defining the minimum design metal temperature

[DerekLJ]

How do you define the MDMT (minimum design metal temperature)?

What ambient temperture do you need to be able to define it?absolute minimum? average minimum?

If i have an absolute minimum of 3.9ºF (-15.6ºC), what would the MDMT.

please help me here, i'm dying with this mess!

 

[JoeTank]

If the issue concerns a storage tank, API-650 uses a map of "low one-day mean ambient temperature". It's the lowest daily average temperature using data from US and Canadian weather bureaus. NFPA-22 for fire protection tanks also has one. API use MDMT = Map Temperature plus 15F. Otherwise, the owner should determine one.

Joe Tank