Why is it necessary to have a relief valve protecting the deaerating feed tank from internal pressure?

Correct Answer: Option A — Because the tank receives high pressure drains.

Deaerating feed tanks (DFT) operate under low pressure but receive high-temperature, high-pressure drains from various auxiliary systems and steam traps. A sudden surge or trapped high-pressure steam flash can overpressurize the shell, making an ASME-approved relief valve mandatory per 46 CFR pressure vessel requirements.