TO STUDY FEASIBILITY AND IMPLEMENT THRUSTER BRAKES IN LT MOTOR OF SCP-1 AT BATTERY 5,6,7 COKE PLANT.

Tata steel is Asia’s first and India’s largest integrated private sector Steel company. It was established in 1907 by its founder J.N.TATA. Over the years, Tata Steel has emerged as the thriving , nimble, steel, enterprise due to its ability to transform itself rapidly to meet the challenges of a highly competitive global economy and commitment to become a supplier of choice by delighting its customers with services and products. Constant modernization and introduction of state –of-the- art-technology at Tata steel has enabled it to stay ahead in the industry and successfully meet the exceptions of all the sections of stake holders. Tata Steel’s four phases of modernization program in the steel works has enabled it to acquire the most modern steel making facilities in the world. Recently, Tata steel commissioned its 1.2 million-ton capacity Cold Rolling Mill complex at “global speed and cost” and the H-Blast furnace to further advance itself among the top steel producers of the world. Its fifth phase of the modernization program leverages the intellectual capabilities of its employees to generate sustainable value of the stakeholders. Tata steel is taking better management initiatives to shift focus from creating new physical assets to utilizing them with ingenuity and study business sense.

 TATA STEEL is the world's seventh largest steel company, today said it has commissioned a new coke oven battery at its Jamshedpur steel plant, making the unit self-sufficient in coke requirement and in turn stabilizing operations there.Built at a production capacity of 700,000 tone, the coke oven battery-11 operates with 88 ovens with stamp charge technology and is the largest coke oven complex in Jamshedpur Plant.

COAL CARBONIZATION OR COKINGWhen coking coal heated in the absence of air they become plastic and soft over a temperature range of 3100C to 5000C. The coal particle agglomerate into a coherent mass, which swells and solidifies to form a porous structure known as coke.When coal is charged in the hot oven, the temperature of oven refractory wall being at about 11000C to 15000C, the portion of the coal in immediate contact with hot wall is heated very rapidly to a high temperature, a thin layer softens, becomes plastic and melts. This layer of plastic material travels towards the center of the oven and some of the gaseous product force their way out of the plastic materials, as the temperature of the charge is raised. On the wall side, the plastic layer hardens into a cellar residue and the volatile matter left in the coke is driven of gradually as the temperature rises during remainder of the coke period. Thus in an oven, during initial stage of coking, the coal exists side by side in several phases, e.g. coke, semi coke, a plastic mass and granular coal.

The phenomenon of conversion of coal to coke may be started in a simplified way as follows:

•Evaporation of the moisture in the temperature range up to 1000C.

•Release the volatile matters in the temperature range of 2000C to 6000C, most of the volatile matter is released between 3000C to 6000C.

• Softening and solidifying zone remains in the temperature range of 3000C to 6000C.

•Plastic zone up to 4500C.

•Sami coke in the range of 4500C to 6500C.

•Release of hydrocarbons up to 8000C.

•Above 8000C only hydrogen is released and coke cake becomes hard.

Time Duration for Coking•Minimum coking time 19 Hrs. 45 Min.

•Maximum coking time 20 Hrs. 45 Min.

Schematic Diagram of COKE Plant

Thruster brake is a device used to retard the speed of moving machinery and to stop it accurately to the desired position. The braking force is applied to the brake shoes by a pre-stressed comprising spring. The shoes press on the rotating brake drum retarding its speed and finally stop it. The releasing of the brake drum and compressing of the spring is done by thruster.

 A thruster shoe brake has a pair of cast iron shoes which are lined up with friction pads. The shoes are hinged on main arm and side arm of the brake, each of them have a hinge pin fitted in the base. They are connected to each other on top by a tie rod, which is hinged in the main arm and locked to the swivel block in the side arm, by a lock nut. A crank lever is hinged on the main arm and the other end is fixed to the top clevis of the thruster by a hinge pin. A brake spring is fixed on the main arm and is pre-loaded by a locknut on the lever. The pre-tension in this spring decides the braking torque. The thruster is fitted on the base by a hinge pin. When the thruster is not energized, the brake shoes are pressed on the brake drum fitted on the drive motor shaft and hold it under the effect of braking force provided by the spring. In such condition, the brake is applied and the drum cannot rotate. As the piston travels upwards the angle lever turns, pushes the brake rod and compresses the brake spring. Simultaneously, the brake lever on the other side of the wheel (Brake Drum) is retracted. When the first lever reaches the stop on the brake base member the brake lever at the thruster begins to move, releasing the brake drum.

TYPES OF THRUSTER BRAKE:-

Disk brake ThrusterDouble shoe brake Thruster

Electrical Design:-Motor-

3 ph AC squirrel cage motor, For performance refer to technical data. Insulation classF.

Modes of Operation-

Continuous operation S1 and intermittent service S3-60 % duty cycle.>50 °C ambient température.

Voltages and Frequencies:-

230/400 V, 50 Hz, 3 ph AC290/500 V, 50 Hz, 3 ph AC400/690 V, 50 Hz, 3 ph ACAll units are on principle star (Y) connected at delivery. Special windings 110 V - 690 V, 3ph AC at extra charge.60 Hz design at extra charge.Single phase versions on request.

Power (switch) Contractor EOCR(Generate command) Break Open

CableTerminal FieldMotor(pusher )

Single line Diagram of Thruster Brake Connection

FLOW OF EOCR

Mechanicalload

Current of motor

Detecting current with LT

sensor

Reducing the down time of

system

Diagonising the condition of machine and

motor

• The EOCR(electronic over current relay) are highly compact and versatile electronic relays which operates on the basis of current sensing principle with inbuilt current transformer of the EOCR.these relays are independent mounting relays and can be used with any make of contractor in the equipment. Besides with independent adjustable time settings for starting delay time and operating time these relays find many applications all spheres of the industry.

EOCR

PumpsFansSingle phase motorsInduction motorsSquirrel cage induction motorsSlipring wound motors

APPLICATION OF EOCR

Dust proof double sealPressure lug

Piston rod

Piston rod protection tube

Double seal of oil chamber

Oil filter inlet

Piston

Braking springHydraulic cylinder

Centrifugal pump Oil guide

Motor shaft double seal

3 ph AC squirrel cage motor Terminal box

Fixing lug

Internal Diagram of Thruster

Thruster VersionsAdditional Equipment

Lifting or Lowering Valve (H, S, HS)Built-in lifting (H) and/or lowering (S) valves for stepless prolongation of normal lifting or lowering times. The adjustable minimum values obtain a level 10-20 times the standard values. Built-in valves in setting ‘open’ result in increased lifting and lowering times for short stroke units of approx. 0.1 to 0.2 seconds and for long stroke units of approx. 0.2 to 0.4 seconds. The valves are adjusted from the outside.Braking Spring (c-Spring)

The c-spring generates the braking force. The specified force of the c-spring applies for 1/3 of the piston rod’s rated lift stroke or 2/3 of the rated lower stroke.Re-setting Spring

Operation similar to c-spring, re-setting force is, however, lower (on request).

Damping Spring (d-Spring)

For an aperiodic transient of the brake. This assists the brake to close smoothly. Only effective in conjunction with a built-in braking spring. No limit switch can be annexed in his case. There is no alteration in the mounting distance A. When determining the operating point of the brake the dimension ‘z’ is to beconsidered. Main application: ELDRO®-regulated brake.High-Speed Lowering Circuit

By means of motor capacitors, or by short-circuiting the stator winding and inserting a contactor. The lowering times are reduced by approx. 15 %.Heater

For operation below – 25 °C a heating element must be installed; also to be used as a stand-by heater. The customer has to provide a separate power supply and temperature regulator.

Application: aggressive media and/or high relative humidity and the resulting danger of formation of condensate. Motor: fully vacuum potted stator, applicable also instead of idling space heater (on request). Special paint: Polyurethane lacquer (KOR). Primer: one coat Paintfinish: two coats polyurethane varnish. Tint RAL 7022 (umbergrey).

Increased Protection against Corrosion

Limit Switches

For electrical indication of the release or closing positions of the brake, mechanical or inductive limit switches can be fitted as standard. The appropriate types of switches are listed in the technical data sheet ‘Limit Switches’. All additional equipment is to be ordered separately at extra charge.

Rated voltageCode for additional equipmentc Braking spring (c-spring)d Damping spring (d-spring)H Lifting valveS Lowering valveE Limit switch, mechanicalEB Limit switch, inductive

Code for exchange unit

Stroke in cm

Lifting force x 10 in N

Ed: ELDRO®, 3 ph AC version

Ed 121 / 6 . 1 c 230/400 V, 50 Hz

Key to Types

Performance in Service depending on Ambient Temperatures

Temperature range Hydraulic fluid Performance in service

– 25 °C to + 50 °C HL 10, DIN 51524, part 1 In the lower range of ambient temperatures the lifting times mayincrease up to four times the specified lifting times when the unit is operated the first time. The lowering times remain unaffected.

over + 50 °C special fluid Enquire.

– 35 °C to + 40 °C special low temp. fluid Space heater not required.

below – 25 °C HL 10, DIN 51524, part 1 Space heater required in unit. Connect up heater in terminal box using an additional Pg 16 cable gland. 230 or 115 volt connected voltage. Thermostatic control be provided by customer.

Method of OperationFunctionsAdvanceBRAKEMATIC® advance is an electronic control with variable parameter presetting for generation of controlled brake torque characteristics. In this case an external reference signal (usually rotation) and a programmed presetting parameter (e.g. time, rotation) are evaluated and a linear or nonlinear time function is calculated in the frequency converter. An integral process controller module makes a permanent set point/actual value comparison of calculated characteristic and the actual values.

Constant brake times for strip guiding systems

Proceeding from the guide signal generated by the controller, the frequency converter modifies the working frequency at the ELDRO® thruster and thus controls the process of braking operation. Safe adherence to brake time stipulations is the initial prerequisite for the realization of the shutdown regime of complex belt conveyor systems. This is the only way to provide protection from surcharges caused by asynchronous stoppage of conveyors. The application of BRAKEMATIC® advance is excellently suited for this job since it ensures the preset braking times independent of the conveying direction (up or down) and the loading status.

ABS-System for track bound travelling

Track bound travelling and trolley gears are another field of application. Due to unfavorable friction (metal to metal contact) in combination with swaying loads, heavy braking torques, (e.g. caused by operation of EMERGENCY STOP) or adverse climatic influences it might occur that wheels are blocked. In those cases the BRAKEMATIC® advance can be used as antilock system.

Using the pedal, the crane operator can actuate the control system. The lifting power of the ELDRO® brake thruster, and thus the braking torque, are changed in proportion tothe pedal travel. When the pedal is not depressed at all, the full lifting power is applied to the ELDRO® brake thruster, and the brake is being lifted. The more the pedal is pressed, the lower is the lifting power on the ELDRO® brake thruster and the higher is the braking torque. A special setting allows a long pedal travel for sensitive variation of the braking torque. In order to avoid full braking, a progressively acting pull-back spring is incorporated in the pedal. When the crane operator slightly retracts the pedal, the braking torque is reduced accordingly. Thus, all conditions required for safety brakes are complied with.

Function of the pedal

Example of pedal control with parking switch

1 ELDRO® thruster2 Control device3 Pedal4 Parking switch

Features:-

• High reliability.• Long service life with minimum maintenance to low wear

operation under continuous self lubrication.• Soft and smooth operation due to the hydraulic principle.• Fast response (short regulating times).• High switching frequency: up to 2000 cycles per hour.• Reversing operation without restrictions.• Simple installation and dismantling.• No reversing contactors required as the motor may rotate in

either direction.• Overloading during operation not possible.• Suitable for adjusting length of stroke from outside as required.• Stepless prolongation of lifting and/or lowering times by the

fitting of valves.• Universal applications also in hazardous areas in which there is

danger of occurrence of explosion.

Precaution:-

Cotter pins at pins have to be opened, so they can’t fall out (left). Cotter pins at castellated nuts have to be opened completely (right)!

RIGHTRIGHT WRONGWRONG

Lubrication:-

Because of the maintenance-free bushings installed on the brake, no lubrication is needed.

Cleaning:-Do not use corrosive or acidic agents to clean the brake. Only use fat dissolving cleaners (e.g. brake cleaner) and proper cleaning material like cloth. Never use high pressure cleaners or a wire brush

CONCLUSION

Our curiosity and eagerness were fulfilled with knowledge at Coke Plant. It was really helpful in knowing about different types of sensor, field instruments, valves, PLC etc. while practically working in machines, as well as knowing about maintenance of the plant .

It was very interesting to know that coke plant of TATA STEEL is continuously for last 12 years and is Steel operating without any Fault where other industries plant degrade after a 5-6 years of Operation. This was only possible because the maintenance is regularly and very brilliantly handled at TATA STEEL.This project made us understand the working and function of different field instruments and the method of their calibration.

While doing this project, we also came to know about the environment norms that a plant has to follow to allow to avoid pollution.

At last we would like to say that we really enjoyed doing this training and would like that Tata steel to continue this Vocational Training every year as it will improve one’s knowledge and will give an individual industrial exposure.