In the propane appliance world whether dealing with a simple grill or a complete system a person frequently hears open the propane valve slowly or you will cause the excess flow valve to close.
Two things lead me to believe this oft repeated instruction is a lot like the take two aspirin and call me in the morning,
The first and least important reason for doubting the open slow advice is I’ve opened a lot of propane valves not worrying about how fast I open the valve and never had a lockup.
The second and most important reason for doubting the open slowly advice is knowing how the excess flow valve works. The excess flow is held open allowing gas to flow by the pressure in the propane system. If the pressure in the propane system drops below a set level like would happen with a large leak, the lack of pressure against the spring loaded valve causes it to close. To make this process work, the excess flow valve has a small hole to allow propane vapor to pass to the other side when the valve is closed (this is why a tripped excess flow valve will limit flow, but not stop flow; to stop flow the plastic nut at the tank melts at about 250 degrees).
When the tank valve is opened if the system isn’t at operating pressure the excess flow valve will be closed because of insufficient pressure (back pressure) in the system to overcome the pressure of the valve spring. The bleed hole in the excess flow valve allows gas to flow into the system until pressure in the system is sufficient to open the excess flow valve.
Two things lead me to believe this oft repeated instruction is a lot like the take two aspirin and call me in the morning,
The first and least important reason for doubting the open slow advice is I’ve opened a lot of propane valves not worrying about how fast I open the valve and never had a lockup.
The second and most important reason for doubting the open slowly advice is knowing how the excess flow valve works. The excess flow is held open allowing gas to flow by the pressure in the propane system. If the pressure in the propane system drops below a set level like would happen with a large leak, the lack of pressure against the spring loaded valve causes it to close. To make this process work, the excess flow valve has a small hole to allow propane vapor to pass to the other side when the valve is closed (this is why a tripped excess flow valve will limit flow, but not stop flow; to stop flow the plastic nut at the tank melts at about 250 degrees).
When the tank valve is opened if the system isn’t at operating pressure the excess flow valve will be closed because of insufficient pressure (back pressure) in the system to overcome the pressure of the valve spring. The bleed hole in the excess flow valve allows gas to flow into the system until pressure in the system is sufficient to open the excess flow valve.
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