Stainless Steel Bolts Used for Switchboard Connections

[jpflying]

I am involved with a project where the electrical contractor has used stainless steel bolts and nuts for the connection of the Hv feeder and LV mains cables onto the 11kV/433V 1.5MVA transformer as well as on the connection of the mains cables onto the LV main switch. In the past I have always used high tensile bolts and was under the impression high tensile bolts are preferrable to stainless steel because of strength. Fault current is about 27kA at the 415V connections.

Can I get peoples opinions of using stainless stell bolts instead of high tensile steel bolts and nuts.

Thanks.

 

[dik]

What is the bolt load? and the environment?

Dik

 

[waross]

Some advantages:
Less eddy currents in stainless. Less current through the bolt.

Bill
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"Why not the best?"
Jimmy Carter

 

[prc]

jpflying: Your understanding is correct. There is no particular advantage for using stainless steel bolts for that purpose.

 

[jpflying]

I guess one of my questions was, is there any disadvantages other than cost??

 

[desertfox]

Hi jpflying

My first question would be what bolts were used for attaching the cables during short circuit test?
The stainless bolts maybe okay provided that they can be tightened to obtain the same preload as the original bolts without being over tightened.
I assume the contractor was given some instruction as to torque settings he should use, if you have that information and details of the joint we might be able to help further.

desertfox

 

[dik]

I think that the stainless steel bolts would be better, but it depends on the environment and the load required of the bolts. It's possible to obtain high strength ss bolts, but they are much more costly.

Dik

 

[ScottyUK]

Threads in SS have a terrible habit of galling, although whether it would occur at the relatively low torque values used in copper joints I'm less certain.


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