The owner/operator of an ethylene facility in North Africa needed an assessment of the 10-year old plant so that a future inspection strategy could be developed. TWI was called in to plan and execute the work.
The first phase involved two engineers visiting the plant for a week to review inspection records, NDT equipment, QA systems and to have discussions with key personnel. One important aspect of this visit was to identify previous failure mechanisms, consider other potential failure mechanisms and draw up an inspection list of vessels and interconnecting pipework in the high pressure envelope, cold blow down system and storage tanks. As a result of their findings, a new set of NDT procedures were written for the client.
The second visit coincided with a planned shutdown and included two engineers and three NDT technicians. The site team inspected the list of critical components using a combination of magnetic particle/dye penetrant, ultrasonic flaw sizing, site metallography and hardness surveys, in addition to the more standard NDT carried out by a contractor.
As defects were detected, the engineers were able to make fitness-for-purpose evaluations using TWI staff at Abington with engineering critical assessment (ECA) expertise. Further, where the defects were considered unacceptable, repair and renovation techniques were developed and implemented.
Other failed components were returned to TWI, where structural and materials engineers were able to investigate the causes of failure and recommend alternative materials or designs. Conclusions were drawn and recommendations made on the future inspection strategy for each component examined, as well as plant inspector training and equipment needs.
In addition, it was concluded that the time between planned shutdowns could be safely extended from two to three years.