UCS-66.1 1

[stesw90]

Dear all,
I have vessel to design at -70 degree Fahrenheit and 50 psi pressure,
I designed it with sa-516 gr.70 normalized at curve D i.e -55degree Fahrenheit,
Required thickness with corrosion allowance 6mm (CA-3mm)I took 8mm to achieve reduced MDMT By limiting MAWP to design pressure,
I got thickness ratio as 0.433 as per which i can go up to -100 to -110 but as per the software maximum MDMT achieved is -55 degree Fahrenheit which has caused a confusion to me,
And flange I expected it to fail below -20 deg.F but is passing up to -155 deg. F
It's creating lots of confusion, I guess I am missing something, Help me to figure it out ,
Regards,

Stephen

 

[stesw90]

can anybody please interpret UCS-66(b)(1)(c)., UCS-66(b)(1)(b).,UCS-66(b)(1)(a).
Regards,


Stephen

 

[stesw90]

[highlight #C17D11]Nobody HAS ANY ANS FOR THIS[/highlight]

 

[XL83NL]

Stephen, dont expect answer within less than a quarter of a day's time.
Please bear in mind this forum is run by engineers who are willing to help anybody with their technical queries, but they do this on a non-profit base in their free time.
With that attitude, no one will help you.

 

[Shmulik]

Stephen,
The meaning of UCS-66(b)(1)(a) is: there is no temperature reduction permitted and you are not able to escape impact testing when your MDMT is already below -55°F.
Temperature reduction is permitted for flanges acc. to UCS-66(b)(1)(c).

I don’t like your material selection: SA-516 Gr. 70 is not expected to provide the required Charpy V-Notch Energy Absorption. See SA-20.
You should select SA-516 Gr. 55 / Gr. 60 / Gr. 65
Or - out of the box thought - you may consider austenitic stainless material (if it fits your working conditions).

 

[weldtek]

Stes,
You didn't ask for suggestions on alternate materials but Shumlik is right in saying there are many better choices for -70F. Recall that you're going to have to make a production test which may be problematic at that temp. SA537 can make that temp as can many others such as SA203, etc. Do a little research and choose the right type and grade.

 

[stesw90]

I am using SS material instead of CS,
But I wanted to take advantage of reduced MDMT since the pressure was not so high and the client didn't had any objection limiting MAWP,
Since my required thickness was 6mm including corrosion allowance I tried to take 8mm with sa-516 gr.70 normalized and fully killed to go below -55°F to achieve -70°F but in PV-elite i didn't get reduced MDMT to -70°F but when done manually i was getting thickness ratio to 0.466 as well as in pv-elite it is showing thickness ratio as 0.46 but it is not showing reduced value, as per ucs-66.1 It can be reduced to -70°F. I just wanted to confirm if there is any limitations for using reduced MDMT.
Thank you for everyone's response,

Regards,
Stephen

 

[SnTMan]

stesw90, generally speaking it should be possible to get to -70 F w/ carbon steel. It is a matter of properly understanding and applying the Code. I had related this aspect to you in a previous thread:

http://www.eng-tips.com/viewthread.cfm?qid=370840

Don't put too much blind faith in your software.

Regards,

Mike

 

[jte]

Stephen

To restate SnTMan's last sentence...

... designers and engineers using computer programs for design or analysis are cautioned that they
are responsible for all technical assumptions inherent in the programs they use and the application of these programs to
their design.- Section VIII Div. 1 Foreword​

Be sure that you are confident with what your software is doing for you. You, not "it" are ultimately responsible for code compliance.

 

[stesw90]

Thank you.............
I am in a learning process so some times i have to depend on software output to understand the base concept,
its doing the calculation reverse