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Vessel Vacuum Due To Pressure Control Failure


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#1 Butterfly

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Posted 12 August 2018 - 02:22 PM

Dear all

 

I have a distillation column, operating at low pressure (less than 1 barg). I have light hydrocarbons on top, and the scheme is: total condenser, with hot bypass pressure control. Main PCV is upstream the condenser, and the hot bypass line includes a differential pressure control valve.

 

If column pressure drops, the main control valve should close. My question is: can a failure in the pressure control loop lead to a vacuum contition in the column? The same way that if the pressure increases and valves does not open when required, I could have an overpressure.

 

Thanks for your help



#2 Technical Bard

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Posted 12 August 2018 - 10:47 PM

Why would you put the main PCV upstream of the condenser?  That is an odd configuration.   Usually pressure control of the column is on the accumulator vessel.  For a total condenser, the pressure is controlled by the vapour pressure at the condensing temperature.



#3 breizh

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Posted 13 August 2018 - 02:04 AM

Hello,

2 documents about controls on distillation columns .

Hope this is going to help you.

Breizh

Attached Files



#4 Butterfly

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Posted 13 August 2018 - 03:24 AM

Thanks. My scheme is similar to Figure 9 in the first attachment (in the scheme the PCV is upstream the condenser), with additional DP control in the vapor equilibrium line..



#5 breizh

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Posted 13 August 2018 - 05:54 AM

Hi Butterfly ,

You should check the design pressure of the tower and the failure modes for PCVs .

You may want to review your existing HAZOP .

Good luck

 

Breizh


Edited by breizh, 13 August 2018 - 08:26 AM.


#6 Butterfly

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Posted 20 August 2018 - 03:04 AM

Thanks for the advice!






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