CLoMechEng
Mechanical
- Nov 10, 2011
- 1
Hello Gents,
I have run across an intriguing situation involving a boiler feed water tank. The control valve on the tank has a Cv value of around 160 and supplies steam at 110psig to the feed water tank. There are a total of four PSVs on the tank, three of which have set pressures of 50psig. One of the PSVs is half the size of the other three and is set a 20psig. The maximum flow capacity of all four PSVs equals approximately 14000 lb/hr. However, according to my calculations, 110psig steam through a 2" control valve with a Cv value of 160 has a maximum flow capacity of around 50,000 lb/hr. My immediate thought was to obviously spec out a control valve with a much smaller Cv in order for the PSVs to be sized correctly. could I be overlooking something here? I dont see how this control valve or PSVs could have been sized this far off. Further more, why are there three PSVs at 50 psi and one at 20 psi?? I cant rationalize it.
Thanks.
I have run across an intriguing situation involving a boiler feed water tank. The control valve on the tank has a Cv value of around 160 and supplies steam at 110psig to the feed water tank. There are a total of four PSVs on the tank, three of which have set pressures of 50psig. One of the PSVs is half the size of the other three and is set a 20psig. The maximum flow capacity of all four PSVs equals approximately 14000 lb/hr. However, according to my calculations, 110psig steam through a 2" control valve with a Cv value of 160 has a maximum flow capacity of around 50,000 lb/hr. My immediate thought was to obviously spec out a control valve with a much smaller Cv in order for the PSVs to be sized correctly. could I be overlooking something here? I dont see how this control valve or PSVs could have been sized this far off. Further more, why are there three PSVs at 50 psi and one at 20 psi?? I cant rationalize it.
Thanks.
