PRESENTATIO ON ELECTROSTAT IC PRECIPITATOR

INTRODUCTION

Production of ash

Need for Fly ash Disposal

Equipment used for Ash collection

Permissible limits

LAYOUT OF ELECTROSTATIC PRECIPITATOR

CONSTRUCTION AND WORKING OF ESP

Principle of working

Ionization and charging

Collection of particle

Removal of particle from electrodes and Rapping

CONSTRUCTION DETAILS

INTERNAL CONSTRUCTION

CASING

GAS DISTRIBUTION SCREEN

EMITTING ELECTRODE

COLLECTING CLECTRODE

RAPPING SYSTEM FOR ELECTRODE

ELECTRICAL SUPPLY SYSTEM

SPECIAL FEATURES

PRECIPITATOR UNDERVOLTAGE

When the precipitator voltage remains below a certain limit for a duration longer than set value ,a relay which is normally in energized condition , will de-energized and the input contactor will be tripped off thus de-energising the power supply thus will give an indication and alarm undervoltage trip level set between 5% to 75% of the rated vtg. the time settable between 4to 30 seconds.

ELECRONIC OVERLOAD TRIP

When the precipitator current exceeds the set value (80% to 120%) of the rated precipitator current a relay will operate which will give a signal to annunciation ckt resulting in tripping of the supply to the T/O unit the overload time can be adjusted by means of a potentiometer between 1 sec to 3 sec

BIMETALLIC OVERLOAD TRIP

The bimetallic thermal overload relay is provided at the a.c. input after the contactor . when the input current exceed the set value , the thermal overload relay trips because of heating of bimetallic element . this gives signal to annunciation ckt resulting in tripping of the supply to the T.R. unit

SCR OVERTEMPERATURE

SCR temperature is sensed by means of a PTC thermistor mounted near the base of the SCR on the heat sink . the resistance of the PTC thermistor is increases with temperature .when temp. exceeds the set value a relay will operate which will give signal to the annunciation circuit resulting in tripping and audio/visual alarm.the temperature setting can be changed by means of potentiometer

VOLTAGE LIMIT

The voltage limit circuit limits the voltage applied across the primary of the H.T. Transformer thus protecting the Transformer against overvoltage the SCR conduction angle is reduced by sensing the transformer primary voltage and thus limiting it within the rated value. the voltage limit is set at 380v.

CAUSES AND REMEDIES

Field Trips on Undervoltage

1.Check electronic controller/High voltage rectifier transformer for Rated Voltage build up on no load 2. Check the functioning of the Ash disposal system 3. Check the functioning of collecting & Emitting rapping mechanism4. Check for cracks in support, bushing insulator5.  Check for cracked shaft insulator in shut down 6.  Check for shorting in the field like snapped loose wire in shut down 7. Check for overfilled hoppers and distorted emitting system in shut down Check for any bent collecting electrodes in shut

down

Rapping Motor Trips on Overload

1.     Check for IR value and winding resistance of motor

2.      Check for functioning of Motor & Gearbox after decoupling

3.      Check for alignment of Gearbox with rapping system

4.      Check the rapping shaft alignment during shut down

5.      Check for dislocation of internals

6.      Check for over-filled hoppers

7.      Check for blown fuses, overload relay healthiness in MCC

Heaters are not operating

1.     Check for any blown fuse

2.     Check for terminals in MCC/Field JBS for

any burnout

Check for any short circuit in heating

elements/cables

For further service/advice contact

High Stack Emission

1.     Check for proper rapping frequency

2.      Check for proper current settings

3.      Check for high flue gas temperature

4.       Check for proper gas flow distribution in the pass during

shut down

5.      Check for eroded guide vanes/splitters during shut down

6.      Check for proper fixing of defector plates of hoppers

during shutdown

Electronic Controller does not

switch ON Check the interlock key

2. Check the control fuses and control supply

3. Check the coil of main contactor for healthiness

4. Check the healthiness of overload relay

5. Check for safety lines

6. Check the healthiness of microprocessor controller

7. Check the selector switch on microprocessor

1. controller for local/remote operation, as required

Output Voltage does not build up

1.                  Check the firing pulses from the controller 2.                  Check the firing circuit and the cabling connections 3.                  Check the healthiness of firing card

Buchholz relay Bottom Float operates

1.                  Analyse the accumulated Gas 2.                  Check the healthiness of A/C reactor 3.                  Check the healthiness of H.F. Choke 4.                  Check for any inter turn short 5.                  Check for any failure of rectifier diodes 6.                  Check for Breakdown value of oil