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Hoop stress in Autopipe Analysis
2

Hoop stress in Autopipe Analysis

Hoop stress in Autopipe Analysis

(OP)
Dear All,
While was doing analysis for 8" high pressure and high temperature pipeline in Autopipe. After running report it shows that the code stress doesn't satisy for hoopstress in the launcher area. Pls help me to over come this and to make the system satisfies the code stress as per ASME.

Please tell me how can i reduce this hoop stress.

RE: Hoop stress in Autopipe Analysis

Well you haven't given any information about pressure, temperature, which part of the code you are referencing, so the only thing I can say is if you want to reduce the hoop stress then increase the wall thickness of the pipe.

RE: Hoop stress in Autopipe Analysis

(OP)
Thanx Desertfox,
The parameters are as follows.
P=250 bar
t=115 deg c
size 8".

Is there any other alternative other than this to increase wall thickness, please suggest

RE: Hoop stress in Autopipe Analysis

Select a better material with a higher allowable stress.

Independent events are seldomly independent.

RE: Hoop stress in Autopipe Analysis

Hi jonjose

You could increase wall thickness or decrease pipe diameter, failing that you could reduce the internal pressure but I guess that not an option.

RE: Hoop stress in Autopipe Analysis

Your problem might be that thre is a Code conflict. I'm assuming that the Autopipe analysis is to B31.3 for the plant area pipework. The launcher area will commonly be to a Pipeline Code such as B31.4, B31.8 or PD 8010. All of these allow a thinner wall than B31.3 would, for the same material and process conditions. Thus the non-B31.3 pipe may get flagged as over-stressed in a B31.3 analysis.

RE: Hoop stress in Autopipe Analysis

If what you are saying is right then the pipe is not thick enough. However I beleive for B31.3 analysis Autopipe will be using the "bog standard" hoop stress equation to calculate the hoop stress and compare with the basic allowable material stress from it's data bank.Whereas at 250 bar the equation falls in the high pressure piping section of the Code which uses another equation for determining the pipe thickness (which is probably where the original thickness was selected from)and if I remember correctly a higher allowable stress.If you do a check to the high pressure piping section then the pipe will be acceptable. Just one of the foibals of Autopipe and also Caesar when you have high pressure.

RE: Hoop stress in Autopipe Analysis

250 bar does not really come into the 'high pressure' regime in B31.3, it's only roughly 1500# flange rating whereas B31.3 defines high pressure in Chapter IX as exceeding 2500# rating.

Check again which Code applies in your launcher area. See my post above.

RE: Hoop stress in Autopipe Analysis

C2it,
Well spotted- you are correct 250 bar is not really high pressure -senior moment on my side. However it is still probably due to the software calculating the hoop stress in accordance with B31.3 rather than the applicable Code formulae.

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