HYDROGEN FABRICATION CRACKING: STRUCTURAL ASSESSMENT INVESTIGATION TO AID THE SELECTION OF NDT TECHNIQUES

摘要

An operator of large LPG storage spheres first alerted HSE to the problems of Hydrogen Fabrication Cracking (HFC). During a routine inspection, a small weld repair was necessary, and during this procedure, large embedded HFC defects were discovered. The HSE and the operator carried out a detailed investigation into the cracking on two spheres. In one sphere, 46% of the total weld length had to be repaired. Samples taken confirmed that the defects had occurred during original manufacture. Further investigation identified that in the UK, a total of 25 LPG spheres had hydrogen related cracking. These vessels had been manufactured by three different organisations, using two design codes and two materials. The HSE's concerns were the condition of the other spheres in similar service, and how vessels with 100% manufacturing inspection could enter service with such large defects.