What testing does PHMSA expect operators to perform to verify the quality of pipe coating?
NACE International Standard Practice NACE SP0490-2007, Holiday Detection of Fusion-Bonded Epoxy External Pipeline Coating of 250 to 760 µm (10 to 30 mil), recommends jeep testing using a voltage high enough to find holidays at the expected maximum thickness. A (typical) 16 mil nominal coating will have some places where it is 20 mils thick. Operators should consider using a minimum voltage level of 125 to 150 v/mil, which equates to an approximate voltage of 2500 v (e.g., 150 v x 16 = 2400 v or 20 x 125 v = 2500 v). All coating holiday detection surveys, whether factory or field, must be set-up to detect defects that will be deleterious to long-term coating performance. The coating holiday detection surveys should follow recommended manufacturer voltage settings.
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