The owner/user should establish a written material verification
program indicating the extent and type of PMI testing to
be conducted during the construction of new piping systems,
retroactively on existing piping systems, and during the maintenance,
repair or alteration of existing piping systems.
For higher-risk systems, the owner/user should consider the
need for employing a higher percentage of examination (up to
100%) rather than random sampling which may be more
appropriate for lower-risk systems. Inadvertent material substitution
problems tend to be sporadic; therefore, small sample
sizes may not locate all inadvertent alloy substitutions.