Stress Measurement Applications

Static Load Measurement

Studs

Repair clamps are mechanical devices used to transfer load across damaged areas of tubular structures or pipes. These are often of split collar arrangement joined together with threaded studs. In order to operate correctly the studs need to be tightened to a pre-set value. As one stud is tightened it relieves load from the adjacent studs as the component deforms and the load redistributes. It is therefore necessary to monitor the load in the studs in order to ensure the clamp is working as designed.

StressProbe has been used subsea on a North Sea offshore platform to measure the static load in studs. The system can be diver or ROV deployed. In this case the system was deployed and spot measurements were made of the stud tension around a number of clamps.

By measuring the stress in the stud, the load can be deduced. Two approaches have been developed so far for threads that either measure stress directly in a loaded thread or, alternatively, determine the stress by comparison between the loaded section and the free end. Both approaches have been successfully tried in laboratory tests and underwater on 34mm and 40mm diameter high strength bolts.