# SF6/Nitrogen mix



## KingNothing (Mar 12, 2017)

Just a quick question to see what everyone else is doing with their maintenance. I have quite a few 345KV live tank PCB's with an SF6/nitrogen mix. Since there is a mix of gases in the breaker, I can't evacuate the gas into our DILO gas cart to clean it. So far I have been pulling wet gas out and pushing into other empty tanks. Then pulling vacuum on the breaker and when that is complete putting the gas back in through a DILO filter. The ppm moisture is then low compared to manufacturer standards but it still has some moisture in the gas. We have replaced the gas completely at times but with the EPA rules, it turns into quite the ordeal. Just wondering what everyone else does when they perform breaker maint. Do you all replace the gas or is there a different way you filter the gas for your breakers? Thanks for your time.


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## Old Brian (Oct 31, 2016)

KingNothing said:


> I have quite a few 345KV live tank PCB's with an SF6/nitrogen mix.


Curious about the SF6/Nitrogen mix. Is that spec for the breaker? I've only ever seen pure SF6 gear.

Cheers,
Brian


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## MechanicalDVR (Dec 29, 2007)

Not really my area of expertise but I'd think a large cubic inch size simple desiccant core filter dryer would take most of the moisture out of the gas going back in.


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## KingNothing (Mar 12, 2017)

Old Brian said:


> Curious about the SF6/Nitrogen mix. Is that spec for the breaker? I've only ever seen pure SF6 gear.
> 
> Cheers,
> Brian


The reason you would mix the 2 gases is because on the older live tank 345kv breakers, there aren't any tank heaters. If you live in a colder climate where there is a chance that you could get lower than -30 degrees, the SF6 gas will go to dewpoint and the breaker will go into lockout. With Nitrogen, the dew point is higher and will allow the breaker to operate in lower temps. This is the manufacturers specs but this breaker has been around since the 70's. We had wet gas and I contacted DILO and was informed to run it through a filter (which I ordered) and as long as it isn't brought into the tanks on the filter trailer I can filter it. They informed me not to onload it into the tanks on the trailer or I would contaminate the compressor, vacuum pump, etc. That's good to know on a $100k plus piece of equipment.


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## Old Brian (Oct 31, 2016)

KingNothing said:


> If you live in a colder climate where there is a chance that you could get lower than -30 degrees, the SF6 gas will go to dewpoint and the breaker will go into lockout.


Very interesting. Learn something new every day 

Cheers,
Brian


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## 508gm1 (May 10, 2017)

Are you using the on-board filters on the recovery cart, or are you going through an external molecular sieve (rocket ship)? What is your ppm? The sf6 / nitrogen mix is a giant pain in the ass because it cannot be compressed down to a liquid with our field storage carts. You need way more storage capacity when compared to pure sf6. Were the desiccant bags replaced in the breaker when you were finished with your maintenance?

SF6 sucks - I miss the days of airblast, so much easier to work on ...


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