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When does an overfill protection device activate?

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May 13, 2008 1:01AM

The OPD activates when the liquid LPG level in the tank being filled reaches 80% of the tank volume. It consists of a float on an arm linked to a valve stem. When the float rises to the 80% point, the valve stem closes the fill port, so no more LPG can enter the tank.

Why limit the fill to 80%? Because as the tank gets hot, say from sitting in the sun, the liquid expands. If it were allowed to completely fill the tank, it would vent gas through its overpressure valve, wasting gas and potentially creating an explosion hazard.