Glossary

A relaxation pass is a controlled re-torque step used on gasketed bolted joints (especially pipe flanges, heat exchangers, and other pressure-boundary joints) to recover bolt load lost shortly after initial assembly. It is performed by reapplying torque to all bolts in a circular pattern at the same final/initial target torque value, after a specified dwell time, typically at ambient temperature and steady-state.

The purpose of a relaxation pass is to compensate for early gasket seating, embedment, and short-term creep (relaxation/cold flow) that can reduce preload soon after tightening, which in turn can reduce gasket stress and increase leakage risk. By re-torquing after the gasket has had time to settle, the installer restores preload that was lost during that initial relaxation period.

Relaxation passes are often contrasted with a startup retorque (formerly “hot torque”), which is a similar circular re-torque performed during warm-up when the joint is heating up; guidance commonly emphasizes doing that retorque before ~450°F (232°C) because lubricant behavior and torque accuracy can change as temperatures rise.