Weld failures in sleeve reinforcements of pipelines

Based on fractographic, metallurgical, mechanical and fracture mechanics an alyses, the causes of three failures in welded full encirclement sleeve rep airs in a 24 in gas pipeline were evaluated. These failures were related to poor manufacturing procedures. The material used to build the sleeves was old and had poor transverse strength. High heat input cellulosic electrodes were used to weld the field joints, which lead to hydrogen embrittlement i n the HAZ, also helped by relatively high circumferential stresses and defe cts of lack of fusion. A series of changes were introduced, including impro vements in the in-plant fabrication and the in-field installation of the re pair sleeves. A low hydrogen weld procedure with controlled penetration, ND E specifications and epoxy fillers were introduced to minimize the risk of sleeve failures and plastic collapse of the pipe. (C) 2000 Elsevier Science Ltd. All rights reserved.