How does a 4 way hydraulic valve work?

Answer 1

4 Way hydraulic valves are often used with double acting cylinders. The valve usually has a handle that is used to change fluid direction. On the 4 way valve there will typically be 4 ports or openings for connections of hoses. Connecting hoses is done as follows: There will be an IN and OUT port and there will be an A and B port. (Different manufactures label differently so sometimes ports A & B are labeled 1 & 2 for example.) The in port is where the hose for fluid under pressure is connected. This may be from a hand operated or motor powered pump. The out port will be connected to the hose going to the fluid reservoir or tank. The A and B ports will be connected to the hydraulic cylinder. Now for the how it works part: Basically the handle controls a piston inside the valve. The piston is machined to allow fluid to run through it in different directions depending on the location inside the valve. There are two fluid paths inside the valve at the same time with fluid running two directions. One path is for the supply hydraulic fluid and one path is for the returning hydraulic fluid. When hydraulic fluid is pumped into the IN port and the handle is pushed one direction the fluid passes from the IN port and goes out the A port leading to one line or hose to the hydraulic cylinder. At the same time the valve allows fluid returning from the other hydraulic hose connected to the cylinder to come into port B and go out the OUT port on the valve back to the hydraulic tank. When the handle on the valve is pushed the opposite direction the fluid paths switch so the pumped fluid coming in the IN port goes out the B port to the hydraulic cylinder and fluid returns coming into the A port and goes through the OUT port back to the hydraulic tank. The 4 way valve allows fluid to run from the pump or (hydraulic fluid source) to the hydraulic cylinder in two different directions depending on the position of the handle so the cylinder can either be extended or retracted. When the handle on a valve is not pushed in either direction it is called a neutral or normal position. Some 4 way directional valves only allow fluid to pass when the handle is moved in one direction or the other while some allow the fluid to come into the IN port and go through to the OUT port when it is in the neutral position. The valves that allow fluid to pass from the IN to the OUT while in the neutral position are often used with powered hydraulic pumps. Once the pump is turned on the fluid begins to flow in and out of the valve until the handle is moved to direct fluid to the hydraulic cylinder.