PSV Inlet Piping design 4

[satya1]

Hello All,

PSV is designed to protect vessels and the PSV size determined 6"x8". The location of the PSV is 5' from Vessel top nozzle. So in order to meet the PSV inlet line 3% pressure drop criteria, selected 12" inlet line can able to meet the 3% pressure drop criteria , until to add the reducer 12"x6" (upstream of PSV).. if i added the reduced than the 12" inlet line pressure drop is higher than the 3% and FYI, i checked with other sizes also like 14" & 16" still cant able to meet the 3% pressure drop criteria..
So could you please check my below questions and clarify,

1. do i need to consider that 12"x6" reducer (upstream of PSV) in the hydraulic calculation ?
2. Do I need to select the inlet pipe diameter, the one that meets with 3% pressure drop ? even if it is a very large size pipe diameter ?

any help would be much appreciated !!

Thanks !

satya

 

[Latexman]

Are you familiar with our FAQs area? Read this one - faq1203-1960. It is pertinent, and it does suggest a potential remedy if you do not find a solution.

1. How are you characterizing the pressure drop of the reducer? Remember, only irreversible pressure loss is in this calculation. That's just frictional losses.
2. Maybe, but you don't want to go overboard/impractical. Question # 1 needs to be fully answered before # 2 can be started.

Good Luck,
Latexman
Pats' Pub's Proprietor

 

[georgeverghese]

Can you find another larger nozzle size PSV for this same orifice size? Say a 8x10inch PSV with the same orifice? Else break this up into 2 PSV's, and stagger them if you should. Also check the details on your reducer losses - the later versions of Crane TP410 has a more detailed method which accounts for the length of the reducer also, if I remember correctly.

 

[Latexman]

George,

I think you are referring to their more detailed method with tees and wyes, or I'm missing something.

Good Luck,
Latexman
Pats' Pub's Proprietor

 

[georgeverghese]

Its been some time since I saw versions of TP410 later than the old one I've got here - but I do remember there is some correction / compensation for the length of the reducer.

 

[The Obturator]

A solution would be to use a Pilot Operated Pressure Relief Valve. Rather than the inlet of the main valve, you would route the sensing line directly to the vessel. This is one of the advantages of using a POPRV.


Per ISO-4126, only the term Safety Valve is used regardless of application or design.

 

[razookm]

I agree with @Latexman on point no 1. Only actual friction loss needs to be considered. Please note that at the reducer, velocity will increase and some portion of the pressure head will be converted to velocity head. I have seen many software report actual pressure without including the velocity head. This reduction in pressure should not be confused with friction drop or irreversible pressure loss

 

[satya1]

Thank you All for the inputs.

Sathiya