The resonance technique utilises the natural resonance characteristics of a pipe in bending to generate a rotating bending stress along its length. It is a quick and efficient means of fatigue testing the full circumference of girth welds and mechanical connectors in full scale pipes.
Small changes in welding process or parameters can greatly influence the geometry and properties of girth welds, and so can affect their fatigue strength. Validation fatigue testing of new welding procedures is therefore required to ensure safety of these systems. This is particularly important in the oil and gas industry, in order to ensure that welds in pipelines, risers or mechanical connectors installed offshore or onshore in remote locations are safe.
Over the past decade TWI has conducted resonance fatigue testing of girth welds and mechanical connectors for all the major contractors and operators. In total, around 1000 tests have been completed on full scale test pipes with diameters ranging from 4-36in. A total of seven resonance fatigue test systems is currently available: four capable of testing pipe diameters in the range 4-16in, two for 12-24inch diameter and one rig capable of testing 18-36in diameter. Tests can be conducted with zero mean stress, or with a tensile axial mean stress introduced either by internal pressurisation with water or a hydraulic actuator.
Oil and gas field developments with which TWI has been involved as a provider of full scale resonance fatigue testing and interpretation services include:
BC10 (South America), AKPO, Block 15, Bonga, ERHA, Greater Plutonio, Kizomba (West Africa), Gumusut, West Seno (Indonesia), Ormen Lange (Europe), Atlantis, Boomvang Nansen, Blind Faith, Cascade Chinook, Constitution, Devil’s Tower, Gunnison, Holstein, King, King Kong Yosemite, Magnolia, Marco Polo, Mardi Gras, Matterhorn, Nakika, Neptune, Perdido Norte, Phoenix, Power Hub, Prince, Princess, Shenzi, Tahiti, Thunderhorse (Gulf of Mexico).
Operators choose TWI for our expertise, especially in interpretation of results, our experience and capability.
'The work carried out by TWI was to good standards as expected. TWI staff was excellent in accommodating the request for testing quickly.'
'The support and advice that was given by TWI was invaluable to the development of our project. Poor weather pushed our schedule late due to restricted deliveries but again TWI conducted the tests to our requirements in a timely fashion to bring our contract back within an acceptable timeframe for our customer. We are completely satisfied with the service provided by TWI and look forward to working with you in the future.'
'TWI's execution of this project was highly competent and timely; both of which contributed to the overall success of our qualification programme.'
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