GWR high high level transmitter false activation problem

[Ahmed Abdelaziz]

Hi everyone
I'm working in amine plant for gas sweetening,a fuel gas filter whose HH level transmitter is GWR do frequently activates so cause total shutdown. I'm tracking the possibility of foam potential, any other problem may I investigate ??
thanks in advance

 

[georgeverghese]

It is unusual( though not incorrect) to use a GWR type LT for this straightforward application. Can you post a P&I diagram of this filter which also shows nozzle connection locations?

 

[Ahmed Abdelaziz]

Thank you Mr George for swift reply

kindly find attached a marked P&ID but let me how on earth this GWR isn't suitable for a fuel gas filter ?

 

[georgeverghese]

Nozzle arrangement for bottom compartment LT on S-5132A/B does not seem to match that typically used for GWR. GWR are usually top mounted, while this LT appears to be a side mounted dp cell - pls check with your instrumentation engineers. For a dp cell type LT, since this is in saturated gas service, it should be remote sealed for both vapor and liquid side sensing legs. Would say that a dp cell is morre suitable for this service.

 

[controlnovice]

It could be GWR if the pipe is really 2" (based on vlv size). Smaller than 2" is more difficult to install (in general). Placing a GWR in a 'stilling well' is similar practice for tanks with levels that get disturbed (falling liquid, etc...).

Be careful that it is not a true activation: Maybe you are getting a true HH Level. It's often the case the Operation manager or someone higher up is tired of the plant shutting down, and looks for other causes instead of what is truly happening. Then they want to bypass the interlock/safety event and continue running, thinking it's not a true event. I've seen this while working in the Middle East and South America, and 20 years ago in N. America (not so much anymore, but I haven't been in the field much in N. America lately)

If it is a true reading, consider adding a timer to the event, so it has to be HH Level for x seconds before actually tripping. This may help avoid any foaming issues. But again, be careful that the selected time will not interfere with a true safety concern/event.

Also: A word of caution: be careful posting whole P&IDs on any website. Consider cutting and pasting only the desired section of topic. You don't want your company of competitor to know this is out there.

______________________________________________________________________________
This is normally the space where people post something insightful.

 

[Ahmed Abdelaziz]

Dear Mr George thank you very much
Dear Mr controlnovice thank you very much for your advice but let me confirm it's impossible to be an actual signal because we keep monitoring level accumulated there

 

[georgeverghese]

The continous process drains from S5132A/B is manually evacuated. So in the bottoms compartment, does the LIA-H, which is also GWR, also show high level at the same time as the LZAHH ?

It would be better if your Company were to enable automate level draining from these vessels rather than relying on Operations.

Must say the process drains configuration in this PID is not safe - I've never seen plants where the continous process drains and the maintenance drains are all routed to the HP flare header. All process drains are usually routed to a closed drain drum via dedicated collection headers; one header for continous drains and another for maintenance drains. If the continous process drains are known to be clean and non fouling, under exceptional circumstances, it may be okay to have these routed to the HP flare drum through a dedicated continous process drains collection header. Some one in Shell UMP or BapetCo should check the previous concept phase HAZOP sheets. Suspect the problem of frequent LZHH on these vessels is somehow related to the constraints currently being experienced by Operations with this awkward drains - HP flare combination. We see that there are no continous process drain lines on S5132A/B bottoms compartment - all are blinded maintenance drains.

 

[Ahmed Abdelaziz]

thank you sir but I don't see a point behind whether it's maintenance drain or operations drain, I do assures that no liquid at all accumulates there, neither the level transmitter nor the HH level transmitter reads any liquid not even the level gauge, nothing at all reads level accumulated

 

[georgeverghese]

So this is a completely false alarm from the HH GWR level transmitter ?? Maybe a field instrumentation engineer reading this can help..

 

[LittleInch]

I think this item is very much an instrument issue ( incorrect set up) or how the instrument itself is located. Some GWR designs are affected by local metal and especially when there is no liquid level to actually measure can become confused by any other contaminant.

See if there is any difference in the two GWR probes and contact the vendor to discuss further.

A photo of the two different probes and the actual piping set up might show where there is a potential issue to investigate.

Is there any liquid in those vessels for the LT to measure? It could just be that they don't like only being in air for long periods.

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