HAT (Heat Actuated Trap) or TV/HAT (Tube Valve Heat Actuated Trap) valves used on tank heating coils limit the temperatures of the heating element. By closing before coil temperatures are too high, the HAT or TV/HAT valves reduce the risk of over-temperature damage.

When used as a sub cooling steam trap, HAT or TV/HAT valves reduce problems associated with overheating.