Catastrophic rupture of dead-leg pipe-work -HSE UK

"A recent failure on a UK refinery involved an 8" diameter vertical relief line, approximately 5m in length, which catastrophically failed during normal operation part way along its length, releasing approximately 75 tonnes of extremely flammable material at elevated temperature and pressure. Connected to an insulated process header and vessels, the failure involved complete separation of the relief line (which was not insulated).

Subsequent examination of the line revealed excessive internal thinning which was very local to the failure point, but relatively normal wall thickness elsewhere along its length. The inspection regime included regular thickness testing at four locations, but not at the area local to the failure. Notably, an adjacent relief line was also found to have very similar localised and severe internal corrosion, which had also gone undetected".

Read the full incident in this link  https://www.hse.gov.uk/safetybulletins/catastrophic-rupture-dead-leg-pipe-work.htm