This paper applies to plant integrity management and the inspection of pressure and non-pressure stationary equipment and systems. The principals and practices of Risk Based Inspection are demonstrated and explained. This approach may also be applied to the management of other types of equipment including, rotating equipment, conveying, etc.
The purpose of Inspection is to:
. Maintain the integrity of an asset,
. Increase/maintain reliability,
. Maintain a safe workplace, operating area,
. Ensure fitness for service,
. Provide and prove due diligence,
. Do all the above at the lowest possible cost!
Inspection scopes (on-stream and off-stream) and inspection frequencies have traditionally been time-based and driven by Regulatory/Insurance requirements5 and industry practices. The frequency was initially based on undocumented, conservative .gut feelings. The inspections when completed were often unfocused and indiscriminate, resulting in large amounts or irrelevant or meaningless data contributing little to the assessment of the equipment4. These practices, although inflexible, have, on the whole, provided adequate safety and reliability. They just have not been cost effective or efficient.
Several organizations, such as the American Petroleum Institute (API), have developed recommended maximum inspection intervals (API . 5103) but there had not been a logical method of determining when these maximum intervals could be utilized.
RISK BASED INSPECTION
Risk Based Inspection (RBI) is a method for using risk as a basis for prioritizing and managing the efforts of an Inspection Management Program. Since a relatively large percentage of risk is associated with a small percentage of equipment, RBI permits allocating inspection and maintenance resources to provide higher level of coverage on the high-risk equipment and an appropriate effort on the lower-risk equipment.
The RBI methodology provides a logical, documented and repeatable system for making informed decisions on inspection frequencies, inspection scopes/details, types of NDE(1), etc. It is not intended for RBI to be any more complicated than this. RBI is not to be confused with, or compared to, HAZOP(2) or Runtime-Between- Failure analyses. While RBI does not normally contribute in a significant manner to operational procedures, operational parameters (and excursions) can contribute greatly to the results of the RBI.