Process control

[MortenA]

Does "process control" imply an instrument loop with a measurements and an actuator - or could an operator adjusting a valve manually also be called "process control" if he has to observe a gauge to do this? The reason that i ask is that we have a skimming pot inside a TEG contactor. This should only be drain when required and is done manually. It is suggested to add a PALL to isolate the outlet if the pot drains completely to avoid gas blow-by to the closed drain system. However, there is no free nozzle for this and it is suggested to use the gauge as a shut down signal. Local regulation requires that contol and shut down signals are installed on separate nozzle (a specific requirement) so could this be said to be OK then?

 

[LittleInch]

MortenA - I assume you mean LALL not PALL looking at your diagram.

For me process control can be anything that is controllable, whether instrumented or not. If the control is what seems to be an on/off isolation valve (the red NC valve), I would struggle to call that "control"

I think using the LT for both operation and shutdown is in the grey zone if the requirement is for separate nozzles. Also might depend to a certain extent on the type of level transmitter and its potential to become blocked. For potential blowby issues, (which might also occur due to coning) I've often see a calculation and orifice required to look at the potential gas volumes and pressure in the closed drain system.

In the end you've only got one instrument providing the information for operation and shutdown. Whether this is used by a control loop using copper cables or a control loop using neurons matters little.

I think you'll struggle to get this one to fly.

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

 

[MortenA]

You are right, i meant LALL,

We wont use the HZV for the actual control, that will be the manual valve (tagged 24-WL-0023 at the left of the snip) so it would be two different valves that closes - but at the end of the day the operator would use the same instrument for determining if the PSD system should close the upstream HZV. The flow is limited by 24-WL-0023 a standard 2" globe valve.

I think you are right wrt. it "not flying" but i will then get to work en the devition because i dont think we will get another nozzle

 

[LittleInch]

I think if you went for two instruments off the same nozzle it might work before any isolating valves. Also if the LALL was a simple pressure transmitter it would be better, or if you could find a single nozzle somewhere for the LL transmitter.

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

 

[MortenA]

You may be right, its a solution that i will consider, thanks for taking your time,

Best regards, Morten