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Pressure Control Loop For Scrubber Vessel

control loop pressure control

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#1 onakarnath112@gmail.com

onakarnath112@gmail.com

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Posted 15 January 2019 - 10:39 PM

hello..I am trying to understand a control loop for pressure on a vessel. I see that there is a PIT for pressure measurement on gas outlet of a scrubber. Now the PIT feeds the pressure to a PIC and then then the PIC control two control valves – one going to process and one to flare. My question is how does this loop work? Is there a single set point on the controller for high pressure? When it reach that pressure control valve on flare should open? Or does it have two set point – one where it has to maintain the pressure and one at which it opens the flare control valve? Please see drawing for representation



#2 breizh

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Posted 15 January 2019 - 10:45 PM

Hi,

no drawing uploaded !

split range?

 

https://instrumentat...-range-control/

 

my 2 cents

 

Breizh


Edited by breizh, 16 January 2019 - 02:17 AM.


#3 onakarnath112@gmail.com

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Posted 15 January 2019 - 10:48 PM

hi breizh, please see attachment

Attached Files

  • Attached File  1234.png   212.42KB   2 downloads


#4 Bobby Strain

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Posted 15 January 2019 - 11:42 PM

There are several ways to implement control, not just one. So the designer must specify how to implement the control. As a student, you should not be too concerned by the actual implementation. Until later.

 

Bobby



#5 breizh

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Posted 16 January 2019 - 12:33 AM

hi,

Bobby is right !  You need to assess the flows and understand the reasons behind the direction to the flare or to the process.

Review my previous answer together with the attached document.

Enjoy the exercise .

Breizh


Edited by breizh, 18 January 2019 - 12:20 AM.


#6 fallah

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Posted 16 January 2019 - 12:37 AM

onakarnath112@gmail.com:


 

Hi,

 

It's appear to be two, say two 50%, split range control, means it have two set points: lower one where it has to maintain the operating pressure hence CV opens to process and higher one at which another CV opens to the flare...



#7 SyedAhmed

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Posted 18 January 2019 - 12:07 AM

You need to update/create the logic in the PLC/DCS. This control can only possible with electronic setup but not possible with pneumatic with single PIC.


Edited by 12345656, 18 January 2019 - 12:23 AM.





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