Structure

• Basic Structure: They typically consist of a valve body, a poppet, a spring, and a control piston. The valve body has inlet and outlet ports for fluid to flow in and out. The poppet is the movable part that controls the opening and closing of the valve, and the spring helps to close the poppet when there is no control pressure. The control piston is used to receive the control pressure signal to achieve the reverse flow function.
• Optional Structures: Some may have additional features like orifices for controlled leakage in the normally blocked direction, which can be used for specific flow control requirements.

Working Principle

• Normal Flow: In the normal flow direction, when the fluid pressure from the inlet is high enough to overcome the spring force, the poppet is pushed away from the seat, allowing the fluid to flow through the valve to the outlet.
• Reverse Flow: When reverse flow is needed, a control pressure is applied to the control port. This pressure acts on the control piston, which in turn overcomes the spring force and pushes the poppet away from the seat in the reverse direction, enabling the fluid to flow backward. Without the control pressure, the poppet remains closed in the reverse direction to prevent backflow.

Functions

• Flow Control: They control the direction of fluid flow, allowing it to flow in one direction as needed and enabling reverse flow only when the control signal is present. This is useful in hydraulic systems where different flow directions are required in different working conditions.
• Pressure Maintenance and Relief: They can help maintain pressure in a specific part of the hydraulic system. For example, in some hydraulic cylinder circuits, they can prevent the pressure in the cylinder from dropping when the pump stops or the system is in a standby state. They also protect the system from pressure surges by allowing controlled reverse flow to relieve excess pressure.
• Locking Function: In certain applications, they can be used to lock the position of hydraulic actuators. By closing the valve in both directions when needed, they can prevent the movement of hydraulic cylinders or other actuators, ensuring the stability and safety of the equipment.

Applications

• Construction Machinery: In excavators, loaders, and cranes, they are used in the hydraulic circuits of boom, bucket, and arm movements to control the flow direction and ensure the safe and accurate operation of the equipment. For example, they can prevent the bucket from dropping suddenly due to hydraulic oil backflow.
• Industrial Equipment: In presses, injection molding machines, and other industrial machinery, they are used to control the movement of hydraulic cylinders and ensure the stability and reliability of the production process.
• Marine Equipment: On ships and offshore platforms, they are used in hydraulic systems for anchor winches, deck cranes, and other equipment to ensure the normal operation of the hydraulic system in a marine environment.

Advantages

• High Sealing Performance: They have good sealing performance, which can effectively prevent fluid leakage and ensure the efficiency and stability of the hydraulic system.
• Good Reliability: With a simple structure and few moving parts, they have high reliability and low failure rates, reducing maintenance costs and improving the service life of the system.
• Wide Pressure and Flow Range: They can be designed to work in a wide range of pressures and flows, meeting the needs of different hydraulic systems.