The full ring test enables detection of susceptibility to cracking in sour service

There are many material standards, specifications and procedures for selecting and testing materials for use in sour service. The majority concentrate on small scale samples, and base material properties. These type of tests can be misleading, as it is assumed that the measured properties from selected samples of a pipeline for instance will provide all the information required to select that item for use in sour service. Small scale tests such as those used in NACE TM0284, NACE TM0177 do not and can not take into account the effect of residual stress from manufacture and welding. In addition sample selection can be arbitrary, in some cases the wrong surfaces are tested. This paper traces the development of a large wale test method which has now been published by the UK Health and Safety Executive and is becoming included in a number of oil company pipeline specifications.