Minimum Design Metal Temperature
Encyclopedia
The Minimum Design Metal Temperature (MDMT) is one of the design conditions for pressure vessel
s engineering calculations, design and manufacturing according to the ASME Boilers and Pressure Vessels Code. Each pressure vessel that conforms to the ASME code has its own MDMT, and this temperature is stamped on the vessel nameplate. The precise definition can sometimes be a little elaborate, but on simple terms the MDMT is a temperature arbitrarily selected by the user of the vessel according to the type of fluid and the temperature range the vessel is going to handle. The so called arbitrary MDMT must be lower than or equal to the CET (which is an environmetal or "process" property, see below) and must be higher than or equal to the (MDMT)M (which is a material property).
Critical Exposure Temperature (CET) is the lowest anticipated temperature to which the vessel will be subjected, taking into consideration lowest operating temperature, operational upsets, autorefrigeration, atmospheric temperature, and any other sources of cooling. In some cases it may be the lowest temperature at which significant stresses will occure and not the lowest possible temperature.
(MDMT)M is the lowest temperature permitted according to the metallurgy of the vessel fabrication materials, that is, according to the low temperature embrittlement range and the charpy impact test
requirements per temperature, for each one of the vessel's components.
Pressure vessel
A pressure vessel is a closed container designed to hold gases or liquids at a pressure substantially different from the ambient pressure.The pressure differential is dangerous and many fatal accidents have occurred in the history of their development and operation. Consequently, their design,...
s engineering calculations, design and manufacturing according to the ASME Boilers and Pressure Vessels Code. Each pressure vessel that conforms to the ASME code has its own MDMT, and this temperature is stamped on the vessel nameplate. The precise definition can sometimes be a little elaborate, but on simple terms the MDMT is a temperature arbitrarily selected by the user of the vessel according to the type of fluid and the temperature range the vessel is going to handle. The so called arbitrary MDMT must be lower than or equal to the CET (which is an environmetal or "process" property, see below) and must be higher than or equal to the (MDMT)M (which is a material property).
Critical Exposure Temperature (CET) is the lowest anticipated temperature to which the vessel will be subjected, taking into consideration lowest operating temperature, operational upsets, autorefrigeration, atmospheric temperature, and any other sources of cooling. In some cases it may be the lowest temperature at which significant stresses will occure and not the lowest possible temperature.
(MDMT)M is the lowest temperature permitted according to the metallurgy of the vessel fabrication materials, that is, according to the low temperature embrittlement range and the charpy impact test
Charpy impact test
The Charpy impact test, also known as the Charpy v-notch test, is a standardized high strain-rate test which determines the amount of energy absorbed by a material during fracture. This absorbed energy is a measure of a given material's toughness and acts as a tool to study temperature-dependent...
requirements per temperature, for each one of the vessel's components.