L51865 Hydrotest Parameters to Help Control High-pH SCC on Gas Transmission Pipelines

This report develops and validates a probabilistic model for high pH SCC on pipelines that can help operators to:

quantify the condition of susceptible transmission pipelines
assess the efficiency of controls for such SCC based on after coolers and periodic hydrostatic re-testing
identify, evaluate, and control the related risks· prioritize rehabilitation to avoid in-service incidents.

The probabilistic model is an adaptation of a first-generation model for high pH SCC known as the Stress-Corrosion Cracking Life Prediction Model, (SCCLPM). Its validation follows from the close match between simulated cracking populations and incident occurrence and that observed for operating pipelines behavior. Because methods to simulate coating failure have not yet been developed, the model assumes the presence of a cracking environment, which according to field experience adds 3 years or more to the simulated pipeline life.