Bosch Rexroth DBW Pilot-Operated Pressure Relief Valve

Overview

The Bosch Rexroth DBW is a pilot-operated pressure relief valve with an attached solenoid directional valve, used to limit the operating pressure of a hydraulic system and to unload it electrically. It belongs to the Rexroth DB and DBW family, component series 5X, documented in data sheet RE 25802. The DB version limits pressure only, while the DBW version adds solenoid-actuated unloading, which lets a pump start against an open relief path and run without load between machine cycles. Sizes 10, 16, 25 and 32 are available for subplate mounting or threaded connection, with a maximum operating pressure of 350 bar and flows up to 650 l/min.

Seven Star LLC supplies the Bosch Rexroth DBW and the plain DB version to hydraulic system builders, maintenance departments and contractors in the Sultanate of Oman and the GCC. Main pressure relief and unloading valves of this type are found on almost every medium and large hydraulic power unit, so they are frequent replacement items for plants in Sohar, Duqm and Salalah and for service companies in Muscat. With engineering support in Muscat, we help match the size, pressure rating, solenoid voltage and connection type to the valve already installed.

Operating Principle

A Bosch Rexroth DBW consists of a main valve with a main spool insert, a pilot control valve with pressure adjustment element and, on top, a directional valve. System pressure in channel P acts on the main spool and, through control lines fitted with nozzles, on the spring-loaded side of the main spool and on the ball of the pilot valve. When the pressure in P exceeds the value set on the pilot spring, the ball lifts, a small pilot flow passes to the tank, and the nozzles create a pressure drop across the main spool. The main spool then opens the connection from P to T and the excess flow returns to tank while the set operating pressure is maintained. Remote unloading or a second pressure stage is possible through port X.

The DBW function is the same, except that the spring chamber of the main spool can be relieved to tank by switching the attached directional valve. Depending on the ordering code (directional valve normally closed, A, or normally open, B), the Bosch Rexroth DBW unloads when the solenoid is energised or when it is de-energised, so the circuit can be designed to fail to an unloaded state or to a pressurised state. An optional switching shock damping plate (version S with nozzle R12) between pilot valve and directional valve reduces pressure peaks and decompression noise when the valve switches. Because only a small pilot flow controls a large main flow, the Bosch Rexroth DBW offers a flat pressure-flow characteristic at high flow rates.

Engineering Design of the Bosch Rexroth DBW

For subplate mounting the Bosch Rexroth DBW follows the porting patterns of ISO 6264-06-09 for size 10, ISO 6264-08-13 for size 25 and ISO 6264-10-17 for size 32. Threaded versions with G1/2, G3/4, G1, G1 1/4 and G1 1/2 connections cover sizes 10 to 32 for in-line installation. Pilot control valves without main spool insert are also offered as cartridge or subplate-mounted pilot stages. The pressure can be adjusted with a rotary knob or other adjustment types, and five pressure ratings are listed, with maximum set pressures of 50, 100, 200, 315 and 350 bar.

The attached directional valve of the Bosch Rexroth DBW can be a directional spool valve to data sheet RE 23178 (version 6E) or a directional seat valve to data sheet RE 22058 (version 6SM), with high-power solenoids and optional UL-recognised coils. Options include a valve for minimum cracking pressure, FKM seals, improved corrosion protection J3 and type-examination tested safety valve versions according to the Pressure Equipment Directive 2014/68/EU. Weight for subplate versions is 4.05 kg for size 10, 4.95 kg for size 25 and 5.85 kg for size 32.

Key Features

The main features of the Bosch Rexroth DBW and DB series 5X are listed below from the manufacturer data sheet.

• Pilot-operated design limits the system pressure precisely while passing high flow with a small pilot stage.
• The DBW version provides solenoid-actuated unloading via an attached directional spool or seat valve.
• Sizes 10, 16, 25 and 32 are available for subplate mounting to ISO 6264 or for threaded connection.
• Maximum operating pressure is 350 bar at ports P and X, with five pressure ratings up to 350 bar.
• Maximum flow reaches 250 l/min for size 10, 500 l/min for size 25 and 650 l/min for size 32.
• Optional switching shock damping reduces pressure peaks and acoustic decompression shocks.
• Remote pressure adjustment or unloading is possible through port X.
• Versions tested as safety valves to the Pressure Equipment Directive and with corrosion protection are offered.

Industrial Applications

Typical uses of the Bosch Rexroth DBW include main pressure relief and pump unloading on hydraulic power units for presses, injection moulding and die-casting machines, steel and aluminium plant equipment, cranes and winches, and the large hydraulic packs that serve valve actuators and wellhead control systems in Oman’s oil and gas fields. Unloading the pump at start-up and during idle periods reduces motor starting current, oil heating and wear, which matters in hot climates where oil temperature directly affects component life.

Seven Star LLC supplies the Bosch Rexroth DBW together with related Rexroth products such as the Rexroth DB10G2-5X/50 pressure relief valve, the Bosch Rexroth MHDBD10K2-1X/315V pressure relief valve and the Bosch Rexroth A10VSO axial piston variable pump. The data sheet calls for a maximum contamination level of class 20/18/15 to ISO 4406 (c), and our team in Muscat can supply matching filter elements for the same power unit across Oman and the GCC.

Technical Specifications

The following Bosch Rexroth DBW and DB data come from data sheet RE 25802 (edition 2021-10) for component series 5X.

How to Order

To source a Bosch Rexroth DBW or DB valve, send Seven Star LLC the type code from the nameplate, or tell us the size, mounting, pressure rating, solenoid voltage and whether unloading should occur energised or de-energised. Our hydraulics team in Muscat will confirm the variant, provide the technical datasheet for download and return a formal quotation. Seven Star LLC supplies Rexroth valves to customers in Oman and the GCC with engineering support.