Balance Valve: Understanding the Structure and Principle | MachineMFG

# Balance Valve: Understanding the Structure and Principle

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The hydraulic balancing valve enables the unrestricted flow of oil from port 2 to port 1, as evidenced by the schematic diagram at the top of the figure below.

When the oil pressure at port 2 is higher than the pressure at port 1, the green part of the spool moves towards port 1 due to the force of the oil pressure, causing the check valve to open and allowing oil to flow freely from port 2 to port 1.

However, the flow of liquid from port 1 to port 2 is blocked until the pressure at the pilot port reaches a certain level, causing the blue spool to move to the left and opening the valve port. This allows oil to flow from port 1 to port 2.

If the pilot pressure is not strong enough to open the blue spool, the valve port closes and the flow of fluid from valve port 1 to valve port 2 is shut off.

The symbol for the balancing valve is shown below:

## The role of the balance valve

The balancing valve helps to prevent the unintended downward movement of the hydraulic cylinder. This allows the operator to lift heavy objects at a specific speed and keep them in a fixed position.

The balancing valve prevents the actuator from moving before the hydraulic pump has had a chance to respond. This helps to eliminate cavitation of the actuator and reduce the risk of losing control of the load.

In the event of a line in the hydraulic system bursting or leaking severely, a balancing valve installed on the actuator helps to prevent the loss of control over the moving load.

## Selection principles for balancing valve application and pilot ratio

The typical relief setting for balancing valves is usually 1.3 times the maximum operating pressure. However, the pressure required to activate a pilot valve depends on the pilot ratio.

The pilot pressure can be calculated using the following formula:

Pilot Pressure = (Relief Pressure Set Point – Load Pressure) / Pilot Ratio

To optimize load control and energy efficiency, the pilot ratio can be selected based on the following guidelines:

• A 5:1 ratio is chosen when the load is highly unstable, such as in the case of long-arm cranes. This ratio is used when the load changes and has a significant impact on the mechanical structure.
• A 10:1 ratio is appropriate for applications where the load is relatively stable.

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