6 replies to this topic

[inkar]

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

[breizh]

Hi,

no drawing uploaded !

split range?

 

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

 

my 2 cents

 

Breizh

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

[inkar]

hi breizh, please see attachment

Attached Files

•  1234.png   212.42KB   2 downloads

[Bobby Strain]

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

[breizh]

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.

[fallah]

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...

[SyedAhmed]

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.