El Paso Natural Gas has received approval from the U.S. Departmentof Transportation’s Office of Pipeline Safety (OPS) to conduct moreinternal inspections on its rebuilt New Mexico pipeline, whichruptured August 19 killing 11 people (see Daily GPI, Aug. 22). Since the explosion, flowsthrough the line, which runs from West Texas to California, have beenreduced to 85% capacity, or about 920 MMcf/d.

OPS said the El Paso line has already been repaired and putthrough hydrostatic testing, which it passed. Hydrostatic testingchecks for cracks by forcing high-pressure water through the line.Now El Paso has the green light to begin smart pig testing, whichwill examine the internal integrity of the line. The device, calleda pig because of the sound it makes during inspections, has sensorsand once placed inside the line, it can detect dents, deformitiesand changes in wall thickness.

Neither OPS nor El Paso released a timetable as to when thepigging would occur or how long it would take. However, once thetesting is completed, the results will be evaluated by OPS, whichthen would determine if the line were safe for commercial use.

OPS has not issued actual regulations on smart pig use, but theyhave become increasingly sophisticated and more widely used. Eventhough hydrostatic testing can actually detect certain flaws thatare invisible to smart pigs, the pigging process is considered acomplement to the water testing and ensures more integrity in testresults.

OPS requires all pipe to undergo at least one hydrostatic testafter construction. Although not mandated, OPS also has proposedrequiring pipelines that transport liquid petroleum products to usedirect assessment methods such as pigging to evaluate thepipeline’s integrity. Other types of inspections include usingmagnetic particles or ultrasound to measure the pipe wall’sthickness.

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