In-line detection and sizing of stress corrosion cracks using EMAT ultrasonics. [Lamb waves]

Technical Report · Sun Apr 01 00:00:00 EST 1990

OSTI ID:5537726

The objective of the program described in this report was twofold. First, to apply the most recent developments in EMAT technology to the problem of detecting and sizing stress corrosion cracks (SCC) in operating gas pipelines and second to exploit the ability of EMATs to generate and detect a wide variety of ultrasonic waves in the walls of a pipeline under operating conditions. Several different types of sound waves were investigated at frequencies ranging from 0.2 to 2 MHz. Certain Lamb wave modes at frequencies in the 0.2 to 0.7 MHz range were discovered to be very sensitive to SCC and could be used for detection and sizing in spite of the fact that the wavelengths involved are much larger than the crack depths. By using the EMATs in pairs, three separate measurements on the flawed region can be made so that the reliability for detecting and characterizing the cracks will be increased. Furthermore, a new technique for simultaneous interrogation of the SCC with Lamb wave modes at different frequencies was demonstrated to be capable of correcting the raw data for variations in the transducer efficiencies and mechanical positions that are expected to arise in the operating pipeline environment. This will allow more quantitative analysis techniques to be applied to the data in order to size the cracks more reliably. It is proposed that the Lamb wave technique be developed further by constructing an EMAT pair on a wheeled carriage that can be pulled through sample pipes under simulations of the pipeline environment. This approach will allow the collection of data on the response of the Lamb waves to various types of pipeline anomalies and different coating materials so that improvements in the SCC detection and sizing algorithms can be developed. 6 refs., 9 figs., 4 tabs.

• Research Organization: American Gas Association, Inc., Arlington, VA (USA); Magnasonics, Inc., Albuquerque, NM (USA)
• Sponsoring Organization: AGA; American Gas Association, Inc., Arlington, VA (USA)
• OSTI ID: 5537726
• Report Number(s): AGA-91014483
• Country of Publication: United States
• Language: English

Related Subjects

03 NATURAL GAS
47 OTHER INSTRUMENTATION
COATINGS
ATTENUATION
PIPELINES
INSPECTION
ULTRASONIC TESTING
PIPES
CRACKS
ULTRASONIC WAVES
ELECTROMAGNETIC FIELDS
PROGRESS REPORT
RECOMMENDATIONS
SIGNAL-TO-NOISE RATIO
STRESS CORROSION
TRANSDUCERS
ACOUSTIC TESTING
CHEMICAL REACTIONS
CORROSION
DOCUMENT TYPES
MATERIALS TESTING
NONDESTRUCTIVE TESTING
SOUND WAVES
TESTING
032000* - Natural Gas- Transport
Handling
& Storage
440800 - Miscellaneous Instrumentation- (1990-)