Evaluating Valves in Cyclic Service
Evaluating Valves in Cyclic Service
(OP)
Pressure components , pipes, welds, fittings, in a piping system, subject to cyclic fatigue condition could be assessed using Sec VIII, Div 2. How can I evaluate the suitability of valves in terms of different classes?
Thanks in Advance.
Thanks in Advance.





RE: Evaluating Valves in Cyclic Service
Alternately you can make a finite element model of the pressure boundary and use rules for analysis provided in ASME sect VIII div 2 or you can use the european norm methods, which may be better suited for the output from finite element models.
Of course, there is a lot more to proving the valve is suitable for cyclic service than just the pressure boundary. Threaded bolts will loosen under cyclic alternating stresses, so a cyclic service valve will miimize the amount of threaded components. Another issue is the different rate of heating up of the valve body vs the cage vs the trim/plug; under fast heat up cycles some slip clearances will bind and the valve will be bound up in a fixed position- not good if a fail open or fail closed action is relied on for safety.
The best method is to find 5 dozen exact same applications with the exact same valve that has laste 30 yrs in cyclic service- good luck.