Hydraulic Flow Control Valves: Speed Regulation Methods

Hydraulic Flow Control Valves for Speed Regulation

Flow control valves are essential components used to regulate the speed of hydraulic actuators. There are three primary methods to implement these valves:

• Meter-In (Entry Regulation): The valve is placed between the pump and the actuator, controlling the fluid entering the system. Excess flow is diverted to the tank via the relief valve. This precise method is ideal for applications where the load consistently opposes actuator movement.
• Meter-Out (Output Regulation): This system is used when the load tends to run away from the actuator, moving in the same direction. The flow controller is installed to restrict the outlet flow from the actuator.
• Bleed-Off (Regulation by Subtraction): The valve is placed in the pressure line, and actuator speed is determined by diverting a portion of the pump flow to the tank. The advantage is that the pump operates at the pressure required by the load, as excess flow returns to the tank through the valve rather than the relief valve.

Types of Flow Rate Regulators

There are two basic categories: pressure-compensated and non-pressure-compensated.

1. Pressure-Compensated Valves

These valves use an equalizer or hydrostat to maintain a constant pressure drop across an adjustable restrictor. They are categorized by their compensation method:

• Series Throttle Compensation: This valve maintains a constant pressure differential. The hydrostat is normally open and closes to block flow in excess of the valve's setting.
• Bypass Flow Compensation: This type combines overload protection with pressure-compensated flow control. Its built-in hydrostat opens to divert excess flow to the tank.

2. Non-Pressure-Compensated Valves

These are used in applications where system pressures remain constant and speed variations are minimal.

Specialized Flow Control Valves

• Temperature-Compensated Valves: These valves account for flow variations caused by changes in oil temperature, ensuring consistent performance.
• Remote-Controlled Flow Valves: These allow for the adjustment of the throttling size via an electrical signal, operating similarly to standard pressure-compensated flow control valves.