Presentation 1

RESOURCE REQUIREMENT

Total Coal 2.1 Million tons

Wash coal 1.7 Million tons

Imported coal 0.4 Million tons

Sea Water (M3/Hr.) 84,000

Sweet Water (M3/Hr.) 300

Background

Introduction DTPS has two wagon tipplers to unload coal received trough railways. It is suitable to handle both C type as well as N type wagons of 100 tons capacity. Wagon tippler system includes Inhaul beetle charger to place wagons on tippler table Hydraulic system to clamp the wagon both horizontally and vertically. Thyrister controlled DC motor to Tip the wagon. Outhaul beetle charger to remove the empty wagon from tippler table. Thruster brake to hold the tippler against gravity. Various protections and indicating systems like photo cells, proximity switches,

pressure switch ,aux current gear limit switch, etc. 20 T EOT crane to assist in routine O&M activity.

Interlock and permissive Relay panel can be charged or ready for operation only if

1. All the emergency stop push buttons are released.

2. All the overload relays reset.

3. Tippler over return , over tip limit switches in reset condition.

4. Thyristor panel ON and reset. On resetting the plant relay panel gets charged and Red signal glows by default. Operator on inhaul side can change the signal as required for loco movement only if

hydraulic clamps are in released condition and tippler at rail level.

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Proximity Switch1

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Pressure Switch

& & Timer

3 Sec

Hydraulic Clamping Indication & Permissive

Clamping OperationHydraulic motor is used to charge the hydraulic system. On initiation of command the clamping of wagon will take place.

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The tippling will be started once following conditions are achieved :

A. Hydraulic clamping is proper B. Both beetles are at beetle clear position C. Photocell permissive is available.

After preset time of tippling command, dust suppression system starts to spay water for preset time.

Before reaching final tip position slowdown limit switch acts to reduce tippler speed. After tip tippler waits for preset time and starts return. Before coming to rail level

slowdown limit switch acts to reduce the speed of tippler.

Tippling Operation

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Tippling cycle

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DC Motor

45 KW DC motor. Kirloskar make, 125 Amps, duty S1, Wdg -shunt, 1000 rpm, IP-55, Armature- 400 volts, excitation-220volts 3.3 amps, Frame Size THDC-280/75

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Aux current gear limit switch.

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DC Motor Characteristic•DC motor has an infinitely variable and wide speed range.•Attractive torque and power speed characteristics•easily controlled and a high overload capacity.

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Speed control at constant torque by armature voltage control upto base speed. The HP varies directly with speed and speed range is below base speed

Function Block Diagram of DC Drive

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DC Drive Tippler is held at rail level against its centre of gravity which is 15-20 degrees

by thrustor brake. On tip command thrustor lifts up and tippler stats tippling, though motor is ON

it is on load and after 15 degrees motor supplies required power up to final tip position. i.e drive is not required to supply starting torque.

If we lift the brake tippler will start returning up to its centre of gravity even if motor is off but its speed will be very high. i.e. during return operation tippler require braking.

It is necessary to brake the motor due to operational requirements. Following braking systems are used in tippler

1. Mechanical braking by thrustor brake.2. Dynamic braking in which the motor is used as generator and the kinetic

energy of the motor is used to heat a resistor connected as load .3. Regenerative braking in which motor acts as generator and feeds back

power to system thus saving power and reducing inconvenience of dissipating heat in dynamic braking.

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Drive-Mode of Operation

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Preventive maintenance schedules

DC motor – quarterly All ac motors – Quarterly Thyristor panel – half yearly MCC – half yearly Relay panel - yearly

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Problems faced

Play in aux gear limit switch, - rail level not matching. Replaced by imported switch. Blowing of semi conductor fuses.– Thyristor failure. Until now 12 are replaced. AC

provided for panel cooling. Failure of control card. Failure of power board Tippler over speeding after flood.- Tacho not giving proportional o/p. Blowing of output semicon fuse – Tacho giving spikes in output replaced. Tippler tripping on inst.o/c. – DCIA card failed giving erratic feedback. Indication and hence permissive not available – Trailing cable cores open,

replaced .until now replaced twice. Presently JBs provided to reduce the requirement from 65 to 33 meters.

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Functions of control card•Power supply•Tacho fail detection•Field fail detection•Phase fail/ sequence detection•Over current detection•Pulse generation ckts.

Control card.

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Trailing cable

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Trailing cable

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Coal Coal + Flue dust Coal + Flue dust + Coal

Raw coal hopper

Blendning at coal yard

1. Rail Unloading House • Coal is transported to the station by coal trains and discharged through bottom

hoppers, which open automatically.

4. Boiler Coal Bunker • Coal bunker supplies coal to pulverising fuel mills..

• Power station coal is not as lumpy as coal used in the home. • Typically around half of it is less than 12.5 millimetres across and 95% is less

than 50 millimetres.

5. Bucket Wheel Machine • Bucket wheel machines are used to put coal out to the stockpile and reclaim coal

from the stockpile.