O&_M mech

7/31/2019 O&amp_M mech

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OPERATION

PREPARATION AFTER MAINTENANCE

Check the precipitator internals and remove the

tools and other foreign materials.

Check all the insulators visually.

Inspect the rapping motors and top-up with oil.

Run the rapping motors and ascertain that they

function normally.

Check that the heating elements.


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Check the dielectric strength of transformer

oil

Megger and test all the fields on air load.

Ensure that the ash handling system is

working properly.


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START UP PROCEDURE

Switch on the heating elements at least 24

hours before the start up of the boiler.

Switch on the rapping mechanisms as soon as

the boiler is lighted up.The HVR shall not be energised until the gas

temperature is above 100C.


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OPERATIONAL CHECKS

Check the normal function of Precipitator

Logging of readings hourly.

Record the failures and outages.


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SHUTDOWN PROCEDURE

Switch off the fields when the gas temperature isbelow acid dew point.Continue the operation of the rapping motors in

intermittent mode for 4hrs.

Evacuate the ash from all hoppers.The access doors may be opened after following

the interlock sequence.


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SHUTDOWN INSPECTION

Inspect the internals for :

Snapped or loose wires.

Excessive ash accumulation.

Dislocation of shock bars, shock bar guides and CE

Rapping system, hammers, plain bearing shaft etc

Insulators

Disconnecting switch and contacts.

All heating elements

Any other abnormality.


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MAINTENANCE

GENERAL

Ensure the guide vanes, splitters, deflector plates

on the gas distribution screen as per original.

R , .

Inspect for corrosion, wear and tear of ,

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MECHANICAL SYSTEM

(i) Collecting Electrode system

Check the alignment of CE, shock bars and

guides.

Replace the shock bars/shock pads if worn out

excessively.

Check the rapping mechanism if dust build up is

excessive.

Tack weld all the fasteners after tightening. Care

should be taken not to tack weld the HSFC bolts if

used for CE and shock bars


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(ii) Emitting Electrode system

Check the emitting electrodes forexcessive electrical erosion and snapping.

Remove the eroded/snapped electrodes, if

any.

Care shall be taken not to disturb the

healthy electrodes while replacing with

new electrodes.

Wherever the access is difficult, the

intervening electrodes may be unhooked


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Insulators

The insulator shall be inspected during shutdown for cleanliness, cracks and rigidity of metal

parts

Dusty insulators should be cleaned with Carbon

tetrachloride / Petrol in both inner and outer

portions.

Cracked insulators should be replaced.

Support insulators shall be replaced, if required,

with the help of lifting tool and alignment jig as

per procedure.


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AIR LOAD TEST AFTER MAINT.,

Please ensure:

All foreign materials are removed.

All heaters are energized

Meggering of fields ( around 500 Meg Ohms)

Charge the fields with still air load and ensure:

Fields building up up to rated current and kV without

sparking. Incase of sparking attend the discrepancy and

repeat the test.

Air load test is a must after every maintenance of fields.

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