Study of two methods for repairing defects in line pipe
Battelle's Columbus Laboratories evaluated the strengthening characteristics of full-encirclement split sleeves and deposited weld metal repairs, currently considered the most effective and economical methods for repairing distribution lines without removing them from service. The investigation, carried out for AGA as part of a long-term program to increase the understanding and consequence of defects in line pipes, evaluated 2 types of full-encirclement split sleeves: Type A, a reinforcing band which restrains the bulging of a defective region while absorbing only 15 to 20% of the hoop stress in the carrier pipe, and Type B which is fillet-welded to the pipe. A properly fabricated Type A sleeve can strengthen nonleaking defective regions at least 70%, is not susceptible to fabrication defect because of the ow stress level in the sleeve itself, and cannot contain nternal pressure itself because its ends are not sealed. A properly fabricated Type B sleeve can restore the strength of leaking or nonleaking defective regions in line pipe to a stress level in excess of 100% SMYS of the carrier pipe. Presently, however, proper methods for nondestructive inspection of the sleeve are still inadequate, forcing the users of Type B sleeves to heavily rely on proven fabrication procedures to assure a high-quality repair. Deposited weld metal repairs on a number of actual corroded areas and several machined notches were found to restore the pipe to a strength level in excess of its actual yield strength. Some potential hazards, however, might accompany their use: the welds can create metallurgical discontinuities and residual stresses. The localized heating can create regions of high hardness and/or low ductility which may crack spontaneously or develop cracks at a later time under stress.
- OSTI ID:
- 6196322
- Resource Relation:
- Related Information: AGA Catalog No. L22275
- Country of Publication:
- United States
- Language:
- English
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03 NATURAL GAS
PIPELINES
REPAIR
ECONOMICS
LEAKS
MATERIALS TESTING
NATURAL GAS
SLEEVES
STRESSES
WELDED JOINTS
YIELD STRENGTH
ENERGY SOURCES
FLUIDS
FOSSIL FUELS
FUEL GAS
FUELS
GAS FUELS
GASES
JOINTS
MECHANICAL PROPERTIES
TESTING
420205* - Engineering- Transport & Storage Facilities- (1980-)
032000 - Natural Gas- Transport
Handling
& Storage