Do You Ever Grease Circuit Breaker Contacts?

[alexlounsbury]

Hello All,

I've seen the question multiple times on practice exams, and I have heard some varying opinions. The question is whether or not you would ever grease main or arcing contacts, generally focusing on whether or not this is acceptable in a corrosive atmosphere.

I lean strongly to the no grease side. I have never seen manufacture's literature recommending to apply grease. I have often wondered if it could effect fault ratings. I especially don't like the idea of grease on arcing contacts. I feel that in a corrosive atmosphere the proper solution would be a filtered positive pressure gear.

Thoughts? Opinions?

[electrolyte]

It is my understanding that you only lubricate contacts in corrosive atmospheres. I am almost positive I read that in a NETA world article.

[mksta1000]

According to the Paul Gill book, ensuring main and arcing contact lubrication is a standard part of air-magnetic CB maintenance. In fact, he lists "loss of lubrication" as a failure mode for contacts.

70B however only states to lubricate CB draw-out contacts, it doesn't seem to address contact lubrication directly.

[Biscuit]

I am pretty sure there is a question on either the level 3 or level 4 exam that addresses this. Can anyone confirm NETA's position on when to lubricate?

[alexlounsbury]

According to the Paul Gill book, ensuring main and arcing contact lubrication is a standard part of air-magnetic CB maintenance. In fact, he lists "loss of lubrication" as a failure mode for contacts.

70B however only states to lubricate CB draw-out contacts, it doesn't seem to address contact lubrication directly.

Any chance you have a page number on that quote? Does he refer to the actual contact mating surfaces, or is there a chance he is referring to the moving linkage?

[mksta1000]

p398: (7.3.2, air-magnetic breakers)
"Inspect primary disconnect studs for arcing or burning. Clean and lightly grease arcing contacts.

Check primary contact gap and wipe. Make adjustment as per appropriate instruction book. Grease contacts with an approved grease and operate breaker several times."

See also table 1.7- he makes a distinction between mechanism lubrication and contact lubrication.

But then look at 8.7.2.1.5:

"Lubrication of Current-Carrying Components
A manufacturer’s breaker manual sometimes recommends renewal of lubrication for specific current-carrying components of a circuit breaker. These components include main contacts, primary-circuit finger clusters and bus studs. Care must be taken when assessing which current-carrying components should be lubricated and which components should not be. Manufacturer’s instruction book on the particular breaker type should be consulted for lubrication of current-carrying components."

So........

[mksta1000]

Ok, the question comes from the NETA World Summer 2012 Tech Quiz:

"1. Circuit breaker contacts should be lubricated:
a. every six months.
b. only in corrosive atmospheres.
c. to prevent burning.
d. only in hospitals.

ANSWER 1 - b. -
Circuit breaker contacts usually should not be lubricated. The heat from the current flow through the contacts breaks the lubricant down and causes contact resistance to increase. Each time the contacts are opened or closed, arcing takes place on the contact surfaces, breaking the lubricant down even more quickly. Bolted pressure switches, however, often recommend lubricating their main contacts. There are some greases that add different ingredients to obtain better characteristics, such as graphite, zinc chromate or silver. They still use an emulsifier, which dries out over time."

So, there you have it!

[Jay Knight]

Thanks for helping clear up this issue!

[TestingProToBe]

Ok, the question comes from the NETA World Summer 2012 Tech Quiz:

"1. Circuit breaker contacts should be lubricated:
a. every six months.
b. only in corrosive atmospheres.
c. to prevent burning.
d. only in hospitals.

ANSWER 1 - b. -
Circuit breaker contacts usually should not be lubricated. The heat from the current flow through the contacts breaks the lubricant down and causes contact resistance to increase. Each time the contacts are opened or closed, arcing takes place on the contact surfaces, breaking the lubricant down even more quickly. Bolted pressure switches, however, often recommend lubricating their main contacts. There are some greases that add different ingredients to obtain better characteristics, such as graphite, zinc chromate or silver. They still use an emulsifier, which dries out over time."

So, there you have it!

We have been using mobile red grease used in aircrafts for years on moving parts. Especially drawout breaker fingers. We don’t know everything but my mentor was a field service engineer for square d in the 80s and grease is what he preaches.

[Csloat217]

I just read the NETA maintenance handbook series 2 and in side is an article titled Lubrication of Electrical Distribution Equipment. This is almost ten years old information but the gist of what is stated is that the correct grease can be used on contacts if there is signs of damage or wear of coating. They do stress that the environment it is in should be taken into account. If it is a corrosive environment then grease will do more good than harm but if it is a dusty environment the grease may trap more dust than it stops corrosion.