Fill scrubber in manually prior to start-up.

"Scrubber" covers many different types.

See why the vendor or the design needs a liquid level first.

Many scrubbers are installed because whilst the risk of wet gas is low or v low, the consequences for the compressor are very big if you get liquid into them. The scrubber doesn't usually cost very much so people stick one in "just in case".

So you need to look at the consequences / issues of operating below LL and if there are no big risks or issues then modify the system accordingly not to be an ESD trip (I assume it is locked out if you operate at no level).

The issue might be accidental gas blow by on the drain valve?

I've seen some scrubbers on transmission lines have the automatic / controlled level system removed and made manual on the basis that any liquid is caught by the first compressor down the line so subsequent ones just "never" see any liquid. Any liquid in there that is not replaced will almost certainly evaporate over time so not surer a static head of liquid works either.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

Folks;

the plant is optimally manned, no manual operation forseen as long as we need operator on place just in case
I am thinking about override the ESDVs for this particular case and monitor the presence of liquids very closely and consider the gas blow by scenario during hazop of downstream ubits

Guess that this is not compressor equipped with scrubber but scrubber equipped with compressor and ESD and LS has nothing to do with compressor.

No details = no valuable answers

In a philosophical sense it is normally better to remove the ESD in a structured manner rather than "override".

Should really be done under a MOC procedure.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

IMO, accept that the ESD signal keeps the safe valve closed all the time. Maybe consider to rename the alarm to a notification and make closure "un-latched" or "auto reset" or whatever you want to call it, if the ESD signal goes away when level is above LL (without an operator re-set/confirmation). Also, remember to exercise your ESD valve once in a while.

Best regards, Morten

--- Best regards, Morten Andersen

There is nothing wrong with this control arrangement, so what is it that you want to fix ? Some unit downstream of this ESD valve cannot handle gas blowby load from this scrubber ??

Actually which ESD valve closes on LL liquid level?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.