Eileen Chant, PhD, PE
In January 2011, Becht Engineering completed a Risk-based Equipment Reliability Planning (ERP) Development Project for a 600 MW Natural Gas Combined Cycle Power Plant. The study was conducted during a month long series of meetings with the Becht team, utility management and plant personnel to forward the utility's stated goal of good stewardship for the young, seven-year-old facility. The work scope included developing risk-based inspection and maintenance plans for all fixed equipment, piping, rotating equipment and some critical control valves in the plant.
Becht used its proprietary Risk-Based Equipment Reliability Planning work process which is embedded in the Becht software program STIER© (Strategy Tool for Improving Equipment Reliability) to develop the inspection plan for the plant equipment items. Our work process is compliant with API RP 580, Risk-Based Inspection and ASME PCC-3-2007 Inspection Planning Using Risk-Based Methods.
The process begins with data collection. Becht Advisors N. Thomas Willie and Joe Geiger spent several weeks at the site gathering the equipment data required by our ERP work process. Once the equipment data were loaded into STIER, a team of five equipment subject matter experts reviewed the information and pre-developed damage mechanisms and failure scenarios for each item. Our participating subject matter experts were Andy Hotaling (materials), Don Frikken (piping), Don Shaneberger (heating equipment), Joe Geiger (rotating equipment) and Frank Masiello (control valves). The failure scenarios require probability of failure and consequences of failure in both economic and Safety, Health and Environmental (S/H/E) terms and are critical to accurately assessing risk.
The Becht facilitation team consisted of Bob Sims, Eileen Chant and Phong Diep. The study reduced the identified economic risk by $4.4M through the accepted $0.9M in inspection and maintenance tasks. The figure below plots a typical cumulative economic benefit of mitigation and cost of mitigation in the order of decreasing benefit-to-cost (BC) ratio for the ERP process, and illustrates the diminishing return nature inherent to the risk-based inspection planning process. Note that this graph only includes economic and not S/H/E risk reduction. Mitigation of S/H/E risk is performed during our work process, independently from economic risk. The project scope also included training utility personnel in our work process and on the use of Becht's proprietary ERP planning software, Strategy Tool for Improving Equipment Reliability (STIER©). The client operated the software during the month long meetings as part of their training. The utility licensed our STIER© software, which will enable internal ERP work and allow them to maintain and update the inspection and maintenance plans.