Recomended overdesign value for Safety Valves Selection
Recomended overdesign value for Safety Valves Selection
(OP)
After calculating required capacity for a safety valve service, the final selection for the rated capacity and/or selected orifice area is normally X times the required capacity or required orifice area. What are recommended values for this "X" value? What might be the impact of selecting a PSV 10 or 20 times the required capacity/orifice area on the PSV performance / calibration needs? Thanks.





RE: Recomended overdesign value for Safety Valves Selection
If you have a planned modification some years down the road that require a higher design capacity that what the initial mode of operation requires (by more than just selecting the first size with an area bigger than required) then i would say its time to step up to the plate as an engineer!
Best regards, Morten
RE: Recomended overdesign value for Safety Valves Selection
RE: Recomended overdesign value for Safety Valves Selection
RE: Recomended overdesign value for Safety Valves Selection
In such cases, I wouldnt get too hung up over chattering during firecase - I've yet to come across designs where another dedicated RV for firecase was provided purely due to this reason. The RV will still relieve and prevent loss of containment though the trim may be damaged - there is probably much more extensive damage done to other equipment during a local fire than this RV. Also the relieving temp reached during a firecase relief scanario is not taken into consideration when setting the design temp for the vessel.
The same criterion would apply for thermal liquid expansion relief loads, where the installed capacity is almost always many times more than the calculated load due to heat gain from ambient.