Hydraulic valve or hydraulic solenoid valve is a directional valve controlled by solenoid valve that is used in the hydraulic system to open, close or change the direction of liquid flow. The valve works with a solenoid, which is an electric coil wrapped around a ferromagnetic core in the center. This valve consists of various chambers, which are also called ports. The solenoid valve is used to pull the spool into the valve, opening or closing the ports. A spool is a cylindrical component that, depending on its position, performs the function of a valve by blocking or allowing fluid to flow through these ports. Hydraulic valves are widely used in industries such as manufacturing, aerospace, construction and Many others are used that require hydraulic systems. The following figure is an example of a hydraulic solenoid valve.
Directional control valves
Directional control valves are designed to start, stop or change the direction of fluid flow. These valves are mostly used in hydraulic and pneumatic systems. We only discuss hydraulic applications for the purpose of this article.
A hydraulic valve is a directional control valve that is widely used in hydraulic systems to change, allow or limit fluid flow. This valve uses a solenoid valve (X and Y) on both sides of the valve to activate, which can be seen in the figure below. The valve consists of a cylindrical spool (Z) with a width (larger diameter) and a groove (smaller diameter). The larger width blocks the flow while the groove allows the valve to pass through.
Directional valves are generally indicated by the number of ports and the number of switching positions. In the hydraulic valve, the valve is 3.4 way up, 4 indicates the number of ports and 3 indicates the number of positions. P is the pressure port, A and B are the working ports and T is the return port. When the solenoid X is activated, the spool is pulled to the left by an electromagnetic force. When the solenoid Y is activated, the spool slides to the right. This slider opens, closes or changes the port connections, which changes the direction of flow.
Hydraulic valve design
A 3/4 hydraulic valve has 4 ports and 3 positions. This is the most common type of valve used in hydraulic circuits. Depending on the design of the spool, the ports can be opened, closed or connected to a specific input / output. The following figure shows additional spool designs. The following spools can be in 3 different positions: PA and BT (left figure), closed (middle figure), or AT and PB (right figure).
As can be seen in the above circuit operation (left figure), when spool moves to the right, port A connects to port P and port B connects to port T. Circuit 2 (middle figure) represents a closed central valve with all ports blocked. When the spool is moved to the left, port P connects to port B and port T connects to port A.
A 2.4-way valve has 4 ports and 2 positions. A and B have two working ports, P is the pressure port and T is the return port.
These solenoid valves can have a single or double coil design. They can be connected normally or openly, so there is a spring that can return it to normal. When the solenoid valve is activated, a solenoid valve displaces the spool unit and returns to its original state after being de-energized. In a double solenoid valve, the spool moves with the energy of one coil and reverses with the energy of the other. It is important to note that only one coil should be powered at a time.
This hydraulic valve is available with features such as socket cap screw with hexagonal socket, magnetic coil, sealing set for pipe, O-ring set for connecting plates or blind plate including 4 O-rings. These features support reliable and sturdy fastening to prevent leakage during the process.
The inhibitory mechanism can be a magnetic or mechanical receptor to prevent the spool from moving. Some hydraulic solenoid valves use this stop mechanism to keep the spool open or closed when the power is off. When the energy is taken, the spool is released and returns to its original neutral state. In a two-position valve, the valve can be kept open so that the spool remains in both positions. For a three-position valve, the valve can be kept open to remain in each of its three positions.
Application of hydraulic valve in industry
Hydraulic valves are used in a wide range of applications that use a hydraulic system. Common applications of hydraulic valves are:
- water supply system
- Turbine system
- Fuel / gasoline supply system
- Wastewater treatment plants
- Process control in manufacturing plants
- Hydraulic motor, failure, pump in the automotive industry
- Hydraulic machines in aerospace and marine industries
- Heavy machinery in construction and landscaping
- Machinery in the agricultural sector
Important points and selection criteria
- Number of ports and positions : This should be selected based on the needs of your application.
- Spool action : This should be based on whether your program needs the spool to return to the center or stay in place when it runs low.
- Flow : The flow required for the application helps determine the size of the valve.
- Material : The valve material must be compatible with the characteristics of the flow environment.
- Temperature : Milk materials can withstand the minimum and maximum temperatures required by your application. Temperature is also essential in determining the capacity of the valve because it affects the viscosity and fluid flow.
- Pressure : The valve must be able to withstand the maximum pressure required for your application.
Frequently Asked Questions about hydraulic valves
What is a hydraulic solenoid valve?
A hydraulic solenoid valve is a solenoid controlled valve that is used in the hydraulic system to open, close or change the direction of liquid flow.
What is a spool?
A spool is a cylindrical piece inside a valve that helps open, close or change the direction of flow in a hydraulic or pneumatic system.
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