The liquid withdrawal valve is often known by its manufacturers given name such as Chek-Lok or Checkmate. However, the proper name is "actuated liquid withdrawal excess flow valve" and it serves a vital role in propane tank liquid evacuation. It also is used in other applications requiring the use of liquid propane.
Do not attempt to extract liquid from a propane tank through this valve. Contact your propane company concerning the operation of the propane tank liquid withdrawal valve.
The liquid withdrawal valve functions only with additional specialized fittings supplied by a propane company for liquid evacuation. Without these required fittings, the liquid withdrawal valve is unusable. The liquid withdrawal valve is attached to the tank and itself is in the vapor space.The diptube that reaches the bottom of the tank is in direct communication with the liquid space of the propane tank which allows it to be used for liquid propane service or liquid withdrawal. The valve itself is consists of a powerful spring holding a seat disc in a firmly closed position. The seat disc (left) is opened by attaching a second valve to the exterior of the liquid withdrawal valve outside the tank. This secondary valve is available only through a licensed propane company. Once the liquid withdrawal valve has been successfully opened by attaching the second valve to the exterior portion of the liquid withdrawal connection, propane liquid can be withdrawn. The liquid withdrawal valve has a safety mechanism built in called an excess flow valve. If the flow of liquid reaches a rate in excess of its design, the valve will close, hence the name "excess flow valve".
Used primarily by propane companies, the liquid withdrawal valve allows the tanks to be emptied of liquid propane before they are transported or moved. They are also used in consumer applications as a means for refueling portable cylinders. The valve attached to the liquid withdrawal valve is used as a service valve in this capacity. The hose and hose-end fittings allow propane liquid to be transferred into smaller tanks and cylinders for use on forklifts, gas grills or other appliances utilizing propane cylinders as an energy source. This actually makes a domestic ASME container into more of a distribution supply source.