Minimum Design Metal Temperature determining

The vessel is determined to be an uninsulated, horizontal, grade-level, cylindrical pressure vessel with a gas volume of 706 ft3 (20 m3). The vessel has a MAWP of 1,480 psig (102 bar) at 650°F (343°C) and a Minimum Design Metal Temperature (MDMT) of 40°F (4°C) since it is constructed of unnormalized steel material. Due to process conditions immediately prior to pressuring the vessel to 1,000 psig (69 bar), the vessel s metal temperature is approximately 30°F (-1°C). When the vessel is pressurized to 1,000 psig, it fails catastrophically. The distances to overpressure endpoints (1, 3, and 5 psig) are calculated as follows ... 

Design Pressure The pressure used in the design of a vessel component together with the coincident design metal temperature, for the purpose of determining the minimum permissible thickness or physical characteristics of the different zones of the vessel. AVhere applicable, the static head and other static or dynamic loads shall be included in addition to file specified design pressure in the determination of file minimum permissible thickness or physical characteristics of a particular zone of the vessel. 

If a CRM lined pressure vessel is to be designed for below -20°F (-29°C) for reasons other than seasonal atmospheric temperature. Section VIII, Division 1 of the ASME Code requires that the materials and fabrication practices meet minimum notch toughness requirements (Paragraph UG-84). Paragraphs UCS-65, 66 and 67 cover the requirements for vessels operating below -20°F. The use of SA-36 or SA-283 is not permitted. Impact tests are required except for seasonai temperature excursions beiow -20°F (-29°C) or when exempted by paragraph UCS-66 (c) which states that "no impact test is required for materials used for metal temperatures below -20°F (-29°C) when the minimum thickness is the greater of those determined under the most severe conditions of coincident pressure (external or internal) and temperature in accordance with UG-21 for temperatures of (a) -20°F (-29°C) and above and (b) below -20°F (-29°C), in which case the coincident pressure (internal if above atmospheric pressure and external if below atmospheric pressure) shall be multiplied by 2%."... 

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