11 replies to this topic

[Nightwish]

Hi everyone,

According to API 520II Section 4.4.2.2, the inlet piping shall be at least equal to PSV nozzle size. But the code, does not mention about the vessel nozzle size. Is there any code clearly stating that " the vessel protected by a PSV, should have a nozzle size equal or bigger than PSV inlet nozzle size" ?

Normally, when designing new equipments, the general rule of keeping nozzle size equal to or bigger than the line size is applied. But, when doing revamp, in case of capacity increase, how should anyone proceed?

[shan]

Hi everyone,

According to API 520II Section 4.4.2.2, the inlet piping shall be at least equal to PSV nozzle size. But the code, does not mention about the vessel nozzle size. Is there any code clearly stating that " the vessel protected by a PSV, should have a nozzle size equal or bigger than PSV inlet nozzle size" ?

Normally, when designing new equipments, the general rule of keeping nozzle size equal to or bigger than the line size is applied. But, when doing revamp, in case of capacity increase, how should anyone proceed?

1. There is no Section 4.4.2.2 in my API 520 II.
2. The nominal size of the inlet piping must be the same as or larger than the nominal size of the pressurerelief valve inlet connection not PSV nozzle (Orifice) size.

[sheiko]

But, when doing revamp, in case of capacity increase, how should anyone proceed?

If no code dictate the vessel nozzle size to be larger than the PSV inlet line, then increase your line size as required. I believe you just have to not forget including the exit loss (from vessel to line) in your calcs.

Maybe you can check with your piping specialists if they foresee any objection to that decision.

Edited by sheiko, 20 July 2011 - 08:52 PM.

[Nightwish]

Hi everyone,

According to API 520II Section 4.4.2.2, the inlet piping shall be at least equal to PSV nozzle size. But the code, does not mention about the vessel nozzle size. Is there any code clearly stating that " the vessel protected by a PSV, should have a nozzle size equal or bigger than PSV inlet nozzle size" ?

Normally, when designing new equipments, the general rule of keeping nozzle size equal to or bigger than the line size is applied. But, when doing revamp, in case of capacity increase, how should anyone proceed?

1. There is no Section 4.4.2.2 in my API 520 II.
2. The nominal size of the inlet piping must be the same as or larger than the nominal size of the pressurerelief valve inlet connection not PSV nozzle (Orifice) size.

1. 4.2.2 Section
2. Exactly, the the connection to the PSV.

Thank you Shan..

[Nightwish]

But, when doing revamp, in case of capacity increase, how should anyone proceed?

If no code dictate the vessel nozzle size to be larger than the PSV inlet line, then increase your line size as required. I believe you just have to not forget including the exit loss (from vessel to line) in your calcs.

Maybe you can check with your piping specialists if they foresee any objection to that decision.

Sheiko, thats another story.. assuming K=0.5 for 3" nozzle (pipe sharp edged entrance) I am already out of 3% pressure drop limit at PSV inlet line. The required piping at PSV inlet is 6" and the Vessel nozzle should be increased to 6". I am not sure if the Client would agree with this solution for Vessel operating at 160 barg. Actually, there is 8" nozzle for blank off. Is it reasonable to use that nozzle for PSV and already occupied 3" nozzle for blank off?

thank you

[Lowflo]

The vessel nozzle is generally regarded as part of the "inlet piping". API 520 Pt2 clearly regards it as that too. Refer to the notation in Fig 1 & 2.

[fallah]

The required piping at PSV inlet is 6" and the Vessel nozzle should be increased to 6". I am not sure if the Client would agree with this solution for Vessel operating at 160 barg. Actually, there is 8" nozzle for blank off. Is it reasonable to use that nozzle for PSV and already occupied 3" nozzle for blank off?

thank you

Nightwish,

If 3" nozzle would make no problem for blank off you can use 8" nozzle for PSV inlet line in revamp, other wise to meet the API requirement,you should consider a new 6" nozlle on the vessel along with all relevant mechanical tests/inspections....(PWHT,new hydrotest,....).

Fallah

[Nightwish]

thank you guys,
we solved the problem by using the blank off nozzle (8") for PSV and adding Tee for blank off operation.

[sukubutsu]

Hi,

I've got one quick question. The problem was solved by using 8" nozzle on the vessel that was previously blanked off, and your PSV inlet connection was 6". That means you will require a reducer between the vessel and the PSV inlet connection right? And you were able to keep the pressure loss within 3% with the reducer?

Thanks

Edited by sukubutsu, 14 September 2011 - 01:09 AM.

[Nightwish]

exactly

[mav9rick]

It might be to late or you may have already considered this but, is there a mesh pad in the vessel? Is the new 8" nozzle located upstream of the mesh pad or downstream?

[Nightwish]

It might be to late or you may have already considered this but, is there a mesh pad in the vessel? Is the new 8" nozzle located upstream of the mesh pad or downstream?

Ma9rick, we do not have a mesh pad.