Check valve analysis and prioritization (CVAP) methodology and wear prediction

3 CHAPTER 1 INTRODUCTION Alternatives to Quantitative Predictive Analysis The alternatives to quantitative screening, prioritization, and optimization are either extensive disassembly and visual inspection or trending qualitative data. Disassembly and inspection is the most conclusive means of determining the internal condition of a check valve wear; however, cumulative fatigue usage cannot be detected by inspection unless it has progressed to a level of a visible crack. Disassembly and inspection is resource-intensive and introduces the risk of future valve performance problems caused by improper valve re-assembly. Also, a program based solely on disassembly doesn’t necessarily guarantee reliable operation. For example, a US plant with a mature disassembly-and-inspect program recently reported four unexpected failures not captured by their tracking and trending program. Valve disassembly on a sampling basis will always play a key role in assuring the reliability of a check valve population; however, this method requires that it be applied judiciously. A “red, yellow and green light” graded approach to valve disassembly would shift the focus to the inspection of valves in the “yellow light” stage prior to the onset of incipient failure. The plant can reallocate maintenance resources by not performing unnecessary disassemblies on valves in a "green light" good condition. Plant safety and reliability will improve because incipient failures will be intercepted before they enter a "red light" failed condition QUALITATIVE VS. QUANTITATIVE PERFORMANCE PREDICTION On the most fundamental level, all check valve populations, regardless of the program they are classified under, can be thought of as requiring three key activities: 1. Screening and evaluation to identify bad actors 2. Performance improvement activities. 3. Re-prioritization based on performance feedback. All three tasks require a mix of qualitative and quantitative data to determine valve condition. For example, the approach underlying the Check Valve Analysis and