What does the minimum metal design temperature refer to, and is it related to the ambient temperature?

It’s okay; it just refers to the lowest temperature that can be achieved during normal operation

If the question posed by the original poster concerns the design of pressure vessels for storage at normal temperatures, it is necessary to fully consider the impact of the ambient temperature under normal operating conditions on the metal temperature of the vessel’s shell. The lowest designed metal temperature must not be higher than the lowest value of the monthly average minimum temperatures over the years (i.e., the sum of the lowest temperatures recorded on each day of a month divided by the number of days in that month) I wonder if it’s what the original poster wanted!

It must be related to the ambient temperature.

The metal temperature is the average temperature along the metal cross-section of the component

This post was last edited by fxy1860 on 2012-2-22 at 13:19. In fact, the minimum metal design temperature is a concept defined in the ASME standards; this concept is hardly used in national standards. In national standards, the classification of low- and medium-temperature pressure vessels is based on the minimum design temperature, which must not be higher than the lowest temperature that the vessel might experience. However, MDMT is used frequently in ASME standards. This temperature can be provided by the user or calculated based on VIII-1. In ASME, MDMT and stress levels, as well as the heat treatment condition and thickness of the material, determine whether a pressure vessel is to be used in low-temperature operations and whether impact energy tests are required; however, this temperature is related to low ambient temperatures. According to national standards and relevant regulations, the average monthly minimum temperature over the years is only taken into consideration when storing pressure vessels at normal temperatures. In fact, this concept sometimes causes unnecessary problems. In foreign process packages, the equipment data sheets are generally based on ASME standards; the minimum ambient temperature must be specified as the design temperature. When the equipment is shut down and there is no pressure in it, even if the temperature reaches the minimum value, according to ASME standards, since there is no stress level or the stress level is very low, the pressure vessel is not considered a low-temperature device, and thus it can be exempted from impact testing. In China, simply entering this temperature as the design temperature means that corresponding measures to deal with low temperatures must be taken into account in the design, even if the operating temperature is several hundred degrees. And some people mistakenly provide the local minimum temperature to the manufacturers, which sometimes results in the entire equipment being classified as a low-temperature device according to national standards. Hehe; if what the original poster is referring to is ASME standards, then this temperature is related to the lowest ambient temperature. But in the case of national standards, this temperature is generally not relevant, unless it involves containers that are stored at normal temperatures. By the way, the national standard mentioned above refers to the old version 150; I haven’t had time to study the new version in detail yet.

The 150-2011 version also includes the MDMT concept. When determining the design temperature of storage containers, the influence of MDMT should be taken into account. As specified in GB50341, the design temperature shall be the minimum value of the daily average lowest temperature plus 13 degrees.

This is the clearest explanation of the minimum design metal temperature I have ever seen. I would like to ask how the pressure vessels stored at normal temperatures, as mentioned in the code for solids, are defined

It’s actually very simple: it’s a container in which the temperature of the storage medium is affected by the external temperature; there are no heat or cold sources, and the insulation properties of the equipment are not sufficient to maintain the temperature of the materials over an extended period of time.