El Paso Proceeding with NM Pipe Integrity Testing
El Paso Natural Gas has received approval from the U.S. Department of
Transportation's Office of Pipeline Safety (OPS) to conduct more internal
inspections on its rebuilt New Mexico pipeline, which ruptured August 19
killing 11 people (see NGI, Special
Report). Since the explosion, flows through the line, which runs from
West Texas to California, have been reduced to 85% capacity, to a rate
of about 920 MMcf/d.
OPS said that the El Paso line has already been repaired and put through
hydrostatic testing, which it passed. Hydrostatic testing checks for cracks
by forcing high-pressure water through the line. Now El Paso has the green
light to begin smart pig testing, which will examine the internal integrity
of the line. The device, called a pig because of the sound it makes during
inspections, has sensors and once placed inside the line, it can detect
dents, deformities and changes in wall thickness.
Neither OPS nor El Paso released a timetable as to when the pigging
would occur or how long it would take. However, once the testing is completed,
the results will be evaluated by OPS, which then would determine if the
line were safe for commercial use.
OPS has not issued actual regulations on smart pig use, but they have
become increasingly sophisticated and more widely used. Even though hydrostatic
testing can actually detect certain flaws that are invisible to smart pigs,
the pigging process is considered a complement to the water testing and
ensures more integrity in test results.
OPS requires all pipe to undergo at least one hydrostatic test after
construction. Although not mandated, OPS also has proposed requiring pipelines
that transport liquid petroleum products to use direct assessment methods
such as pigging to evaluate the pipeline's integrity. Other types of inspections
include using magnetic particles or ultrasound to measure the pipe wall's
Carolyn Davis, Houston
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