Laboratory Simulation of Hydrostatic Test in Near-Neutral pH Soil Environments

Hydrostatic testing is the principle method for managing stress corrosion cracking (SCC) of natural gas transmission pipelines. The long-term benefit of such testing relates to the stress margin between testing and operation and the effect of overstress on the surviving population of sub critical defects. This research was initiated to understand the response of these subcritical cracks of varied dimensions to hydrostatic testing in typical soil electrolytes that are conducive to SCC. More than 10 laboratory hydrostatic simulations have been conducted in this investigation. The results obtained provide insight into such issues as whether there will be crack advances during the hydrostatic test and the effect of hydrostatic testing on the subsequent growth of surviving cracks during service.