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#33629 - 03/15/10 12:30 AM Div2, Defining Allowable Stress Table 5a
Auwis Offline
Member

Registered: 03/15/10
Posts: 28
Loc: Malaysia
Hi all,

I got a query here, could anybody advise why PVelite & A.I. interprete that values from ASME II,D, Table 5a should be interpolate? It is a bit different from Table 2a which shown "exact" value compare with Table "5a" which shown "in range" value since mark "<" is there.

anybody share opinion please?

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#33647 - 03/15/10 08:35 AM Re: Div2, Defining Allowable Stress Table 5a [Re: Auwis]
Ray_Delaforce Offline
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Registered: 01/02/03
Posts: 743
Loc: Houston, TX
Hello Auwis

I am not too sure what you mean. First of all, PV Elite uses the Imperial (American Units) tables from ASME Section II - Part D, not the metric tables. If the design temperature lies between two temperatures designated in Part D, PV Elite does a linear interpolation to get the desired allowable stress value. I am not sure what you mean by the statement: 'exact'.
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Ray Delaforce
CADWorx & Analysis Solutions
Hexagon PPM

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#33661 - 03/16/10 12:45 AM Re: Div2, Defining Allowable Stress Table 5a [Re: Ray_Delaforce]
Auwis Offline
Member

Registered: 03/15/10
Posts: 28
Loc: Malaysia
So sorry all if my word confuses you,

let me give an example:

From ASME II,D (Costumary, 2007) Table 5A, line 1 (SA 675-45):

allowable stress for: <40C (mark "<" means below) = 103 Mpa
<65C (mark "<" means below) = 97.3 Mpa
<100C (mark "<" means below) = 94.3 Mpa
Case 1:
If my temperature is 65C, we cant use 97.3 Mpa because (it was meant for below 65C).
Case 2:
If my temperature is 80C, should we just take value 94.3 Mpa? because it is meant to be for (65~99C) ?

Different from Table 2a; there is no mark "<", then we could interpolate it.

Opinion someone?
Thanks.

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#33668 - 03/16/10 06:14 AM Re: Div2, Defining Allowable Stress Table 5a [Re: Auwis]
Ray_Delaforce Offline
Member

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

As I explained above, we use the Imperial Tables not the Metric Tables internally in our software. The two tables are different, and that is the source of so much confusion. Frankly, it is about time ASME abandoned the Imperial system and get in step with the rest of the world. In my opinion there is no point in duplicating everything.
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Sincerely,
Ray Delaforce
CADWorx & Analysis Solutions
Hexagon PPM

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#33679 - 03/16/10 09:56 AM Re: Div2, Defining Allowable Stress Table 5a [Re: Ray_Delaforce]
Auwis Offline
Member

Registered: 03/15/10
Posts: 28
Loc: Malaysia
Hi Ray,

Nice to hear from you again. Thanx sooo much for ur kind reply.
For the matter above, i believe i had get you confuse again.

I also agree on ASME should abandon the imperial system or make it generaly with properly shown with good conversion system. not simply round up or down which make everybody stick with their figures. ASME B16.5,2003 also another cases. I believe PVelite still stick with imperials.

Getting back to our topic, actually it is not a matter of conversion because both ASME II D metric & Imperial got Table 5a with metric system.

This is only the matter of ASME purpose putting mark "<" infront of the temperatures. Different from the way they show on Table 2a.

Really hope you are getting understood on what i explain.

sorry..sorry..sorry if my english are not as good as yours.

Thanks Ray..

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#33681 - 03/16/10 10:11 AM Re: Div2, Defining Allowable Stress Table 5a [Re: Auwis]
Ray_Delaforce Offline
Member

Registered: 01/02/03
Posts: 743
Loc: Houston, TX
Hi Auwis

The ASME committee had a problem (of their own making) in that the temperatures in the Imperial table could not be properly matched with the temperatures in the Metric table. The whole thing is a mess. That is probably why they used the '<' symbol. They will continue to have problems until some strong willed person gets them to see the light.

I have used the metric system nearly all my life and I find it more logical and much simpler. To have a system that uses feet, inches and fractions of an inch is daft. The Imperial system completely messes up Newtons Second Law, and most of the time when using pounds in the imperial system, confusion reigns when dealing with weight and mass. That is a total catastrophe.
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Sincerely,
Ray Delaforce
CADWorx & Analysis Solutions
Hexagon PPM

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#33812 - 03/22/10 11:18 AM Re: Div2, Defining Allowable Stress Table 5a [Re: Ray_Delaforce]
Mandeep Singh Offline

Member

Registered: 12/15/99
Posts: 600
Loc: Houston, Tx, USA
Auwis,

Where do you see the '<' marks in the printed allowable stress tables? I could not find it.

But, in my opinion it <= so you can 97.3MPa value for 65C. For temperatures between 40C and 65C you have to interpolate the allowable stresses at 40C (103MPa) and 65C (97.3MPa)

But, as Ray pointed out, PV Elite uses Imperial version of these allowable stresses. Because of rounding offs in the ASME code to get pretty looking values, these 2 versions are not exactly the same but very close.

But, if you refer to ASME Sec. VIII Div. 1 Appendix GG-1 (last line of 1st para in A-09) it allows the use of unit conversion constant with least 3 significant digits to convert from Imperial allowables to Metric allowables.
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Mandeep Singh
CADWorx & Analysis Solutions
Hexagon PPM

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#33823 - 03/22/10 07:34 PM Re: Div2, Defining Allowable Stress Table 5a [Re: Mandeep Singh]
Mukesh Offline
Member

Registered: 11/12/06
Posts: 125
Loc: Ahmedabad, Gujarat, India
Mandeep, I think Auwis is looking properties in excel table from ASME Electronic Stress Tables.

There is no "<" markes given for properties in the Sec II tables as said by Auwis. As Ray said, one need to interpolate between temperatures if your design temperature is not exactly matching with Code tabulated temperatures.

Mukesh
www.theculminates.com

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#34645 - 04/28/10 11:47 AM Re: Div2, Defining Allowable Stress Table 5a [Re: Mukesh]
kalra Offline
Member

Registered: 06/04/09
Posts: 17
Loc: india
YES YOU CAN INTERPOLATE.. I WILL PROVIDE YOU SOME INPUT ASAP HOW IT ISALLOWED.

REGARDS
MUKESH KALRA

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#34653 - 04/28/10 02:44 PM Re: Div2, Defining Allowable Stress Table 5a [Re: kalra]
Ray_Delaforce Offline
Member

Registered: 01/02/03
Posts: 743
Loc: Houston, TX
I hope one day that ASME will go 100% SI Metric, and smell the coffee. They must forget thier former life in the dark ages.
_________________________
Sincerely,
Ray Delaforce
CADWorx & Analysis Solutions
Hexagon PPM

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#35768 - 05/28/10 10:43 PM Re: Div2, Defining Allowable Stress Table 5a [Re: Ray_Delaforce]
SK Tan Offline
Member

Registered: 01/15/09
Posts: 66
Loc: Malaysia
Dear all,

To my monitoring on this cycle of discussion, I need to share my understanding of what Auwis brought up and what confusion went to Coade Moderators and forum members.

First of all, Auwis's question came from Table 5A in temporary Excel file when ASME VIII Div 2 Edition 2007 was enforced. Table 5A was not ready to published in ASME II Part D.

This Excel file did shown stresses in temperature range with sign of " < " and different from "Not Exceeding" used on Table 1-A.

This was what all about confusion Auwis had.
" < " mean EXCLUDING the temperature data in table 5A
" Not Exceeding " mean INCLUDING or " = < "

Anyway, situation now changed. Table 5A is inserted to ASME Part II D already. The sign of " < " was corrected to "Not Exceeding" just like Table 1A. Interpolation is allowed.

Indeed, both general notes behind Table 1A and Table 5A do state allowable stress data can be interpolated (even before Table 5A be inserted back to ASME II D).

All the while, ASME committes intend to let Code user to do interpolation but may be a human error applied " < " on the temporary Excel version. Sharp-eye people who caught & realized the difference between " < " with " Not Exceeding " and will confuse and eager to seek for clarification.

Wish above explanation clear doubts and helpful. In summary, Table 5A allows interpolation just like Table 1A.

Attach along 3 images as graphical illustration.

SK Tan


Attachments
Extract from ASME IID Table 5A - Excel version.JPG

Extracted from Table 5A published in ASME II D.JPG

Extract from General Notes of Table 5A about interpolation.JPG



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#35780 - 05/30/10 07:28 PM Re: Div2, Defining Allowable Stress Table 5a [Re: SK Tan]
Auwis Offline
Member

Registered: 03/15/10
Posts: 28
Loc: Malaysia
LOUD & CLEAR Sir!.. I Missed out to check that note. blush..
Thank you very much for all the effort.

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