Maintenance technicians can get accurate readings of bolt tension by connecting a digital reader to a datum disk affixed to the end of a Valley Forge fastener.

Correct tension within critical bolted connections is linked to safety, performance and maximum uptime. Valley Forge & Bolt said it is shifting the paradigm with SPC4 Load-Indicating Technology that makes it possible to measure the actual tension in a fastener, not just the preload that is being applied by torque or tension tools. By using SPC4 and any of its specially designed interchangeable readers, technicians can quickly gauge tension — even remotely with an optional configuration — within SPC4 bolted joints, according to the company. 

Valley Forge said its SPC4 technology is ASTM F2482 compliant and accurately measures direct tension in the fastener within +/- 5%. It provides absolute, real-time knowledge of fastener tension and performance from installation through fastener life. SPC4 measures the bolt stretch, or tension, directly from the fastener. Because stretch is the force that creates clamp load, this capability makes SPC4 the most accurate method available to monitor the clamp load of critical joints, the company claims.

Technicians can use any type of tightening tool — hydraulic, pneumatic, electric, or a hand wrench — and still achieve even and optimal load on a bolted joint, according to Valley Forge. SPC4 can measure preload in the fastener at installation, monitor load while in service, or measure load and load loss during maintenance inspections. The result is optimal joint integrity, less downtime, and safe performance of equipment.

Valley Forge engineers and manufactures a variety of SPC4 readers in analog and electronic formats. Technicians quick-connect the reader to a datum disc on the end of the SPC4 fastener, and the tension is displayed in real time on the reader as a percentage of minimal yield strength. Any reader can be used with any SPC4 fastener. Wireless readers allow for real-time remote load monitoring and include Wi-Fi and low frequency options.

SPC4 technology is available in standard bolts, studs, custom designs, and retrofits for customer-supplied fasteners, each modified with Valley Forge’s exclusive datum disc and gauge pin and compatible with any Valley Forge-supplied reader.