Minimum Temperature
A minimum permissible temperature is required to be displayed on the nameplate of a Division 2 vessel. Unlike the nameplate for a Division 1 vessel, a coincident pressure is not displayed for the minimum permissible temperature. However, the pressure during startup or shutdown is explicitly not permitted to exceed 25% of the design pressure (defined in the Code as 20% of hydrotest pressure) at temperatures below the minimum permissible temperature.
The minimum permissible temperature can be determined for a Division 2 vessel in the same way the minimum design temperature is determined for a Division 1 vessel, as discussed above. However, the curves in Division 2 concerning CVimpact test requirements for the various materials of construction differ somewhat from those in Division 1. The curves in Division 2 tend to require CV-impact testing at slightly higher temperatures for the same material of construction and component thickness, which is probably related to the greater toughness required to resist brittle fracture at the higher design stresses in Division 2.
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