Full-scale tests of an in-line inspection tool specifically designed to detect stress corrosion cracking (SCC) were completed last month with the tool's first ever run in an in-service U.S. gas pipeline.

British Gas Inspection Services Inc., Houston, brought the 36-in. crack-detection tool (CDT) to the U.S. after trials in Canada earlier this year. Commercial availability is set for 1994.

AXIAL CRACKING

The CDT is transported be product flow through the interior of the pipe and provides information about the pipeline's condition much as does the magnetic inspection tool which monitors corrosion. But magnetic techniques cannot detect SCC, san,s Michael Sharp, BG Inspection Services' vice-president and general manager.

SCC cracks occur singly or in clusters, oriented axially at right angles to the hoop stress of the pipe.

The CDT transmits ultrasonic signals pulsed in cumferentially a line around the pipe wall. AnN, defect oriented longitudinally ind radially will provide an ultrasonic reflector which is collected and recorded aboard the vehicle.

The transducers are mounted in complaint-filled wheels. This means, says Sharp, that as well as operating in liquids pipelines, the vehicle also operates in gas without the need for couplant in the form of a liquid slug.

TRIALS

The CDT was tested in an active 36 km, 34 in. crude-oil pipeline some 60 miles south of Winnepeg and operated by Interprovincial Pipe Line Ltd.

Trials in the U.S. have been conducted in Texas on two segments of a 30-in. natural-gas pipeline, one 23 miles long and the second 31 miles.

BG Inspection declines to reveal the operator.

From its base in Houston, BG Inspection expects to make the tool commercially available in the entire Western Hemisphere later next year targeting natural gas and oil pipelines in the 24-36 in. range. The company will aim for detection of cracks deeper than 20% W.T.

Copyright 1993 Oil & Gas Journal. All Rights Reserved.

TOOL FOR DETECTING CORROSION CRACKING UNDERGOES U.S. TRIALS

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