Product Overview

The Bosch Rexroth DB10, DB20 and DB30 are pilot-operated pressure relief valves designed to limit hydraulic system operating pressure.

The latest verified Rexroth technical documentation, RE 25802, Edition 2024-12, covers DB and DBW pressure relief valves in component series 5X, sizes 10 to 32, with maximum operating pressure up to 350 bar and maximum flow up to 650 L/min.

The DB valve consists essentially of a main valve with main spool insert and a pilot control valve with pressure adjustment element.

When pressure at port P rises above the pilot-stage setting, the pilot valve opens and generates a pressure differential across the main spool. The main connection from P to T then opens, allowing excess hydraulic fluid to return to tank while limiting system pressure.

Technical Specifications

DB20

• Manufacturer: Bosch Rexroth
• Product Type: Pilot-operated pressure relief valve
• Series: DB
• Component Series: 5X
• Size Code: 20
• Nominal Size: NG25
• Mounting: Subplate or threaded connection depending on ordering code
• Porting Pattern: ISO 6264-08-13-*-97 for NG25 subplate mounting
• Maximum Operating Pressure, Port P: 350 bar
• Maximum Operating Pressure, Port X: 350 bar
• Maximum Operating Pressure, Port T: 315 bar
• Maximum Operating Pressure, Port Y: 315 bar
• Maximum Set Pressure: 50 / 100 / 200 / 315 / 350 bar, depending on configuration
• Maximum Flow, Subplate Mounting: 500 L/min
• Maximum Flow, Threaded Connection: 500 L/min
• Minimum Set Pressure: Flow-dependent
• Viscosity Range: 10–800 mm²/s
• Maximum Hydraulic Contamination: ISO 4406 Class 20/18/15
• Installation Position: Any
• Ambient Temperature, NBR: −20 to +80 °C
• Ambient Temperature, FKM: −15 to +80 °C
• Mass, DB Subplate Version: 3.5 kg
• Pilot Control: Hydraulic
• Adjustment Options: Multiple configurations according to ordering code
• Seal Options: NBR / FKM
• Pump Displacement: Not applicable
• Pump Rated Pressure: Not applicable
• Pump Peak Pressure: Not applicable
• Maximum Pump Speed: Not applicable

DB10

• Nominal Size: NG10
• Size Code: 10
• Maximum Operating Pressure P/X: 350 bar
• Maximum Operating Pressure T/Y: 315 bar
• Maximum Set Pressure: Up to 350 bar
• Maximum Flow, Subplate Mounting: 250 L/min
• Mass, DB Subplate Version: 2.6 kg
• Porting Pattern: ISO 6264-06-09-*-97
• Example OEM Configuration: DB10-2-5X/350

Bosch Rexroth’s current product page identifies DB10-2-5X/350 as a Size 10 P→T pressure relief valve with hydraulic actuation.

DB30

• Nominal Size: NG32
• Size Code: 30
• Maximum Operating Pressure P/X: 350 bar
• Maximum Operating Pressure T/Y: 315 bar
• Maximum Set Pressure: Up to 350 bar
• Maximum Flow, Subplate Mounting: 650 L/min
• Maximum Flow, Threaded Connection: 650 L/min
• Mass, DB Subplate Version: 4.4 kg
• Porting Pattern: ISO 6264-10-17-*-97
• Main Spool: Ø24 mm standard; Ø28 mm option for NG32
• Control Method: Pilot-operated hydraulic pressure control

Key Technical Advantages

1. Pilot-Operated High-Flow Pressure Relief

The DB design uses a pilot stage to control the main spool.

This architecture allows the same basic operating principle to cover:

• DB10 — 250 L/min
• DB20 — 500 L/min
• DB30 — 650 L/min

making the series suitable for medium- and high-flow industrial hydraulic circuits.

2. Multi-Range Pressure Limitation

The DB 5X series provides maximum setting ranges of:

• 50 bar
• 100 bar
• 200 bar
• 315 bar
• 350 bar

This allows the valve to be selected according to the target system pressure rather than simply applying a maximum-rated configuration.

3. Efficient Main-Spool Control

The operating sequence is:

System Pressure → Pilot Valve → Pressure Differential → Main Spool → P-to-T Relief Flow

The pilot stage therefore controls the main pressure-relief path without requiring a large direct-acting spring mechanism to handle the entire system flow.

4. Flexible Pilot Routing

The DB ordering system provides:

• Internal pilot supply / internal return
• External pilot supply / internal return
• Internal pilot supply / external return
• External pilot supply / external return

This enables integration into different hydraulic circuit architectures.

5. Multiple Pressure-Adjustment Options

Depending on the ordering code, DB valves can use:

• Rotary knob
• Protective adjustment sleeve
• Lockable rotary knob with scale
• Rotary knob with scale

This supports both general industrial service and applications where the pressure setting must be protected against accidental adjustment.

6. Subplate and Threaded Installation

DB Series valves are available in subplate-mounted and threaded configurations, allowing integration into hydraulic manifolds as well as standalone hydraulic assemblies.

7. Corrosion-Protected Design

The current Rexroth 2024-12 technical documentation lists corrosion-protected design as a DB/DBW feature.

Specific corrosion-resistance levels should still be verified from the complete ordering code rather than assumed from the DB family name alone.

Engineering Materials and Manufacturing

Rexroth does not provide complete public material certificates for every internal component of DB20 in the reviewed documentation, so specific alloy grades or heat-treatment values should not be invented.

For a pilot-operated pressure relief valve, the key manufacturing factors include:

Main Spool Precision

Spool geometry, roundness, alignment and spool-to-bore clearance influence leakage and response stability.

Pilot Valve Seat

The pilot valve determines when the main spool begins to unload. Seat contamination or wear can shift the actual response pressure.

Nozzle and Control Orifices

The internal nozzles generate the pressure differential required to move the main spool, making their geometry and cleanliness critical.

Seal Integrity

The 5X series supports NBR and FKM seal configurations. Actual seal selection must match the hydraulic fluid and temperature range.

Application Areas

Typical applications include:

• Hydraulic power units
• Machine tools
• Hydraulic presses
• Metal-forming equipment
• Steel processing systems
• Industrial automation
• Material-handling equipment
• Hydraulic test rigs
• Heavy industrial machinery
• Pump outlet pressure protection
• Centralized hydraulic systems

DB30 is particularly suitable for large-flow circuits because its subplate configuration is rated for up to 650 L/min.

DB10 vs DB20 vs DB30

DB10

NG10 / 250 L/min maximum subplate flow

Suitable for smaller industrial hydraulic circuits.

DB20

NG25 / 500 L/min maximum subplate flow

A strong choice for medium-to-large hydraulic systems.

DB30

NG32 / 650 L/min maximum subplate flow

Designed for larger high-flow hydraulic circuits.

The key point is that DB20 corresponds to NG25, not NG20.

Expert Maintenance Tips

1. Check the Pilot Stage Before Replacing the Complete Valve

A recommended troubleshooting sequence is:

Port P Pressure → Pilot Pressure → Pilot Valve → Main Spool → Tank Pressure

This helps distinguish pilot-stage problems from main-spool or system-pressure problems.

2. Account for T-Port Back Pressure

Rexroth specifies that hydraulic back pressure can add to the response pressure.

For example:

Pilot Spring Setting = 200 bar

plus:

T-Port Back Pressure = 50 bar

can result in:

Response Pressure = 250 bar

Therefore, spring adjustment pressure and actual system relief response pressure are not necessarily the same.

3. Maintain Hydraulic Cleanliness

Rexroth specifies a maximum hydraulic contamination level of:

ISO 4406 Class 20/18/15

Effective filtration helps protect:

• Pilot seat
• Nozzles
• Control passages
• Main spool
• Sealing surfaces

4. Use the Correct Mounting-Screw Torque

Typical Rexroth mounting requirements are:

• DB10: approximately 75 Nm ±10%
• DB20: approximately 185 Nm ±10%
• DB30: approximately 248 Nm ±10%

These values apply to the specified mounting screws and should not be confused with adjustment or internal valve torque.

5. Verify the Pilot-Routing Configuration

Before commissioning a valve with X, Y or XY pilot routing, confirm the actual pilot supply and pilot return connections.

Incorrect pilot routing can prevent the valve from reaching the intended pressure response.

6. Verify the Pressure Setting Dynamically

A complete commissioning sequence should include:

No-Load Pressure → Progressive Pressure Increase → Relief Opening → Full-Flow Relief → Reseating → Back-Pressure Verification

This is more reliable than checking the adjustment screw position alone.

7. Recommended Replacement Validation

For aftermarket DB-series replacement, the recommended sequence is:

Model Verification → Mounting Verification → Port Verification → Pressure-Rating Verification → Pilot-Routing Verification → Seal Verification → Pressure Setting Test → Flow Test → Leakage Test → Dynamic Relief Test → Full Working-Condition Simulation

This provides a solid engineering basis for in-place interchangeability.

Your company’s 100% simulated working-condition testing can then be presented as an aftermarket quality-control advantage, provided it is clearly identified as your own validation process rather than a Bosch Rexroth OEM claim.