Superimposed Relief Valve: Working Principle, Types, and Applications

What Is a Superimposed Relief Valve?

A superimposed relief valve is a hydraulic safety device designed to limit pressure in a system by diverting excess fluid when the pressure exceeds a preset limit. Unlike conventional relief valves, a superimposed design allows it to be mounted directly onto a hydraulic manifold, saving space and improving system integration. These valves are widely used in hydraulic circuits where compactness, precision, and reliability are essential.

How Does a Superimposed Relief Valve Work?

The operation is based on pressure control:

1. Normal Operation: When system pressure is below the set value, the valve remains closed, allowing normal flow through the hydraulic system.

2. Overpressure Condition: When pressure exceeds the preset limit, the valve opens, directing excess fluid back to the tank or return line to prevent damage.

3. Reset: Once pressure returns to a safe level, the valve closes again, maintaining optimal system performance.

This design ensures continuous protection for pumps, actuators, and other hydraulic components.

Types of Superimposed Relief Valves

1. Direct-Acting Superimposed Relief Valve

Opens directly when the set pressure is reached. Known for quick response but typically used for lower flow rates.

2. Pilot-Operated Superimposed Relief Valve

Uses a pilot valve to control the main valve, allowing high flow rates and stable operation under varying pressures.

3. Adjustable Superimposed Relief Valve

Allows the user to change the set pressure to suit different operating conditions.

Applications of Superimposed Relief Valves

Superimposed relief valves are essential in many hydraulic systems, including:

• Industrial presses – To protect equipment from overload.

• Injection molding machines – For precise pressure control.

• Hydraulic lifts and cranes – To ensure safe operation under heavy loads.

• Construction machinery – Such as excavators and loaders.

• Marine hydraulics – For steering and deck machinery systems.

Advantages of Using Superimposed Relief Valves

• Space-Saving Design: Mounts directly onto manifolds, reducing piping.

• Improved Efficiency: Minimizes pressure losses and improves response time.

• Easy Maintenance: Accessible for inspection and replacement.

• High Reliability: Stable performance under continuous operation.

• Versatility: Compatible with a wide range of hydraulic applications.

Installation of Superimposed Relief Valves

To install a superimposed relief valve correctly:

1. Select the Correct Model: Match pressure rating, flow capacity, and connection type to your system.

2. Clean the Mounting Surface: Remove any debris before installation.

3. Position and Mount: Attach directly to the hydraulic manifold using the recommended bolts and torque.

4. Set the Pressure: Adjust the relief setting according to system requirements.

5. Test the System: Check for leaks and ensure the valve operates at the desired pressure limit.