Minimum Design Metal Temperature (MDMT)

MDMT will be lowest of operating temperature or atmospheric temperature (lowest possible
temperature during entire year where the vessel / piping being installed for operation) and/or any
other source of cooling such as:
The lowest temperature determined for any of the following conditions
- normal operations;
- start up and shut down procedures;
- possible process upsets, such as flashings of fluid, which have an atmospheric boiling point
below 0 °C;
- during pressure or leak testing.
For e.g
Lowest Operation Temperature 10°C
site Temperature -10°C
The MDMT of system = 0°C (mean metal temperature (through the thickness)
Secondly for save side we can use how MDMT of system -29°C Without any problem, because
below -29°C, ductile Carbon steel starts converting into brittle material
LODMAT= Averaging the daily low temperatures for any particular period results in a mean
minimum temperature for that period. (Suggestion) A day’s lowest (minimum) temperature usually
occurs in the early morning