Valves are on just about everything, especially in hydraulic systems. No matter the industry, such as construction, agriculture, and manufacturing, they are used to generate and transmit mechanical power. Specifically, valves control the flow of media (that’s fancy talk for “whatever is moving through the hose / system”). 

There are several different types of valves used in hydraulic systems, each with its own unique function and application. These valves can be broadly categorized into the following types:

1. Check valves - These valves are used to prevent the backflow of fluid in a hydraulic system. They typically have a spring-loaded disc or flapper that opens when fluid flows in the desired direction and closes when the flow reverses. This ensures that the fluid only flows in one direction and prevents damage to the system. Think of it as a one -way door. You can go in that way, but not back out that way. Make sense? Aside from being spring operated, check valves also came as a swing check, which as stated before is like a flapper or swinging gate. 
2. Pressure relief valves - These valves are used to regulate the pressure in a hydraulic system. They typically have a spring-loaded plunger or piston that opens when the fluid pressure exceeds a predetermined limit, allowing excess fluid to bypass the main flow and return to the reservoir. This prevents the system from over-pressurizing and damaging components. In the industry, you may hear this called a PRV. Another term you may have heard of is a pop-off valve. A pop-off valve is a pressure relief valve that does not reroute the fluid or air to a reservoir, it simply allows excess pressure to escape the system into the air if the system becomes over pressured  
3. Flow control valves - These valves are used to regulate the flow rate of fluid in a hydraulic system. They are typically installed in a pipeline and have a moveable orifice or spool that can be adjusted to restrict or increase the flow of fluid. This allows the operator to control the flow rate and adjust the system's performance to suit the task at hand. A gate valve would be a type of flow control valve. Think of your living room window. The more you open it, the more air can move through it. So flow control valves act as a gate, which can be opened a lot or a little, regulating the flow 
4. Directional control valves - These valves are used to direct the flow of fluid in a hydraulic system. They typically have a series of ports, spools, and pistons that can be moved to redirect the flow of fluid or vapor. This allows the operator to control the direction of fluid flow and activate or deactivate hydraulic and air components as needed. An easy way to think of a directional control valve is to think of a 4-way traffic stop. The flow (of vehicles) changes as certain lanes are instructed to stop or go. If you hear the term 3 way or diverter valve, those would be directional control valves as well.
5. Pilot-operated valves - These valves are used to control the flow of fluid in an air or hydraulic system using a separate, smaller flow of fluid. They are typically installed in a way so a secondary inlet port allows a small amount of fluid to act on a piston or spool, which in turn controls the main flow of fluid. So think of this as using the force of the material that is already present in the system, having a small amount of that force that also flows through another small system, and that system can be used to open or close a valve on the big system. Confused yet? This allows the operator to control the flow of fluid using a smaller, more precise input. A pilot valve can be used in a situation where there is a very large pipeline with a very large valve that would be difficult to manually operate. 

The different types of valves used in hydraulic and air systems vary, depending on the application. It is true, however, that there is no set rule for when to use each valve.  Each type has its own unique function and application and is essential for the effective operation of a hydraulic or air system.

If all this blog did was confuse you on what valve you need, then two things need to be said: 1. - sorry. 2. - Call the experts at American Hose and Supply, they are ready to help