When to Intervene? Using Rates of Failure to Determine the Time to Shut Down Your PCCP Line

Performing structural evaluations of aged civil engineering structures has traditionally been performed on a static basis. The condition of the structure is tested either destructively or non-destructively to determine its present day condition and the strength is evaluated to determine if the structure can safely withstand anticipated loads. One of the problems with managing structures in this fashion is that structures do not behave in a static fashion. This is especially true for large diameter PCCP (Prestressed concrete cylinder pipeline) mains that have wire break damage resulting from corrosion or cracking from hydrogen embrittlement. Given the variability in rate of deterioration in a PCCP main the risk associated with a pipe section changes with time. Pipe sections where risk is deemed to be acceptable may change to a point where risk is not acceptable in a relatively short duration of time. This phenomenon has been observed on multiple pipe sections. This paper examines the rate of deterioration of PCCP mains to evaluate how risk changes or does not change with time and how this information can be used to determine when a pipeline should be repaired.