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#17149 - 04/08/08 09:10 AM Allowable stress for hydro load case
shan Offline
Member

Registered: 01/14/08
Posts: 28
Loc: sharjah
In CII, I am doing a job for HP steam line. I found that the allowable for SUS load case is 1Sh
and for EXP is Sa (ie) Sa=f(1.25Sc+0.25Sh)
and for OCC is 1.33Sh.
all these are as per code that the software follows. But for HYD load case, it has taken the yield strength (Sy) as allowable. Is it correct?

I guess usually we consider 0.9Sy. am i right?

In this case, can i change the allowable in CII?

kindly explain in deatil.
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shan

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#17151 - 04/08/08 09:15 AM Re: Allowable stress for hydro load case [Re: shan]
Richard Ay Offline
Member

Registered: 12/13/99
Posts: 6226
Loc: Houston, Texas, USA
That depends on what Code you're working to. If this is B31.3, check out Paragraphs 345.2.1.a and 345.4.2.c.

If you want to adjust the allowable for the Hydrotest case, just change the Sy value on the Allowable Stress dialog.
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Richard Ay - Consultant

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#18120 - 05/20/08 04:32 AM Re: Allowable stress for hydro load case [Re: Richard Ay]
ssmith Offline
Member

Registered: 06/07/07
Posts: 11
Loc: sh
Hi,Richard,

in b31.3 Hydrotest case,why use longitudinal stress,not nominal pressure stress in cii?

Is there any reason?

Thanks

ssmith


Edited by ssmith (05/20/08 04:33 AM)

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#18130 - 05/20/08 10:17 AM Re: Allowable stress for hydro load case [Re: ssmith]
anindya stress Offline
Member

Registered: 04/12/04
Posts: 493
Loc: London, UK
Internal Pressure results in longitudinal PD/4T, hoop PD/2T and the radial traction -P on inside and 0 on outside.Try to find out the answer from here.

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anindya

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#18134 - 05/20/08 01:18 PM Re: Allowable stress for hydro load case [Re: anindya stress]
CraigB Offline
Member

Registered: 05/16/06
Posts: 378
Loc: Denver, CO
Agree, anindya. Just another question that demonstrates how little effort some people think is needed to get by in this career.
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CraigB

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#18144 - 05/20/08 11:55 PM Re: Allowable stress for hydro load case [Re: CraigB]
ssmith Offline
Member

Registered: 06/07/07
Posts: 11
Loc: sh
thanks.i forget hoop stress is not code stress.i am confused.


Edited by ssmith (05/21/08 12:31 AM)

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#18145 - 05/21/08 12:45 AM Re: Allowable stress for hydro load case [Re: ssmith]
anindya stress Offline
Member

Registered: 04/12/04
Posts: 493
Loc: London, UK
Smith,

Pl. read and understand the code.The piping codes are not books on theory of relativity which are difficult to comprehend.There are ample supporting documents also like the book by Charles Becht, George Antaki and also Compansion guide to ASME Boiler and PV codes Edited by K.R.Rao. There are WRC Bulletins also like WRC 329 for example. If after reading all these you have confusions and questions, ask them.

I totally agree with Craig. Few days back somebody wanted to know baout piping spans.I agree that the person is new to this field, but from basic strength of materials he/she should be having some idea on the the first approach to estimate piping span, however the person did not feel like doing that much homeowork and decided to put the question in the forum.

Regards
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anindya

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