UCS-68(b)

[c8829]

Hello Everyone,
I have vessel MDMT -60°C. with MOC SA-516 Gr 60.
As per PV Elite calculation it gives me excemption for Impact test with the help of UCS-68(c).
As per UCS-68(b) PWHT is mandatory but PV Elite still considering UCS-68(c) which i think is not-correct.
Here is the calculation highlight.
So please need your Expert Advice which is correct way?

Minimum Design Metal Temperature Results:

Govrn. thk, tg = 10.000 , tr = 7.331 , c = 0.5000 mm , E* = 0.80
Stress Ratio = tr * (E*)/(tg - c) = 0.617 , Temp. Reduction = 21 °C

Min Metal Temp. w/o impact per UCS-66, Curve C -44 °C
Min Metal Temp per UCS-66 and UCS-68(c),PWHT credit -61 °C
Min Metal Temp. at Required thickness (UCS 66.1) [highlight #FCE94F] -65 °C[/highlight]

 

[SnTMan]

c8829, if PWHT is mandatory due to other Code rules, which your software will not likely know, UCS-68 exemption cannot be taken. If the UCS-66.1 reduction in your post is correct, you're not getting there.

Regards,

Mike

 

[c8829]

Thank Mike
As per UCS-68(b) MDMT is colder than -48°C and as per calculation coincident ratio is greater than 0.35 which reults in Mandatory PWHT. So i think Impact test excemption can be taken only upto -44°C.

 

[c8829]

Plus resulting excemption temperature cant go below -48° as PWHT excemption in UCS 68(b)is not applicable.

 

[chevproe]

c8829,
Sorry for late reply on this post..i just came across a simialr situation recently...

I would tend to agree with your interpretation...UCS-68(c) exemption cannot be claimed when resulting exemption temperature is colder than -48(-61 for your case) and PWHT exemption as per UCS-68(b) is not applicable.Note that PWHT is mandatory due to UCS-68(b) for your case..

However, you can stil claim Impact test exemption with the help of UCS-66.1 as correctly mentioned in the reply post by SnTMan.

So, my question is - How did you infer that PV-Elite is considering Impact test exemption by UCS-68(c)??Could you please upload the relevant page from your output file to help me understand?

Also, did you try discussing this issue with PV-Elite support team??What respose did you get??


Thanks,
Chevproe

 

[chevproe]

c8829,

Further to the above, did you consider UCS-66(b)(2)??
Impact testing is required for all materials when MDMT is lower than -48C, unless exempted by UCS-68(c) or if the coincident ratio is 0.35 or lower (for MDMT from -48 till -105).
However, for the case stated above, none of the exemptions are applied since there is no PWHT exemption of UCS-68(c) and the coincident ratio is more than 0.35.

So, I see no reason that PV-Elite should throw you the output stating "Exempt from Impact testing"....

Please share your opinion.

 

[r6155]

Use your software only for calculations, not for fabrication and inspection.
Check periodically the software by hand calculations.
My opinion only.
Regards
r6155