A PRACTICAL GUIDE FOR RECOGNIZING ELASTIC FOLLOW-UP IN EXISTING POWER PIPING SYSTEMS AND MINIMIZING ITS EFFECTS

摘要

High temperature, high pressure steam piping can fail for many reasons. This can include some combination of metallurgical, operational, fabrication, erection and design short comings. This has proven that high-energy piping systems are not maintenance free and have a finite service life. From a safety and reliability point of view it is increasingly important to determine when this life is expended before failure occurs. This requires that conditions that can reduce life are recognized. Once recognized, it is equally important that these conditions be addressed in a manner that will help prevent personnel injury, forced outages and high repair costs. The ASME B31.1 Code states that piping is "subjected to strain concentrations due to elastic follow-up of the stiffer or lower stressed portions." However, the phenomena of "elastic follow-up" is often overlooked in the design of creep prone piping such as main steam and hot reheat. It is also difficult to identify in the field. This paper addresses a methodology to recognize elastic follow-up in existing piping systems, possible consequences and the means to minimize its effect.