F1 - External loads

Hello fellows...

I´ve been instructed to include Load F1 (external force POP of Force) in both, the SUS and HYD cases. Why to do that if the relief valve won´t be open in those cases. Or am I wrong??

L3 WW+HP+H+F1 HYD Hydrotest case
L15 W+P1+H+F1 SUS Sustained case

Thanks

The 'pop' force of a psv is a primary load since it is not self limiting, albeit a very short duration. It should therefore be considered in a sustained case. You could consider an increased allowable stress since it is an occasional load. The psv should not even be fitted (may be blinded off or removed) during a hydrotest. If it were, you would obviously never reach your required pressure. Don't included 'pop' loads in a HYD case.

I agree with moverz.. and for sustain, you must verify it if comply to the requirements of the code and line service for occasional or you will end up over designing(for conservative approach, I consider this one sustain when data are not enough).

My opinion...

Regards!

hello friends,

My name is bhavin.

I want to tell you my view on this topic.
PSV load is occasional load.

So first it is added in operating load case.
then sustain case should be minus from operating case.so you will get effect of PSV oad.

than it is added in suatain case.
for more datail read techanical reference manual.
ok

hope it is clear.

Hello guys,



I am confuse about the direction of PSV load.


Is it acting in opposite to the direction of flow in psv as well as upward dirction?

Plz help me .

any notes regarding this topic?

Work with your senior..

Regards!

Thanks for the clarification about the pop force as a primary load. I was considering the increase for the allowable as well.

Regards,

IMHO designating it as an occasional load is entirely appropriate. Even with the 1.33 Sh allowed by B31.3 your still likely to be below SMYS at temperature because the Sh value at temperature is based upon 2/3 SMYS at temp for systems below the creep range. (ref B31.3 2006 Para 302.3.2 (4))

But in doing so one should also use a DLF that is apropriate do a search on DLF or Dynamic Load Factor (Also read B31.1 Non Mandatory section on relief piping and also articles on this web site as well)

I always used to consider a DLF=2 for static analysis.

Regards,

From what I see, my sustained evaluation would come from W+P1+H and my occasional evaluation would be the scalar summation of stresses from F1 alone plus the stresses from W+P1+H. That's for a linear system. Nonlinear support response would have me run more cases to tease out the F1 response (F1 response = operating+F1 - operating).