Product Overview

The Bosch Rexroth SV20PA1-4X/ is a hydraulically pilot-operated check valve / isolator valve from the SV/SL 4X family, designed for actuator load holding, hydraulic isolation and controlled unlocking.

The valve provides:

A → B: Free Flow

B → A: Pilot-Opened Flow

The SV configuration uses internal pilot-oil return, while the A version provides pre-opening to reduce pressure shock during decompression and unlocking. Bosch Rexroth identifies the valve as an NG20, subplate-mounted hydraulic check valve.

The complete model code can be interpreted as:

• SV: Pilot-operated isolator/check valve with internal pilot-oil return
• 20: NG20 nominal size
• P: Subplate mounting
• A: With pre-opening
• 1: Cracking-pressure version 1
• 4X: Component series 40–49

For NG20, cracking-pressure options are 2.5, 5, 7.5 and 10 bar, making the “1” configuration a 2.5 bar cracking-pressure version.

For OEM replacement and retrofit projects, the valve can be engineered for in-place interchangeability based on the original type code, mounting interface, pilot configuration and hydraulic operating conditions, with 100% simulated working-condition testing before shipment.

Technical Specifications

SV20PA1-4X/

• Manufacturer: Bosch Rexroth
• Product Type: Pilot Operated Check Valve / Isolator Valve
• Series: SV/SL 4X
• Model: SV20PA1-4X/
• Nominal Size: NG20
• Component Series: 4X
• Mounting: Subplate Mounting
• Connection: P
• Flow Direction: A → B free; B → A by pilot opening
• Actuation: Hydraulic
• Pilot Oil Return: Internal
• Pre-opening: Yes
• Cracking Pressure Version: 1
• Cracking Pressure: 2.5 bar
• Minimum Pilot Pressure: 5 bar
• Maximum Pilot Pressure: 315 bar
• Maximum Operating Pressure: 315 bar
• Maximum Flow: Determined from Bosch Rexroth characteristic curves
• Pilot Volume, Port X: 10.8 cm³
• Viscosity Range: 2.8–500 mm²/s
• Fluid Cleanliness: ISO 4406 Class 20/18/15
• Approx. Weight: 4.7 kg
• Installation Position: Any
• NBR Temperature Range: -30 to +80 °C
• FKM/FPM Temperature Range: -20 to +80 °C
• Porting Pattern: ISO 5781-08-10-0-00
• Mounting Screw: ISO 4762 M10 × 70 – 10.9
• Mounting Screw Torque: 75 Nm ±20%

Displacement and Maximum Speed

As a hydraulic valve rather than a pump or motor:

• Displacement: Not applicable
• Maximum Speed: Not applicable

Peak Pressure

The verified manufacturer parameter is:

Maximum Operating Pressure: 315 bar

No separate model-specific peak-pressure rating is assigned here without additional verified transient-pressure documentation.

SV10PA1-40B Verification

The model SV10PA1-40B is associated with the Bosch Rexroth SV hydraulic pilot-operated check-valve family, but its complete 40B coding could not be independently mapped to the current Bosch Rexroth 4X ordering system.

The currently documented SV10PA1-4X family specifies:

• Nominal Size: NG10
• Maximum Operating Pressure: 315 bar
• Cracking Pressure Options: 1.5 / 3 / 6 / 10 bar
• Minimum Pilot Pressure: 5 bar
• Maximum Pilot Pressure: 315 bar
• Flow Direction: A → B free; B → A by opening

Therefore, SV10PA1-40B should be treated as a legacy/model-verification-required designation, rather than automatically equated to a current 4X model.

SV20PA1-40B Verification

The SV20PA1-40B is also associated with the SV hydraulic pilot-operated check-valve family, but the exact meaning of its 40B suffix has not been sufficiently verified from current Bosch Rexroth technical documentation.

For the current SV20 4X family:

• Maximum Operating Pressure: 315 bar
• Minimum Pilot Pressure: 5 bar
• Maximum Pilot Pressure: 315 bar
• Cracking Pressure Options: 2.5 / 5 / 7.5 / 10 bar
• Flow Direction: A → B free; B → A by opening

The exact 40B configuration should therefore be confirmed from the original nameplate, legacy datasheet or material number before commercial specification.

Key Technical Advantages

1. Pre-Opening for Controlled Decompression

The A configuration incorporates pre-opening.

During pilot activation, the valve can initiate a controlled decompression process before opening the main seat, helping reduce switching shock, noise and excessive mechanical loading.

2. 315 Bar High-Pressure Capability

The SV/SL 4X series is rated up to:

315 bar / 31.5 MPa maximum operating pressure

This supports high-pressure industrial hydraulic circuits requiring reliable actuator isolation and load holding.

3. Seat-Poppet Architecture

The valve uses a combination of:

Seat Poppet + Compression Spring + Control Spool

to provide positive reverse-flow blocking and hydraulic pilot-controlled opening.

4. 2.5 Bar NG20 Cracking Pressure

For SV20PA1-4X/:

Version 1 = 2.5 bar cracking pressure

This configuration establishes the required differential pressure for free flow in the normal direction.

5. Internal Pilot-Oil Return

The SV configuration uses internal pilot-oil return.

This differs from the SL configuration and should be considered when designing or replacing the pilot circuit.

6. ISO-Standardized Subplate Mounting

The NG20 version uses:

ISO 5781-08-10-0-00

as its porting pattern, supporting standardized hydraulic manifold integration.

7. Reliable Long-Term Actuator Isolation

The SV/SL family is designed to isolate actuator ports during extended periods of inactivity, making it appropriate for load-holding and hydraulic locking circuits.

Application Areas

Typical applications include:

• Hydraulic Cylinder Load Holding
• Vertical Lifting Equipment
• Hydraulic Presses
• Injection Molding Machines
• Material Handling Equipment
• Machine Tools
• Hydraulic Clamping Systems
• Industrial Hydraulic Power Units
• Position-Holding Circuits
• Hydraulic Safety Locking Circuits
• Construction Machinery
• High-Pressure Hydraulic Manifolds

The SV20PA1-4X is especially suitable for applications combining high actuator loads, standstill position holding and controlled hydraulic release.

Expert Maintenance Tips

1. Verify A, B, X and Y Connections

Correct installation requires confirmation of:

• Port A
• Port B
• Pilot Port X
• Pilot/return Port Y

Pilot plumbing errors can prevent proper unlocking or produce unintended hydraulic behavior.

2. Do Not Replace Pre-Opening with Non-Pre-Opening Without Analysis

The difference between:

A = With Pre-opening

and:

B = Without Pre-opening

has direct dynamic consequences.

Rexroth documentation warns that valves without pre-opening can release stored pressure volume suddenly, potentially causing switching shock, noise and premature wear.

3. Match the Cracking Pressure

For NG20:

• Version 1 = 2.5 bar
• Version 2 = 5 bar
• Version 3 = 7.5 bar
• Version 4 = 10 bar

The complete configuration must therefore be verified during replacement.

4. Use the Specified Mounting Torque

For the NG20 subplate-mounted configuration, published installation data specifies:

M10 × 70 – 10.9 mounting screws

with:

75 Nm ±20% tightening torque.

5. Maintain Hydraulic Cleanliness

Bosch Rexroth specifies:

ISO 4406 Class 20/18/15

and a hydraulic-fluid viscosity range of:

2.8–500 mm²/s

Proper filtration reduces the risk of contamination-related control-spool movement problems and seat leakage.

6. Consider Pilot Volume in Dynamic Circuits

The NG20 valve has a 10.8 cm³ pilot volume at Port X.

Long pilot lines, restrictive fittings or additional throttling can affect pilot-pressure build-up and release response and should therefore be included in the hydraulic design.

7. Verify Legacy 40B Models Before Replacement

For:

SV10PA1-40B

and:

SV20PA1-40B

do not rely on the nominal size alone.

Recommended verification sequence:

Nameplate → Complete Type Code → Material Number → Original Revision → Mounting Interface → Pilot Circuit → Cracking Pressure

This is especially important because the current Bosch Rexroth catalog uses the 4X series designation, while the supplied 40B suffix has not been sufficiently documented as an identical current ordering code.