2 replies to this topic

[hoyar]

Is there any limitation or criteria for maximum allowable  pressure drop in a flow control valve?

I have a water stream with pressure around 120 bar, water will pass through a control valve and pressure after CV will be around 50 bar. is this control valve usual? is this pressure drop acceptable for CV?

[Chemengineer112]

 Dear  hoyar ,

 

The design drop  across  the  valve  is  sometimes  expressed  as  a
percentage of the friction drop in the system, exclusive of
the valve. A good working rule is that 50% of this friction
drop should be available as drop across the valve. In
other words, one-third of the total system drop, including
all  heat  exchangers,  mixing  nozzles,  piping    is
assumed to be absorbed by the control valve.

 

 For valves installed in extremely long or high-pressure drop
lines, the percentage of drop across the valve may be
somewhat  lower,  but  at  least  15%  (up  to  25%  where
possible) of the system drop should be taken.

[PingPong]

If you have to reduce the water pressure from 120 to 50 bar then you can do that with a control valve.

 

In Hydrocrackers control valves are used to let liquid down from a separator at ~150 bar to a separator at ~10 bar, whereby that liquid is moreover flashing. Those valves are expensive but it is possible.