The air compressor pilot valve controls when the air compressor stops compressing air by regulating the pressure inside the tank.
Here's a breakdown of how it works:
-
Normal Operation (Compressing Air): While the air compressor is running and the pressure in the tank is below the pre-set "unload" pressure, the pilot valve remains closed. This allows the compressor to build pressure in the tank.
-
Reaching Unload Pressure: As the compressor runs, the pressure inside the tank increases. When the pressure reaches the unload setting (the maximum pressure), the pilot valve opens.
-
Activating the Unloader Valve: When the pilot valve opens, it directs compressed air to the unloader valve. The unloader valve is typically located on the compressor pump.
-
Unloading the Compressor: The pressurized air from the pilot valve causes the unloader valve to open. This action serves two main purposes:
- Venting Excess Air: The unloader valve opens a path allowing excess air from the compressor head (and often from the discharge line between the pump and tank) to vent to the atmosphere. This prevents the compressor from continuing to pump air into an already full tank.
- Reducing Load on the Motor: By venting the pressure in the compressor head, the motor no longer has to work against a high-pressure load to start the next compression cycle. This is especially important for start-stop operation.
-
Pressure Drop & Reset: The compressor will remain "unloaded" and not build more pressure until the pressure in the tank drops below a certain "cut-in" pressure (lower than the "unload" pressure). Once the pressure drops sufficiently, the pilot valve closes again, sealing off the unloader and allowing the compressor to start building pressure again.
In summary: The pilot valve acts as a pressure-sensitive switch. It monitors the tank pressure and, when the upper limit is reached, signals the unloader valve to vent excess air, stopping the pressure-building process. When the pressure drops below the lower limit, it closes, and the compressor resumes building pressure.
