cleaning buss connections 1

[sparky970]

We have a rectifier where I work that produces 100,000 amps DC at about 330V. It has copper splice plates that mate to aluminum buss off the load side of the rectifier. Last week, we found one of these connections in excess of 520 degrees F. After about 12 hrs of finding the problem, management finally decided to shut down the plant to repair the problem. When we disconnected the splice plates they were very black on the mating surfaces. We ended up using scotchbrite pads, fine sandpaper, and HP Cleaner/Degreaser, which took some time to get them clean. We were about 75% done with the cleaning, when the Maintenance Manager stopped by. He wanted to know what was taking so long and said we should be using grinders with wire wheels or the wire cups to clean them. I told him I didn't think this was a good idea because of the grooves and valleys this would create and that it is important to have a flat smooth surface to make the best connection. He scoffed and made comments to other employees that I was f-ing him to death by taking so long. Any thoughts about using a wire wheel to prep the surface.

 

[Zogzog]

Whiskers

http://nepp.nasa.gov/whisker/other_whisker/silver/index.htm

 

[edison123]

Thanks Zozzog. Them whiskers deserve a LPS.

 

[controlsdude]

ZogZog

So silver whiskers are caused by a chemical reaction in the air where H2S is in the air? So you can not prevent this by air filters, this is the switch gear in a bad enviroment?

Or is this the reason not to use silver plating or silver oxide on bus connections?

 

[Zogzog]

It can be prevented with charcoal based filtering or positive pressure system for your substations. We see this alot in the paper industry.

Nickel plating will also prevent this, that is what we do for remanufacturing breakers that will be in this environment.