the protective hood is made of special heat resistant chromium- nickel steel to cover the coils. An inert atmosphere is maintained inside the hood.

3. ANNEALING FURNACE: there are six burners at the height of 400mm and other six at the height of 1200mm from the floor level. The air pipe of these burners are enclosed in the circular wall lining and at the top flue gases escape through an opening and flow around recuperators attached to thse air pipes thereby giving up part of their sensible heat to the incoming air.

The inside 125mm of lining is of light fireclay and the remainder is insulation bricks. The temperature of these furnace is about 850°c max.

4. COOLING HOOD: after heating and soaking period is over, the cooling of the material is done under protective environment but with the forced air circulation outside the protective hood. This forced air is given by the cooling hood provided with a fan at top.

Continuous annealing process

TECHNICAL DATA OF CONTINOUOUS ANNELLING LINE

The entire line can be divided into 3 section: a) Entry or cleaning section b) Furnace or annealing section c) Delivery or finishing section

Entry or cleaning section: COIL FEEDING SECTION: it is arranged before the expanding drums of the uncoiler and serves for the reception of three coils there are two coil feeding devices for two uncoiler. 1. COIL BUGG: coil in the coil feeding device is guided into the uncoiler drum by means of coil buggy which is operated by hydraulic cylinder. Max. admission coil weight: 15 tons Piston dia of coil lifting device: 350mm & 800mm stroke Displacing cylinder, dia stroke: 3300mm Working pressure: 60 kg/cm2

2. UNCOILER : when the coil is pushed on to the uncoiler drum by buggy, the drum segment are hydraulically expanded to clamp the coil tightly on the drum. Coil is then lowered and retracted back to its starting position.

3. PINCH ROLL UNIT: it is arranged between the two uncoiling drums and is meant for allowing the strip into the double pinch roll unit. top pinch roll has a dia of 160mm and the bottom one has a dia of 250mm. after the strip has been threaded into the double pinch roll unit ,the top pinch coil is lifted up by a compressed air cylindrer.

4. DOUBLE PINCH ROLL UNIT: It is arranged after the uncoiler and is meant for conveying the strip from the uncoiler to the crop shera and hten to the welder.

Dia of driven rolls;l 200mm Dia of idle rolls: 250mm Barrel length of the driven rolls ; 480mm Barrel length of the idle rolls: 1200mm Working pressure of air cylinder: 6 atms

5. DOUBLE CROP SHEAR: it has two steady top knives and two bottom moving knives lifted and lowered by compressed air.

6. WEILDING MACHINE: It is basically hydraulically operated machine and is equipped with a compact hydraulic power system.

7. BRAKING SET: It is provided just before the degreasing section and is meant for maintaining strip tension after the tail end of the strip has run off the reel. two pinch roll are braked by the means of brake arrangement on the driving trunnions.

8. NO.3 PINCH ROLL UNIT: Pinch roll-iii pulls the strip through the pickling line and convey it into dry looping pit. A strip guide table with lateral guides is provided before these pinch rolls for proper strip alignment . they have a crowned dia of 350 mm with a barrel length of 2000mm.

9. PRELIMINARY SCRUBBER: the function of the preliminary scrubber is to roughly degrease the strip by acid of detergent solution and the driven scrubber rolls. The strip is cleaned by spraying an alkaline solution at 85-90°c .

10. ELECTROLYTIC CLEANING CELL: in the electrolytic cell strip is guided through the grid alternately arranged as anode and cathode and the grease residue are dissolved in the solution, 2-3% solution of sodium ortho-silicate at 80-90°c is used for the purpose. Three leach separator are provided in the line which separate out the dirt etc. by centrifugal pumps.

11. FINISHING SCRUBBER: the design and function of the finishing scrubber is same as preliminary scrubber. Finishing scrubber is covered with nylon fiber instead of high speed steel wire as in primilary scrubber.

12. HOT RINSE TANK: the strip running through the hot rinse tank is rinsed with hot water and later squeezed by the squeezr rolls at the exit. The two dipping rolls hold down the strip to the desird depth.

13. HOT AIR DRIER: Hot air is blown on top and bottom strip surface to dry out the strip. Air is heated in hot air drier by superheated steam(at about 180°c and 10 atm pressure).

14. BRINDLE ROLL SET NO.1: It is provided with two pressure rolls and three deflector rolls driven by electric motors, through flexible coupling. Deflector rolls no.1& 2 are cylindrical and no.3 is a self aligning roll by with the strip is aligned to the center of the unit.the pressure roll above the deflector roll acts as a pinch roll unit.

Dia. Of deflector rolls = 600mm Dia. Of pressure rolls = 250mm Barrel length of deflector roll I & II = 1200mm

15. LOOPING TOWER NO.1: it is meant for maintaining a strip stock to keep the furnace section in running condition when a coil is being changed at entry side.

SKIN PASSING MILL.

EQUIPMENTS OF 1700MM &1200MMSKIN PASS

1. COIL RAMP: the coil from the annealing plant are placed on a slightly inclined coil ramp by means of crane. Coil ramp is provided wit three coils stops which are operated by compressed air .

2. UNCOILER: the coil can be rolled into the uncoiler box by hydraulically lowering the coil positioner. This can only be done when the side plates are moved apart. The strip guide table is then moved backward and the roller basket is moved forward. Ther are lateral disc mounted which can be hydralically displaced individually or together to align the coil exactly to the rolling center.

3. ENTRY PINCH ROLL: top roll dia. 215mm. bottom roll dia. 400mm. pressure 5kg/cm3

4. MILL STAND: The strip coming from the uncoiler through pinch roll is seized by driven work load and is led over a guide roller to the coiler behind the mill. The top work roll and the bottom work roll with chocks are balanced by 4 hydraulic cylinder arranged in the bottom work-roll chock. Main technical data given below:

SP-I SP-II

Weight of the housing 87 tons 87 tons
Height of the housing 7100mm 7100mm
Width of the housing 4000mm 4000mm
Rolling pressure 600 T/housing 600t/housing
Pressure screw dia. 420mm 420mm
Weight of top back-up roll with
Chock including morgil bearings 48.5 tons approx. 44 tons approx.

Weight of bottom back-up roll with
Chock including morgil bearings 47.5 tons approx. 43 tons approx.

Weight of top back-up roll with
Chock including roller bearings 5560 kgs. approx. 4900kgs. approx

Weight of bottom back-up roll with
Chock including roller bearings 5760 kgs. approx 5080 kgs. approx.

5. SCREWDOWN DEVICE: the screw device serve the purpose of setting gap as desired.
6. ANTI-CRIMP ROLLER: Anti-crimp roller prevent fluttering of the strip when being skin passed. This is done by raising the pressing roller upwards before the strip is fed into the mill rolls. Pressing cylinder is operated by a cylinder control valve.

7. DEFLECTION ROLLERS: There are two deflector rollers, each of them arranged on two sides of the mill. The strip, when being fed is led over the deflector roller on entry side. Similarly, strip passes over the deflector roller of exit side before it is clamped in the coiler reel.

8. STRIP GUIDE: the strip leaving the looping pit is first drawn over the strip guide rollers to the disc guides. The strip is then guided to the top tension roller and is pressed against the same by top pressure rollr. Tension rolls are rigidly mounted in the housing and are individually driven. By looping angle of the strip they cause a back tension , which is necessary for coiling.

9. COILING REEL: the strip is threaded into all the 5 rotating at threading speed and then led on to the expanded reel of the coiler via a deflector roll. After a few laps have been wound over the reel, the belt wrapper encircling the reel is retracted backwards. At the end of coiling the is collapsed and coil is stripped off by the transfer car.

10. COIL RAMP: coil is strapped on the first coil stop and is then rolled over to the coil conveyor.

12. OILING MACHINE: coil is strapped on the first coil stop and is then rolled over to the coil conveyor

ELECTROLYTIC TINNING SECTION

Electrolytic tinning line is divided into three main section:
1.)Entry section
2.)Processing section
3.)Delivery section

Entry section: same as all other unit.

Processing section: i) Electrolytic cleaning unit: this unit consist of 2 cleaning tank, rollers, the electrodes, the drive. ii) Electrolytic pickling unit iii) Electrolytic tinning unit: 8 plating tank and tin anodes iv) Hot air drier v) Melting tower vi) Chemical treatment unit: 2 treatment tank first provided with carbonate treatment and second with chromate treatment . vii) Hot air drier
Delivery section

CONTINUOUS GALVANIZING LINE

Continuous galvanizing line consist of three main section

1. Entry section 2.) Processing section 3.)Delivery section
Entry section: same as all other unit

Processing section: i) Flame heating section: the furnace is heated with 48 type of mixed type of burner.this section serve as a strip cleaning section by oxidizing oil and also it preheat the strip. ii) Reduction furnace: the reduction furnace consist of entirely close glass steel sheet.the furnace is heated by horizontal radiant tube. iii) Controlled cooling section: cooling is done by blowing air through heat resistant alloy tube. iv) Galvanizing pot: The zinc bath is heated by 360kw furnace, consist of a three row of heating element . v) Weld detector: it detect the hole at the weld region.

Delivery section: same as other units.