Control valves in series

[mort78]

I have sour water stripper where by-passing the HP column results in two control valves in series. Is there any way to use the first FC to control the flow to the LP column without generating too much noice in the system for the control to function?

Alternatively, are there issues about forcing the second valve open and sending the liquid at a relatively high pressure and allowing it to flash over the inlet device to the LP column (12 to 2 bar abs)?

 

[sshep]

In most cases there is no problem to just put the second controller in manual at 100% open, or some lesser % open to give backpressure if the first valve operates too closed as result of extra dP (which may also dampen noise).

As always there are safety implications to bypssing equipment which may need to be considered for your specific case.

best wishes,
sshep

 

[JLSeagull]

The reason for two valves could be errosion instead of noise. You did not mention the size but these could be small valves with a low flow rate. This is often the case on a separator with a sour water boot. It may not be the case on your sour water stripper.

In a small valve that is taking a high pressure drop near the valve seat the sour water can wire-draw even the hardest of plug and seat material. Where a level control accommodates some level flexibility such as the boot on a large vessel I like to use gap control. Keep the level valve closed until the demand requires the valve to move to about 20 % travel. However, this scheme is likely inconsistent with your application.