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Emergency Shutdown Action On A Control Loop


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#1 SawsanAli311

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Posted 01 January 2019 - 01:46 AM

Hi, 

 

I would like to get your feedback regarding whether the code allows to have a link between an ESD trip singal acting on its final SIF elements (SDV) in addition to sending a signal to another DCS pressure control loop to change the controller output to higher opening of a PCV for example. The reason for such a proposal is to help in mitigating pressure build up at the suction of a tripped compressor. 

 

Since control DCS elements are not SIF and hence cannot be SIL assessed, I am doubting whether it is acceptable to take credit for the above described linking action between ESD and DCS.

 

Appreciate your feedback and views based on your experience. 

 

Regards, 



#2 Bobby Strain

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Posted 01 January 2019 - 10:28 AM

Sounds like you are doing something wrong if you need to complete this action.



#3 SawsanAli311

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Posted 01 January 2019 - 12:00 PM

Hi Mr.Bobby, 

 

Actually I have seen this proposal in one of the field modifications proposed for a gas compression plant, In one of the design review workshops , I clearly highlighted that there shall be no signal inter-link between an ESD function and a DCS control loop.. Yet, Contractor stated that this is acceptable, I am highly doubting this I am seeking more views on the subject with specific quotes from the code if anyone has..

 

Thanks 



#4 fallah

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Posted 01 January 2019 - 12:32 PM

 

Actually I have seen this proposal in one of the field modifications proposed for a gas compression plant, In one of the design review workshops , I clearly highlighted that there shall be no signal inter-link between an ESD function and a DCS control loop.. Yet, Contractor stated that this is acceptable, I am highly doubting this I am seeking more views on the subject with specific quotes from the code if anyone has..

 

 

Hi,

 

I don't think such a matter being dictated by a specific code and i think it might mostly be mandated by engineering practices rather than the code...

 

I have seen control valves, say FV, received DCS signal for normal function also equipped with a solenoid valve being activated by an ESD signal in an emergency case and override the flow signal from the DCS to be situated at the relevant fail safe position...



#5 Technical Bard

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Posted 01 January 2019 - 07:55 PM

Most owner companies I have dealt with would NOT allow this.  They would require separate sensing devices for the SIF and DCS actions.  






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