AN INDUSTRIAL TRAINING REPORT ON “VISAKHAPATNAM STEEL PLANT”
PREPARED AND SUBMITTED BY ANISH GRANDHI DINESH ADARI DIVYA SAI TEJA S. HARISH KURAPATI KALYAN AMMU MADHURI K. SAMPATH V. V. PHANEENDRA
UNDER THE GUIDANCE OF Er.VISWANADHAN
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ACKNOWLEDGEMENT We thank our Prof. Surya Kiran of GITAM University for helping us on what to focus during this training. We thank Er. S. Viswanathan and Er. Sanyasi Rao for giving us continuous guidance throughout the whole training period in Visakhapatnam Steel Plant. We extend our thanks to Incharges each and every department of Visakhapatnam Steel Plant who made us knowledgeable with their valuable teaching.
Place: Visakhapatnam Date: June 2nd 2012
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Abstract
Each and every department in an industry needs to have a maintenance department that is a service department that looks after the machines. They should have a thorough idea of the working of the machines and need to constantly check on them to ensure smooth running. Periodical check-ups and emergency repairs come under this section. Replacement and Repair of the part of the machine broken down in the fastest and the cheapest method is very important. This is exactly what the Maintenance Dept of every zone does. The report covers what we have learnt during the training in Visakhapatnam Steel Plant- The process of making steel from the raw materials and the role of Central Maintenance-Mechanical (CMM).
Signature of Students
Signature of Faculty
Date:
Date:
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TABLE OF CONTENTS 1. RMHP (Raw material handling plant) 2. Maintenance management systems 3. CM (M) 4. Coke Zone 5. Iron Zone 6. Steel Zone 7. Mills Zone
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MAINTENANCE MANAGEMENT SYSTEMS (MMS) MMS is a central maintenance department which implements, monitors and controls essential activities of Maintenance And Management Systems (MAMS), Budget Management, Catalogue management and Contract Bills Management through IBM ORACLE Environment. All the business riles adopted in the existing systems will be incorporated in the system Maintenance And Management Systems (MAMS) is to ensure high availability of equipment with high reliability resulting in minimum breakdowns and optimum utilization of resources. Aiming at Systemising the Planning of Maintenance activities, creating a system of reviewing and Accounting of Reactive Maintenance activities after analyzing the breakdowns and to stop their recurrence. It covers Mechanical, Electrical, Instrumentation and Telecom Sections of Works Division. MAMS is also helping the Plant Maintenance in various Resource Planning activities such as Contract Outsourcing Management, Field Machinery Management, Departmental Stores Management, Rotable Spares Management, Replacement Analysis etc. MMS monitors and Control the expenditure incurred/to be incurred is within the budget provided by Board for the following heads of expenditure of Works Division i) Repair and Maintenance ii) Other Expenses of Operational needs iii) Administration iv) Specified Special Activities v) Replacement & Monitoring-Capital Expenses 5
vi) Stores, Spares & Consumables MMS allots and maintains a unique number called Catalogue Number for Equipment /Spares/Any item of purchase for effective tracking of all transactions of that material right from its indenting stage. It covers Works & Non-Works division of entire plant.
MMS keeps the following details for preparation of various reports - Payment Details of R&M expenses - Shop floor inventory - Outstanding liability - Costing Data - Capitalization - Local expenditure Visakhapatnam Steel Plant is a large scale Integrated Steel Plant characterized with variety of complex Chemical, Metallurgical and Mechanical processes at very high temperatures and in hazardous environment. The interruptions in the process due to stoppage breakdowns of equipment not only result in huge economic and production loss but also affect the equipment performance and prove hazardous to the personnel. Hence these breakdown call for methodical planning to carry out maintenance activities to avoid such occurrences. This necessitates on the part of the maintenance activities to evolve systematic maintenance procedures to safe guard the health of the equipment and to ensure their high availability for profitable operation of the plant at minimum maintenance cost.
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Maintenance is an activity over the equipment to improve the reliability and availability of the equipment. These maintenance activities are broadly classified as 1. Preventive Maintenance
2. Breakdown Maintenance
1.1Preventive Maintenance (PM): Its based on the principle of carrying out mandatory predefined maintenance activities on the equipment. It is further classified as-
Short Term Maintenance Activities: Regular Time Based Inspection, Routine repair and Lubrication activities & Condition Based Activities, which provides for regular monitoring of critical equipment with suitable tools, instruments and in the event of abnormality appropriate maintenance activity will be taken up
Long Term Maintenance Activities: These are the Capital repair activities during which the equipment is under shutdown for longer periods. These repairs involve the repairs and replacement of major spares structural, etc. the capital plan is made well in advance to ensure the availability of resources and services.
1.2Breakdown Maintenance (BM): Breakdown Maintenance is done in the failure or abnormal interruption in the functioning of the equipment.
The primary goal of the Maintenance Management Systems (MAMS) is to avoid the occurrence of breakdown and minimize the unplanned breakdown maintenance and to ensure high availability of the equipment at minimum
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maintenance cost. It‘s a computerized application system designed for methodical planning, scheduling, execution and control of the maintenance activities. Maintenance Management System aims at establishment effective Maintenance practices with the technical expertise through systematic procedures laid out for the maintenance.
MAMS depend very much on reliable info system. The data pertaining to both technical and relevant commercial aspects of various equipment of the plant are stored in the maintainable data repositories. The main repositories on which the successes of this system depend on are-
1) Equipment Master, 2) Assemble Master & 3) Repair Cycle Master of different assemblies of various equipments. All the material requirements will be taken up with and fulfilled bu the Material Management System, like raising MPR for spares, procurement, material issues etc. Repair Shop scheduling system takes care of the management of manufacturing and repair activities for spares of the equipment. Appropriate check sheets and work orders are generated for execution of the maintenance activities. The execution of these activities is controlled and accounted by effective feedback system. The feedback is accounted resource wise. The maintenance personnel respond quickly to the breakdowns as and when they occur and the first informational details and the relevant details are accounted into the system. These breakdowns sometimes call for emergency work orders. The maintenance experts analyze the repetitive breakdowns by
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scientific means, evolve the reasons, and suggest the appropriate remedial measures. The maintenance personnel implement the remedial actions for all the similar assemblies in due course. Any defects observed by the maintenance personnel during the inspection or work order execution are accounted for and liquidated accordingly. The defects observes are logged and the maintenance work required by the operation personnel is intimated to the maintenance personnel time to time through the Operation log and Maintenance Work request respectively. The maintenance personnel still suitably respond and fulfill the operations requirement. The system provides the exhaustive report feature to assist the decision making process of the management. In addition, the system provides the facility to download some predefined data set from the MAMS‘s database to process any analytical reports in other platforms.
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RMHP(Raw Material Handling Plant)
The raw material handling plant (RMHP) receives the basic raw materials for the steel making process from various sources through railway wagons and by road. These are stacked by stackers and reclaimed by reclaimers and distributed to various departments through conveyor system. The iron ore fines, iron ore lumps, sized iron ore, lime stone(BF and SMS grades),sand ,quartizite and manganese lumps are stacked at ore and flux yard. The imported coking coal(ICC),Boiler coal(BC), are stacked in coal yard .Coal is sent directly to Blast furnace after tippling ore and flux wagon tipplers. These raw materials are sent to various departments as indicated below :
Sinter plant: Iron ore fines, Limestone(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, dolo chips CRMP: limestone (SMS),Dolomite(SMS),dolo chips TPP: crushed boiler coal
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COCCP: Imported coking coal (ICC),Medium coking coal The RMHP is divided into two sections Coal handling plant(CHP) and Ore handling plant(OHP). The facilities available in two sections are as follows:
CHP
OHP
2 wagon tipplers 5 ground and 10 track hoppers Stockyards(10)beds Boiler coal crushing plant Stackers, reclaimers and stacker
3 wagon tipplers 10 ground and 10 track hoppers stock yards(12 beds) lump ore crushing plant stackers and reclaimers
Cum reclaimer Stacking conveyors Reclaiming conveyors
stacking conveyors Reclaiming conveyors
Salient features of RMHP:
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->Peripheral unloading system for railway wagons coming directly upto pushers ->blender reclaimers for blending of ores and flux in which the bucker wheel has a lateral motion across the bed
Raw Material Specifications:
The iron bearing burden materials are iron ore fines supplied from baladilla mines and manganese ore from the deposite in the vizianagram district. The various raw materials handled in the OHP are as follows: Sl.no
raw materials 1
Iron ore fines
2
Iron ore lumps
3
Sized iron ore
4
Limestone(bf grade)
5
Limestone sms grade
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Dolomite (bf grade)
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Dolomite(sms grade)
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Sand
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Manganese lump
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Quartzite lump
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Sponge iron
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Pillets
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Ld slag
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coke
The various raw materials handled in CHP are as follows 1
imported coking coal
2
imported soft coking coal
3
medium coking coal
4
prime coking coal
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5
boiler coal
These raw materials are sent in different proportions to various customer departments as indicated below
Customer
raw materials
1.coke ovens
ICC,MCC,PCC
2.TPP
Boiler coal
3.sinter plant
iron ore fines, limestone(bf grade)
4.BF
sized iron ore , limestone, manganese lump, quartzite
lumps 5.steel melt shop
sized ironore ,dolomite(sms)
6.crmp
limestone and dolomite (sms grade)
Raw material specifications : 14
The different raw materials are stored in the beds of stock yard and ground hoppers (GH) and track hopper (TH) and their identification, color and sizes are as follows: Material
size
sms limestone returns
-25mm
Limestone bf grade
6 to 40 mm
Dolomite(BF grade)
6 to 80 mm
Manganese lump
-40 mm
Sand quartz fines
0 to 3mm
Sized iron ore
10 to 50mm
Iron ore lump
-150 mm
Iron ore fines
-10mm
Limestone(sms grade)
-50mm
Dolomite(sms grade)
-50mm
Coke
10 to 60mm
Quartzite lump
10 to 30 mm
Sponge iron
3 to 20mm
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Pillets Ld slag
20 mm -10mm
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CM (M) Central Maintenance Mechanical CM (M) in steel plant is a service department which looks after the mechanical aspects of maintenance. This particular department looks over the inspection of the machines. Every department of the plant has its own maintenance section. It is also called the emergency department of the plant. This is so called because the importance of this department increases when there is a trouble in any mechanical aspect of any department. The central maintenance places the order for the conveyor belts which run all over the plant. This is mainly due to the fact that there may be a possibility for several departments to place the order for the same kind of conveyor belt which indeed may lead to the increase in the storage costs. There are basically 5 zones in the steel plant namely: 1. Coke Zone 2. Iron Zone 3. Steel Zone 4. Mills Zone 5. Workshop Zone In the steel plant generally two types of maintenance processes are adopted: 1. Breakdown Maintenance: Breakdown maintenance is when the whole system breaks down and the whole process gets disturbed.
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2. Planned Maintenance: Planned maintenance is done with prior intimation to all the authorities regarding the maintenance that is going to take place as a part of general maintenance. There are two types of jobs: 1. Critical Jobs. 2. Parallel Jobs. In the plant generally the critical jobs and the parallel jobs go hand in hand. For a parallel job to start the role of the critical job becomes crucial. The Critical jobs can also be called as the jobs that have to be done initially so that the other jobs can be done after that.
As mentioned in the very beginning the central maintenance mechanical deals with the conveyor belts of the plant. We have a total conveyor belt over a length of 140Km which would be further extended by another 110Km, leading to a total sum of 250Km all over the plant. There are two main criterions that are to be checked by the CM (M). They are: 1. Conveyor changing. 2. Inventory should be minimum.
Procurement
The important things that are looked after before the procurement are:
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1. Money. 2. Requirement. 3. Market Rate. 4. Should check minimum requirement. In the plant we basically have 26 different varieties of belt that are being used so, the procurement has a very major role.
Procedure followed in the plant to place an order for equipment: 1. Making a Plan: A certain plan is prepared and the total dates for notifications, the calling of tenders are given.
2. Making a list of necessary requirement: A plan is prepared so that the total list of all the requirement of the departments can be considered in the process of placing an order.
3. Tenders are called: The plant calls the tenders and here the person who wants to participate in the tender for the plant should have previously supplied material to the plant, if he has never supplied the material to the plant previously he should supply some material and it is tested for certain period after which the plant decides his/her participation in the tender.
4. Finalizing of the tender: The tenders are finalized on the basis of the lowest cost given by the supplier. The one who gives the least
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cost for any certain material would be considered for giving the supply for that material.
5. Delivery schedule is given: The plant then gives the necessary delivery schedule to the supplier so that he gets the idea of when the requirement occurs and by that date he should supply the material.
Belt Conveyors The belt conveyer consists of standard parts, which are advanced and simple in structure, easy to maintain. The vibrating equipment is adaptable for stationary and mobile crushing plants. The belt Conveyor are widely used in mining, metallurgical and coal industry to transfer sandy or lump material, or packaged material. The belt conveyer can be installed horizontally or aslope to meet the needs of different transfer lines. The belt conveyers can be operated temperature range from 20°C to 40°C. The temperature of transferred material by this belt conveyer is lower than 50°C. Features of Belt Conveyor High capacity Standard parts Simple structure Easy Maintenance
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How does the belt conveyor work?
The belt conveyors are the most commonly used powered conveyors because they are the most versatile and the least expensive. Product is conveyed directly on the belt so both regular and irregular shaped objects, large or small, light and heavy, can be transported successfully. Belt Systems use only the highest quality premium belting products, which reduces belt stretch and results in less maintenance for tension adjustments. Belt conveyors can be used to transport product in a straight line or through changes in elevation or direction. In certain applications they can also be used for static accumulation or cartons. Generally, this philosophy calls for belt cleaners that are: As far forward (as close to the conveyor discharge) as possible. Positioned out of the material flow. Designed to minimize risk to belt, splice, and cleaner itself. Designed to stand up to ―worst case‖ conditions. Designed for ease of maintenance, including simple blade replacement and reduced frequency of re-tensioning, Belt conveyors are available with either rollers (roller belt) or a solid surface (slider bed) to support the carrying belt. When the materials fall down on the conveyor, the roller under the belt will drive the belt come forward. In this way, we convey the stuff.
Conveyor Components Supporting Structure
The supporting structure is designed to hold conveyor sections firmly and in proper alignment. If it does not, for whatever reason, it is likely to have
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an effect on belt tracking. Support structure should be checked as a first step in belt tracking. Conveyor sections are bolted to the supporting structure. Diagonals across the frame should be measured. They should be equal. Conveyor bed sections (slider or roller) must be properly aligned with no vertical off-set between sections. A taut line should be stretched over the top surface of the bed and adjustments made so that all points are in contact. The entire bed (and each section) must be horizontal (across the width).
Pulleys/Rollers/Idlers
All pulleys, snub rollers, carrying idlers, and return idlers must be perpendicular to belt centre line, parallel to each other and level.―Squaring‖ with the frame is a good preliminary adjustment. The final adjustment, however, requires that this ―squaring‖ be done with the belt centre line as the reference. All pulleys must be at right angles to the direction of belt travel.
Take-up
The take-up device in a conveyor belt system has three major functions: To establish, and preferably to maintain a predetermined tension in the belt. To remove the accumulation of slack in the belt at startup or during momentary overloads–in addition to maintaining the correct operating tension. To provide sufficient reserve belt length to enable resplicing, if necessary. 22
Manual, as well as automatic, take-up devices are normally used in a typical conveyor belt system. The manual or screw take-up consists of a tension pulley which can be moved to tighten the belt by means of threaded rods or by steel cables which can be wound on a winch. They are unable to compensate for any length changes in the belt between adjustments and thus, permit wide variation in belt tension. The manual take-up must be such that when tension is applied to the pulley, the pulley remains at right angles to the direction of belt travel. Also the tension must be high enough to allow elastic recovery of elongation due to starting forces, load changes, etc.
Automatic take-ups depend upon suspending a predetermined weight (gravity), by activation of a torque motor, by hydraulic pressure, or by spring loading. These devices maintain a predetermined tension at the point of takeup regardless of length changes resulting from load change, start-up, stretch, etc. This permits running the belt at the minimum operating tension and should be used on all long length conveyors and moderate to highly stressed conveyors. The automatic take-up alignment must be such that the pulley or pulleys are maintained at right angles to the direction of belt travel. In a gravity or spring loaded take-up, the carriage must be guided to maintain the pulley axis on a line perpendicular to the belt centre line. The amount required depends on type of belting and on service conditions.
Conveyor Belting
There are many types of belting available, some of which are more popular than others. The most widely used types are described below. 23
Conveyor belts are usually manufactured of polyester, nylon, cotton, rubber, elastomers, and plastics in 100% pure form or in some combination. The resulting product is flexible and if designed, manufactured, slit and laced properly will go where directed by the conveyor system as designed and built. One of the most widely used types now is PVC belting.
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TYPES OF IDLERS Carrying Idlers Impact Idlers Return Idlers Carrying Belt Training Idlers Return Belt Training Idlers
1. Carrying Idlers Support the belt in the section of the conveyor that transports the material. These idlers may be flat or troughed to shape the belt to prevent
or unequal roll lengths. Normal spacing is 3 to 5 feet.
2. Impact Idlers Prevent damage to the belt at the loading point. These idlers may be troughing or flat types with grooved, molded rubber rolls. It is standard practice to use impact idlers at all loading and transfer points when the impact
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force exceeds 40 foot pounds To insure maximum belt protection for optimum life and to reduce skirtboard leakage the impact idlers should be at least six inch diameter and spaced at one foot intervals.
3. Return Idlers Support the empty belt between the discharge point and the tail pulley. Normal spacing is 10 feet. Steel — Used where materials are not sticky, corrosive, or abrasive. Available with urethane covering. Six inch diameter also available in 1⁄₄" wall thickness. Spiral— Used where sticky materials adhere to the belt, where a corrosive environment is present or abrasive wear is a problem. Unique construction minimizes belt fleet and damage to the return belt due to material build-up on the idler rolls. Spiral roll idlers can be used for belt travel in one direction only. Disc — Used under the same conditions as the spiral idler. These idlers can be used for belt travel in either direction. Massed end discs are standard. Ceramic, urethane and rubber disc rolls available.
4. Carrying Belt Training Idlers Assist in keeping the belt cantered on the conveyor. Actuating shoe type is used on belt traveling in either direction. Positive type is used on belt traveling in one direction only and is illustrated. Normal spacing is 100 feet and not within 50 feet of the head or tail pulley. 25
5. Return Belt Training Idlers Used for the same purposes as are Carrying Training Idlers. They are of the actuating shoe type, belt travel — either direction, or the positive and inclined pivot types, belt travel — one direction only. The positive type is illustrated. Normal spacing is 100 feet and not within 50 feet of the head or tail pulley
Belt conveyor systems Conveyors are durable and reliable components used in automated distribution and warehousing. In combination with computer controlled pallet handling equipment this allows for more efficient retail, wholesale, and manufacturingdistribution. It is considered a labour saving system that allows large volumes to move rapidly through a process, allowing companies to ship or receive higher volumes with smaller storage space and with less labour expense. Rubber conveyor belts are commonly used to convey items with irregular bottom surfaces, small items that would fall in between rollers or bags of product that would sag between rollers. Belt conveyors are generally fairly similar in construction consisting of a metal frame with rollers at either end of a flat metal bed. The belt is looped around each of the rollers and when one of the rollers is powered the belting slides across the solid metal frame bed, moving the product. The rollers allow weight to be conveyed as they
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reduce the amount of friction generated from the heavier loading on the belting. Belt conveyors can now be manufactured with curved sections which use tapered rollers and curved belting to convey products around a corner. These conveyor systems are commonly used in postal sorting offices and airport baggage handling systems. A sandwich belt conveyor uses two conveyor belts, face-to-face, to firmly contain the item being carried, making steep incline and even vertical-lift runs achievable. Care and maintenance of conveyor systems A conveyor system is often the lifeline to a company‘s ability to effectively move its product in a timely fashion. The steps that a company can take to ensure that it performs at peak capacity include regular inspections, close monitoring of motors and reducers, keeping key parts in stock, and proper training of personnel. Increasing the service life of your conveyor system involves: choosing the right conveyor type, the right system design and paying attention to regular maintenance practices. A conveyor system that is designed properly will last a long time with proper maintenance. Here are six of the biggest problems in overhead type conveyor systems: Poor take-up adjustment: This is a simple adjustment on most systems yet it is often overlooked. The chain take-up device ensures that the chain is pulled tight as it leaves the drive unit. As wear occurs and the chain lengthens, the take-up extends under the force of its springs. As they extend, the spring force becomes less and the take-up has less effect. Failure to do 27
this can result in chain surging, jamming, and extreme wear on the track and chain. Take-up adjustment is also important for any conveyor using belts as a means to power rollers, or belts themselves being the mover. With poor-take up on belt-driven rollers, the belt may twist into the drive unit and cause damage, or at the least a noticeable decrease or complete loss of performance may occur. In the case of belt conveyors, a poor take-up may cause drive unit damage or may let the belt slip off of the side of the chassis. Lack of lubrication: Chain bearings require lubrication in order to reduce friction. The chain pull that the drive experiences can double if the bearings are not lubricated. This can cause the system to overload by either its mechanical or electrical overload protection. Contamination: Paint, powder, acid or alkaline fluids, abrasives, glass bead, steel shot, etc. can all lead to rapid deterioration of track and chain. Ask any bearing company about the leading cause of bearing failure and they will point to contamination. Product Handling: In conveyor systems that may be suited for a wide variety of products, such as those in distribution centers, it is important that each new product be deemed acceptable for conveying before being run through the materials handling equipment. Boxes that are too small, too large, too heavy, too light, or too awkwardly shaped may not convey, or may cause many problems including jams, excess wear on conveying equipment, motor overloads, belt breakage, or other damage, and may also consume extra man-hours in terms of picking up cases that slipped between rollers, or damaged product that was not meant for materials handling. Drive Train: Notwithstanding the above, involving take-up adjustment, other parts of the drive train should be kept in proper shape. Broken O-rings
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on a Lineshaft, pneumatic parts in disrepair, and motor reducers should also be inspected. Loss of power to even one or a few rollers on a conveyor can mean the difference between effective and timely delivery, and repetitive nuances that can continually cost downtime. Bad Belt Tracking or Timing: In a system that uses precisely controlled belts, such as a sorter system, regular inspections should be made that all belts are traveling at the proper speeds at all times. Timing is also important for any equipment that is instructed to precisely meter out items, such as a merge where one box pulls from all lines at one time. If one were to be mistimed, product would collide and disrupt operation. Since a conveyor system is a critical link in a company‘s ability to move its products in a timely fashion, any disruption of its operation can be costly. Most ―downtime‖ can be avoided by taking steps to ensure a system operates at peak performance, including regular inspections, close monitoring of motors and reducers, keeping key parts in stock, and proper training of personnel.
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COKE ZONE
COKE ZONE :- Coke zone is the major zone of all the zones in maintanence department main function of COKE ZONE in VSP (visakhapatnam steel plant) is to produce coke from coal DIVISION :-
coke zone is divided in to two divisions
i. Coke oven ii. Conveyor belts Coke oven :- In coke oven Coal is converted into coke by heating the prepared coal blend charge in the coke ovens in the absence of air at a temperature of 1000°C-1050°C for a period of 16/18 hours.
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Coke oven is the main source to Blast furnance and sinter plant for coke
Functioning :- Main functioning of coke zone is divided in to four steps i. Coal handling plant ii. Batteries iii. Coke dry cooling plant iv. Coke sorting plant Coal handling plant :a. Coal which is used to convert in to coke is stored here. b. Coal is transferred to batteries by using bunkers. c. Coal handling plant gets coal as input from RMHP (raw material handling plant) by using conveyor belts.
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Batteries :a. In vsp (visakhapatnam steel plant) we are having four in number of batteries. b. Each battery consists of 67 ovens c. Input and output of oven is done by Charging car and Pusher car d. Charging car is used to charge coal in ovens from top by three openings e. Discharging the coke is done by Pusher car f. Charged coal is gradually heated by heating walls of the oven, heating is done in absence of air g. Oven is allowed to attains the temperature 1000°C1050°C at the central axis of the coke mass towards the end of coking period h. Coking period is generally specified between 16hrs to 19hrs depending upon oven condition and production requirement i. Volatile matter of the coal liberated during carbonization is collected in gas collecting mains in form of RAW COKE OVEN GAS j. The coke is cooled to 80°C from 800°C by direct contact cooling with ammonia liquor spray k. Each oven handles 32tons of dry coal charge and gives 25 tons of red hot coke as output
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Coke dry cooling plant :a. Coke dry cooling plant takes RED HOT COKE at a temp of 1000°C-1050°C as input and gives coke at temp of 150°C to 180°C as output b. Red hot coke is charged from the top of tower and collected at bottom. Cooling takes place at center of the tower by circulating the gases c. Gas is forced by mill fans in to chamber d. The cooled coke from cooling chamber is discharged on to the conveyor belt continuously through rotary discharging system e. Each coke dry cooling plant consists of four number of chambers f. Each chamber can produce 50 to 52 tonnes/hrs
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Coke sorting plant :a. Coke sorting plant differentiate the coke to blast furnace and sinter plant which is collected from coke dry cooling plant b. At first collected coke from dry cooling plant is crushed by crushers c. Crushed coke is divided depending up on the size d. Coke is divided in to two divisions +70mm and 70mm e. +70mm coke is send to roller toothed crushers f. -70mm is divided in to two ways (0-25)mm &(2570)mm g. 25mm-70mm coke is send to blast furnace h. (0-25)mm is separated in to null coke (10-25)mm and Breeze coke (0-10)mm i. Null coke is send to blast furnace and yard depending up on requirement j. Breeze coke is send to sinter plant
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IRON ZONE SINTER PLANT
Sintering : Sintering is a process of aggiomerating iron ore fines into a porous mass by incipient fusion caused by combustion within the mass of the ore particles. History of sintering : Iron ore fines (0-10 mm) which were a result of mechanized mining could not be charged in a blast furnace they reduce the permeability of burden in a blast furnace. These iron fines that were generated at mines could not ignored because of their
Huge quantity and
High iron content.
Raw materials used in sintering : Iron ore fines (0-10 mm) Coke – used as fuel Lime stone & Dolamite – to maintain required sinter basicity Sand – to maintain required sinter basicity Metallurgical wastes – to use wastes effectively and thus reduce the cost of sintering Lime – to enchance the process of sintering
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Sintering process : Preparation of various raw materials Mixing & Blending Mixing with sinter returns in presence of water to form green balls Charging on to the machine Ignition and suction. Factors effecting : Broadly the productivity of a sinter machine depends on the following factors :
Quality of input raw materials Permeability of sinter bed Vaccum under grate Quality of sinter
1. Quality of input raw materials : 2. 3. Physical properties: 1. Iron ore fines used for sintering should be of the size of (0-10 mm). 2. More of -1 mm fraction will reduce the bed permeability and will reduce the vertical speed of sintering , reducing the machine productiviy.
3. Chemical properties:
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1. Low amount of alumina in iron ore fines and low loss on ignition factor of various raw materials increases the productivity of the sinter. 2. At VSP alumina in iron ore fines varies from 2-3 % and total loss of ignition of base mix varies from 18-20 % 2. Vaccum under grate : The vertical speed of sintering depends up on the suction that is created under the grate more the suction higher will be the vertical speed of sintering and more the productivity. 3. Quality of sinter: Sinter plant quality also plays an important role in the productivity of sinter machines. Higher Feo gives the strength & productivity increases but sinter with more than 11 % of Feo in undesirable of a blast furnace. Low amount of Mgo increases productivity but sinter with 2.4% of Mgo is required by the blast furnace to form non-viscous slag. 4. Permeability of sinter bed: Permeability refers to the amount of space that is provided by the sinter bed to allow atmospheric air to pass through it. A bed with higher permeability will increase the vertical speed of sintering and thus productivity will rise . A bed with low permeability will offer resistance of the flow of air and vertical speed of sintering will reduce resulting in low productivity. VSP Sinter plant – an over view:
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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 .Two sinter machines of Dwight Lloyd type having 312 MT total grate area are provided for the purpose .Sinter machine is designed to operate at the rate of 1.2T/Hr/M for 330days in a year. Sinter plant consists of the following main sections 1. Flux crushing section 2. Fuel storage yard 3. Coke crushing and flux screening section 4. Receiving bins 5. Raw material bins 6. Material mixing and Distribution plant 7. Base mix yard 8. Secondary sinter mix and Pelletizing plant 9. Sinter machine building with sinter cooling 10.Fan building 11.Slime-dewatering pump house 12.Sinter Screening plant 13.Gas Cleaning plant 14.Air cleaning plant Apart from the above some auxiliary units are provided 1. Area repair shop 2. Area laboratory 3. Pump house no .5 & Cooling tower no .2 4. Sample preparation section
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5. Gas mixing station
1. Flux crushing plant: Flux crushing plant consists of four reversible hammer crushers to crush limestone & dolomite to (0-3 mm). Whereas they are of (6-40 mm) & (6-80 mm) respectively are received from RMHP. Crushers are fed with the help of vibro feeders. The crushed material is conveyed to screening plant by a conveyor. 2. Fuel storage yard: Coke screening from coke oven & blast furnace of 0-25 mm size are received in the section and stacked in different piles with the help of a tipper car conveyor. Pay loaders feed the screening to nine nos. of hoppers in turn send the material to coke crusher‘s plant. 3. Coke crushing, Lime stone and Dolomite Screening plant : The coke screenings are crushed in 7 four-roll crushers of 11T/hr capacity to a size of 0-3 mm. The crushed lime stone and dolomite are fed to eight screens for separating the +3mm and 63 mm fractions. The +3mm fractions are send to raw material bins. 4. Receiving bins: All the metallurgical wastes generated in the plant such as flue dust , cast house dust. Main scale etc. in this section into 8 number of bins . The disc feeders provided below with the each bin proportionate the raw materials and feed to the conveyors to raw material bins.
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5. Raw material bins: This section receives prepared raw materials from different sources to store in different bunkers. The raw materials are proportionated as required by means of automatic disc feeders tube feeders and weigh feeders. It acts as a junction house to various conveyors. 6. Material mixing distribution plant: This section receives the proportionated raw material by means of conveyors and mixers it is a mixing drum of 1200 t/hr to get uniformly in size and composition and sends it to base mix Yard for further processing. 7. Base mix yard: In this yard the raw materials from mixing bins is stacked in different piles with the help of twin boom stacker. This yard can stock of base mix for about 32 days requirement. The stacked material is reclaimed with the help of two blender re-claimers and dispatched to secondary sinter mix and pelletizing plant by means of conveyors. 8. Secondary Mixing and Pelletizing Plant : In this the base mix from base mix yard, Lime stone & coke fines from raw material bins sinter returns from sinter screening plant, sludge from slime dewatering pump house and ACP dust are fed in the required proportion to mixing drum and water is added to get required moisture content in the burden which is the final raw material for making sinter. 9. Sinter Machine Building and Sinter Cooling:
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1. The already prepared sinter of 10-25 mm size of received from sinter screening which is fed as bed material to a thickness of 40 mm over the grate bars of moving pallets of sinter machine. 2. The material in the pelletizer is charged over the bed material to a thickness of 40 mm over the grate bars of moving pallets of the sinter machine. 3. The raw material comes in to the ignition hearth the top layer of the charge & is ignited to1000‘c. 4. The furnace is of three sectional chamber type with 10 burners that heated with coke oven gas & B.F gas. 5. The grate is placed over vacuum chambers of 26 nos. 6. The sinter machine consists of endless chain of 135 pallets moving over 26 vacuum chambers. 7. By the end of 26th the sinter is completed and discharged to single roll crusher through a hopper. 8. The crusher crushes the sinter lump in to 0-150 mm, then the hot sinter passes over the hot screen, which separate from +8mm screenings. 9. The -8 mm screenings are cooled to 100‘c with water and passed through the conveyors for screening. Technical parameters of sinter machine: Type
:
Dwight Lloyd
Total grate area
:
312 m2
Effective / Sintering area
:
276 m
Length between sprockers
:
93.4 m 42
Width of the machine
:
4m
No . of pallets
:
135
No . of wind boxes
:
26
Drive arrangement
:
Left hand
Wind box arrangement
:
Right hand
Speed of machine pallets
:
1.5 to 8 m/min
Capacity of the machine
:
up to 450 TPH
Bed height
:
500 mm
Height of bed layer
:
40 mm
Technical parameters of straight line cooler : Active working area
:
420 m2
Length
:
118.4 m
Height of the sinter bed
:
0.75 m to 1.0 m
Capacity
:
Up to 550 t/hr
No . of wind boxes
:
16
No . of blower fans Specific flow rate
: :
8
66,000 m3/ton
10. Fan building :
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1. Sinter plant is designed for four exhausters with individual capacity of 15,000 m3/mm, two for each sinter machines. 2. These exhausters are meant to create suction required below the grate of the sinter machine which are of centrifugal type and are designed for a suction of 1500 water column. 11. Slime De-watering Pump House : 1. This plant is designed to separate out dust and skill of 0.15 to 0.25 mm size from water slime which comes blast furnace and all sections of sinter plant at 2000 m3/hr. 2. The separated dust is used with sinter return fines.
12. Sinter screening plant: 1. In this sinter screening plant there are two double deck screens and two single deck screens. 2. Sinter of size 0-50 mm coming from sinter machine building is screened to 0-5 mm, 5-10 mm, 10-25 mm & 25-50 mm fractions. 3. 0-5 mm sinter is dispatched to secondary sinter mixing plant along with BF sinter screenings. 4. The sinter of 10-25 mm is used in machine building & +5-50 mm is dispatched to B.F 13. Gas cleaning plant: The gas sucked from sinter machine through wind boxes by exhausters passeas through electro static precipitators in gas cleaning plant which cleans out
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the gas and dust is discharge @ 4772 kg/hr over emerged scrapper conveyors. The cleaned gas is let out through chimney. 14. Air cleaning plant: Air cleaning plant is for cleaning the sucked air under hoods of St. Line cooler, sinter crushers, sinter screens and transfer points. The air is sucked by suction fans 8 no‘s through Electro static precipitators, which cleans out the dust @ 8741 kg/hr is discharged into the scrapper conveyor. The cleaned air is let out through a chimney.
CALCINING AND REFRACTORY MATERIAL PLANT
CRMP, i.e calcining & refractory plant is an integrated unit of VSP. It plays an important role in the manufacturing of liquid steel and its customer is Seetl melt shop (sms). It is of two units. Calcining plant Brick plant
1. Calcining plant: It produces the lime and calcined dolomite, which are used for refining of hot metal to steel.
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It has 5 rotary kilns of 325 T/day capacity. Lime is produced from calcining limestone and calcined dolomite from calcining dolomite. The limestone and dolomite of size (30-60)mm, (25-50)mm are procured from U.A.E and Madharam mines of VSP respectively. And stacked at R.M.H.P. R.M.H.P reclaims the materials and conveys to ‗limestone & dolomite screening plant‘ through conveyors . It has two screens to screenout the minus fraction and sent to RMHP for use in sinter plant. The +30 mm size of limestone is stored in bunker 5 and +25 mm size of dolomite in bunker 6. Then conyed to the stone bins of all the kilns by operating the weigh feeders below the two bunkers. The material from the stone bin flows by gravity into the preheater and gets preheated by the hot flue gas coming out of the kiln by the operation of hydraulically operated rams. The feeding is regulated by the frequency of ram pushing. The fuel used for firing of kiln is Pitch Creosote Mixture (PCM) is supplied by (coal chemicals plant) ccp. And its calorific value is 9000 k.cal/kg. The fuel is stored in 4 tanks in pump house and pumps the fuel through the pumping,heating & filtering unit (PHF) of each kiln at 4-8 kg /cm2 pressure. The fuel generates a temperature of 1250‘c to 1300‘c inside the kiln and the product is discharged to a contact cooler provided for each kiln.
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The cooled product is screened and stored separately in flux storage building. The stored material is sent to SMS as per the demand and some +10 mm size lime to PCM. 2. Brick plant : It produces the pitch bonded magnesia carbon bricks for lining of converters and steel laders. The main raw materials of brick are sea water magnesia and fused magnesia which are imported from Ire land, Israel and China respectively. Flakes is used as additives and aluminium powder as antioxidant. Liquid pitch as binder which is supplied from CCP by tankers. In mill house , SWM is crushed ground and screened into different sizes of (0-0.2), (0-0.5), (0.5-1.6), (1.6-3) & (3-5) mm and graphite & aluminium powder are stored in separate blending bunkers. These fractions of SWM and additives are collected by scale car from blending bunkers in predetermined quantities and discharged into mirror. The pitch is added during mixing. The brick plant has 1600 T capacity hydraulic presses to press these bricks. After pressing the green bricks are placed on take off belt and are lifted to place on a tempering pallet manually and the pallet on a tempering car. The tempering of bricks is done at a temperature of 300‘c-350‘c .
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The tempered bricks are packed on packing pallets , strapped with polyethylene straps and stored in brick store, then dispatched to SMS as per requirement. Moreover, bottom jointing mass and back filling mass are also produced in the brick plant for use during converter relining & productiion of bottom jointing mass resin is used as binder in place of pitch.
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STEEL MELTING SHOP INTRODUCTION: In steel melting shop of Visakhapatnam steel plant, LD process of steel making has been adopted . The liquid steel obtained from LD process is cast into Blooms through Continuous Casting Machines (Bloom Casters).
For better exploitation of the available facilities and to have efficient administration in the biggest department of VSP, Steel Melting Shop is divided into two major sections, 1). Converter Shop 2). Continuous Casting Shop Each of these shops have been further divided. CONVERTER SHOP: Bulk Material Handling Section (BMHS) Mixer Shop Converter Bay Scrap Yard Ladle Preparation Bay CONTINUOUS CASTING SHOP: Tundish preparation Bay (TP Bay) Argon Rinsing Station (ARS) & IRUT & LF
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Continuous Casting Machines Gas Cutting Machines Bloom Storage Yard
DESCRIPTION OF FACILITIES: MIXER SHOP: It
is very difficult to supply the hot metal
from Blast Furnace to the
converter as per requirement, unless there is an arrangement for storing the hot metal in SMS. Mixer serves this purpose. There are two mixers in SMS. The Capacity of each mixture is 1300T Hot Metal. In mixer , temperature of hot metal is maintained by burning coke oven gas with air. The Mixer vessel is in cylinder form with two removable spherical ends. Length of the vessel is 10.67M mixer
platform and
and diameter is 7.64M. The mixer is installed on a is served by mixer crane (2 nose of capacity
180T/63T/20T). The main units of the mixer are shell assembly, roller support, tilting mechanism, hand brake mechanism, charging hole cover winch, charging hole platform, spout door opening mechanisms , gas & air distribution system, installation of
blower , lubrication system, electrical
system. The average life of mixer is about 1.6-1.8MT (Million Tonne), Lining duration is about 30 days. To reduce abnormalities in LD Steel Making, Blast Furnace is supplying Hot Metal to SMS in the following composition & temperature range.
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C = 4.0 - 4.5% Si = 0.4 - 0.7% Mn = 0.10% P
= 0.11% max
S
= 0.04% max
Temperature = 1250 - 1425 Deg. C. 1300 to 1350 Deg.C Through Mixer route 1350 to 1450 Deg C Through TLC (Torpedo Ladle Car) route. BULK MATERIAL HANDLING SECTION ( BMHS): The following bulk materials are used in converter shop of SMS. Calcined lime and Calcined dolo - used as flux in LD converter. CaO
= 89 – 90%
LOI
= 6 – 8%
SiO2
= 2.5 % Max
Size
= 10 – 25 mm
MgO of dolo
= 28 to 32%
Requirement = 6 - 10 T as per heat weight and hot metal composition, iron Ore Lump - Used as Coolant in steel making. Fe
= 66.9%
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SiO2 = 0.9% Al2O3 = 1.6% MnO2 = 0.05% Size = 15 – 60mm Requirement = 0.5 – 3T as per blowing conditions. Raw or Calcined Dolo – Used to increase lining life of converter. Lump Coke – Used to preheat the lining of newly lined converter. One of the requirements for continuous casting process is that the liquid steel should be killed. For this and to make different grades of steel, ferro alloys Coke breeze/ Petroleum coke & Aluminium are added in the ladle during tapping of steel from convertor to ladle. CONVERTER BAY: Hot metal contains different impurities above safe level which make pig iron brittle. But steel is nothing but refined hot metal. Refining is only possible when things are in molten phase. Refining is done by blowing oxygen in the LD converter charged with hot metal,scrap,flux,iron ore,etc. In this refining process, temperature of liquid steel is aimed at 17000 Deg.c. Different grades of steel is made by adding various ferro alloys & additives in different quantitie during tapping of liquid steel from converter to steel ladle. There are 3 LD converters in SMS. Oxygen is blown in converter through oxygen lance. CHARACTERISTICS OF OXYGEN LANCE: During blowing LD gas is generated. LD gas cooling,cleaning and collection system comprises of tube bar-tube type skirt, gas cooling hood and stack. When 52
the gas composition is acceptable, it is recovered and collected in gas holder. Unacceptable LD gas is discharged through Flare Stack. SCRAP YARD: Scrap is used as coolant. Scrap may be heavy or light. Length should be less than 1.5M. Sometimes cast pig iron is used as scrap incase of shortage in steel scrap. Purpose of scrap yard is to supply scrap to the converter periodically without any interruption. Following equipments are available in scrap yard. 1). Scrap Box Transfer Car 2).Scrap Weigh Bridge 3).Scrap Box 4). Magnetic EOT Crane SLAG YARD: The Slag generated in LD converter during refining of hot metal is collected in vessels called slag pots. This slag is dumped in pits which are present in slag yard. For doing so, slag pot transfer cars, slag dump cars, EOT cranes,etc. are needed. TUNDISH PREPARATION BAY: Tundish is a refractory lined container having 4 nozzles through which liquid steel is poured in all moulds of a C.C machine at a time. Pouring of liquid steel from tundish to mould is controlled by stopper rod mechanism. In tundish preparation bay, used tundishes are cooled by water/ compressed air and lining is demolished. All the relinng activities, stopper-rod assembly fixing,etc. are done in this bay. CONTINUOUS CASTING MACHINES (CCM): 53
Continuous Casting may be defined as teeming of liquid metal in a mould with a false bottom through which partially solidified ingot is continuously withdrawn at same rate at which liquid metal is poured in mould. FACILITIES AND EQUIPMENTS AT CCM PLATFORMS: Lift and Turn Stand To accommodate the steel ladles and place them in casting position as and when required to facilitate sequence casting. Its lifts the ladle and places the ladle at casting position by turning it and swing back the empty ladle after completion of casting. STRAND COOLING: Strand cooling is carried in 2 stages: Primary and Secondary cooling. PRIMARY COOLING: The soft water is used for this purpose with PH 7-9, total hardness – 0.2 dh. This water is repeatedly pumped through the moulds in a closed cycle with recooling blot. This water has to be treated and anti corrosive agent etc. should be added. This water is supplied at a pressure of 5-6 bar. The inlet water comes from the bottom & leaves the mould through the outlet valve which is located at top of the mould. This is indirect type of cooling. SECONDARY COOLING: The water that is sprayed over the strand should cool the strand uniformly throught the length, to avoid under cooling of some parts of strand. The pressure will be 6 bar. The secondary cooling zone begins from just below the mould.
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BLOOM STORAGE YARD (BSY): To synchronise the production in continuous casting machine and requirement of rolling mills for blooms, Bloom storage yard has been established. Inspection & selective conditions are also carried out in BSY. Blooms of particular grade of steel are stored at a particular place. Every bloom is marked by heat no. and machine no.
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MILLS
There are 5 major zones in VIZAG STEEL PLANT: RAW MATERIAL ZONE COKE ZONE IRON ZONE STEEL ZONE MILLS ZONE
The final products are produced in this MILLS ZONE. Blooms formed in CCD (Continuous Casting Department) are converted into billets and then carried into the MILLS ZONE where the final product is obtained. Billets formed generally are of sizes 250x250 and 250x325. These billets are sent to their respective MILLS according to their sizes. There are 3 MILLS in VSP WIRE ROD MILL LIGHT AND MEDIUM MERCHANT MILL MEDIUM MERCHANT AND STRUCTURAL MILL
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 will produce 6 ltpy of
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plain rounds in coil form. The wire rod size will be in range of 5.5 to 20 mm. Provision is kept for the mill for producing 7.7 ltpy on the market demand. The rolling mill will use the cast billets of size 150 x 150 mm having length of about 12 m and rolled billets of size 125 x 125 x 9.7 to 10.2 M. The mill will roll Low carbon (85,000 tons/ yr), Medium carbon (93,000 tons/yr), High carbon (93,000 tons/yr), spring steel (25,000 tons/yr), cold heading (1,34,000 tons/yr), welding rod (85,000 tons/yr), Bearing steel (25,000 tons/yr), Free cutting steel (35,000 tons/yr) and case hardening (25,000 tons/yr). The billet will be charged into 200 ton / hr capacity reheating furnace one by one. The billets after heated upto 1200 deg C will be discharged. The billets will be rolled down in the breakdown mill and passes through pre –finishing mill. The finished product will come out of reducing and sizing mill in coil form. The output of size wise product mix are - 5.5.mm mm – 1,50,000tons/ yr , 6.0-7.5 mm – 2,40,000 tons/ yr, 8.0-16 mm – 1,75,000 tons/ yr, 17-20.64 mm – 35,000 tons/ yr. Facilities 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) Features Evaporating cooling systems are present in Rolling Mill furnaces. Rolling Mill is totally computerized
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Cooling of Wire Rods are controlled by ‗Stelmore‘ process which gives high strength and good ductility. Capacity A Mill of 0.85 MT per annum production capacity.
LIGHT AND MEDIUM MERCHANT MILL Blooms from Continuous Casting Division are rolled into billets, some of which are sold and rest are sent to WRM. The continuous multi-line mill comprises 8 stand double strand roughing train, 2 Nos., 4 Stand Single strand finishing trains. Loopers are provided in between the finishing stands for tension free rolling in order to obtain good surface quality and tolerances. Housings are of closed top type. Roll necks are mounted in anti friction bearings. Facilities 7 Strand Break-Down Mill 8 Strand Roughing Mill 5 Strand intermediate Mill (2 Strand rolling) 2*4 Strand Finishing Mill (Single Strand rolling)
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6 nos. of 4-Strand Continuous Bloom Casting machines.
Features Evaporating cooling systems in Rolling Mill furnaces. Computerization in Rolling Mill Tempcore cooling process facilitating high strength with good bendability and weldability. Capacity A Mill of 0.710 MT per annum production capacity.
MEDIUM MERCHANT AND STRUCTURAL 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 8,50,000 T/year. The important feature of this mill is that Universal beams (both parallel and wide flange) have been rolled first time in India using Universal stands. Parallel flange beams have advantage over conventional beams as per the same weight the section is stronger and stiffer due to greater moment of inertia and higher radius of gyration.
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Facilities 8 Strand Roughing Mill 6 Strand Intermediate Mill 6 Strand Finishing Mill Features Evaporating cooling systems in Rolling Mill furnaces. Sophisticated, High speed rolling mills with computerized controls
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