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#34909 - 05/12/10 05:16 AM Include pressure stress Indices per Div2 in Code calc
RSVTVL Offline
Member

Registered: 07/17/09
Posts: 25
Loc: HARYANA INDIA
Dear all
When we tick to include the pressure stress Indices of ASME Sec VIII Div2 i(Appendix 5 D), the software increases the values of Pm , Pl+Pb , Pl+Pb+Q by applying the stress Indices

As per my understanding this is not correct. The first line in Appendix : 5D makes it clear that the stress indices may be used to determine peak stresses. Peak stresses are to be checked for fatigue.

I would be glad to have expert comments please

Regards

_________________________
R.SRINIVASAN
Senior VICE PRESIDENT,
Head DESIGN and Engineering
ISGEC
YAMUNANAGAR
HARYANA INDIA

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#34914 - 05/12/10 09:22 AM Re: Include pressure stress Indices per Div2 in Code calc [Re: RSVTVL]
Ray_Delaforce Offline
Member

Registered: 01/02/03
Posts: 743
Loc: Houston, TX
Hello RSVTVL

I am puzzled why you say we are not correct. The user (not us) decides if he wants the pressure indices to be include in his calculation or not. The stress indices are really the stress concentration factors at 8 points around the nozzle in the shell. ASME Division 2 Section 5 treats these the pressure indices as peak stress. Even if you do not elect to include the pressure indices, you will still get the Pm, Pl, Pb and Q stresses. Those stress are still there.

The user makes the decision.
_________________________
Sincerely,
Ray Delaforce
CADWorx & Analysis Solutions
Hexagon PPM

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#35409 - 05/15/10 11:40 PM Re: Include pressure stress Indices per Div2 in Code calc [Re: Ray_Delaforce]
vishaltailor Offline
Member

Registered: 05/15/10
Posts: 56
Loc: Gujarat, india
Dear Mr. Ray

I am not clear from your reply. The Stress indices are only used to calcualte the peak stresses at nozzle junction, then How Pm, Pl, Pb ,Q is getting incresed?

And,let us consider, User want to add Stress indices in WRC calculation, then how he can limit Pm & Pl upto sm * 1.5 Sm. Is he need to increase Local Thickness of shell/ dish-d'end ?


Regards
vishal

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#35427 - 05/17/10 06:54 AM Re: Include pressure stress Indices per Div2 in Code calc [Re: vishaltailor]
RSVTVL Offline
Member

Registered: 07/17/09
Posts: 25
Loc: HARYANA INDIA
Dear Mr.Ray
I agree with you that the user (not software) decides if he wants the pressure indices to be include in his calculation or not. Also I agree with you that the stress indices are really the stress concentration factors at 8 points around the nozzle in the shell.
The difference is once you apply stress indices the resulting values are peak values but not Pm,Pl, PB or Q. It should be F. The PV Elite output should show the net value at the surface with stress indices as Pl+Pb+Q+F which means the total stress including the stress concentration and to be checked only for fatigue.
But the software is checking for (a)primary membrane (Pm), (b) primary membrane plus bending PL + Pb and (c) primary plus secondary stress intensities (PL+Pb+Q) and limiting to Sm, 1.5 Sm and 3 Sm respectively which is not correct.
These limits are not meant for fatigue failure mode and stress concentration is to be considered only for fatigue failure mode but not for membrane stress intensity etc

I hope I have clarified my views. Kindly let me know if there is any other view

Thanking You and With regards





_________________________
R.SRINIVASAN
Senior VICE PRESIDENT,
Head DESIGN and Engineering
ISGEC
YAMUNANAGAR
HARYANA INDIA

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#35431 - 05/17/10 07:05 AM Re: Include pressure stress Indices per Div2 in Code calc [Re: RSVTVL]
Ray_Delaforce Offline
Member

Registered: 01/02/03
Posts: 743
Loc: Houston, TX
Hello guys

If you are worried about fatigue, you can do a fatigue calculation for a nozzle in PV Elite as a separate issue. You can check the fatigue check box on the nozzle dialogue screen. The pressure indices are then taken into account and the number of permissible cycle can be computed. The stresses are treated as peak stresses.
_________________________
Sincerely,
Ray Delaforce
CADWorx & Analysis Solutions
Hexagon PPM

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#35556 - 05/21/10 07:09 AM Re: Include pressure stress Indices per Div2 in Code calc [Re: Ray_Delaforce]
RSVTVL Offline
Member

Registered: 07/17/09
Posts: 25
Loc: HARYANA INDIA
Dear Mr.Ray Delaforce

I think I have not made my stand clear. I 100% agree with you that for fatigue evaluation, stress indices shall be used.

I would like to add that stress indices shall be used only for fatigue analysis but not for anything else.

In otherwords, the stress indices shall not be used for checking stress limits of Pm, PL+Pb and PL+Pb+Q.

By definition and by purpose the three stress intensities Pm, PL+Pb and PL+Pb+Q shall not include any stress concentration effect

Thanking You and With regards

_________________________
R.SRINIVASAN
Senior VICE PRESIDENT,
Head DESIGN and Engineering
ISGEC
YAMUNANAGAR
HARYANA INDIA

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#35563 - 05/21/10 07:52 AM Re: Include pressure stress Indices per Div2 in Code calc [Re: RSVTVL]
Mandeep Singh Offline

Member

Registered: 12/15/99
Posts: 600
Loc: Houston, Tx, USA
Dear Mr. Srinivasan,

I agree with you that after applying the pressure stress indices you get the peak stress used for fatigue. That stress should be used in fatigue evaluation and not really compared to the code allowables.

I will add an item to our request list for this change.
_________________________
Best Regards,
Mandeep Singh
CADWorx & Analysis Solutions
Hexagon PPM

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#35577 - 05/22/10 03:52 AM Re: Include pressure stress Indices per Div2 in Code calc [Re: Mandeep Singh]
Kunal_Shah Offline
Member

Registered: 05/09/10
Posts: 4
Loc: Hazira-Surat, India
I agree that the inclusion of stress indices shall be used in computation of peak stresses only. however, PVElite also includes the effect of stress indices in the calculation of Pm and Pm+Pl. The final value indicated by PVElite shall be Pm+Pl+Q+F when stress indices are included, which can be used for fatigue evaluation. If the equipment is not in a cyclic service, it is not required to consider the stress indices.
_________________________
Asst. Manager-Product Engineering,
Larsen & Toubro limited,
Hazira Manufacturing Complex,
Hazira-Surat, India-394 510

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#35607 - 05/25/10 12:33 AM Re: Include pressure stress Indices per Div2 in Code calc [Re: Kunal_Shah]
tahirq Offline
Member

Registered: 12/08/09
Posts: 50
Loc: India
Respected R.Srinivasan Sir,

Thank you very much for your valuable guide on this particular topic.
There was a comment on Nozzle Local load calculation from one of our client to include Pressure stress indices, & found that Primary bending streses where increased beyound allowable.

Your inputs have given a proper guideline to take necessary action rather blindly increasing shell thickness to compensate for the induced stresses.

I hope Coade will definately incorporate the same in there next build.

Remaining on the above topic, Annex 5.D of ASME SECVIII DIV-2 Cl-5.D.1.2 states that material which increases the thickness of a vessel wall locally at the nozzle shall not be included in the calculation of these components.When the thickness of the vessel is increased over that required to the extent provided herein after, the values of r1 & r2 in fig 5.D.2 shall be reffered to the thickneed section.

In such what shall be resoultion action to be taken if stress are exceeding beyound the limit aftre carrying out fatigue considering stress indices.

Please advise.

Regards
Tahir Quraishi
Design Engineer
TEMA INDIA LTD.
Navi Mumbai, Vashi.

_________________________
Tahir Quraishi
Technip

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#36366 - 06/23/10 10:35 AM Re: Include pressure stress Indices per Div2 in Code calc [Re: tahirq]
tahirq Offline
Member

Registered: 12/08/09
Posts: 50
Loc: India
Any expert opinion on the above query.

Thanks in advance.
_________________________
Tahir Quraishi
Technip

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#37043 - 07/25/10 09:47 PM Re: Include pressure stress Indices per Div2 in Code calc [Re: tahirq]
Mukesh Offline
Member

Registered: 11/12/06
Posts: 125
Loc: Ahmedabad, Gujarat, India
Mandeep/Ray/RSVTVL/Kunal/Tahirq/Other Participants,

Yes I am agreed to all that stress indices should be considered for cyclic service..i.e. fatigue evaluation.

However when client insist that irrespective of cyclic service, one need to consdier the stress indices in local load analysis then what will you do...? You need to consider it.

This is for your information that EIL has recently modified its allowable nozzle load specification with 2 new notes...New note no. 5 is as follows:

"Pressure Stress indices shall be considered as per ASME SEC.VIII Div.2 while calculating the stresses due to pressure for all Process nozzles irrespective of presence of cyclic service/ fatigue requirement. These stress indices shall be considered for analysis at nozzle to shell junction and need not be considered at edge of pad analysis."

EIL is forcing through its specification to consider the stress indices in WRCB calculation for nozzle to vessel joints irrespective of cyclic or fatigue requirements.

One more point to be highlighted is that stress indices calculation shall be part of report when ever considered in design.

Thanks.

Mukesh Chopra
www.theculminates.com
M: +91-9428500192



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#37089 - 07/27/10 11:36 PM Re: Include pressure stress Indices per Div2 in Code calc [Re: Mukesh]
tahirq Offline
Member

Registered: 12/08/09
Posts: 50
Loc: India
Dear Moderator,

Request Integraph to implement the improvements discussed under this topic.
This shall majorly help us in correct local load analysis.

Thanks a Lot.
_________________________
Tahir Quraishi
Technip

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#55622 - 07/29/13 06:30 AM Re: Include pressure stress Indices per Div2 in Code calc [Re: RSVTVL]
mayank Offline
Member

Registered: 11/04/12
Posts: 28
Loc: ISGEC Heavy Engineering Limite...
Dear Mr. Mandeep/Ray,

As mentioned in above conversation, have you incorporated the above requirement that "the values of Pm , Pl+Pb , Pl+Pb+Q shall not get increased after checking the stress Indices box in nozzle dialog window."

As far as my understanding it is not corrected in PV Elite 2013 also.

If possible please update it through a patch file.
_________________________
Thank You & With Regards-
Mayank Mittal
ISGEC Heavy Engg. Limited,
Haryana, India

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