Preinstallation Verification Test – Hex Assemblies
The Preinstallation Verification Test is required by RCSC/AISC specifications. This test must be conducted on site to ensure that all bolt assemblies, lubrication, and installation tools can achieve minimum bolt tension prior to installation.
Pre-Installation Verification testing verifies that the installation method and your bolting assemblies can achieve tension.
In this video, we tested a two and three quarter inch A325 bolt, A563 DH nut, and F436 type 3 3/4” washer.
Preinstallation Verification Turn of Nut Method
To perform the preinstallation verification test, ensure you have a properly calibrated Skidmore Wilhelm device, also called a Bolt Tension Measuring Device. This is a mobile unit designed to use in the field. Be sure it is properly certified for the test and has the correct plates for your bolt. Gather three bolt assemblies for each length, diameter, grade, and lot.
Put the bushing for the hex bolt onto the device, then put the bolting assembly, including nut and washer, in place. For this assembly, we are adding one spacer washer behind the test washer and tightening the nut by hand until 2 to 3 threads stick out. For bolts of that are different sizes, refer to the RCSC guidelines regarding stacking washers and bolt stickout.
Next, match mark the nut and the socket with the line on the machine to track the full rotation.
We will start by tightening to 3,000 kps. Set the valve at zero, and tighten to 3000 kps. Once it is at 3000 and snug tight, then continue to tighten the bolt with your non impacting wrench to the required load weight. Here we’re going to at least 28,000 kps.
Repeat this test two more times and record results.
For the bolting assemblies to pass the test, the results must meet 105% of the value. If this doesn’t occur, first check your tool and try again with three new bolts. If a hex assembly first fails the preinstallation verification, you may apply a wax lubricant and test again.
Why Bolts Fail Preinstallation Verification Testing
There are a few common reasons bolting assemblies fail the preinstallation verification test:
One is lubrication. Without proper lubrication, the nut can strip out the bolt. Additional lubrication, such as stick wax, is only acceptable for hex assemblies.
Another common problem resulting in failure is using the incorrect plate, or bushing. Be sure you have the correct size plate installed. The plate or bushing can become warped overtime, so it’s equally important to inspect items before use.