During fire exposure, allowable pressure accumulation may increase to what percentage?

During fire exposure, allowable pressure accumulation may increase to what percentage?

• A. 25%
• B. 15%
• C. 50%
• D. 5%

Answer: (A)

During a fire, the contents of a vessel heat up and the gas inside tends to expand, causing pressure to rise. The code provides a specific allowance for this temporary pressure increase, permitting the allowable pressure to accumulate by up to 25% beyond the vessel’s maximum allowable working pressure. In other words, the pressure may reach about 1.25 times the MAWP during fire exposure. This value is chosen to accommodate the expansion and the need for relief action without compromising safety. The other percentages don’t align with this established allowance and would either underprotect or be unnecessarily conservative.

During a fire, the contents of a vessel heat up and the gas inside tends to expand, causing pressure to rise. The code provides a specific allowance for this temporary pressure increase, permitting the allowable pressure to accumulate by up to 25% beyond the vessel’s maximum allowable working pressure. In other words, the pressure may reach about 1.25 times the MAWP during fire exposure. This value is chosen to accommodate the expansion and the need for relief action without compromising safety. The other percentages don’t align with this established allowance and would either underprotect or be unnecessarily conservative.