ECN Forum Forums General Topics of the Trade General Discussion Area how tight do i tighten the lugs?

Are not most fuels and solvents "Oxidizers" of some sort or another? Not cool for electrical connections over the long haul. (Flamable too.) A little residue, and ten years from now they get a lost neutral.... Like spraying bleach on Al clad buss, a few months later it will be white chalk. Oils on the other hand have Anti-oxidizing properties. And not all oils are the same.... Some are great mechanically, but not electricaly inert. Some like WD-40 actually soften metals over time. Remember this is for an electrical connection and should be purpose specific, especially with AL conductors.

Among others, I like a product called "corrosion-X HD" for GP reasons when working with copper buss, cutting KO's, etc. (Word of caution - aerosols, dielectic, or conductive oils and live electrical circuits don't mix!)

Back on topic though, there is no way to measure PSI inside a connection... "Erk's" could lead to one of two things failure of the lug or the treads in it, or over-compression reducing the conductor size. the NEC handbook also has some listed in the commentary after 110.14.

oxidizers?....I have no idea, but, whatever should be used is not always available....

I can't say I've seen any of the effects you describe....but I haven't seen everything yet either. and as far as flammable, I'm talking about a drop on the threads .....not drenching the gear.!

penetrox works too, if you don't mind the mess....

Thanks everybody. Sounds like the best place to go is right to the manufacturer. And if no info is available from them, go with the values UL uses.

Thanks again.

There is no need to "go to" the manufacturer because the manufacturer generally comes to you. The tourqe values for these types of terminals are listed on the equipment.
I like to tourqe them goodentight.

Yes, the torque values are generally affected by various thread lubes- with one exception: anti-seize compounds.
Why? I don't know. But that's what it says on the lable.

If you want to be a stickler, and use a listed product, the various anti-ox pastes are essentially thick anti-seize compounds, and are listed for this use. Two brand names as "Noalox" and "Penetrox."

I thought that the torque specs listed on the panels were for dry threads. The use of a lubricant may result in excessive pressure on the conductor and lug and that in turn may result in early failure of the connection.
Don

i agree with Don, torque values are for dry fasteners. A long time ago I read that if you lubricate the threads of a fastener, you have to reduce the maximum allowable torque by at least 10%.

Anyone know any airplane or race car mechanics? I bet they know the answer.

I think the answer is you torque it the way they spec it. For engines they may say to lube the bolts first. It makes a big differance if you clean the bolts, and run a tap in the holes.

Some automakers went to a torque to yeald with a torque angle meter. First you torqued it in sequence sometimes in several steps to a higher torque each time. Then you put a an angle meter or gauge that measured the degrees of turn. A spec might be 20 ft/lbs, then 45 ft/lbs, next 90 degrees. The idea was to be more accurate of streching the bolts to the limits. Many times it was recomended to not reuse the bolts for this reason. It was a pain and not allways a good result IMO.

A torque wrench is never 100% do to factors like how clean the threads are, lub, liquid or material in a blind hole, was the bolt or threads streched too much before, thread condition. For that reason I have seen torque wrenches break bolts, strip threads, or torque a bolt before the head is making contact with the other surface. That's why it is up to experiance to help tell you that thing is not getting any tighter or is too loose. I'm not saying not to use a torque wrench, just to pay attention.

I used to joke that my arm was a torque wrench and I could measure the effort in grunts. Like you torque this to 1/2 a grunt (50 ft/lbs). Just as your eyes allow you to judge inches you arem can estimate torque.