Info on NRV?
Info on NRV?
(OP)
Hi,
Is it mandatory to provide NRV's in centrifugal discharge line?.What exactly demands NRV in pump dischagre?
Sounds too silly? Help me out
Is it mandatory to provide NRV's in centrifugal discharge line?.What exactly demands NRV in pump dischagre?
Sounds too silly? Help me out





RE: Info on NRV?
RE: Info on NRV?
1. If the flow diverted through the idle pump(s) does not compromise the required performance of the fluid system. This may rarely be true for critical heat transfer fluid systems like boiler feed or reactor coolant systems although it might be accomodated in initial design so as to avoid non-return valve problems like waterhammer piping loading and NR valve failures usually caused by fatigue of movable components.
2. The idle pumps can withstand the reverse flow through the pump that also drives the motor shaft in reverse. If the bearings can operate in both rotational directions and the reverse flowrates are relatively low, the rotor "runaway" speeds might be no higher than forward rotation. This is usually true for low specific speed centrifugal pumps but not for axial flow pumps of high specific speed. If the runaway speeds are too high, then anti-rotation pawls can be used on the motor shaft to prevent reverse rotation.
RE: Info on NRV?
Regards,
RE: Info on NRV?
RE: Info on NRV?
a.
RE: Info on NRV?
If you want to eliminate non return valves for two 100% capacity pumps you need to have one dedicated disharge line per pump. To tolerate the reverse flow when the pump is shutdown make sure the impeller is a keyed on design. For sumps with a lot of trash and debris that will clog a non return valve a good design basis will eliminate the non return valve.
RE: Info on NRV?
Thanks!
Pete