5 replies to this topic

[CSNK]

Dear all,

 

How any PV (Pressure control valve - PIC  kind of On/Off valve) is sized for relief scenario.

For example i have a vessel, which during pressurization will relief into flare header.

It will relief from PV (On / Off valve) into flare.

 

Of course ultimate safeguarding of PSV is provided but that is set at higher pressure as compared to the PV.

Would like to know the basis of sizing the PV.

 

Thanks in advance.

Edited by chiks, 22 July 2016 - 12:23 AM.

[fallah]

chiks,

 

Even though mentioned PV is normally closed but it's a control valve not on/off valve...

 

Indeed, as far as i know this PV is normally sized based on around 60% of maximum ouggoing flow through the main overhead line...

[CSNK]

Thanks fallah for quick response,

 

Let us say this is sized for 60% flow then how is it sized, i mean at what downstream condition (i.e pressure).

Will it be sized for superimposed back pressure (normally atmospheric pressure) or built-up back pressure due to relief?

Can u please brief.

[fallah]

chiks,

 

It will be sized based on superimposed back pressure plus built-up back pressure due to fluid relieving...

[CSNK]

Thanks, just one more question.

 

In case if the PV is replaced with On/Off kind of valve i mean kind of XV(either fully open or fully close).

In such case also, it needs to be sized based on built up back pressure + superimposed back pressure?

Edited by chiks, 22 July 2016 - 12:57 AM.

[fallah]

chiks,

 

Yes, it should be sized based on total back pressure (superimposed+built-up)...