How Propane Safety Relief Valves Work
Safety relief valves are held in the closed position by the force of a powerful spring. As long as the pressure inside the tank is less than that of the spring, the valve will remain closed. If the pressure in the tank rises to that of the spring, the valve will open, which results in a hissing sound outside of the tank. If the If tank pressure rises significantly higher than that of the spring, the valve will fully open. When the valve fully opens, it initially results in a loud pop followed by a blast of released propane gas. Once the pressure is released and the tank pressure falls below that of the spring, the valve closes.
Internal Pressure Relief Valve
The majority of propane tanks in residential and commercial service have internal safety relief valves. The reason for an internal valve as opposed to an external pressure relief valve is it presents less of an obstruction when moving the tank. Typically, internal relief valves are placed near the end of the propane tank on above ground containers.
External Pressure Relief Valve
External relief valves are found primarily on older tanks. They operate in the same manner as an internal relief valve with the spring mechanism being outside of the propane tank itself. Relief valves on multvalves are always fitted with external safety relief valves. Older propane tanks with an external relief valve installed on the container are typically replaced with internal pressure relief valves, provided they are connected to a dedicated tank opening specifically designed for the placement of the relief valve.
Important Pressure Relief Valve Information
The safety relief valve performs a vital role in the protection of the propane tank, so it should be maintained and repaired by licensed propane professionals only. Do not ever look into a relief valve or stand over it.
- Tanks must be empty before relief valves can be replaced
- Safety relief valves may need to be replaced if they “pop-off”, meaning that the valve has opened.
- A protective cover should be placed over the relief valve to ensure proper operation. If the valve has debris in the upper mechanism of the relief valve and it opens, the debris may cause the valve to remain open resulting in a potentially dangerous situation and/or excessive loss of propane. A simple protective relief valve cover can be made from a plastic bag fastened around the external portion of the valve with a rubber band.
- If you encounter a relief valve that seems to be “hissing” (opened to relieve pressure) do not tap it or mess with it. If the tank has been recently filled in hot weather and the face gauge reads over 80 or 85 percent, spray some water from a hose on the tank. This may cool it down and reduce the expansion of liquid in the tank. Contact your propane company immediately and inform them of the situation.
Relief Valve Problems – A Job for LPG Professionals
If your propane relief valve is leaking, contact your propane company immediately. Do not try to fix this issue yourself. AS a relief valve that is sealed shut will not allow the tank to vent excess pressure if it is overfilled or the pressure inside the tank exceeds the working pressure of the container. In a case where the tank is unable to vent to the outside, the tank is subject to rupturing causing more harm and damage than money saved by trying to fix it yourself. Let your propane company or LPG professional handle any issues with the safety relieve valve.
