CO2 suppression contamination on generator windings 2

[ghostbuster7]

At our site,a contractor accidentally tripped(while x-raying the floor above) our CO2 systems for our back-up generators(not running at the time of the trip) that are in a totally enclosed soundproof enclosure within our building.Once the CO2 is replaced,can these generators be immediately started or is there a dryout/cleaning process req'd? I am concerned about the old winding insulation(15 years) absorbing the condensed moisture etc. and having a flashover occur in the alternator.
Thanks

 

[edison123]

CO2 does not affect the windng insulation much. Check the IR & PI of the winding. If they are good, then you should be good to go. If they are not, dry out the windings (external space heaters, DC injection, short-ciruit run etc.)

 

[electricpete]

To further edison's point, I can think of 2 times when machines are routinely exposed to CO2:

1 - In our hydrogen cooled generator during maintenance air is allowed in. When we put the machine back in service we cannot mix the H2 with air, so we need another gas to flush the air out before we put the H2 in. CO2 is the gas we use.

2 - Dry ice pellets made of CO2 are routinely used for field cleaning of electrical machine windings. The pellets turn into gas and disappear.

I'm not sure exactly what type of CO2 system you have... is there any residue left (indicates something other than CO2 mixed in) or the CO2 gas vanished?

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[edison123]

pete

Very good points. Proof of the pudding..

Another point - If CO2 is going to damage the winding, why would it be used be as a fire retardant in the generator ?

 

[waross]

CO₂ is usually stored as a liquid. When it vapourizes it absorbs a lot of heat. It can cool surfaces below the dew point, and/or it can cool surfaces below the dew point. When that happens you have the moisture of condensation.
BUT this may or may not happen. It depends.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[electricpete]

Yes, I think I missed the point the original poster is (rightly) more concerned about condensation than CO2.

edison has mentioned megger/PI which would be the primary means to assess this. But perhaps not foolproof. If it is a 460vac, I don't have any hesitation to say there is no concern as long as passes those tests. But the higher the voltage and larger the machine the more inclined I would be to suggest (as a conservative approach) consideration of a period of time with heat applied to provide added assurance all surface moisture is removed.


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[electricpete]

Sorry, I spend so much time working with motors I forgot a generaotr would be rated for 480vac, not 460vac.

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