6 replies to this topic

[shivaprasad]

Hi,

I have one question.

If the rupture disk is inlet to PSV. Required flow rate will be same for both or different? and the following sentence is correct?

"flowrate for ruture disk(PRD) will be calculated by dividing PSV required flow rate with 0.9, because ruture disk located in the PSV inlet line".

Please helpme out

shiva

[fallah]

shivaprasad,

The sentence about the capacity of PRD/PSV combination isn't correct, and the 0.9 is called CCF (Combination Capacity Factor, ratio of combination capacity to the PSV capacity alone) which may be higher than 0.9 if specific testing has been done with a particular combination of PRD/PSV. Hence, PRD capacity in combination with PSV would be calculated by multiplying the PSV capacity by the CCF.

Fallah

Edited by fallah, 09 February 2012 - 12:12 AM.

[shivaprasad]

Fallah,

Thank you for your support,

As per API 520 Part1 (8th edition, page no. 77, Sub heading ; 5.11.2 Rupture Disk Devices Used in Combination with PRVs), "The capacity of a rupture disk device in combination with a PRV, where the rupture disk device is located at the valve inlet may be determined by multiplying the ASME stamped valve capacity by the combination capacity factor, Kc."

As per the above reference, " rupture disk capacity will be = rated capacity of PSV multiply with Kc(0.9).
But in above sentence(yesterday post) ""flowrate for ruture disk(PRD) will be calculated by dividing PSV required flow rate with 0.9, because ruture disk located in the PSV inlet line".

Both sentence are same.

Now iam doing calculation for PSV/PRD sizing.
In my case PRD is installed upstream of PSV.
PSV Calculated flowrate is 9461 kg/hr( for fire case). Rated flow rate is 10619 kg/hr (by considering kc =0.9 for psv and PRD combination factor) and 11799 kg/hr ( by considering Kc = 1.0, no PRD installed upstream of PSV ).

What could be the required flow rate for Rupture disk?

Will it be = 9461 kg/hr (same flowrate) or
= 9557.1kg/hr (10619*0.9) or
= 10512 kg/hr (9461/0.9)?

Please help me out

shiva

Edited by shivaprasad, 08 February 2012 - 07:33 PM.

[fallah]

shiva,

As far as i did understand there are below information about the PSV alone:

PSV required (calculated) capacity=9461 kg/hr
PSV rated (ASME stamped) capacity=11799 kg/hr

PRD required capacity used in combination with PSV=9641 kg/hr (same as PSV alone), because required capacity is a process requirement
PRD rated capacity used in combination with PSV=11799*0.9=10619 kg/hr

It should be noted that, at all conditions the rated capacity of PRD in combination with PSV shouldn't be lower than its required capacity.

Fallah

[shivaprasad]

Fallah,

Thank you very much for your answer.

Shiva

[sheiko]

shiva,

See the attached article for your information.

Attached Files

•  AnatomyOfKdKrCEpublication.pdf   171.35KB   37 downloads

[shivaprasad]

Thanks sheiko