CRITERIA TO AVOID SULPHIDE STRESS CRACKINGPROVIDED BY EFC AND ITS VERIFICATION

In accordance with the criteria to avoid SSC provided by European Federation of Corrosion (EFC),the constant tensile load testing and three-point bend testing for low alloy and high strength steel WH610D2 were carried out and an acceptable environment of H 2S-containing 100×10 -6 solution was identified.To verify the validity of the EFC criteria,a series of welded plate testing simulating the anticipated field conditions of pressure vessels was conducted and the results show that the EFC criteria can be used well in services.The testing plate used includes both welded state and heat-treated state.The working stresses were produced by loading with bolts.The welding residual stresses and working stresses were measured by PSM-2F X-ray analyzer.Three sets of testing plate were conducted respectively in three different H 2S content solutions:1500×10 -6 ,500×10 -6 ,100×10 -6 .Upon termination of exposure after one and two months,the testing plates were examined to determine whether cracks occurred.The examinations showed that,on the plates in the solutions of H 2S content being 1500 ×10 -6 and 500×10 -6 ,many cracks occurred; and on the plate in the solution of H 2S content being 100×10 -6 ,no crack was examined.So the results show that the EFC criteria can be used well in services.