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AvatarIndo
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Indonesia - Member - New Member

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ASME B31.8 Wall Thickness Calculation

10/03/2014 5:50 AM

Dear pipeline engineer

Regarding our new project, we will execute gas pipeline project in Indonesia.

We already perform wall thickness calc. as para para 841.1.1 ASME B31.8. Unfortunately, some people say that we have to consider both of pressure design and hydrotest pressure (1,25xDP). Even though from ASME B31.8 there were not mention about hydrotest pressure to define wall thickness. Is our understanding correct(without consider hydrotest pressure to calculate wall thickness)?

As hoop stress calculation criteria, we found that hoop stress generated by pressure design is 37%SMYS, and 47% of SMYS generated by hidrotest pressure. Is our design safety?

Thank you
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Tornado
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#1

Re: ASME B31.8 Wall thickness calculation

10/03/2014 6:52 AM

You are correct; you do NOT need to use the hydrostatic pressure to calculate the pipe thickness.

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Crabtree
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#2

Re: ASME B31.8 Wall thickness calculation

10/03/2014 7:19 AM

You could also use published tables and your client's piping standards to get there as well.

I wonder why you are not using your client's procedures and instead coming to a rag-bag of anonymous reprobates on the internet?

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lyn
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#3
In reply to #2

Re: ASME B31.8 Wall thickness calculation

10/03/2014 2:08 PM

Desperation breeds panic.

Any answer will be grasped by a man drowning from a lack of knowledge.
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Crabtree
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#4
In reply to #3

Re: ASME B31.8 Wall thickness calculation

10/03/2014 5:33 PM

True, true.

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TonyS
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#5
In reply to #2

Re: ASME B31.8 Wall thickness calculation

10/04/2014 8:13 AM

"a rag-bag of anonymous reprobates"

That's not very nice!

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AvatarIndo
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#6

Re: ASME B31.8 Wall Thickness Calculation

10/06/2014 3:43 AM

After exploring more detail, there some example at appendix F. My understanding is no need to consider hidrotest pressure at wall thickness calculation.
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Whitephone
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#7

Re: ASME B31.8 Wall Thickness Calculation

10/06/2014 12:46 PM

"no mention"?
API B31.8 2010 Parr. 805.2.3
S=PD/2t
S= Hoop StressP= PressureD= Diametert = Thickness
After This go to Appendix N (Same Code)
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AvatarIndo
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#8

Re: ASME B31.8 Wall Thickness Calculation

10/07/2014 10:39 PM

"no mention', i mean that for wall thickness calculation, there only consider pressure design. Hidrotest pressure shall be consider as appendix N, especially to keep hoop stress (mention by whitephone) generate by hidrotest under 100% SMYS.
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