Low Temperature in ASME B31.3

This forum discusses specific topics about the stress codes such as ASME, EN 13480, KTA, FDBR, CODETI ...
Antworten
Benutzeravatar
r2user
Beiträge: 139
Registriert: Mi 14. Sep 2011, 10:18

Low Temperature in ASME B31.3

Beitrag von r2user » Mi 20. Jun 2012, 07:41

Dear Support

I have defined a user material A671 CC65, which has temperature beyond the minimal value TEMPERATURE in the database. Rohr2 use the option LOW TEMPERATURE to get the allowable stress. when I run the calculation, I got the allowable stress is 62.5 MPa at the temperature -40 C for 12.5mm wallthickness of pipe, and several parts are overstressed. I think the allowable stress is very low, so I wonder if that is right?

Best regards

Benutzeravatar
rohr2support
Beiträge: 422
Registriert: Mi 14. Sep 2011, 08:23

Re: Low Temperature in ASME B31.3

Beitrag von rohr2support » Mi 20. Jun 2012, 07:51

Hi

I think there is a confusion about the interpretation of the "allowable stresses".
If you are in the low temperature zone below the allowable of the material (Fig. 323.2.2A)
ASME_B31_3_Fig323_2_2A.png
you can either do impact testing or you can use the material without any additional test by reducing the allowable values using the reduction curve
from FIG 323.2.2B.
ASME_B31_3_Fig323_2_2B.png
So in other words you are using the material outside of specification but you can still use it.
In your case you have -40°C where 10°C is allowable (Curve A). So you go 50° below the limit.
The reduction factor for 50°C is 0.43 so you can only use 43% of the allowable stresses at 10°C
or you can do impact testing.

Best regards

Rohr2Support
Sie haben keine ausreichende Berechtigung, um die Dateianhänge dieses Beitrags anzusehen.

Benutzeravatar
r2user
Beiträge: 139
Registriert: Mi 14. Sep 2011, 10:18

Re: Low Temperature in ASME B31.3

Beitrag von r2user » Mi 20. Jun 2012, 10:12

Hi Rohr2support

Thank you for your prompt response. I think it helps me a lot. The two figures are used for carbon steel material.
I want to ask a simple question, can we use that for A671 CC65?

Best regards

Benutzeravatar
rohr2support
Beiträge: 422
Registriert: Mi 14. Sep 2011, 08:23

Re: Low Temperature in ASME B31.3

Beitrag von rohr2support » Mi 20. Jun 2012, 10:23

Hi

The material A671 CC65 is listed in Table A1 as carbon steel with temperature curve B.
So my assumption of curve A was wrong.
You should use curve B of fig. 323.2.2.A and the allowable temperature for 12.5mm wall is about -28°C.
So the reduction factor from fig. 323.2.2.B should be taken at (40-28)=12° and is about 0.8 instead of 0.43.
You may need to update your material description by clicking on "Low temperatures" and change to curve B like this:
ASME_Material_Temperatur_Curve.png
Best regards
Sie haben keine ausreichende Berechtigung, um die Dateianhänge dieses Beitrags anzusehen.

weiyi duan
Beiträge: 4
Registriert: Sa 24. Sep 2011, 04:02

Re: Low Temperature in ASME B31.3

Beitrag von weiyi duan » Fr 29. Jun 2012, 07:11

Hi Rick,
Yeah, I see it.
Thank you for your professional technology support.
Every time I talk with you about problems, I will learn some new technology knowledge.
it's very exciting.


weiyi duan

Antworten

Wer ist online?

Mitglieder in diesem Forum: 0 Mitglieder und 1 Gast