high pressure piping and Bourdon effect 2

[papiesz]

Hi all

I have to analyse feedwater pumps piping according to B31.1. Design pressure of discharge pipe is 23.4 MPa. Calcs during FEED was made by another company using Caesar II. They calculated standard operating cases W+P1+T1 but Bourdon option was set to "none" which results in no displacements due to pressure. While recalculating system in Autopipe I skiped pressure analysis to have the same as Bourdon effect = "none" in Caesar.

But I have doubts. B31.1 code is silent on including pressure elongation in analysis. Reason tells me to include bourdon effect, also my B31.3 experience incline me in that direction. But FEED calcs was made by big, international, German originated company with "thousands" years of experience in power. Maybe they are right.

The main problem is with pump nozzle load. When Bourdon is triggered on it is impossible to keep loads within allowable without significant routing change. I wonder what client will say as in this particular system only valve and strainer weight/length was changed since FEED.

Could someone give me a little piece of advice?

Regards

papiesz

 

[papiesz]

BigInch

Thats true what you saying about stress. But I mean strains
From mechanics of materials we have the following:

?H=pD/2t

?L=pD/4t

From Hooke's law:

?H=1/E(?H-??L)

?L=1/E(?L-??H)

let's assume that hoop stress is 2 (Mpa, ksi whatever you want)
axial must be equal 1

after substituting this into Hooke equation we get:

?H=1/E(2-0.3*1)=1.7/E

?L=1/E(1-0.3*2)=0.4/E

so we have elongation in both directions although as you said hoop stress reduces axial strains.

Thank you BigInch and others for discussion.

I think I will skip this Bourdon effect or pressure elongation.

regards

papiesz