Retorque & cold flow

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brentp

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Does anyone have technical information as why you would not retorque a mechanical lug? I've searched the forums but have only come up with dead links. Searching the web has also not given me exactly what I'm looking for.

There are some jobsite inspectors that will want to spot check my torqued connections at a later date and I need some info to show why they may seem loose.

Any help will be greatly appreciated.

Brent
 
I am in the inspector camp that does NOT believe in touching any terminations and connections especially with tools. However, I am not opposes to seeing evidence or asking for proof proper torquing has occured.

You have the correct term, so I assume have an idea of is occuring when you retorque a connection - cold flow.

Try a search on the IEEE web archives. I have read some good research papers on this subject matter that have been published by them.
 
chris kennedy said:
What kind of proof do you ask for?
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Affidavit from the contractor.

Torque the terminations when I am on site performing inspection.

Pictures of the torquing being performed and the tool on site with the pics.

But this is in just a few cases. Most of the time I simply ask the contractor to verify the terminations are torqued.
 
Mechanical connectors, especially aluminum connectors, are designed to work at specific levels of pressure. Over tightening will shorten the effective life of a connector the same as under-tightening will. I will put together a letter of explanation and send it to you later.

Regards,

Andy Zwit
Market Development Mgr.
ILSCO Corp
E-mail: azwit@ilsco.com
Voice: (513) 533-6220
Fax: (513) 533-6280
Web: www.ilsco.com
 
dezwitinc said:
Mechanical connectors, especially aluminum connectors, are designed to work at specific levels of pressure. Over tightening will shorten the effective life of a connector the same as under-tightening will. I will put together a letter of explanation and send it to you later.

While I am sure this is correct (at least this is what I have been taught), I would say there is a huge fudge factor involved, as 98% of all connections are way OVERTIGHTENED. 1% are loose these typically fail under load and 1% are torqued.

The percentages (which have a large fudge factor) stated here are strictly based upon personal experience 38 years in the trade 30 years of perform electrical testing and maintenance and 25 years of infrared scanning.
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