Re potting Magneblast breaker bottles
Re potting Magneblast breaker bottles
(OP)
What are the recommended materials for re potting GE Magneblast breaker bottles. Ours are showing signs of cracking and seperation between the bar and potting compound. We were smelling ozone, and called in a specialist. He chiseled out the old potting compound re wrapped the bars with silicone tape, and bought some tar from Home Depot to fill the bottle up with. We had a few bus joints that showed signs of partial discharge also. The joints were enclosed within a plastic case tied together with string and filled with a tar like compound. These cases were removed, the bolts retorqued, and were covered with silicone tape. The cases were not reinstalled.
Is there a special compound that should be used, or is roofing tar sufficient? We would like to inspect the bus during our outage, but are unsure whether to use the same contractor.
Is there a special compound that should be used, or is roofing tar sufficient? We would like to inspect the bus during our outage, but are unsure whether to use the same contractor.






RE: Re potting Magneblast breaker bottles
In the absence of hard data, I seem to recall that the original potting compound was derived from pine tar, and the roofing compound you're likely to get from Home Depot is of petroleum origin, but as long as it does not contain conductive fillers such as carbon black, it should be sufficient.
I think I'd have created a test sample for testing breakdown voltage out of a couple of electrodes and a bit of both compounds and then subjected them to elevated test voltages, but that's because I worked with some folks who were trying to keep archaic equipment going.
The old guys who used to KNOW about potting compounds and such are getting hard to find. Sounds like you found one.
Please keep us informed of further activities.
old field guy
RE: Re potting Magneblast breaker bottles
I am not convinced MC switchgear or bus joints were ever "PD Free", or meant to be, when they were new. Many mfg did go to great lengths to do the best they could to insure bus joints made in the field would last. Dux Seal, Solorite with semicon tape were mostly used. ITE used two hard plastic covers with a hemispherical shape on each that was painted with a semi conducting paint. The bolted joints had thin copper "tangs" that made contact with painted semi conducting surface. This would act as a "corona ring" of sorts. The covers were simply taped together in place. No filler at all. This arrangement worked well and accomplished much more then fillers and tapes. The basic rubber boots on MC gear joints used today make no attempt to "suppress" corona or PD as far as I know.
I am sure the experts will help me out here.
RE: Re potting Magneblast breaker bottles
RE: Re potting Magneblast breaker bottles
RE: Re potting Magneblast breaker bottles
RE: Re potting Magneblast breaker bottles
RE: Re potting Magneblast breaker bottles
RE: Re potting Magneblast breaker bottles
http://www.gwelec.com/support/msds.cfm
RE: Re potting Magneblast breaker bottles
RE: Re potting Magneblast breaker bottles
When you wrote about finding "evidence of PD" does this mean you found visual or audible indications? Can you describe what you found associated with the bottles and joints other then shrinkage and cracking of the compound. What is the voltage class of the equipment?
I am unsure of the risk vs reward for your situation. Are you removing the bottle assemblies from the switchgear to perform the re-potting operation? This would be very time consuming. You run the very real risk of altering the alignment of the primary tulips relative the breaker. This would be catastrophic should you drive the breaker up into the mis aligned primary disconnect and break the porcelain housing.
Thank you.
RE: Re potting Magneblast breaker bottles
RE: Re potting Magneblast breaker bottles
RE: Re potting Magneblast breaker bottles
RE: Re potting Magneblast breaker bottles
RE: Re potting Magneblast breaker bottles
Doesn't sound like you have a lot of choice. If you don't do something, the bus will eventually disassemble itself.
old field guy
RE: Re potting Magneblast breaker bottles
Do you know specifically which bottles have PD?
RE: Re potting Magneblast breaker bottles
RE: Re potting Magneblast breaker bottles
RE: Re potting Magneblast breaker bottles
----------------------------------
If we learn from our mistakes I'm getting a great education!
RE: Re potting Magneblast breaker bottles
I am not sure I would go to the trouble of re-potting the bottles on 5kV switchgear. Maybe I would pour new compound in the cracks or spaces at best. But we covered all that in earlier posts.
I hope you have small techs with long arms on hand for this project. Please keep us posted and good luck.
RE: Re potting Magneblast breaker bottles
RE: Re potting Magneblast breaker bottles
RE: Re potting Magneblast breaker bottles
RE: Re potting Magneblast breaker bottles
RE: Re potting Magneblast breaker bottles
RE: Re potting Magneblast breaker bottles
RE: Re potting Magneblast breaker bottles
RE: Re potting Magneblast breaker bottles
RE: Re potting Magneblast breaker bottles
RE: Re potting Magneblast breaker bottles
Read the original posts. He is just trying to fix his existing switchgear. What he is doing is done all the time. He wants to do it right and deserves credit for trying to do so. Thats why he posted here in the first place. Many of my clients have 40 year old (some older) switchgear and would rather have it then what is available today regardless of price. It is their choice after all.
It's easy to recommend replacing something with new when its not your money. Even I can do that.
RE: Re potting Magneblast breaker bottles