Dear Friends,

Here I put some queries what we had checked with CODE 31.3 2012.

1)Clause 302.3.5 - Allowable Displacement Stress Range.

Sc = 138 MPA & Sh =138 MPA.

Also, mentioned as "MAXIMUM".

== The Value of SC & Value of SH were not given in code 2010.

== Does it affect to allowable SA?

== Do we have to input any value in CAESAR?

SA = f(1.25Sc+0.25Sh)
= 1.2 (1.25 * 138 + 0.25 * 138)
= 248.4 MPA

Is this Maximum Value?

== From Where these values are derived based on Yield or Tensile?

2) Clause 319.3.6

Stress Intensification Factors may be developed in accordance with ASME 31J.

== Request if any one expert has some overview/idea how to calculate SIF based on 31J, please share here.

3) Clause 319.2.3

(c) Average Axial Stress - for Buried,core-jacketed etc.

== This point has been added in 2010 for checking Axial
Stresses, however it has been removed from ASME Code 2012.

== Does it mean now all calculations need to consider Axial Stress (all piping)?


Friends, wishes to have a reply / suggestion here.

Regards
SND.

3. Clause 319.2.3

2010 Code Says:

Average Axial stresses are not normally included in the displacement stress range.

Check Eq.319.4.4(7) SE= Sqrt (sb2+4st2). Axial stresses are not included in this equation.

If u check the Config file  SIF& STRESSES  B31.3 sec 319.2.3 c Saxial  NO(DEFAULT)
But in special cases user want to include axial stresses in displacement stress range (ex: jacketing, buried piping) Two options 1. Appendix-P ON. 2. In Config file  SIF& STRESSES  B31.3 sec 319.2.3 c Saxial  YES

Then, CAESAR-II uses P319.4.4 (p17b) SE= Sqrt ((|sa|+sb)2+4st2). ). Axial stresses are included in this equation

2012 Code Says:

This statement is removed “Average Axial stresses are not normally included in the displacement stress range”.

Check Eq.319.4.4 (7) SE= Sqrt ((|sa|+sb)2+4st2). Axial stresses are included in this equation.

As per 2012 code. Yes we have to include the Axial Stresses in all calculations. CAESAR-II Software will do the same.

I think in the latest CAESAR-II version(BASED ON 2012 CODE) : In Config file  SIF& STRESSES  B31.3 sec 319.2.3 c Saxial  YES(DEFAULT)
Please correct me, If I am wrong.

Dear Friends, Richard/ Dave share your views to the above said our queries.

Thanking you

Regards
SND

1)maximum allowable stress for expansion stress range is determined by (1a) or (1b). I would guess (1b) (the CAESAR II default) gives a larger number.
2)Currently, B31J shows how to develop SIFs through mechanical testing, not calculation. (This is expected to change. I see B31J replacing Appx D.)
3) the 2012 code dropped that axial stress paragraph because (as Durga says) the equation for SE now has that axial stress term in the equation.

Dear Dave,

Thanks for providing useful information,

1) I know the Equ 1(b) gives the higher allowable. however 1st time Code committee introduce the value of Sc & Sh in 2012.

Any interpretation of these values for calculation of "SA" (allowable)?

Like "SA" shall not be greater than 248.4 MPA.

Is this correct?

2) Please update us also when it will be come. Thanks.

3) Thanks Durga & Dave. We shall apply for all lines the Axial Stress - Default as YES.

Any other friend would like to share for these queries, can post here.

Regards
DAVE

1) the B31.3 2012 code now mimics B31.1 in limiting Sc & Sh used in calculating SA. For SA, Sc & Sh cannot exceed 20ksi. Markl did not test high strength steel. There is no indication that higher strength steels perform better in fatigue, therefor, the 20ksi limit.

This has no effect on the sustained or sustained-plus-occasional stress limit

Dear Experts, Dave & Richard,

1) Can you please clarify, In code of ASME B 31.3 2012 why only Axial Stress (Sa) has provided with Bar lines in the formula?

Formula contains that bar lines but after Squaring it will come +Ve in any way.

Is this any specific reason why only AXIAL STRESS is marked as ===> lSal with Bar lines.?

2) Axial Stress & Torsional Stress

- Nomenclature of 319.4.4 (31.3 2012) tells

Sa - axial stress range due to displacement strains

where for Torsional case it is said as St = torsional stress. (ONLY)

Is that any reason that torsional stress is not due to displacement strains?

3) In code compliance report of CAESAR II.

In the stress output Axial Force & Torsional Moments shows the direction (+Ve or -Ve) where as Shear Force & bending moments are not showing any direction,i.e all are +Ve.

aa) Kindly guide, what CAESAR is taking inside its back calculation for the above said my query?

bb) If piping is in X direction, Axial force value is coming into FX column,but taking direction of force opposite.

Sorry for inconvenience.

Q-3 Not the Code compliance report. it is " Global Element Forces Extended Report"

Dear Azley,

1. If the formulae is like this; SE= Sqrt ((|sa|2+sb2)+4st2. Then no need of bar for Sa.

Check the formulae correctly. SE= Sqrt ((|sa|+sb)2+4st2). There are no individual squares for Sa & Sb.

Mathematically.

If u see Sb is always +ve. For St individual square so if any –ve value turns to +ve.

To get the maximum calculated value (for the sake of conservative). Sa may be provided Bar.

2. How can you club torsion with Axial?

Torsion stress due to shear force.
Axial stress due to Axial forces/Displacement strains(along the axis).

3. Global Element Forces Extended Report

Check this example.

FX=56
FY=-446
FZ=98
MX=94.3
MY=-131.6
MZ=-387.2

AXIAL FORCE = along the axis (say pipe is in Z direction)= Fz =98.

SHEAR FORCE= Sqrt(FY^2+FX^2)=449.50 (That is why; shear force is always positive)

TORSIONAL MOMENT= MZ=-387.2

BENDING MOMENT= Sqrt(MX^2+MY^2)=161.89. (That is why; BM is always positive)

Shear force and bending moments are resultant values. That is the reason, why these two values are always positive.

please correct me, If Iam wrong..

Dear Dave,

I randomly checked for the materials in CAESAR-II Whether these allowable are below 138 Mpa or not.

I observed that, for the material A 335 P91 in CAESAR-II VERSION 6.0 it is showing Sh & Sc = 195.117 Mpa. @ 500 oC & 20 oC

But in 2012 code it is limited to 138 Mpa. Then it effects the all allowable calculations (SUS, OCC, and EXP)

Please correct me if I am wrong.

CAESAR II will apply the limit on Sc and Sh in the computation of the Expansion Allowable Stress. You do not have to do tis manually.

Thank you Mr. Richard.

But, sorry I am not clear. I will try to make doubt clear.

According to ASME B 31.3 2012 code, it limits the Sc & Sh value to 138 Mpa.

1. In CAESAR-II I found a material A335 P91 which has a Sc & Sh values 195.117 Mpa i.e, greater than 138 Mpa. Now what CAESAR-II does for this material (according to CODE 2012)?

2. For this type of materials also (whose Sh & Sc values greater than 138 Mpa), it will limit the value to 138 Mpa or not?

Please correct me if I am wrong

When CAESAR II determines the allowable stress (1.25Sc + 1.25Sh - Sl), the values for Sc and Sh are tested against the limit of 138 Mpa. So:

Sc_Used = MIN( Sc, 138 )
Sh_Used = MIN( Sh, 138 )

SA = f*(1.25*Sc_Used + 1.25*Sh_Used - Sl)

Thank you Richard,

1.so from next version of CAESAR-II CODE 2012 it follows

for SUSTAINED = MIN(Sh, 138)
for Exp.SA = f*(1.25*Sc_Used + 1.25*Sh_Used - Sl)
for Occ = MIN(1.33Sh,138)

Is this correct.

2. But for materials which has higher values of Sc & Sh it doesnt become over conservative?

3. If a system pass in 2010 CODE, may fail in 2012 CODE because of these limitations.

Sc_Used = MIN( Sc, 138 )
Sh_Used = MIN( Sh, 138 )

Any comments ?

CAESAR II has always imposed the Code Defined limits.

Thank you Richard,

please check whether these statements (my understanding) are correct or not?

1.From next version of CAESAR-II CODE 2012 it follows

for SUSTAINED = MIN(Sh, 138)
for Exp.SA = f*(1.25*Sc_Used + 1.25*Sh_Used - Sl)
for Occ = MIN(1.33Sh,138)

2. If a system pass in 2010 CODE, may fail in 2012 CODE because of these limitations.

Sc_Used = MIN( Sc, 138 )
Sh_Used = MIN( Sh, 138 )

please correct me if I am wrong

The 138MPa limit on Sc & Sh applies only to the evaluation of the expansion stress range. This limit does not apply to sustained and occasional stress evaluation.
High strength materials do not necessarily have a higher fatigue limit.

Dear Dave, Durga,

Do Inter graph released the version with ASME B 31.3 2012?

If not, than why to check these limits ?

Still CAESAR follows 2010 code.

please correct me,if I am mis understood?

Regards
SND

Dear Snehal sir,

I think at this end of the month or before, CAESAR-II ver.7.0 is releasing according to ASME B 31.3 2012. As said by "Mandeep singh" Intergraph person.

Dear Durga,

Thanks,

yes ,we are also checking these criteria & what is impact of changing or additional requirement in Code,as I raised the 1st post by myself for this issue.

In our Current project - client asked to use ASME B 31.3 2012.

Also, APPENDIX _ P may be updated in newer CAESAR version.

Lets see.


Regards
SND

Dear Dave & SND,

Thank you very much. For your patience explanations.

Now it is clear.