Why MDMT must be correspond to the coincident pressure MAWP ?

[lslcpfcc]

as the statement of ASME VIII-1 UG20(b）
“The minimum metal temperature used in design shall be the lowest expected in service expect xxx”，
The MDMT marked on the nameplate shall correspond to a coincident pressure equal to the MAWP”
Background: a pressure vessel,the internal pressure is direct proportional to the temperature, when temperature increased,the pressure increased, simultaneously the pressure will reduce when the temperature reduced.
when the temperature at 50℃（highest），the coincident pressure will be 1.6 Mpa, and the pressure will be 0.1Mpa at the lowest temperature 0 ℃. The MDMT can’t occurs at the WAMP.

How can i stamp the MDMT at WAMP in the nameplate ？

 

[GenB]

Opposite, by design, by press decreases at higher metal temp.
Stamp by Code instructions.right, you can stamp per design MDMT at xxx calculated designed pressure. It can be lower than the MAWP at xxx temp.
By design...good luck.

 

[DSB123]

lslcpfcc,
What is the WAMP ? Also to answer your question "How can i stamp the MDMT at WAMP in the nameplate ？"
Use a minimum of 6mm high metal stamps on the nameplate. Impact other end of stamp with a 2Lb hammer!!

 

[moltenmetal]

Background: a pressure vessel,the internal pressure is direct proportional to the temperature, when temperature increased,the pressure increased, simultaneously the pressure will reduce when the temperature reduced.

That would ONLY be true of a pressure vessel filled to some initial pressure with an ideal gas, with no gas then being fed or removed.

That is NOT how most pressure vessels are used!

 

[jte]

Wait a minute! Is that what you Chem E's use those "inlet" and "outlet" nozzles for?

 

[SnTMan]

lslcpfcc, you may design and stamp your vessel such that different MDMT's are associated with various design pressures (or MAWP's if calculated) and design temperatures.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand