Safety and reliability are the preeminent concerns in the design, operation, and maintenance of power piping. Recent additions to the ASME B31.1 Power Piping Code (Code) have addressed condition assessment of covered piping systems (CPS). Mandatory requirements for the condition assessment of CPS are discussed in Chapter VII of the Code and nonmandatory guidelines are discussed in Appendix V of the Code. These documents discuss design, fabrication, construction, operation, and maintenance issues, and do not provide detailed guidance in the evaluation of high pressure piping systems subject to creep.
An asset integrity management (AIM) program should integrate and consider all attributes that influence the intended function of the original design. In addition to the evaluation of specified design, fabrication, construction, operation, and maintenance issues, an asset integrity management program should also consider and evaluate significant time-dependent anomalies, such as flexible operation modes, malfunctioning supports, and creep redistributed stresses. An AIM program includes the identification of governing drivers that accelerate piping system damage and then develops countermeasures to mitigate or reduce the driving mechanisms.
This paper discusses the large range of piping system stresses and the sensitivity of stress increase to 50% creep life reduction, indicating the need for a robust stress ranking methodology. The process results in an accurate selection of the most critical creep damage weldments for nondestructive examinations.