Air compressor unloader valves play a crucial role in the function and operation of an air compressor. Their main purpose is to release or unload the pressure that builds up in the compressor's discharge line or head when the compressor stops or reaches its maximum pressure.
Here's how the function and operation of air compressor unloader valves typically work:
Pressure Buildup: When an air compressor is running, it generates compressed air that is stored in a tank. As the air pressure builds up in the tank, it also increases in the discharge line or head of the compressor.
Compressor Shutdown: When the compressor reaches its maximum pressure setting or is turned off, the compressed air trapped in the discharge line creates what is known as "head pressure."
Unloader Valve Activation: To relieve this head pressure and prevent it from affecting the compressor's startup, an unloader valve comes into play. The unloader valve is typically located near the compressor's pressure switch.
Unloading Process: When the compressor stops or reaches its maximum pressure, the unloader valve opens a pathway for the compressed air to escape. This action reduces the pressure in the discharge line, preventing it from affecting the compressor during startup.
Unloader Valve Types: There are two common types of unloader valves: constant speed unloader valves and load-sensing unloader valves.
a. Constant Speed Unloader Valve: This type of unloader valve operates at a constant speed, regardless of the compressor's load or demand. It unloads the entire discharge line pressure when the compressor stops.
b. Load-Sensing Unloader Valve: Load-sensing unloader valves are more advanced and designed to adjust the unloading process based on the compressor's load. They unload only a portion of the discharge line pressure, maintaining a minimum operating pressure to facilitate quicker startup and reduce energy consumption.
Unloader Valve Mechanism: Unloader valves can use different mechanisms to achieve their function. Some common mechanisms include:
a. Pressure Relief Valve: This mechanism uses a spring-loaded valve that opens when the pressure in the discharge line exceeds a specific threshold. It allows the compressed air to escape until the pressure is reduced to a safe level.
b. Piloted Unloader Valve: This mechanism uses a pilot valve that is connected to the compressor's pressure switch. When the pressure switch signals the compressor to stop or reach maximum pressure, the pilot valve opens, activating the unloader valve and releasing the trapped air.
In summary, air compressor unloader valves are critical components that relieve the pressure in the discharge line when the compressor stops or reaches its maximum pressure. They help protect the compressor during startup, ensure efficient operation, and prevent excessive strain on the system.
