Bolt Tension Monitors are instruments designed to monitor stresses on threaded fasteners. Threaded fasteners are one of the most versatile methods for assembling structural components. Most industrial environments contain hundreds, if not thousands, of bolts holding machinery and equipment in place. When nuts and bolts are fastened together under load, the action of tightening the nut increases the force applied to the bolt causing elongation and stress which can lead to failure resulting in leaks, costly downtime, and potential safety hazards.

The health of bolted joints is defined by a single parameter: the clamping force (CF). The CF is the force that holds the elements of the joint together. If the CF is too low, separation and bolt fatigue may occur. On the other hand, excessive CF may produce damages in the structural members such as excessive distortion or breakage.

Like many instruments, Bolt Tension Monitors are becoming increasingly digital, which requires the application of membrane swicth or graphic overlay as the control panel.

The most common method of monitoring these critical bolts for tightness is to physically inspect each bolt and take a mechanical torque reading. At best, this is an imprecise way of measuring tightness due to the various conditions of the bolt threads, and the accessibility of the bolt itself.