WEEK 1

IRON MAKING DEPARTMENT (IMD)Iron Making Plant comprises of many small and big working units, the biggest one is Blast Furnace unit. This unit consists of two Blast Furnaces (BF-1 & BF-2) and both are in operation since 31st August 1981 and 07th August 1984 respectively, Inner volume of each furnace is 1033 cubic meters and its working volume is 893 cubic meters. Whereas the daily production capacity is 1750 tons of Pig Iron per furnace.

BF-1 had two notches:-a) Iron notchb) Slag notch.

Both notches have been closed permanently and another iron notch has been prepared instead. Blast Furnace No.2 still has one iron notch and one slag notch but its slag notch is rarely operated. Each furnace has 14 tuyers through which hot blast is injected at high temperature (1100 - 1200 C). Raw Material is charged from the top of the furnace through charging system comprising of double bell charging system. Hearth of the furnace is lined with carbon blocks whereas the inner walls of the furnace are lined with refractory bricks with embedded plate coolers of different types. The hot air blast alongwith a calculated quantity of natural gas is fed into the furnace through tuyeres at high pressure (up to 2.5 atm.) and high temperature (1200 C). As soon as the blast rises up the furnace shaft, the raw material gains heat and coke starts burning which produces CO and Co2. These gases further react with different oxides of the raw material and reduce them into their elementary shape (Fe, Si Mn etc.), and different oxides (such as A12O3, CaO, MgO) are also formed. The mixture of Fe, Si, Mn and carbon is called pig iron whereas the mixture of A12, O3, SiO2, CaO, MgO, MnO and other oxides is called slag. Both the molten iron and slag are collected in the hearth of the furnace from where they are tapped after a scheduled period through iron notch altogether. Slag is separated from the iron in the main runner just before the skimmer box. The pig iron is collected in the iron ladles and slag is separately collected in slag pots.The working area around the furnace, where a network of iron and slag runners is laid down is called cast house. The heavy equipment installed in the cast house are:-

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i. To open the tap hole.ii. To close the tap hole after the completion of the tapping.iii. An E.O.T Crane of 20T/5T capacity to shift the materials and equipments from bottom house and to clean and prepare the iron and slag runners.

There are three hot blast stoves for each furnace. One stove is on blast at a time while the other two remain on heating regime. The stoves are lined with Dinas Silica bricks and chequered brick work. The stoves are heated with mixture of N.Gas and B.F.Gas. When the dome temperature reaches 1350 C, the stove is ready to provide the hot blast to the furnace. The gases in the furnace, after completing the chemical reaction, leave the furnace at the top. These gases carry fine particles of raw materials with them. These gases (called B.F. Gas) are brought down the furnace through pipes of bigger diameter (internally lined with refractory bricks) into a vessel called dust catcher. Due to sudden drop of pressure in the dust catcher, the dust particles settle down at the bottom of the dust catcher, and the semi-cleaned gas is transferred to gas cleaning plant for further purification. All the raw materials charged into the furnace are initially stored in separate bins, called burden bins. Iron ore and fluxes are supplied to burden bins by RMHD, and Coke and Sinter by Coke Oven and Sintering Plant respectively. These materials are then sieved and weighed according to charging schedule and continually fed into the furnace. There are two pig casting machines in Iron Making Department. A pig casting machine consists of two metallic chains (conveyers) containing metallic moulds. The molten metal is poured into these moulds and due to their continuous forward movement the filled moulds travel ahead and empty moulds take their places. After covering 10-15 m distance, water is sprinkled over molten pigs and the outer surface gets harder. At the end of the machine, pigs are struck away by a metallic hammer and collected in a railway gandola placed underneath.

PCMNo. of Machines – 2Pigs weight - 18 / 23 / 45 KgCapacity - 140,000 Tons/year

Pouring time of 140 T ladlei) 45 Kg Pigs - 55-60 minutes

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ii) 23 Kg Pigs - 60-65 minutesiii) 18 Kg Pigs - 70-75 minutes

SLAG GRANULATION PLANT

The slag produced in the blast furnace is separately collected in slag pots at the furnace. The slag pots are then transported to SGP by railway locomotive for slag granulation. The molten slag is poured on a huge trough at a point where a heavy jet of water granulates the slag and throw it away in the yard. This granulated slag is then collected and shifted to open yard directly on trucks for cement factory or other purposes.

SLAG DUMP YARD

All the molten slag is not possible to pour out, however, some slag still remains at the bottom of the pot. After granulation, the slag pot is transported to slag dump yard far away from the SGP. It is an elliptical open yard where railway track is laid down at a sufficient height. The slag pot is placed at one of the post and electrically tilted up to maximum. A metallic bob (attached with the excavator) strikes the bottom of the ladle and the residue falls down the ground. Now the ladle becomes completely empty. The slag ladle coming from slag dump yard on way to blast furnace is stationed for a while at slag ladle sprinkling unit where a cold solution of lime water is sprinkled in the ladle so that the slag could not stick to the inner walls of the ladle at the time of pouring slag into it.

CENTRAL AIR SUPPLY STATION

This is the unit where two huge fans are installed to supply cool air to the control rooms and other operational units of blast furnace where sensitive electrical and automation equipment are installed. The air is cooled by counter-flow of chilled water in pipes (at 8C) and passed through filters to make it clean and dust free.

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CENTRAL ASPAIRATION UNIT

Due to fine particles in raw materials, a cloud of dust may appear during receiving these materials at burden bins. Therefore to keep the atmosphere clean and clear, a network of suction pipes is installed over conveyors and bins. These pipes suck the dust with the help of huge fans installed at central aspiration unit for this purpose. This dust or fine particles are collected in an electric filter from where the dust is supplied to sintering plant.

HOT METAL LADLE REPAIR SHOP

This is the shop where hot metal ladles are repaired partially or completely re-lined with refractory bricks. More over the ladles are also cleaned by removing solidified skull in the them before placing them under furnaces for tapping.

CONTROL ROOM

The most important place of the blast furnace is its control from room where too many electrical and automation instruments have been installed to control the process of blast furnace.

BLAST FURNACE

No. of Blast Furnace - 2 NosEffective volume - 1033 Cu.mEffective Volume Utilization Factor - 0.59 Cu.m/day/ton pig ironPig iron rate - 1.7 T/Cu.m.

DIAMETER

Hearth - 7200 mmBelly - 8200 mmTop - 5800 mmLarge Bell - 4200 mmHeight (Iron notch axis toUpper part of top bearing Flange) - 28950 No. of tuyers - 14 each BFNo. of tap holeBF #1 - 2 NosBF # 2 - 1 No.

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Blast temperature - 1200 C.Top pressure - 1.5 Kg/Se.cm.Natural gas injection - 77 Cu.m/ton pig ironCoke consumption - 520 Cu.m/ton pig ironNo. of taping - 8-10/day B.F.Production Capacity - 1750 T/day/B.F. and 1.230 T/year.Top gas Temperature - 350-300 C.Taping Temperature - 1400 C.

THE COMPLETE PROCESS DIAGRAM

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WEEK 2

COLD ROLLING MILL (CRM)This plant is used for the production of the cold rolled coils which are more beneficial for various types of works such as sheets for the vehicle, as well as the body of the aeroplanes and etc. another assignment is also fulfilled which is of the slitting and shearing. These sheared sheets are used for the flouring, as well as ceiling and in various other functions where there hot rolled sheets are not beneficial. CRM is one of the cleanest and largest department of the whole steel mill. It is one of the largest department which is always clean. All the products of the steel mill depends on the CRM department because each and every product has to pass from this department.

CRM contains following units:

1)Continuous picking unit2)Reverseble unit3)Annealing furnace4)Tempering mill unit5)Combined slitting and shearing units6)Galvanizing unit7)Profile bending

1) Continuous picking unit

It is the unit where the coil comes from Hot Strip Mill (1700mm) by the underground conveyer belt which directly connects the HSM and CRM. When the coil reach at the pickling section there is a lifter fixed in the machine whose work is to lift the coil and wear it on the uncoiler which uncoils the coil and stretch it to the length of about 5-6m through the coils after that these coils are dipped into the acid bath where all types of scales has been removed and then

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goes to the other stand where it’s width is maintained by trimming the rough edges, it is set as follows:

1250 12201030 1000950 900

After that it passes through gracing stand where it is grecced/oil is applied as it can be kept prevented from the corrosion and the natural effects.

Function of Pickling Unit

The most important function is that hot rolled coils are pickled in order to remove the scales and layers of the FeO (iron oxide) by the emersion of the sheet into the HCl (Hydrochloric acid).

2) REVERSIBLE STAND

One stand mill is laid out in the line and strip will pass the mill reciprocally till termination product. This line is characteristic with low cost, small occupation and flexible production. Here sheets get timmed.

3)ANNEALING FURNACE

It is the furnace which is used to improve the internal structure of the coil or to increase the strength of the material.

MAIN PARTS OF ANNEALING FURNACE

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Main stand Tower Furnace Stove

In annealing furnace at a time there are 4 coils of width 950mm and 3 coils of the width 1220mm can kept. Duration of the furnace is minimum 18-44 hours depending upon the grade of the coil. Internal atmosphere of the furnace is of nitrogen gas and the heating process takes place in absence of oxygen/air. After discharging from the furnace these coils are cooled.

4)Tempering mill unit

A Temper mill is the steel sheet and/or steel plate processing line composed of the horizontal pass cold rolling mill stand, entry and exit conveyer and upstream and downstream equipment depending upon the design and nature of the processing system. A typical type of temper mill installation includes entry equipment for staging and accepting hot rolled coils of steel which have been hot wound at the end of the hot strip mill or hot rolled plate mill. Also included in a typical temper mill installation are pinch rolls, leveler and a shear for cutting the finished product to pre determined lengths, a stacker for accumulating cut lengths into bundles. Sometimes a temper mill installation includes a re-coil line where the finished product is a coil instead of bundles of cut length of product. The heart of the tempering mill is the cold rolling mill stand which produces the temper pass. It will include electric powered drive motors and speed reduction gearing suited to the process desired. Pinch rolls provide back tension for the pay off reel in the entry section and entry and exit tension for the temper pass. The primary purpose of the tempering mill is to improve the surface finish on the steel products. The output from temper mill goes into either sharing unit or slitting unit.

5)COMBINED SLITTING AND SHEARING UNITS

The slitting mill was a water mill for slitting bars of irons into rods. The rods were then passed to nailers who made the

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rods into nails by giving them a point and head. The slitting unit consists of two pairs of rolls turned by water wheels. Mill bars were flat bars of ironabout three inches wide and half an inchthick .A piece was cut off the end of thebar with shears powered by one of thewater wheels and heated in a furnace. This was then passed between flat rolls which made it into a thick plate. It was then passed through the second rolls also known as cutters which slit it into rods. The cutters had intersection groves,which sheared the iron lengthways.

Shearing is the process for cutting sheet metal to size out of a larger stock such as roll stock. Shears are used as the primarily step in preparing stock for stamping processesor smaller banks for CNC presses. Material thickness ranges from 0.125mm to 6.35mm (0.005 to 0.250 in).The dimensional tolerances ranges from ±0.125 mm to ± 1.5mm (±0.005 to ±0.060in).The shearing process produces a shear edge burr which can be minimized to less than 10% of the material thickness. The burr is a function of clearance between the punch and the die(which is nominally designed to the material thickness) and the sharpness of the punch and the die. Material selected for shearing should be standard stock sizes to minimize the extra costs associated with special slitting.

6)Galvanizing unit

In this unit iron is painted with the suspension of zinc particles in an organic solvent so that a zinc coating remains following evaporation of the solvent. The principal method of making steel resist corrosion is by alloying it with metal zinc. When steel is submerged in melted zinc the chemical reaction permanently bondsthe zinc to the steel through galvanizing. The zinc goes through a reaction with the iron molecules within a steel to form galvanized steel. The most external layer is all zinc but successive layers are the mixture of iron and zinc with an interior of pure steel. These multiple layers are responsible for the property of the metal to withstand corrosion inducting circumstances such as salt water or moistures. Zinc also protects the steel. If for some reason rust takes hold on the surface of the

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galvanized steel, the zinc will get corroded first. This allows the zinc that is spread over the breach to prevent rust from reaching the steel. Galvanized steel can be mostly found everywhere. You might be living in a steel frame house. You are no doubt surrounded with steel parts of your car that allow it to emerge from rainstorms unscratched.

7)Profile bending

Rolling is the fabrication process in which the metal,plastic,paper and glass etc. is passed through a pair of rolls. There are two types of rolling process flat and profile rolling. In profile rolling the final product may be round rod or other shaped bar such as structural section. Rolling is also classified according to the temperature of the metal rolled is above it’s re crystallization temperature then the process is called hot rolling.If the temperature of the metal rolled is below it’s re crystallization structure then the process is called cold rolling. Another process is called hot bending is induction bending whereby the section is heated in small sections and dragged into a required radius.

THE COMPLETE PROCESS DIAGRAM

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WEEK 3STEEL MAKING DEPARTMENT (SMD)

It is one of the important department of steel mill.We will be not wrong if we say it as the heart of steel mill. At this stage we prepare the steel of the required grade and shape into various form. Castingprocess slabs, billets and bloom are the products.

PROCEDURE OF SMD:

Hot metal is transported from the two blast furnaces by rail cars in 130 tones open transfer ladles and charged into the mixer by crane. The capacity of the mixer is 1300 tons. The mixer acts as a buffer storage vessel to accommodate variation between iron production and the steel making operation. To maintain the temperature in the mixer natural gas burners heat the surface of the hot metal. Hot metal is poured from the mixer into a charging ladle on the self propelled rail car. During pouring the ladle car is positioned on a weighbridge. The hot metal is charged into the converter by crane. After charging the converter is rotated to the vertical position and one of the two water cooled oxygen lances nozzles relative to the liquid metal surface is important in order to create the optimum reaction conditions. To obtain the desired carbon content in the refined and to oxidize other impurities a calculated volume of oxygen is blow into the converter at a controlled flow rate. During blowing process a pre determined quantity of calcinated lime is added to the vessel to produce a slag which aids the refining process. Flouride is added for slag fluidity control. Iron ore is sometimes added for temperature control. Coke can be added for carbon control. If the desired steel temperature and carbon contents are not attained then a reblow is undertaken. When the end point conditions are achieved, the converted is tilted is poured into a 130 tons steel ladle through a tap hole. Alloying metals are added to the ladle during tapping. Ladle activities, namely for ferromanganese and ferrosilicon are weighed out of storage bins and loaded into boxes which are transported by fork lifter truck to the steel ladle side of the converter. Two boxes can be positioned together on a discharging device and the contents added to the ladle. Aluminum bars by bags of coke breeze are added to the ladle by hand. For certain steel specification calcium silicate is also added to the ladle. On completion of tapping the steel ladle is moved by the

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self propelled rail car into the ladle bay of casting area. The converter is tilted in the opposite direction and the slag is discharge into the slag pot which is given by a self propelled rail car to the slag bay.

STEEL CONVERTER SPECIFICATIONS

No. of converters 2Type Top blown oxygen converterCapacity 130 tonsWorking volume 93m3

Specific volume 0.6M3 / T

Ration 1.68Mouth dia 2430 mmInner dia 4240 mmInner height 7125 mmTotal thickness of wall brick work 920 mmWorking lining Ten bonded dolomite

MIXER SPECIFICATIONS

No. of mixers 2Capacity 1300 tones

CONTINUOUS CASTING PROCESS

There are 3 machines 1)4 stand bloom caster2)2 slab stand caster3)6 stand of billet caster

The bloom and slab casters are similar in operation and the differences between the instruments and control systems of the two types of machine are described in the individual zone report. The ladle from the steel making shop is moved by crane to a prepared caster. When stabilization of chemical composition or temperature of the steel is necessary the ladle is taken to a stirring station and nitrogen is blown through an immersed lance. The temperature of the steel is measured before the ladle is placed on a caster turret. When the ladle is positioned correctly on the turret arms the crane is unhooked and an operating cylinder is fitted to the slide

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gate valve of the discharge nozzle. The turret can accommodate two ladles. One in the casting position and the other in reserve or awaiting removal.

A prepared tundish on a tundish car is positioned over the strands of the caster and the immersion nozzle for each water-cooled copper mould is dixed in position. A mounld is sealed by the head of a dummy bar inserted through the rollers of the strand. The turret is rotated to bring the ladle into the casting position above the tundish. The slide gate valve of the ladle is opened and the tundish is filled to required level. The tundish stoppers are opened and when the liquid steel in each mould reaches the required level the respective mould oscillating mechanism and withdrawal drive are started. The continuous cast bloom or slab, on being withdrawn from the mould. Is sprayed with water in the secondary cooling zone. During casting the levels in the tundish and moulds are regulated. The casting speed is set according to the steel temperature; the latter being measured periodically in the tundish by means of an expandable immersion thermocouple. Waster flow to the secondary cooling zones is regulated as a function of casting speed. Samples are taken, from the steel flowing into the tundish, for analysis at the express spectrographic laboratory. The continuous cast bloom or slab is cut to specified lengths at the gas cutting section A gas cutter clamps onto the cast steel at a pre-set length and moves in synchronism until cutting is completed. The cut lengths are moved by roller table. Transfer car and crane to the stockyard. Series casting can be undertaken if the interval between converter tappings allow a new ladle to be placed on the turret before the slide-gate valve of the previous ladle is closed.

CASTING MACHINE SPECIFICATION

SLAB CASTER

No. of machines 2No. of Strands Two strands eachSize: thickness 150-200 mmSize: width 700-1550 mmType of machine Radial CurvilinearMachine radius 10 meterCasting speed 0.6-0.9m/minutesCapacity 825000 tons/yearMachine length mould top to 22 meter

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last roller mould top to cutter 36.5 meterMetal flow control in mould Mono block

tundish stopper

BLOOM CASTER

No. of machines 1No. of Strands 04 No’s eachSize: thickness 260 x 260 mmType of machine Radial CurvilinearMachine radius 12 meterCasting speed 1.1-1.2m/minutesCapacity 400,000 tons/yearMachine length mould top to last roller mould top to cutter

20 meter30 meter

Metal flow control in mould Hydraulically operated mono block tundish stopper

BILLET CASTER

Mould top to last roller 20 meterMould top to cutter 30 meterMetal flow control in mould Hydraulically operated mono-block

tundish stopperNo. of machines 01No. of Strands 06Size: thickness 150 x 150 / 125 x 125 / 100 x 100 / 80 x

80Type of machine Radial CurvilinearMachine radius 12 meterCasting speed 1.1-1.2m/minutesCapacity 400,000 tons/year

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WEEK 4

ELECTRONICS DEVELOPMENT CELL LAB (EDC LAB)

Electronic Development Cell of Pakistan Steel is engaged in designing and development of indigenous electronic instruments/systems by employing modern micro-controller based digital electronics for the replacement of outdated/obsolete equipment and for enhancement of existing instrumentation and automation of various production units.

Electronics design engineers in EDC have ability of programming in low level (Assembly language) and high level programming languages and designing hardware based on micro-controllers and digital electronics which are the basis of all new instrumentation and automation such as PLCs, DCS, and Hybrid Controllers.

In last two decades EDC has designed and installed more than 200 instruments at various complexes of Pakistan Steel.   These instruments are working round the clock for the measurements of industrial parameters which includes:

1.   Temperature Instruments (Indicators & Controllers for various furnaces)

2.   Flow Indicators (For the measurement of Gas, Liquid and Steam)

3.   Batch/Hopper Weighing (For the preparation of blend of different materials, Measuring capacity depends on silos or weighing hoppers)

4.   Conveyor Belt Weighing Scales (Online weighing of raw materials transported through conveyor belts.   Maximum weighing capacity is 1000 tones/hours.)

5.   Weighing platform Scales (These are portable weighing platforms easily moved or installed anywhere.   These are used for weighing of finished product up to 15 tones)

6.   Process Control Instruments (Like length/speed/width measuring, sheet  centering, sheet detection, coil diameter measuring, level measurements,  jumbo process data display, panel meters etc.)

7.   Jumbo Clock (14X4.5 Feet) for Main Gate Entrance Our strong area of specialty is to meet customer requirements of plant .In the field of instrumentation & automation.   They can design & develop electronic  instruments  to  meet  specific  requirements  of  process for Which  instruments  are  not  readily  available  in markets.  Further, we have also developed expertise in the below mentioned areas:

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·         EDC can design and develop functionally equivalent, electronic cards for the replacement of irreparable electronic cards of various process machines to keep machines and process in operation.

·         EDC can design and develop electronic cards required for interfacing latest sensors/transducers with legacy  systems  and  interfacing of old sensors to latest instruments.

·         Designing of artwork for single and double sided PCBs (Printer Circuits Boards).

·         They may extend our skills and expertise for the preparation/vetting of technical specifications of electronic instruments/equipments required for the procurement from local or foreign agencies.

·         EDC is fully capable of implementing new technologies emerging in the field of automation and instrumentation.   They can provide consultancy for selecting and configuring a wide array of available instruments according to process requirements.

After obtaining ample experience of designing and development of electronic equipment, they are now in position to extend our expertise and service through this letter to develop bidirectional relationship for resolving problems and helping you in the field of instrumentation and electronics technology.   They will very much appreciate your interest and enquiries in the specific areas of your interest.

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SUGGESTIONS

Management must pay attention to the capital repair of the plant which otherwise will prove costly for the organization.

Old, conservative and costly employees should be replaced with the young, qualified and intelligent generation.

The human resource management should aware us with the safety rules which are employed in industries

Proper orientation should be given to the market and sales promotion activities.

There are always need to improve working condition and safety measures in the production unit.

Pakistan Steel can increase it’s profitability and efficiency by promoting downstream industries.

Role of the Electronic development cell in the modernization of the system is praiseworthy. But their exposure of work should be exceeded.

Pakistan Steel mill is just like the back-bone of our economy. Being student of electronic engineering, for the higher production level in the industry we strongly recommend use of latest industrial automation techniques such as controlling through latest PLC based systems & micro controller based systems, thyristor etc. Although some control systems has been digitalized but still most of the systems are controlled through Old Russian technology.

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