DBDH8G10B/25/2 DBDH6K18/315 Rexroth Pressure Relief Valve 630 bar

Product Overview

The DBDH series direct-acting pressure relief valves are high-performance pressure limiting valves engineered by Bosch Rexroth for industrial hydraulic systems, widely used for system pressure limitation and overload protection. Featuring a direct-acting ball poppet or cone poppet design, these valves balance system pressure directly against spring force, opening rapidly for relief when the set pressure is reached to provide precise system overload protection. The DBDH series is also type-examination tested according to Pressure Equipment Directive 2014/68/EU and is approved for use as safety valves.

The DBDH series covers sizes from NG6 to NG30, supporting both screw-in cartridge and inline (threaded connection) mounting configurations. Valve bodies are manufactured from high-strength materials with hardened and precision-ground internal components, offering fast response, high pressure regulation accuracy, and excellent sealing performance. The full series supports maximum operating pressures up to 630 bar with maximum flow rates up to 350 L/min.

Our complete range of Rexroth DBDH pressure valves strictly adheres to OEM technical standards, achieving 100% direct interchangeability with original components. Every unit undergoes 100% simulated operating condition bench testing prior to shipment, ensuring performance parameters are fully consistent with genuine Rexroth products. Direct replacement of same-model Rexroth valves significantly reduces equipment downtime and maintenance costs.

⚠️ Model Attribution Note: “DBDH” in the original title is the generic series code for Rexroth direct-operated pressure relief valves. DBDH8G10B/25/2 is an NG8 screw-in cartridge model; DBDH6K18/315 is an NG6 inline-mounted model. Although HYDAC also uses the DBDH series naming convention, publicly available data for specific models such as DBDH8G/DBDH6K clearly points to the Rexroth brand.

⚠️ Model Code Decoding (using DBDH8G10B/25/2 as example) :

• DBDH = Direct-Operated Pressure Relief Valve

• 8 = Nominal size NG8

• G = Screw-in cartridge type

• 10B = Component series / design code

• 25 = Set pressure (25 bar)

• 2 = Seal material / design variant code

Model Code Decoding (using DBDH6K18/315 as example) :

• DBDH = Direct-Operated Pressure Relief Valve

• 6 = Nominal size NG6

• K = Inline mounting (threaded connection)

• 18 = Design series

• 315 = Set pressure (315 bar)

Technical Specifications 

DBDH8G10B/25/2

• Product Series: Bosch Rexroth DBDH series direct-acting pressure relief valve

• Model Code: DBDH8G10B/25/2

• Brand: Rexroth

• Product Type: Direct-acting pressure relief valve (safety valve)

• Nominal Size: NG8 (Size 8)

• Mounting Type: Screw-in cartridge

• Set Pressure: 25 bar

• Maximum Operating Pressure: 630 bar

• Maximum Flow Rate: 120 L/min

• Poppet Type: Ball poppet / cone poppet

• Sealing Material: NBR (standard)

• Operating Fluid: Mineral oil-based hydraulic fluids

• Installation Torque: Refer to Rexroth technical manual

DBDH6K18/315 (R900424201)

• Product Series: Bosch Rexroth DBDH series direct-acting pressure relief valve

• Model Code: DBDH6K18/315

• Material Number (MPN) : R900424201

• Brand: Rexroth

• Product Type: Direct-acting pressure relief valve (safety valve)

• Nominal Size: NG6 (Size 6)

• Mounting Type: Inline mounting (threaded connection)

• Set Pressure: 315 bar

• Maximum Operating Pressure: 315 bar

• Maximum Flow Rate: 50 L/min (size dependent)

• Connection Thread: G1/4″

• Valve Body Material: Cast iron

• Operating Fluid: Oil

• Media Temperature: Up to 40°C

• Operating Pressure Differential: 0 – 350 bar

• Weight: Approx. 1.6 kg

DBDH Series General Specifications (NG6 – NG30)

• Product Series: Bosch Rexroth DBDH series direct-acting pressure relief valve

• Size Range: NG6 to NG30

• Component Series: 1X

• Maximum Operating Pressure: 630 bar (ball seat design, NG10 only)/ 400 bar

• Maximum Flow Rate: 350 L/min

• Poppet Type: Ball poppet or cone poppet

• Sealing Material: NBR / FKM (optional)

• Design Standard: Pressure Equipment Directive 2014/68/EU

Key Technical Advantages

1. Direct-Acting Design for Fast and Reliable Response
The DBDH series employs a direct-acting design where system pressure acts directly on the poppet, overcoming spring force to initiate relief. Compared to pilot-operated relief valves, the direct-acting design delivers significantly faster response—opening for relief instantaneously upon pressure overshoot to provide the fastest possible overload protection. Additionally, the direct-acting design does not rely on pilot oil circuits, maintaining reliable opening characteristics even during severe system pressure fluctuations.

2. Ultra-High Pressure Rating for the Most Demanding Applications
The full series supports maximum operating pressures up to 630 bar. NG10 models with ball seat construction can withstand 630 bar extreme pressures. This pressure rating positions the DBDH series among the highest-rated direct-acting relief valves available, making it particularly suitable for ultra-high-pressure hydraulic systems, heavy machinery, and extreme-duty applications.

3. Ball/Cone Poppet Design for Superior Sealing Performance
The ball poppet or cone poppet hard-sealing design delivers extremely low internal leakage in the closed position. Compared to spool-type designs, the ball/cone poppet configuration maintains excellent sealing performance even after extended service, making it particularly suitable for applications requiring long-term pressure holding (such as accumulator circuits and clamping circuits).

4. PED-Compliant Design for Safety Valve Applications
The DBDH series is type-examination tested according to Pressure Equipment Directive 2014/68/EU and is approved for use not only as a conventional relief valve but also as a safety valve. This certification makes it particularly suitable for pressure vessels, boilers, power generation equipment, and other applications with strict regulatory safety requirements.

5. Multiple Sizes and Mounting Configurations for Flexible Integration
The DBDH series covers NG6 to NG30 sizes, supporting both screw-in cartridge and inline (threaded connection) mounting configurations. Inline models offer G1/4″ to G1″ thread options, while cartridge models can be integrated directly into manifold blocks, accommodating diverse system design requirements.

6. 100% Direct Interchangeability and Simulated Condition Testing
All models strictly adhere to Rexroth original mounting dimensions and interface standards, enabling direct drop-in replacement of original valves without piping modification or system adjustment. Every unit undergoes 100% simulated operating condition bench testing prior to shipment, ensuring consistent, stable performance at rated pressure and flow.

Application Areas

• Ultra-High-Pressure Hydraulic Systems: Overload protection for presses and hydraulic tools

• Heavy Construction Machinery: Pressure limitation for excavators, large wheel loaders, mining equipment

• Pressure Vessels and Boilers: Regulatory-compliant overpressure protection as safety valves

• Accumulator Circuits: Long-term pressure holding with superior sealing performance

• Hydraulic Clamping Systems: Clamping force protection for machine tools and workholding fixtures

• Wind Power: Pressure protection for hydraulic pitch control and brake systems

• Metallurgical Equipment: Overload protection for rolling mills and continuous casting equipment

• Test Equipment: Pressure limitation and safety protection for hydraulic test benches

Expert Maintenance Tips

1. Verify Model Compatibility Prior to Installation
Confirm that the valve model matches system requirements—pay special attention to: nominal size (NG6/NG8/NG10/NG20/NG30), set pressure range, and mounting type (cartridge cavity dimensions for screw-in types; thread specifications for inline types). Note that maximum flow rates vary significantly across DBDH sizes (NG6 approx. 50 L/min, NG20 up to 250 L/min)—ensure selected flow capacity meets system requirements.

2. Inline Mounting Precautions
For inline models (e.g., DBDH6K18/315) with threaded connections, use appropriate sealing materials (PTFE tape or thread sealant)—apply sparingly to prevent sealing material from entering the valve body and affecting poppet movement. Tighten to torque values specified in Rexroth technical manuals to avoid body distortion or thread damage from over-tightening.

3. Cartridge Mounting Precautions
For screw-in cartridge models (e.g., DBDH8G10B/25/2), ensure the cavity is clean, free of burrs, and free of metal debris prior to installation. Use proper tools for installation and torque to specified values. Never use impact or hammering methods during installation, as this may damage internal poppet components or springs.

4. System Cleanliness Management
The DBDH series features tight poppet clearances and demands high oil cleanliness. Recommended system cleanliness: ISO 4406 Class 19/17/14 or higher. Thoroughly flush system piping prior to installation. Install high-precision filters in the system return line and inspect filter elements regularly.

5. Pressure Setting and Commissioning
Factory set pressure is nominal—recalibrate on-site according to actual system requirements. During commissioning, start from low pressure and gradually increase to the set value while monitoring pressure gauge response for smooth operation. As a direct-acting relief valve, rotate the adjustment mechanism slowly to avoid pressure shock.

6. Periodic Functional Checks and Safety Valve Certification
If the valve is used as a safety valve, periodic functional verification is required in accordance with Pressure Equipment Directive 2014/68/EU and applicable national regulations. Perform opening pressure verification and seal integrity testing every 12 months or as required by regulations. If set pressure drift, abnormal leakage, or sluggish response is observed, arrange for servicing or replacement.