Minimum Design Metal Temperature (MDMT)

[liberoSimulation]

Does any one have an idea about the basis of MDMT of an equipment?
Is the basis depressing the equipment to atmospheric pressure assuming control valve failure or opening PSV or draining the equipment with cold liquid rapidly or de-pressurzing the equipment with cold material before drying the equipment?
Many cases that lead to design the equipment MDMT to be based on atmospheric pressure.
I know that by this basis low temperature material shall be used for such equipment that fall in one of these cases.

Regards

 

[liberoSimulation]

I have discovered that no concern has been found of my worry of MDMT selected for some equipment.
As per ASME and reference to one of the related references it has been found that the code gives much lower margin lower than the certified MDMT selected of an equipment and to a limit up to -105C depending on the conditions of the studied system.

Now, I can not see any concern while the code gives much lower and lower temperature than the certified MDMT for any material selected.

This is just to update you with something is totally the first time I know in my job!

Cheers

 

[sechon302]

In general, ethylene/ethane service equipment designed at atm, -104 degree C.
Hence,Stainless steel(SUS 304) is selected for such alow temp.service.CS is very very dangerous even low cobon content. See ethylene plant metalogy,if you can.
Regards,