Thanks again 'moltenmetal' and 'GD2' are your comments. They are very much appreciated. The stresses in the pipes that are welded to the valves were checked and to our surprise, the stresses were low. The balls valves have polymer seat (PEEK) material. So, the following consensus has been...
Thank you LittleInch. These valves have continued to fail over a period of time in the four locations. It appears that the pipes they are welded to are overstressing these valves and if the 1500# class valves were indeed used, then the increased structural strength would hopefully keep these...
Thank you mk3223, KevinNZ, moltenmetal, davefitz, and GD2 for taking the time to respond to this thread. I appreciate all the good information. davefitz and GD2, is there an ASME standard that discusses the approach that small bore components (valves, fittings) are more designed for structural...
Why are small bore valves (2" and under) usually spec'ed out at a higher ASME pressure class rating than the other components in the system?
For example, based on the piping design table, for a 600# Pressure Class System, 2" and under valves are spec'ed out to be ASME 1500# pressure class...
