WATER MANAGEMENT DEPARTMENT:

The supply of huge amount of water required in BF, Roll mills, SMS, Pig Casting Machines, sludge tank, Gas cleaning plant, Water supply, Fire fighting, Captive power plant, etc. comes under the jurisdiction of this department.

SOURCE OF WATER:

Diamond river, which is almost 5 miles distant from DSP source gate.

DISTRIBUTION OF WATER:

The water from the river comes through canals to the settler cum underground reservoir by the action of canal pumps. The work pumps then suck the water from the reservoir and supplies to various sections of the plant after proper treatment of this water. The reservoir is of about 1 mile radius, bifurcated from the middle in a way that it takes water about 3-4 days to traverse from canal pump house to works pump house. Meanwhile, the sediments get flocculated and a primary separation is affected here.

After post modernization scenario, lots of changes are occurred in DSP. Seven pump houses under WMD control, the first four are important. They are:

1.     Canal pump house,

2.     Works pump house,

3.     Rolling pump house,

4.     Foundry pump house,

5.     Old water treatment plant,

6.     Second use pump house,

7.     New drinking water treatment plant.

I.                  CANAL PUMP HOUSE

It is the first water consuming point on 8 kms long DVC canal. The raw water from the canal is lifted by 5 pumps (3 running, 2 stand by) and discharged in to storage cum settling reservoir. There is also a bi pass channel of 8’×6’ cross section through which raw water can be fed to WPH directly.

Typical Pump

Capacity 10000GPM     Head 50 ft   Speed 730-990 rpm

II.               WORKS PUMP HOUSE:

The pump house is considered to be the heart of DSP, as the entire supply of water to DSP works area is from this pump house only. Settled water from ground water reservoir is led into the suction chamber of WPH located near to reservoir through a concrete flume and rotating drum screen (2 nos.). There are 13 pumps in WPH of which four supply water to captive power plant and four to diesel driven pump. Settled water from WPH is conveyed to various unit by 3 settled water mains.

Typical pump

          Capacity 5000GPM       Head 80ft    Speed 970rpm

III.&  IV. ROLLING MILLS & FOUNDRY PUMP HOUSE

Water from various roll cooling, scale flushing, skid pipe cooling and furnace cooling are sent to rolling mills water treatment plant via scale pump house. This plant is having 3 nos. clarifloculators. Each clarifloculator remove oil & mill scale through sedimentation and sent clean but hot water to hot well sump. On the other hand water from various mills after furnace cooling is sent directly to the hot well. This hot water is pumped by 5 nos. of hot well pumps and sprayed in a natural draught cooling tower. Hot water after cooling down is sent to cold well. This cold water is pumped via 5 nos. cold well pump and it send to the mill for their service. One balanced header tank is provided to store water when drawl from mills is less than supply from pumps.

Typical pump

          Capacity 65000 m³/hr    Head 60ft    Speed 735rpm

Foundry pump house is smaller but similar to rolling mills pump house.

Typical pump

          Capacity 800 GPM        Head 110ft  Speed 735rpm

COST ASPECTS

          Since water is costly, adequate steps should be taken to optimize its consumption. For 1000 gallons of raw water, Rs.1.57 is to be paid to DVC. In addition, a pollution tax of Rs0.0225 per Kl of water intake is to be paid to the govt.

ENERGY MANAGEMENT DEPARTMENT

          Previously known as ‘Energy & Economy Department’, its main objective is to economize the process and suggest the best method to minimize the energy consumption in an otherwise highly energy consuming steel plant. Total energy required in making 1 T crude steel is at present around 7.0 Gcal. [1 Gcal =10⁹ cal.]

          Steel industry consumes a lot of energy; in 2001-02, e.g. the coke ovens consumed around 1.1086 Gcal/T of coal charged while sinter plant and blast furnace consumed 0.7035 and 3.9697 Gcal/TCS respectively. Similarly various sections like SMS, CCP, Roll Mills, Boiler House , etc. have their own energy demands. Before modernization (when O.H. furnace was operating), the energy consumed was 10-11 Gcal/TCS which has sufficiently lowered down to around 7 Gcal/TCS; the saving of 5 Gcal/TCS is really a great achievement by EMD.

The department has four broad sections:

1.     Gas Control: The energy in the plant is in the form of combustible gases, i.e. mainly BF gas & CO gas. To maintain proper continuous supply to different energy demanding sections of the plant in any climate 24 hours a day 365 days a year, even during emergency is the duty of this section. The main control room monitors  therefore the whole distribution through various instrumentation meters.

2.     Thermotechnique unit (4 nos.): Two units; primary site (CO, BF, etc.) and finishing site (reheating furnaces in Rolling Mills) maintain the proper fuel to air (O₂) rates. The combustion survey of flue gases by Orsat analysis is done from time to time and the new better ratios of flue to air are maintained.

3.       Thermotechnique gas control: The whole processed is monitored and controlled from the section.

4.     Light Mechanic Maintenance: The major functions of this section is to look the gas-safety of the plant pipelines (which contain highly inflammable gaseous compounds). It includes looking after 16 km long CO, BF, BOF & mixed lines, 7 km nitrogen pipeline, and 4 km long inter-plant compressed air line; giving the gas clearance for jobs on pipes; looking after bleeding of BF, BOF, or steam gases.

In addition, to ensure continuous gas supply, gas holders for BF gas, BOF gas & CO gas function as reservoir to hold the excess or to supply in emergency are also provided. The capacities of this gas holders are 100000 m³, 50000 m³ and 4000 m³ respectively of BF, BOF, CO gases each in turn having a specified lower limit as well.

CONTINOUS CASTING PROCESS

         

It is the modernized plant for casting billets. Here billets produced directly from the liquid steel. It has a system of turret where two ladles are placed. Turret can move through its axis, when one ladle is full of steel and goes into operation, other  is open and on the opposite side of the turret to get steel ladle capacity is 110 tons each. Steel falls down from the ladle through slide gate which is at the bottom of the ladle. It passes through the  billetmoulds and gets its size. Here some nozzles are provided to cool down hot billets and helps in acquiring the solid shape. Billets pass through curved channel. The radius of curvature is 6 mts. Here 6 strands are there to produced to 6 billets simultaneously. The billets are passed through shears by means of rollers where they are cut to  the required size.

          The length of the billets are 6m, 9m,12 m. weight is 78kg/mt. billet size is 100×100 mm, casting temperature = 1530-1580⁰ C, shear angle is 12⁰ 4^’ and cutting is 2⁰. Lubricant used is rapeseed oil. Inlet and outlet temperature difference is 40 to 50⁰C.

          There are two casting machines in CCP. Each machine has 6 stands.

The shop has following facilities:

·        Pouring of argon gas from homogenization of liquid steel.

·        Ladle turret for quick change of ladles

·        Shrouding system for protection of metal from oxidation

·        Automatic mould level control

·        Mechanized shear.

·        Turnover cooling bed for uniform cooling of billets.

The main advantages of this process are:

·        Cost of production is very low

·        Productivity is very high

·        Very good quality

·        Very low heat loss and considerable fuel  saving.

·        More control

·        Less pollution(since no scrap)

·        Less time required

WHEEL & AXLE PLANT

    

Wheel and axle plant is a special feature of Durgapur steel plant. Till recently it was the only plant in the public sector, which produced  the wheel sets. The main customers of the wheel sets are the Indian railways, although the wheel sets are exported to various countries

     Wheel and axle plant was commissioned in 1962 with a capacity to produced 46,000 sets/yr. subsequently its capacity was raised further to 76000 sets/yr. The wheel and the axle plant has undergone modernization recently.

     In wheel and plant of DSP, wheels are produced by pressing and rolling while axle are produced by forging, subsequently both are heat treated and machined. For the case of production, wheel manufacturing section and axle manufacturing are located in two different bays. Tested wheels & axles finally meet only in assembly.

WHEEL PLANT:

    

The raw material for wheel is 12 side fluted bottom poured steel ingots of diameter 16”,14”. The chemical composition of wheel ingots is:-

·                  C=0.62 to 0.68%

·                  Si=0.24 to 0.28%

·                  S=0.04 to % [max]

·                  P=0.045% [max]

·                  Mn=0.70 to 0.85%

AXLE PLANT:

     The raw material is square bloom rolled in the blooming mill. Typical composition of axles steel [killed steel] :

·                  C=0.33 to 0.37%

·                  S=0.04%

·                  P=0.04%

·                  Mn=0.65 to 0.80%

·                  Si=0.12 to 0.17%

·                  Al=0.01 to 0.025%

The fluted ingots are sliced into 4-ingot block of which  three blocks are usually  used for wheel making. They are then subjected to heating, descaling, forging to get the rough shape of a wheel. Ultrasonic testing is done on a randomly selected wheel of a batch after it has undergone

normalizing in presence of  (C + Mn) as per Railways norms. Similarly axles are manufactured by rough  shaping of blooms, heats treatment, Ultrasonic testing and machining (that includes removing dust and scales drilling holes). Assembly of wheel and axle  is done  so as to obtain interference between the wheel seats and the bore  of  the wheel to obtain mounting  pressure build up to 400-500 kg/mm of wheel seat diameter.

BASIC OXYGEN FURNACE

INTRODUCTION:-

                   BOF is the core of a steel plant and the tonnage capacity of any steel plant is normally designated by the tonnage capacity of its BOF or SMS. Basic Oxygen Furnace was added under modernization scheme of DSP. It has a production capacity of 1.86 MT of stell per year. The BOF shop in DSP consists of a newer mixer bay, one VAD unit, 3 converters, a lade treatment section, which is intermediate between BOF and the CCP.

               Hot metal comes from the Blast Furnace to Furnace to the mixer bay of the BOF shop. These mixers (2 in nos.) are of capacity 1300T. In the mixers a temperature of about 1300-1400 degree Celsius is maintained. Mixers mixes the liquid metals of two or more ladles comong from blast furnace and homogenizes the composition of liquid iron to be charged in the BOF converters. Fuel for the mixers is a mixer of coke oven gas and air in the ratio of 1:5. To measure the ladle temperature of hot metal, the slag layer above is broken by anchor punch or by oxygen lancing.

               Each converter has a capacity of 110-130T per heat  and due to nitrogen splashing, the average life of each of the converter has increased from 500 heats to 1000 heats. The converter has tap hole for tapping slag & steel. Each converter has its own lance system. Lance is used in the converter for blowing the oxygen at a high pressure (42 kgf/cm²) so as to form an emulsion on the surface of the metal which increases the surface area to an extent; the separation of impurities takes place very fast, thus giving the process unique distinction i.e. a very fast process for the steel making. There are two lances for each converter operated by separate lance carriages. The oxygen blowing rate is 450Nm³/min and the blowing pressure is 16 bar from the top and 12 bar from the bottom.

               Oxygen is passed through the molten pig iron and thus steel is produced, as there is reduction in carbon percentage. The charge consists of molten metal, cold pig iron, steel scrap, lime, dolomite, bauxite, iron ore, mill scale etc. They have got the facility to stir the mass by non reactive gas like argon or nitrogen from bottom.

The  quantity of material  required for the production of one ton of steel:-

Hot metal	962 kg
Scrap	142 kg
Iron ore	29 kg
Dolomite	40 kg
Lime	120 kg
Limestone	15 kg

Tap to tap time in BOF:

Scrap charging	3 min
Hot metal charging	4 min
Oxygen blowing	18 min
Initial slag off	5 min
Sampling temp. measure	6 min
Final slag off	3 min
Tapping of steel	6 min
Reserve delays	57min
Total time	57 min

Tapping temperature at converter=1700⁰C

Tap-pouring temperature =1640-1650⁰C.

Total blowing time is 18 min

BOF gas rate=75Nm³/ton with C_v=2100kcal/m³

Slag obtained =250 kg/TMH

The composition of the molten metal of the BOF is as follows:

·        Carbon: 4.1-4.3%

·        Phosphorous: 0.1-0.25%

·        Silicon: 0.65-0.85%

·        Manganese: 0.7-0.8%

·        Sulphur: 0.03-0.04%

NEW LIME CALCINATIONS PLANT:

Introduction:

          Lime is considered as the most important raw material in BOF steel making next to hot metal only. The role of lime is to fix acidic compounds of undesirable metals and metalloids from metallic bath to slag and to protect the basic lining of the vessels from attack of acidic compounds.

          NLCP after modernization ensures consistent quality of lime to BOF shop. It is the first of its kind in India steel plants. The kiln is controlled by PLC bar. A single operator can run the entire plant from the main controlled room with the help of control panel. There are 3 kilns of 300 TPD each (so total 900 TPD). Klin is constructed with two concentric cylinders and the annular space between the cylinders is used for the calcination of limestone. It is fired with coke oven gas through 10 combustion chambers. Two levels are there each having 5 combustion chambers.

1.     Limestone(25-55mm) 1530 tpd

2.     CO gas 7600 Nm³/hr.

3.     Electrical energy 1765 kW.

4.     Air 51000 Nm³/hr.

5.     Nitrogen 95 Nm³/hr.

6.     Compressed air 140 Nm³/hr.

7.     Water 3.52 Nm³/hr.

OUTPUTS FROM THE NLCP:

                  

1.     Lime (20-50) 765 tpd.

2.     Lime (0-20) 135 tpd.

3.     Limestone (-25) 150 tpd.

4.     Limestone (+50) 75 tpd.

5.     Lime and limestone dust (0-1) 14 tpd.

6.     Exhaust gases 73500 Nm³/hr.

BATTREY DIMENSION:

         

          Length 440 cm, breadth 9.0 m, height 54 m.

KILN SIZE:

         

          Height=531.5 m, O.D=6.8 m, structure=400 tonnes

          Refractory lining=700 tonnes, limestone holding capacity=765 tonnes.

CENTRAL CRANE MAINTENANCE

          This division takes care of the cranes used in the rolling mill only. The cranes employed in the rolling mills are Electric Overhead Travel cranes of commonly known as EOT cranes. The other type of crane in use is the Vertical Ingot Charger or VIC. Central Crain Maintenance takes care of the mechanical maintenance and the structural part whereas the motors are maintained by the electrical maintenance division. The crane in operation varies in the capacity from 3 T to 75 T. And total number of cranes in operation in the whole of rolling mills are 52 cranes. The cranes in operation are both single hoist and double hoist. In case of single hoist there is only one hoist and in case of double hoist two hooks are there, which are operated simultaneously and the capacity of the crane is given by the sum of the capacity of each of the hoists which are equal. There are a few cranes with a main and auxiliary hoist, and they can be operated separately, and their capacity differs. The terms used in the reference of the cranes are:

·        LT or long travel – this motion takes place along the bay

·        CT or cross travel – this motion takes place across the bay.

The third kind of drive is the hoist drive.

          The assembly of the crane consists of a girder under which wheels are fixed, the trolley or the cabin. And the hoist consisting of the pulley, hooks & the ropes. The ropes used are the metal wire ropes, stranded together and wound across a fiber core. But in case of a VIC, mast like structure is used. It can be rotated through 360⁰ in both clock wise and anti clock wise direction. It has got two jaws at the end of the mast, which is used to grip the ingot and then place it in the ingot feed car. The drive is given by a motor and very simple mechanism is employed. Most of the gears used are worm wheel type. The maintenance work involves weekly greasing, recharging of gear oil and replacement of the worm out parts and also conditional repair.

          The safe working load is the parameter used to determine safety. Factor of safety is kept very high for the hooks and pulley ropes.