An unloader valve malfunction is one of the more common air compressor issues. The type of unloader valve found in an air compressor depends on the machine’s make and size. By venting the air, the unloader valve reduces the load over the piston, facilitating the restarting process. If you own a smaller reciprocating air compressor, you’ll likely find the unloader valve mounted on or inside the pressure switch. A small tube or pipe runs from the check valve, a device that keeps the entire tank from draining, to the unloader valve. A larger air compressor often features a more sizeable unloader valve controlled by air pressure emanating from a smaller pilot valve. As a leading provider of high-quality compressed air equipment for companies in a wide range of industries, Quincy Compressor can answer all your questions about unloader valves, their purpose and how they work.
Your reciprocating piston compressor will have a smooth start up, thanks to the unloader valve. The air compressor unloader is valve is a small, but important, part of the reciprocating piston compressor. There is another type of unloader valve, which can be found at the inlet of rotary screw compressors, also called inlet valve or loading valve). On bigger compressors, there is often a big unloading valve, which is controlled by air pressure from a small pilot valve. Big unloader valve which is controlled by a small pilot unloading valve. On the left side of the big valve we see the compressor output and the connection to the air tank. A common fault is that the unloading valve stays always open, or the opposite: the unloading valve does not open anymore.
There are few components on an air compressor that can multi-task quite like the piloted unloader valve. The following blog post will help you understand the piloted unloader valve by pointing out its components, explaining how it works and describing the adjustment process. The diagram below shows the components of our most common piloted unloader valve, part number 131B. How It Works. Piloted unloader valves combine a pilot valve and an unloader valve to run an air compressor continuously. As the compressed air is used and the pressure drops to the load setting, the pilot closes and depressurizes the unloader valve. The unloader valve then closes and the pressure begins to build again and repeats the cycle. As tank pressure approaches 135 PSI, the unloader valve should begin unloading at felt muffler and cause gas engine to slow down to idle speed.
The air compressor unloader valve provides a critical function in preparing your air compressor to restart. A failed air compressor unloader valve is one of the most common reasons why your air compressor cannot restart after you have used air from the compressor tank. Compressor unloader valves are common pieces of equipment on many types of air compressors including reciprocating, rotary screw and even gasoline or other fossil fueled air compressors. The air compressor unloader valve vents trapped air. What the unloader valve does is that is responds to the compressor pressure switch turning the power off to the motor and allows any air that may be trapped over the piston, or pistons on a multi-cylinder air compressor, to vent to atmosphere, removing any load that the trapped air may have created over the cylinder piston. The movement of those points is connected to an arm or finger inside or outside of the pressure switch, and that arm or finger pushes or pulls on a small valve pin, which operates the air compressor unloader valve. I expect you have a question about unloader valves at this point? That is, when the unloader valve is opened to atmosphere, why doesn’t all the air in the compressor tank escape too? For the answer to that, you will have to see the tank check valve page though we can say that some air compressors unload all the time.
If you’re interested in the broader principles of how an air compressor works – not just the unloader valve, you should check out our guide explaining how each type of air compressor works. Gas air compressor unloader valves are one of the numerous small, common and essential parts of an air compressor and the whole pressure maintenance process. The air compressor unloader check valve keeps the entire tank from draining and has a pipe running to the unloader valve. That hole is bleeding air all of the time the compressor is running, and then, when the compressor stops, that hole, the unloader for that compressor, continues to bleed air until all the air over the piston is gone. This leveling includes diverting and discharging air pressure when the air compressor tank top pressure setting is reached and when the maximum air pressure setting is reached within the air compressor respectively. The air evacuating from the unloader valve does not stop the unloader valve from continuing leaking air after the compressor is stopped. If there was no way to prevent it, when the unloader valve opened, all of the air already compressed into the tank would escape out of the unloader valve which is open to the atmosphere the whole time the compressor is off.
The unloading valve is a small part of the compressor measuring approximately 4-5 inches and width, which performs the critical function of releasing trapped air inside the tank, enabling a motor to restart. Technically, the unloading valve is the most important part of an engine because, without a well and functioning unloading valve, we can do nothing when it comes to motion. We would discuss the unloading valve’s functions next to grasp a full understanding of how the unloaded valve works and gaining full fundamental knowledge. A very good functioning unloaded valve ensures a reciprocating compressor’s effectiveness because when the unloaded valve functions effectively, having issues of a halt in motion wouldn’t be noticed. You would find it at the unloaded valve mounted on or inside the pressure switch when you come across an air reciprocating compressor. On a much bigger compressor, there is often a big unloading valve controlled by air pressure from a small valve, and it sits just beside the compressor. A large air compressor often features a more sizeable unloaded valve controlled by air pressure emanating from a smaller valve.
how do air compressor unloaders work Related Question:
How do unloaders work on a compressor?
While the air compressor is running, the pilot remains closed until the pressure reaches the unload setting. When that happens, the pilot opens and pressurizes the unloader valve, causing the unloader valve to open and excess air from the compressor to vent to atmosphere.
How do you know if your air compressor unloader is bad?
You can have two problems. Air leaking from an “unloader” valve on the pressure switch continuously (after the motor shuts off) is an indication of a leaking tank check valve, not a bad pressure switch. Air leaking from the unloader while the motor is running is an indication of a bad unloader valve.
How does a pressure unloader work?
The pressure-actuated unloader is a simple valve and spring arrangement set in a meal (usually brass) body. A channel drilled through the body gives water access to the back side of the valve ball. When pressure against the valve increases to a point where spring tension is overridden and water is diverted by bypass.
