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Product Positioning
The DBW30 Solenoid Pilot Relief Valve NG30 650 L/min 35 MPa is the largest size in the DBW series. It combines a pilot-operated relief valve with a built-in solenoid directional valve. The relief function sets a maximum system pressure. The solenoid provides on-command unloading.
This page is written for system designers who are working with high-flow hydraulic circuits - presses, large power units, and heavy industrial machinery - where 650 L/min flow capacity is a practical requirement rather than an oversizing choice.
Key Specifications (Size 30 / NG30)
| Parameter | Value |
|---|---|
| Size | NG30 |
| Max Flow | 650 L/min |
| Max Working Pressure | 35 MPa |
| Adjustment | Knob / hexagon socket with protective cap / lockable knob with scale |
| Mounting Standard | DIN 24340 form E / ISO 6264 / CETOP-RP 121H |
| Voltage | DC12V/24V, AC110V/220V |
Products Description
System Matching at High Flow
The DBW30 Solenoid Pilot Relief Valve is rated at 650 L/min. That flow class is not a casual choice. At this level, the valve becomes a central component in the system, and several design factors become more critical than they are at smaller sizes.
Line size and flow velocity. At 650 L/min, the flow velocity inside the piping rises noticeably. If the lines are undersized, pressure loss through the piping increases, which can lead to heat generation and noise. When planning the piping, size the inside diameter according to the system's maximum flow, and leave some pressure margin for line losses. That means the relief valve setting needs to be higher than the pressure required by the actuators to compensate for line losses.
Back pressure and unloading performance. The Y port on the DBW30 allows a certain amount of back pressure. But in high-flow systems, the return line itself may develop back pressure due to pipe size or length. If the back pressure approaches the upper limit allowed at the Y port, the pilot stage may unload erratically. At the system design stage, confirm the back pressure range in the return line and make sure it stays within the valve's allowance.
Stability of the pilot control oil. The pressure setting accuracy of a pilot-operated relief valve depends on stable pilot pressure. In a high-flow system, opening and closing the main valve can cause system pressure fluctuations. If the damping orifice size does not match the pressure fluctuation characteristics of the system, pressure oscillation may occur. The design number 5X indicates the internal design version. The damping orifice configuration is part of that design. If the system has unusual pressure fluctuation characteristics, confirm with the supplier whether alternative damping options are available.
Commissioning Notes for High-Flow Systems
Commissioning a relief valve in a 650 L/min system is different from doing it in a smaller system. The main reason is that pressure changes faster at high flow, and the valve is expected to respond more quickly.
Bleeding. If air remains in the pilot cavity of a pilot-operated relief valve, pressure becomes unstable and vibration can occur. Before starting the system, bleed the pilot cavity. If an air bleed screw is provided, open it, raise pressure slowly, and close it once air is expelled. This step is especially important in high-flow systems because air has a more noticeable effect on pressure stability under high-pressure, high-flow conditions.
Pressure setting. Back the adjustment knob all the way out (lowest pressure). Start the system and let it run at no load. Confirm there is no leakage and no abnormal noise. Then slowly turn the knob in while watching the pressure gauge. Set it to the working pressure and tighten the lock nut. In high-flow systems, raise pressure more slowly than you would in a smaller system so you can watch whether the pressure stays smooth.
Electrical wiring check. Confirm that the solenoid voltage matches the system control voltage. The DBW30 supports DC12V/24V and AC110V/220V. After wiring, energize the solenoid and test the unloading function.
Common Faults and Troubleshooting
System pressure will not build, or is too low. Possible causes include the pilot valve set too low, a stuck pilot valve, a stuck main spool, or a blocked damping orifice. First check whether the adjustment knob has been accidentally backed out. Then check the pilot valve and main spool for contamination.
Pressure fluctuation or oscillation. In high-flow systems, pressure fluctuation can have several causes. Air in the pilot cavity, a partially blocked damping orifice, poor seating between the poppet and seat, or oil contamination affecting damping. Bleed the system first, then check oil cleanliness, then inspect the pilot valve components.
No unloading response. If system pressure does not drop when the solenoid is energized, check whether the solenoid is receiving power, whether the coil is damaged, and whether the pilot spool is stuck. In high-flow systems, pilot spool sticking can be caused by fine particles in the oil. Check the system filtration rating.
External leakage. Check whether the mounting surface is flat and clean, whether bolt torque is even, and whether O-rings are damaged. High-flow valves have larger mounting faces, and uneven bolt torque is more likely to cause leakage.
Selection Boundaries
The DBW30 is suitable for hydraulic systems with a flow up to 650 L/min and a working pressure up to 35 MPa. If the system flow is below 250 L/min, consider a smaller size in the same series. If the system flow exceeds 650 L/min, a larger size or a parallel valve arrangement is required.
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