high current bolted connection paste

[Tmoose]

We have some tinned lugs bolted to copper blocks using bronze bolts and beryllium copper belleville washers, but SS bellevilles may have to be substituted.
A low load test is planned that will last a few weeks.
Future full load testing will likely be done with different lugs.

Connection Options discussed so far:
- torque them up clean and dry
- apply dielectric grease and torque
- apply electrolytic grease and torque
- rub or burnish with dry silver powder/flake, and torque

Internet searches find products and methods for aluminum and aluminum>copper connections, but generally suggest copper>tin is OK by itself.

 

[stevenal]

What's the environment? Penetrox E is intended for copper to copper connections. It is an oxide inhibitor with copper particles.

 

[Tmoose]

The >> 4 kV connnection is inside a motor housing. IT >>should<< be warm and dry, but it may spend some time in New England ambient temperatures, perhaps even by the seashore.

I figure if I'm supposed to put some dielectric grease on my spark plug connections we probably ought to do SOMEthing.

update - the copper blocks were supposed to be silver plated, and now must have a green patina cleaned off before plating

 

[stevenal]

Dielectric (insulating) properties do not enhance an electrical connection. Its purpose on the spark plugs is to help the boot seal to the porcelain to prevent a leakage path. For connections, oxide inhibition is the property you want. Penetrox is further enhanced by conductive particles. Probably not a great idea to introduce a third metal between the tin and silver though.

 

[subtech]

I would give the copper a good cleaning. Scuff the tinned surfaces very lighty with a medium or fine scotchbrite pad just to remove any crud or dirt. Use No-ox or similar oxide inhibitor that is recommended for copper connections. Lube your bolt threads and bottoms of your bellevilles lightly with your choice of inhibitor and torque using proper specs for lubricated hardware. Make sure all excess inhibitor is wiped clean after assembly. Where I'm currently employed, such connections are made almost daily and we have little or no trouble. The problems we do have usually turn out to be self inflicted and are the result of improper torque levels (don't allow gorillas to set the torque wrench or use it for that matter) or improper torque sequence on larger bolted connections. Although we have used stainless bellevilles with bronze/beryllium bolts for temporary connections in the past, I'd check with the manufacturer of your bolts before I made a permanent connection with the mix.