Pressure Valves
Pressure relief valves, mechanical
- Selection criteria
- Frequently asked questions
- Pressure relief valves, proportional
- Pressure reducing valves, proportional
Mechanical pressure relief valves from Bosch Rexroth limit the system pressure to a spring-set value and return the excess flow to tank. Direct operated valves of the DBDS and DBDH series respond quickly and are used as screw-in or threaded valves, pilot operated valves of the DB and DBW series handle large flow rates at stable pressure. On the DBW a solenoid directional valve sits on the pilot stage and unloads the valve electrically.
Sandwich plate valves ZDB and Z2DB are mounted between subplate and directional valve and protect individual actuator ports, for example from A to T. The range extends up to NG 32 and 630 bar, for subplate mounting, with threaded ports, as screw-in cartridge or as sandwich plate, with NBR or FKM seals.
Narrow down the selection by actuation, seal material or threaded port.
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Buying guide
How to choose Pressure relief valves, mechanical
What matters when choosing: properties, comparison and typical applications.
Selection criteria
| Criterion | Options | What to look for |
|---|---|---|
| Operating principle | direct operated (DBDS, DBDH), pilot operated (DB, DBW) | Direct operated valves for smaller flows and short response time, pilot operated valves for large flows. |
| Design | subplate mounting, threaded port, screw-in cartridge, sandwich plate (ZDB, Z2DB) | Subplate mounting for manifolds with a hole pattern, threads for in-line mounting, sandwich plates to protect individual ports of a directional valve. |
| Pressure rating | up to 630 bar, coded in the type designation, e.g. /315 | The pressure rating is the highest adjustable pressure. Choose the next rating above the required setting. |
| Unloading | mechanical, electrical via 24 V DC solenoid (DBW) | With solenoid unloading the pump circulates at low pressure while the machine is idle. |
| Seal | NBR, FKM | NBR for mineral oil, FKM for higher temperatures and special fluids. |
Frequently asked questions
- What is the difference between direct and pilot operated relief valves?
- In a direct operated valve the spring acts directly on the closing element. It responds quickly but is limited to smaller flow rates. In a pilot operated valve a small pilot stage controls the main spool, so the pressure stays stable even at large flow rates.
- What is a sandwich plate pressure relief valve used for?
- ZDB and Z2DB are fitted between subplate and directional valve and limit the pressure in individual lines, for example from A to T, without additional piping. Z2DB contains two valves for both actuator ports.
- What does the solenoid on the DBW do?
- The mounted directional valve unloads the pilot stage. The system pressure then drops to a low circulation pressure and the pump delivers to tank without being switched off.