As it pertains to safety valves, what is the definition of blow down?

Correct Answer: Option C — Blow down is the difference between the valve popping pressure and the valve reseating pressure.

Blowdown is the pressure drop required for a safety valve to reseat after it has lifted. It is defined as the difference between the set (popping) pressure and the pressure at which the valve disc returns to its seat, ensuring the valve does not chatter or leak.