We’ve talked about torque and tension before, and why it’s important to understand that you must achieve the proper tension when installing structural bolts. Fortunately, there are special structural bolting components on the market that can make it easier to ensure proper torque and tension. Tension control (TC) bolts come built with a spline that pops off when the nut is properly torqued. For hex bolts, DTI washers can be just as helpful in displaying the proper tension. Two of the four methods of installing structural bolts cover tension control (twist-off type bolts) and DTI washers, respectively. Let’s look at these two components and how they’re helping workers on the jobsite every day.
Tension Control Bolts
Tension control bolts are pre-assembled fasteners with a rounded head and a splined end that shears off when the nut achieves proper torque. This is a great advantage to using TC bolts, as it provides a quick installation procedure that maintains accuracy. TC bolts are also faster to install for this reason. It is still important to remember that though TC bolts help confirm that you have achieved proper torque, you still need to ensure your bolts are properly tensioned.
Direct Tension Indicators
Direct tension indicators (DTI) are washers manufactured by Applied Bolting Technology and Turnasure. These washers are used on a hex assembly and are designed to ensure proper tension on bolts. There are two types of DTIs, both resulting in the same outcome. Traditional DTIs have bumps around the washer that flatten once proper tension is achieved. This allows you to have a visual confirmation that tension is achieved.
The other type of DTI, also made by ABT, are DTI Squirters®. When properly tensioned, these washers will squirt out a colored silicone that gives you a visual confirmation that tension has been achieved. An extra advantage to this is that inspectors can easily see the bolts were installed properly, saving time on the jobsite.
Bottom Line
Both tension control bolts and DTI washers can help save you time on the jobsite by easily confirming tension or torque is achieved. Regardless of what you use, remember that bolts are tightened in order to achieve tension – torque is only a by-product of this relationship to reach proper tension.