Eileen Chant, Ph.D., P.E.; J. Robert Sims
Becht Engineering was awarded a project in 2007 by the Materials Technology Institute (MTI) to develop a Risk-Based Inspection (RBI) work process for above-ground, fiberglass reinforced polymer (FRP) storage tanks containing one of five designated chemicals. The process complies with American Petroleum Institute's Recommended Practice 580 – Risk-Based Inspection and the ASME PCC-3 Inspection Planning Document and uses Risk-Based methods that were developed for fixed equipment and piping in the hydrocarbon and chemical process industries. However the basic methodology can be adapted to any class of industrial equipment, such as FRP equipment.
Risk-Based Inspection Approach
Damage mechanism documentation for five selected chemical and tank construction combinations was developed to provide guidance in developing failure scenarios. The damage mechanism documentation included the following information for a given stored chemical:
- Description of appropriate containment systems
- Description of damage mechanism and appearance, including photos
- Recommended temperature and concentration ranges of the stored chemicals
- Typical fluid contaminants and their effects on damage rates
- Failure modes and failure locations
- Guidance on probability of failures
- Inspection and mitigation techniques to detect and mitigate failures
- Guidance on mitigated probability of failures
The RBI work process includes a benefit-cost analysis that compares the economic benefit of mitigation to the cost of the actions selected to mitigate the risk. Mitigation of the S/H/E risk is also an inherent part of developing the inspection and maintenance plan. This RBI work process allows plant personnel to monitor reliability while delivering a task-focused, cost effective inspection and maintenance plan for a FRP storage tank. This project was completed in June 2008.
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