Full scale experimental analysis of stress states in sleeve repairs of gaspipelines

This study discusses the experimental determination of stress states in sle eve repairs of underground gas pipelines. Work was done to define the effec ts of the reduction of pressure during welding, the load and place of posit ioning clamps, the length of the repair sleeve, and the use of O'ring-based devices to prevent gas leakage. Tests were carried out in reinforcements, welded with internal pressure equal to 60, 80 and 100% of the service press ure. High stresses were generated in tests carried out with short sleeves a nd O'rings, and occurred once the sleeve was fully welded and the pipeline pressure re-established. Maximum stresses, up to 270 MPa, were generated af ter about 1 min following closing of venting valves, on tests with artifici al gas leaks. From the results of these experimental studies, it is conclud ed that several operative aspects could be optimised, to minimise the stres ses in the reinforcements and to reduce the risk of failures. (C) 2001 Else vier Science Ltd. Ah rights reserved.