MDMT temperature 1

[static_engineer_07]

Dear Community members,
currently, I'm designing a pressure vessel 6 mm thk, with 1400 mm long shell having OD of 500 mm. I'm getting a warning in PV elite report which says, Computed overall MDMT was higher than the required value !
, could you please guide me to resolve it ?. I'm not deeply familiar with ASME sec VIII codes.

 

[dig1]

Static Engineer 07,

The MDMT would be an input. I believe it is on the "Design Constraints" tab on the lower left and is under "Miscellaneous Design Data". The specifier of the vessel needs to make the determination of the MDMT using the definition in UG-20, assuming Div. 1.

I hope this helps.

 

[GD2]

Static Engineer 07,

Your limiting MDMT (warmer) are the two flanges limited to -25C. Try changing it to Curve B, you should be cleared of the warning.

Check what it says in the latest version of Sec Viii Div 1 UCS-66 about flanges. Most likely, it has been moved to Curve A from earlier Curve B for A105 flanges.

If this is the case, check if the A105 forged flanges now require a Post heat treatment to fall in Curve B.

GDD
Canada

 

[static_engineer_07]

dig1,
Thank you for your guidance. is MDMT a user input ? or we are supposed to take it from Sec II part d ?
I had written 28.9 Deg celcius as it is MDMT for SA 516 gr 70 as per SEC II part D.
is MDMT depend upon the surroundings of Pressure vessel or location where vessel will be working ?

 

[static_engineer_07]

GD2,
Thank you for your valuable reply.
Actually while selecting nozzle material in PV elite, there is not any option to select the curve A, curve B, C or D. It only takes material input. Kindly guide me if there is any such option.
Apart from that, I have selected SA 516 gr 70 curve B for shell, dished end & other parts.

 

[dig1]

static engineer 07,

The required MDMT is a user input and information on that is in UG-20(b). The required MDMT may be related to the surroundings but is most likely process driven. Again, please read UG-20(b).

Please study UCS-66. As GD2 stated the Curve for the SA105 depends on the condition it is supplied in. As forged is Curve A but if it has been manufactured per Note 2 in Figure UCS-66 then it will be Curve B.

In PVElite you can see/control this by selecting the "..." to the right of the Material name in the Element Data under General Input.

I'm offering a comment at which I hope you don't take offense to based on your initial comment where you state you are not deeply familiar w/ ASME Codes. You need to be familiar with the codes. I do not know you situation with respect employment, education, etc. Sitting down and using PVElite, Compress, or even worse an FEA package that states just plug in the data and have ASME compliant reports in a few minutes w/o knowing the applicable portions of the Code you are designing to is not a good and potentially a disastrous situation. It appears you need to get some training on both ASME Code and the software. ASME has on-line, self guided training and there are online free resources for PVElite. Also, you need to have someone experienced look at your work. Eng-Tips is good but w/o knowing the details of the project the advice may be limited and potentially inaccurate as the responder does not know exactly what is being designed and may be unaware of a condition which would impact their response. Please take this comment in the spirit it was intended which is to be helpful.