A vessel's maximum pressure rating is independent of temperature.

• A. True
• B. False
• C. Depends on Material
• D. Cannot Be Determined

Answer: (B)

The maximum pressure a vessel can safely handle depends on temperature. As temperature rises, the material’s strength and the performance of seals can weaken, so the allowable pressure is reduced. Standards specify a pressure rating at a reference temperature and then require derating for higher service temperatures. That means a vessel’s MAWP is not the same at all temperatures; it changes with temperature. So the statement is false. For example, steel’s strength decreases with heat, leading to a lower allowable pressure as temperature increases. Always check the temperature–pressure rating tables in the applicable code to determine the safe operating pressure at the actual service temperature.