FTM 115: Tension Control Bolts

Fastener Training Minute 115: Tension Control Bolts

This edition of the Fastener Training Minute with Carmen Vertullo was originally published April 13, 2017 as “installing and inspecting tension control bolts during episode 115 of Fully Threaded Radio.

Hi everybody, welcome to the Fastener Training Minute. This is Carmen Vertullo coming to you from the Carver FACT Center in El Cajon, California, and the Fastener Training Institute.

Just recently I conducted some training for some structural bolting people. The classroom involved some suppliers, some testing folks, inspectors, and some installers. They had some very interesting questions and we ran into a situation with one of our attendees that I think we can learn something from, having to do with tension control bolts and what the role of the inspector is on the job site. We run into situations where the inspector wants us to do something or wants to complain about something that really is not a valid issue, and we have to have a way to deal with that. So when we return we’re going to talk about a really interesting and valuable piece of information that all structural bolting installers and suppliers should know.

Today we are in structural bolt territory. We’re going to be talking about the tension control bolt. One of the most popular bolts in the structural world. And in this case, we had a supplier and an installer who came under fire from an inspector because when the inspector was witnessing the test called the lot assembly verification tension verification test the results of that test did not match exactly what the manufacturers test report said and the inspector wanted to complain about that. The inspector’s feeling was that those two results should have been the same.

The fact of the matter is that there is nothing in the standard that requires them to be the same. In fact the nature of the tension control bolt, the way it’s tested at the factory and the way it’s tested in the field preclude them from being exactly the same.

At the factory we have brand-new possibly even wet lubrication on the bolt. That lubrication is a very big factor in making the system of the nut, bolt, and washer work. By the time we get that bolt out into the field, the lubrication is still there, of course and it’s probably still wet, but it may not work exactly the same. But the only requirement is that it provide enough lubrication to make the bolt perform its intended function. That function is to give the amount of tension required by the standard when the tail brakes off of the tension control bolt. In this case because the numbers were coming out a little bit lower. Although they were within specification, the inspector was complaining about that. Now, it was only a small number of bolts, so the supplier and the installer decided just to replace them instead of having an argument. But if it were a larger number of bolts, or maybe there were some severe financial or possibly job schedule implications with this.

You need to be able to make your case and the RCSC specification simply states that we have to be able to prove that the tension control bolt delivers the required tension, not that it matches the original manufacturer’s test reports.

Well, this is a very important piece of information for structural bolting people to have.
I assume this is probably not the first time this has happened nor will it be the last.

This has been Carmen Vertullo with your Fastener Training Minute. Thanks for listening.

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