Unless the plant engineer knows what he has, how can he be assured that his critical piping systems aren’t imposing potentially damaging loads and stresses on his equipment if not on the piping itself? Piping Codes provide guidance for the operation and maintenance of piping systems and pipe hangers and supports. But is it enough? This article introduces portions of a “Best-In-Class” Fitness-for-Service (FFS) program that includes the performance of regular visual inspections of pipe supports and hangers, coupled with in-situ load testing of suspect supports. Such a program will help give the plant engineer the knowledge he or she needs to make sound operational and maintenance decisions.
A best in class FFS program for piping systems has 5 major steps. They include:
Collect and review design, operating, maintenance and inspection history of the piping system;
System walk down in both the hot and cold condition, and design verification;
As-Found pipe linear elastic stress analysis;
Creep stress analysis; and
Appropriate inspections and testing. With this information at hand, the plant engineer has verifiable information that will help him maintain his piping as safely and reliably as possible.
The first two steps described above involve performing regular pipe support surveys aimed at documenting the visual condition of the pipe and supports. If pipe supports are in distress, it generally means that the associated piping is in distress. However, not all pipe supports that appear to be operating normally are. Spring hangers may be aged or internally fouled and rigid rod hangers located in critical locations may not be carrying the design loads. Without this actual operating data, the analyses may provide erroneous results. In-situ pipe support load testing allows the operator to physically determine the load and operability of the hanger without uncoupling the support from the pipe. The testing can even be done online.