generator stator cleaning

[tinashe8]

what are the dangers of running a 60MW generator with an unclean stator and rotor. the stator and rotor is contaminated with coal dust. also is it possible to clean the stator with the rotor inside? if possible what method of cleaning can be used to clean the stator with the rotor inside? thanx

 

[racookpe1978]

Destruction of the unit.
Grounds (worse than now.)
Fire.

 

[racookpe1978]

What part of the country are you in?

 

[ScottyUK]

Probably that part of the USA called 'the rest of the world'.

Adding to the list:
Coal is carbon-rich, so flashover is a real possibility. That could lead anywhere from localised core damage to a stator wreck.
Coal is a fairly good thermal insulator, and it is a dust which likes to accumulate in small air passages. You will almost certainly suffer overheating problems. On the rotor these problems may not be easy to detect until the rotor winding fails.

Presumably this is an air-cooled unit - is it really an ODP design? The only reasons for using an ODP machine would be either cost, lack of water for a cooling tower, and/or very high ambient temperature. ODP machines need good filters at the front end - what happened to the filter?

 

[Motorwinder]

Dry ice cleaning.

Link

 

[eeprom]

You are asking for trouble to run the machine full of carbon.

You cannot clean the stator without removing the rotor. Or at least you cannot clean it very well.

Rotor: to clean the rotor properly you will have to remove the end bells (expensive, not including the down time). I have encountered problems with rotational exciters where the carbon from the brushes gets sucked into the rotor. Because the rotor voltage is usually less than 300VDC, you generally don't have to worry about the rotor insulation. There are some tests you can do to determine the rotors health, such as megger, and AC impedance tests. A rotational AC impedance test can tell you a lot about a rotor.

Stator: the end turns are the likely culprits for problems. There are numerous tests available to determine the health of the insulation. The end turns can be cleaned using a NON-SOLVENT cleaner. The coating on the end turns is most likely glyptol. What I have done in the past is to have testing done. Then have the end turns cleaned by an outfit who specializes in cleaning machinery. They will have guys in there with toothbrushes to get the carbon from between the windings. Once the cleaning is done I have the testers come back out. You should see a difference in AC and DC hipot tests. Then have a recoating of glyptol. FYI, this is about 4 days of down time.

ee