Establishing the requirements for internal examination of high hazard process plan
Low pressure cryogenic storage vessels are routinely left in service for long periods of time without examination of the internal surfaces. This approach to examination is being considered and applied for pressure vessels storing other products at warmer temperatures, but where the ‘service' may also be declared ‘clean and non-corrosive'. However, there is a need to establish the circumstances where intervals between internal examinations could be justifiably extended on the basis of a risk-based inspection (RBI) assessment, especially when the consequences of failure would be high.
http://www.hse.gov.uk/research/rrhtm/rr729.htm