In advanced hydraulic systems, controlling flow, pressure, force, and position with fine accuracy is vital. That’s where hydraulic proportional valves and hydraulic servo valves come in. Marginal Hyd is a specialist distributor, supplying hydraulic proportional valves, servo valves, pumps, and spare parts to meet industrial demands.

Let’s explore how each valve type functions, where they’re best used, and how Marginal Hyd supports customers in selecting the right solution.

What Is a Hydraulic Proportional Valve?

A hydraulic proportional valve is an electro-hydraulic device that modulates flow or pressure in proportion to an electronic input signal (voltage or current). Unlike simple on/off valves, proportional valves allow a controllable intermediate position, enabling smooth regulation of hydraulic actuation.

Key features and advantages:

• Continuous control of flow or pressure, matched to input signals
• Simpler construction compared to servo valves
• Better suited for many industrial automation tasks (e.g. machine tools, presses, material handling)
• Lower cost and lower maintenance compared to servo valves in moderate-precision applications

Proportional valves are widely used in applications where you need variable control but not extreme precision or high dynamic response.

What Is a Hydraulic Servo Valve?

A hydraulic servo valve (also called an electrohydraulic servo valve) is a high-precision valve designed for demanding, dynamic applications. It often operates as part of a closed-loop system, using feedback to precisely control position, force, pressure, or flow.

Notable characteristics:

• High responsiveness and bandwidth
• Very low deadband / hysteresis
• Fine control even under varying load
• Usually used in high-performance systems like test rigs, aerospace simulators, precise motion control

Servo valves can often use internal feedback or sensing to maintain accurate control over actuators.

How These Valves Work in Practice

Proportional Valve Operation

An electrical command signal energizes a solenoid or torque motor that shifts the spool against hydraulic forces and spring forces. The spool’s position adjusts proportionally to the input, controlling flow or pressure accordingly.

Servo Valve Operation

Servo valves frequently use a multi-stage approach: a pilot stage that modulates flow, which then drives a main spool. Feedback (such as a position sensor) is used to regulate the spool’s movement and correct deviations from the desired output.

For example, servo valves may use internal feedback loops so that changes in hydraulic load are compensated by adjusting the spool position automatically.

Applications & Use Cases

• Hydraulic Proportional Valves are suited to many industrial and mobile systems such as presses, injection molding machines, valves in material handling, and general machinery where moderate precision is sufficient.
• Hydraulic Servo Valves are used when precision, speed, and dynamic control are essential — in testing rigs, flight simulators, robotics, manufacturing systems requiring tight feedback, and aerospace systems.

Marginal Hyd, as a distributor, can supply both types (and their spare parts), making them a resource for varied industrial needs.

Considerations in Selection & Use

When evaluating whether to use a proportional or servo valve, consider:

• Required accuracy, speed, and dynamics
• Load variations and feedback needs
• System bandwidth and response time
• Cost, complexity, and maintenance
• Compatibility with the hydraulic system’s pressure, flow, and interfaces
• Availability of parts, support, and distributor services

Marginal Hyd can assist with matching valve specifications to system requirements and provide relevant spare parts and technical support.