J31 Series can be used on stationary or mobile tanks to visually indicate the amount of LP-Gas or anhydrous ammonia (NH3) in the container.
The gauge is operated by opening the small bleed orifice when the tube is in the vapor space of the tank. Moving the pointer on the dial causes the end of the tube to move until it contacts liquid in the container, at which time discharge from the bleed orifice turns from vapor to liquid giving the volume percentage of liquid in the tank.
