FAQ:

1. What is DRS control, and how does it work?

DRS​ is a combined pressure-flow control​ with load sensing (LS).

• Pressure Control: Limits system pressure to a set maximum (like a DR control).

• Flow Control (LS): The pump automatically adjusts its swashplate angle to deliver only the flow required by the actuators, maintaining a constant pressure differential (Δp) across the control orifice. This results in significant energy savings​ compared to constant flow pumps.

2. Can I mount an additional pump on the back?

Yes.​ The code VPB22U​ indicates this pump has a through-drive shaft​ (through-drive). You can mount a second pump (e.g., a gear pump for pilot flow or a second circuit) directly onto the back flange of this unit.

3. What are the critical installation precautions?

• Case Drain (L port): Must be connected separately to tank​ with minimal backpressure (max 2–3 bar). Do not tee it into the main return line. This is critical for flushing heat and preventing seal/bearing failure.

• Suction Conditions: Ensure inlet pressure at port S is ≥ -0.8 bar​ (absolute) to avoid cavitation. Use short, large-diameter suction lines.

• Rotation: Confirm motor rotation matches the pump's "R" (clockwise) designation. Running backwards can destroy the pump.

4. Why is my pump noisy or overheating?

• Noise: Usually caused by cavitation. Check suction filter, inlet line for leaks, or oil viscosity being too high at startup.

• Overheating: Often due to excessive case pressure​ (blocked or undersized case drain line) or operating for long periods at high pressure with small displacement (high power loss).

5. How do I adjust the pressure setting?

The DRS control has a pressure limiter screw (usually under a cap on the control housing). Always adjust under controlled conditions with a pressure gauge:

1. Loosen the locknut.

2. Turn the screw clockwise to increase​ pressure, counterclockwise to decrease.

3. Tighten the locknut and re-check the setting.

6. Is an external relief valve still needed?

Yes.​ While the DRS control limits pressure, it is not a safety valve. You must install a separate system relief valve​ (e.g., a DB/DBW type) in the main line as a safety backup against control failure.

7. What is the difference between DR and DRS?

• DR: Only pressure control (constant pressure variable pump).

• DRS: Pressure control + Load Sensing. DRS adds the ability to match flow to demand, which is more energy-efficient for systems with varying flow requirements.

Disclaimer:​ For precise installation and commissioning, always refer to the official Rexroth technical data sheet RE 25700​ for A10VSO Series 32 pumps.