Functions of an Unloader Valve in Reciprocating Compressors

How much do you know about an unloader valve and its many functions? It’s always ideal to learn more details about this compressor part. Read everything you need to know below.

Functions of an Unloader Valve in Reciprocating Compressors - KB Delta

Have you ever wondered what makes an engine re-start when it’s been worked? Have you ever thought of the processes involved to get it to shift gears and move an object forward? Of course! There is something in charge that makes it all happen in a few minutes. It is called the unloading valve.

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. This is a special tool that should be found inside every engineer’s playbook.

When the unloaded valve malfunctions, it begins to start experiencing air compression. So, it is very important for proper understanding to be taught before ever mounting an engine. Everything is about understanding the technical aspect of it. Once that is being understood, there is nothing that can’t be done.


How Does an Unloader Valve Work?

Understanding what makes a motor restart is important. Still, it is also very important to learn more about the functions of the unloading valve in reciprocating compressors – where it can be located, its purpose, and grabbing a basic knowledge of how the valve works.

A brief layout of its functions will be shed below to help users understand how everything about the unloading valve works and how its knowledge can be implemented in our everyday work with machines at the workplace, personal offices, and homes accordingly to the level of importance.

How does all this work? This works in a simple explanation. When the piston compressor’s output is connected through a pipe to the air receiver, the compressor stops, and the pressure in the pipe is blown off. When the compressor starts up again, the pipe would be placed under pressure to be put into full execution.

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.


The Specific Functions

The function the unloaded valve does on a compressor if taken for an exam synonymous with a tap switch which, when turned around, makes the water splash out. But in this situation, we are talking about trapped air. Let’s take a quick look at the functions of the unloading valve in a reciprocating compressor, and it’s as follows:


  • The unloading valve is a positive displacement mechanical device that relies on a cylinder to produce air.


This is a system whereby the valve’s effectiveness depends on the cylinder to produce air to repair its displacement. The unloading valve is so important that the air has to be produced to ensure the full functionality of an engine for a motion to take place. This is a system in which every engineer or mechanical personnel has to understand an unloaded valve’s uniqueness.


  • It ensures the efficient operating of a reciprocating compressor.


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.


  • Makes the switch trip again.


One function of the unloaded valve is that it makes the switch trips again after the air has been passed through, enabling an engine to regain its switch process. When the air pressure inside the compressor’s tank reaches the pressure when air is no longer delivered, the switch automatically trips off and interrupts the motor’s power supply. But, when the pressure drops to the predetermined pressure switch, it causes the switch to trip again.


  • It reduces the load over the piston.


This is another unique function of the unloaded valve. It helps when a motor attempts to restart; the air trapped inside the cylinder generates a load that makes it more challenging to execute the task. And by venting the air, the unloaded valve reduces the load over the piston. When the pressure placed upon the piston is lifted, effectiveness begins to occur.


  • It facilitates the restarting process.


The unloaded valve also helps maintain and facilitate a restart process. They say the pressure switch responds to the air accumulation to be working effectively and perfectly well for maximum productivity.


More to Know About an Unloader Valve

Knowing about the functions of the unloaded valve, it is also important to know where it is located. You would find it at the unloaded valve mounted on or inside the pressure switch when you come across an air reciprocating compressor. But we often find this location on smaller units.

Furthermore, 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. And they are also just found sitting beside the compressor.

When running an organization that uses a compressor, it is very much important to understand the regulation. And that is what the unloaded valve does. It helps in performing a proper regulatory system in an air compressor. This is more likely to be known as the fundamentals of learning regulation when working with a compressor.



Every new technician coming into the field must have a basic knowledge about this and know how to go about it when fixing a compressor problem or issue that may arise during the day to avoid a breakdown during operations. All this knowledge would help a technician or an engineer if troubleshooting problems arising in the future.


Functions of an Unloader Valve in Reciprocating Compressors - KB Delta

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