Abstract

Pneumatic testing is beneficial as an alternative to hydrotesting particularly in remote areas where access to hydrotest fluids becomes logistically difficult or impossible. The present work is aimed at addressing two salient questions often face pneumatic testing. First is related to the appropriate piping volume to consider for calculating the stored energy in use with ASME PCC-2 calculation for determining the safe exclusion distance for a given piping geometry and test conditions. It was found that the 8D criteria specified in ASME PCC-2 cannot be generalized for all pipe sizes, different material toughness, grades, wall thicknesses and test conditions. A criterion is developed based on the ductile fracture arrest length that considers all these factors combined. The second criterion is related to the ability to detect pinhole leak from the pneumatic test data, again for a given geometry and test conditions, and what constitutes the minimum pinhole effective area in relation to the system total volume, measured uncertainties in the test pressure and temperature over the duration of the test. A semi-normalized physics-based parameter is suggested that can be applied to determine the effective pinhole leak size in relation to the volume of the piping assembly and conditions for detectability limit. A methodology is developed and applied to a pneumatic filed test on DN200, 12.2 km pipeline lateral.

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