Risk based inspections (RBI) are used to understand and manage the risk of failure of potentially hazardous plant to a level that is deemed to be acceptable.
At its heart RBI is a screening technique which reduces the uncertainty over future plant condition. To get optimum benefit from an RBI the inspection should be tailored to identify the progression of expected defects, not just with respect to the corrosion or degradation rates, but importantly, the type, extent and typical locations of those defects.
Integrity management specialist Plant Integrity Management (PIM) is emphasising that, on its own, inspection is not enough. Adequate resources must be allocated to the review and evaluation aspects.
Fran Chalmers, PIM’s in-service inspection technical manager, said: “As part of the RBI approach, written schemes of examination (WSEs) are developed. These have an important role to play as they provide comprehensive information about items of plant or equipment and their associated maintenance requirements. But WSEs are only as effective as the information they are based on and its interpretation.
“It is imperative that we make best use of our available resources, this means getting the balance between data targeting, gathering, evaluation and reviewing right.
“The importance of gathering inspection information and its associated costs is usually considered the norm within the oil and gas industry whereas, generally speaking, more limited resources are usually assigned to the tasks of evaluating and reviewing data.
“Given the high volume of data that inspections can generate, especially pipework inspection reviews, this means that the margin for error or misjudgement is higher when resources and time are limited.”
Asked about good practice when it comes to WSE and RBI programmes, Ms Chalmers said: “The written schemes of examination and RBI programmes should seek to confirm the progression of specific types of defects throughout the life of an asset.
“The inspection techniques selected to detect expected defects need to be suitable with respect to the coverage of preferred locations and, of course, have the ability to detect the expected defect types. Inspection coverage in terms of the number and size of inspection locations should be driven by how extensive or widespread existing reported defects are.
“This can be successfully achieved by high quality analysis and interpretation of previously enacted inspections.”
She added: “Where finite inspection resources are concentrated on enactment at the expense of proficient analysis and interpretation it is likely that there will be weakened cost performance from your inspection programme.
“This may manifest itself as a poor relationship between planned and unplanned work orders that can indicate less control over plant technical integrity management.”
She concluded: “The inspection element of RBI is a vital piece of the integrity management puzzle, but it is just that, one piece. For RBI to be effective inspection needs to sit alongside the review and interpretation elements of the RBI. It’s counterintuitive to gather information and not make best use of it.”