In many industrial hydraulic systems, simply starting and stopping an actuator is not enough.

A hydraulic cylinder may need to accelerate gradually, move at a controlled working speed, slow down before reaching its final position, or operate at different speeds during different stages of a machine cycle.

The 2FRE proportional flow valve is designed for this type of continuously adjustable hydraulic flow control.

Instead of relying on a manually fixed throttle setting, the valve changes hydraulic flow according to an electrical command. The controlled oil flow then determines the operating speed of a hydraulic cylinder or motor.

An important feature of the 2FRE family is pressure-compensated flow regulation, which helps maintain more consistent flow even when load conditions change.

Bosch Rexroth currently lists 2FRE as a 2-way proportional flow control valve family, including size 6 versions with maximum flow up to 25 L/min and larger size 10 and 16 versions for substantially higher flow requirements.

What Is a 2FRE Proportional Flow Valve?

The 2FRE is an electrically controlled proportional valve designed primarily to regulate hydraulic flow.

Its basic control process can be understood as:

Electrical Command → Proportional Valve Opening → Hydraulic Flow → Actuator Speed

When the electrical input changes, the valve adjusts its metering opening.

A larger opening allows more hydraulic oil to pass, while a smaller opening reduces flow.

For a hydraulic cylinder:

Higher Flow → Higher Cylinder Speed

Lower Flow → Lower Cylinder Speed

For a hydraulic motor:

Higher Flow → Higher Rotational Speed

This makes the 2FRE useful when actuator speed needs to be changed continuously rather than using only fixed fast/slow settings.

Why Pressure Compensation Matters for Speed Control

A simple throttle valve can regulate hydraulic flow, but the actual flow through the restriction may change when the pressure difference across the valve changes.

That means a cylinder adjusted to a certain speed under a light load may move differently when the load increases.

A proportional flow valve with pressure compensation is designed to reduce this effect.

The pressure compensator helps maintain a more stable pressure difference across the metering section, allowing the commanded flow to remain more consistent when system load changes.

This is important because:

Stable Flow ≈ More Stable Actuator Speed

For industrial machinery, this can improve:

• Cylinder speed consistency
• Process repeatability
• Machine motion quality
• Hydraulic motor speed regulation
• Production accuracy

It is especially valuable where the machine load is not constant throughout the operating cycle.

How 2FRE Provides Smooth Actuator Speed Control

Imagine a hydraulic cylinder used on an automated production machine.

The required movement may be:

Stage 1 – Fast Approach
The cylinder moves quickly toward the workpiece.

Stage 2 – Controlled Working Speed
The cylinder slows down during the actual process.

Stage 3 – Slow Final Movement
The actuator approaches its final position smoothly.

Stage 4 – Return
A different flow may be required for the return stroke.

With conventional fixed flow control, multiple valves or switching arrangements may be needed to create different speeds.

With proportional flow regulation, the electronic controller can change the command and therefore change the hydraulic flow continuously.

The simplified sequence becomes:

PLC / Controller → Amplifier / Electronics → 2FRE → Controlled Flow → Cylinder

This allows the machine control system to change actuator speed according to the operating program.

2FRE6 for Compact Proportional Flow Control

The 2FRE6 is the smaller version of the family and is suitable for lower-flow industrial hydraulic systems.

Bosch Rexroth currently specifies the 2FRE6 as a size 6, two-way proportional flow control valve with:

• Maximum operating pressure: 210 bar
• Maximum flow: 25 L/min
• Component series: 2X
• Size 6 mounting interface

Multiple nominal-flow characteristics are available, including linear and progressive versions. The current selector lists options ranging from very low flows such as 1 L/min and 2 L/min through progressive flow versions up to 25 L/min.

This makes the 2FRE6 suitable for applications requiring relatively fine flow adjustment in a compact valve size.

Linear and Progressive Flow Characteristics

Different 2FRE versions can provide different command-to-flow characteristics.

This is important because not every application benefits from the same response curve.

Linear Flow Characteristic

With a linear characteristic, flow increases relatively proportionally as the command increases.

This is useful where operators or controllers require predictable flow change across the working range.

Progressive Flow Characteristic

A progressive characteristic can provide finer control at lower flows while allowing greater flow as the command increases.

This can be useful when a machine requires:

• Precise low-speed movement
• Fine positioning during part of the stroke
• Higher speed at larger command signals

Bosch Rexroth currently lists both linear and progressive nominal-flow options in the 2FRE family.

For replacement projects, the flow characteristic should therefore be checked from the complete valve model, not just from the basic 2FRE designation.

2FRE10 and 2FRE16 for Higher Flow Applications

Larger hydraulic equipment may require more flow than a size 6 valve can provide.

For these applications, the 2FRE family also includes nominal sizes 10 and 16.

Bosch Rexroth currently specifies the size 10 and 16 family as component series 4X with maximum operating pressure of 315 bar. Current available nominal-flow options extend up to 60 L/min for NG10 and 160 L/min for NG16.

This allows 2FRE valves to cover both relatively compact systems and larger industrial hydraulic circuits.

A simplified comparison is:

Version	Nominal Size	Max. Operating Pressure	Max. Flow
2FRE6	6	210 bar	25 L/min
2FRE10	10	315 bar	Up to 60 L/min
2FRE16	16	315 bar	Up to 160 L/min

Exact available flow ratings depend on the complete model configuration.

Why Bigger Is Not Always Better

When selecting a proportional flow valve, choosing the version with the highest possible flow capacity is not necessarily the best solution.

An oversized valve may spend most of its operating time within a very small part of its control range.

This can reduce the usable resolution available for fine speed adjustment.

On the other hand, a valve that is too small can create:

• Excessive pressure drop
• Limited actuator speed
• Increased hydraulic heating
• Reduced system efficiency

The selected rated flow should therefore match the actual flow required by the actuator.

For a hydraulic cylinder, the required flow is related to:

Cylinder Area × Required Speed = Required Flow

Correct valve sizing helps achieve a useful balance between maximum speed and fine control.

2FRE vs Conventional Flow Control Valve

A manually adjusted flow-control valve can be sufficient for machinery that always operates at one fixed speed.

But the 2FRE is more suitable when actuator speed must change electronically during operation.

Conventional Flow Control Valve

Typically suitable for:

• Fixed speed adjustment
• Simple hydraulic systems
• Manual setting
• Low automation requirements

2FRE Proportional Flow Valve

Better suited to:

• Variable actuator speed
• PLC-controlled machinery
• Multiple speed stages
• Smooth acceleration and deceleration
• Automated production processes
• Remote electronic adjustment

In simple terms:

Manual Flow Valve = Fixed Adjustment

2FRE = Programmable Flow Control

2FRE vs Proportional Directional Valve

A 2FRE should also not be confused with a proportional directional valve such as a 4WRA or 4WRAE.

The main control objectives are different.

2FRE

Primarily designed for:

Proportional Flow Regulation

Its main purpose is controlling how much hydraulic oil passes through the valve.

4WRA / 4WRAE

Primarily designed for:

Directional + Proportional Flow Control

These valves determine both the direction of flow and the metering opening through the directional spool.

Therefore, the correct solution depends on the hydraulic circuit.

Some systems may use a directional valve together with a separate 2FRE flow-control valve, while other machines may use a proportional directional valve to perform multiple control functions.

Optional Check Valve Function

Certain 2FRE6 configurations are available with an integrated check-valve option.

Bosch Rexroth’s current 2FRE6 selector distinguishes versions without a check valve and versions with a check valve.

This can be useful when the circuit requires proportional flow regulation in one direction while allowing different or freer flow behavior in the opposite direction.

Therefore, replacement selection should also confirm whether the original valve includes this feature.

Two valves may both be marked 2FRE6 but still have different internal circuit configurations.

Start-Up Behavior and Pressure Compensator Configuration

Some 2FRE6 configurations also distinguish how the pressure compensator is handled during start-up.

Bosch Rexroth lists variants associated with suppression of the start-up jump, including configurations with external closing of the pressure compensator and versions without external closing.

This can matter in applications where sudden initial actuator movement must be reduced.

For machinery requiring smooth motion from standstill, the complete configuration should therefore be checked carefully rather than replacing the valve based only on size and maximum flow.

Typical Applications for 2FRE Proportional Flow Valves

2FRE valves can be used in many industrial systems requiring electronically adjustable actuator speed.

Typical applications include:

Machine Tools

Hydraulic cylinders may need different speeds during:

• Tool approach
• Positioning
• Clamping
• Machining
• Return movement

Hydraulic Presses

A press may require:

Fast Approach → Controlled Working Speed → Return

Proportional flow regulation allows these speed stages to be programmed.

Industrial Automation

Automated machines can adjust hydraulic actuator speed directly according to controller commands.

Material Handling Systems

Lifting or positioning equipment may require smoother acceleration and deceleration to reduce mechanical shock.

Test Equipment

Flow can be adjusted electronically to simulate different operating conditions.

Hydraulic Power Units

A proportional flow valve can be integrated into a power unit when downstream equipment requires adjustable flow.

Smooth Speed Control Can Reduce Mechanical Shock

Sudden movement is not only a control-quality problem.

Rapid acceleration and deceleration can create mechanical shock in:

• Hydraulic cylinders
• Machine frames
• Couplings
• Workpieces
• Fixtures
• Hydraulic piping

By gradually increasing or reducing flow, a proportional valve can help create smoother actuator transitions.

For example:

0% Flow → 30% → 60% → 100%

can produce a gentler acceleration than immediately switching from zero to full flow.

Similarly, decreasing the flow command before the end of cylinder travel can help reduce impact.

This can improve both machine operation and component life.

What to Check When Replacing a 2FRE Valve

Providing only “2FRE” is not enough for accurate replacement.

The complete model should be checked.

Important parameters include:

• Nominal size
• Complete model number
• Component series
• Nominal flow
• Linear or progressive characteristic
• Pressure compensator configuration
• Check valve option
• Electrical connector
• Seal material
• Operating pressure
• Required system flow
• Mounting interface

For larger 2FRE10 and 2FRE16 versions, the pressure compensator and stroke-limiter configuration should also be checked according to the original model. Bosch Rexroth’s current size 10/16 selector distinguishes configurations with a pressure-compensator stroke limiter.

Information to Provide for a 2FRE Inquiry

For faster model confirmation, customers should ideally send:

• Complete 2FRE model
• Product photos
• Nameplate photo
• Hydraulic symbol
• Nominal size
• Rated flow
• System pressure
• Required actuator speed
• Existing electrical control information
• Mounting details
• Equipment application
• Required quantity

If the complete model cannot be read, clear photographs of the valve from multiple sides can help identify the configuration.

For replacement projects, it is also useful to provide information about the hydraulic cylinder or motor being controlled.

Common Problems in Proportional Flow Control Systems

When actuator speed becomes unstable, the 2FRE itself is not always the only possible cause.

Possible problems include:

• Contaminated hydraulic oil
• Incorrect electronic input
• Amplifier problems
• Pressure-compensator sticking
• Valve spool contamination
• Incorrect valve sizing
• Pump flow instability
• Excessive system pressure fluctuation
• Cylinder internal leakage
• Hydraulic motor wear

Typical symptoms may include:

• Cylinder speed changing under load
• Jerky motion
• Poor low-speed control
• Valve not responding smoothly
• Maximum speed too low
• Excessive pressure drop
• Hydraulic system overheating

The hydraulic circuit and electrical control should therefore be checked together before replacing the valve.

Hydraulic Oil Cleanliness Matters for 2FRE Performance

Proportional flow valves depend on accurate movement of internal metering and compensation components.

Contamination can interfere with these parts.

Possible consequences include:

• Unstable flow
• Pressure-compensator sticking
• Poor repeatability
• Slow response
• Internal wear
• Premature valve failure

Before installing a replacement 2FRE valve, technicians should check:

• Hydraulic oil cleanliness
• Filters
• Manifold surfaces
• Hoses and piping
• Hydraulic tank condition

A new proportional valve should not be installed into a system with unresolved contamination problems.

How XYIYEYA Supports 2FRE Valve Selection

XYIYEYA supplies proportional hydraulic valves and flow-control products for industrial equipment, maintenance and replacement applications.

Our related products include:

• 2FRE proportional flow valves
• 2FRM flow-control valves
• Z2FS modular flow-control valves
• 4WRA proportional directional valves
• 4WRAE proportional valves
• 4WRZ proportional directional valves
• Proportional pressure valves
• Other hydraulic flow-control products

Customers can send the original model, valve photos, nameplate, hydraulic symbol and operating requirements.

For a 2FRE replacement, we recommend confirming:

Valve Size + Rated Flow + Flow Characteristic + Pressure Compensator Configuration + Check Valve Option + Electrical Specification + Mounting Interface

This helps reduce both hydraulic performance and installation compatibility problems.

Conclusion

The 2FRE proportional flow valve provides electronically adjustable, pressure-compensated flow control for industrial hydraulic systems.

By regulating hydraulic flow according to an electrical command, it can help control the speed of cylinders and hydraulic motors more smoothly than a fixed manual flow-control valve.

The 2FRE family covers different application ranges, from compact size 6 versions up to larger size 10 and 16 valves for higher-flow industrial systems. Current Bosch Rexroth configurations extend from a maximum of 25 L/min for 2FRE6 to as much as 160 L/min for the larger family.

Main benefits include:

• Proportional flow regulation
• Smooth actuator speed adjustment
• Pressure-compensated control
• Programmable machine speed
• Better low-speed control
• Reduced mechanical shock
• Flexible automation integration

However, accurate replacement requires more than identifying the basic 2FRE series.

The following should all be confirmed:

Complete Model + Valve Size + Rated Flow + Flow Characteristic + Pressure Compensator + Check Valve Option + Electrical Configuration + Mounting Interface

Correct selection helps achieve smooth, stable and repeatable hydraulic actuator speed control.