Bosch Rexroth A10VSO28 open circuit variable hydraulic pump

The A10VSO28 is a variable displacement axial piston pump built on a swash plate design, intended for open circuit hydraulic systems. "Open circuit" means the pump draws fluid from a reservoir, sends it through the system to do work, and returns it to that same reservoir — as opposed to a closed circuit, where fluid flows in a continuous loop directly between pump and motor. Open circuit is the standard architecture for most industrial machine tools, injection molding presses, cranes, and general mobile equipment.

How the A10VSO28 Works

Axial Piston, Swash Plate Architecture

Inside the housing, a cylinder barrel holds a set of pistons arranged parallel to the drive shaft — hence "axial piston." As the shaft rotates, the pistons ride against an angled swash plate. That angle forces each piston to move in and out of its bore as the barrel spins, drawing fluid in on one side of the stroke and pushing it out under pressure on the other.

Change the angle of the swash plate, and you change how far each piston travels — which directly changes the volume of fluid displaced per revolution. Tilt it to zero and the pump produces no net flow even while the shaft keeps turning. This is what makes the A10VSO28 a true variable displacement unit rather than a fixed one.

Control Options

The letters that follow "28" in the model code identify which control the pump uses to move that swash plate. The most common variants include:

DR – Pressure controller (pressure compensator). Holds outlet pressure at a set value by reducing displacement as pressure rises.

DFR1 – Pressure and flow controller. Combines pressure limiting with load-sensing style flow control, useful where multiple actuators share one pump.

FR – Flow controller only.

EO / EP – Electric proportional control, allowing displacement to be commanded electronically rather than hydro-mechanically — common in systems with a PLC or motion controller in the loop.

Choosing the right control isn't optional trivia — it changes how the machine behaves under load, so it has to match the original design intent, not just the displacement size.

Installation and Maintenance Notes

A few points come up repeatedly in the field:

Mounting orientation matters. Rexroth publishes specific installation positions (some units are designed for below-reservoir mounting, fully submerged in the tank). Installing outside the approved orientation can starve the pump on startup.

Pilot/control fluid consumption is real flow. Pressure and flow controllers consume a small amount of control fluid (roughly 3–5.5 l/min depending on variant) that has to be accounted for in reservoir sizing and filtration, not just the main working flow.

Case drain matters for shaft seal life. Like all axial piston pumps, the A10VSO28 needs a functioning case drain line back to the reservoir, sized so case pressure stays within the shaft seal's rated limit.

Filtration is cheap insurance. Piston pumps have tight internal clearances between the pistons and cylinder bores; contamination is the single biggest cause of premature wear on this pump family.

Don't ignore the hysteresis spec. For pressure-controlled variants, static hysteresis is typically under 3 bar — if you see a pump hunting or overshooting well beyond that, it's usually a sign of a worn compensator spool or contaminated control oil, not a design flaw.

For more information on the A10VSO28 hydraulic pump, please visit https://www.baolilaihydraulic.com/product/.

Specifications

Selection Table

Q1: How is the A10VSO28 different from the A10VSO18 or A10VSO45?

A1: Purely displacement. The control logic, mounting philosophy, and general design are shared across the series; only the swept volume per revolution (and the physical size/torque capacity that comes with it) changes between sizes.

Q2: Does the A10VSO28 need a through-drive to run a second pump?

A2: Only if the application calls for a tandem pump setup. Many A10VSO28 units are ordered "without through drive" for single-pump applications; through-drive versions exist specifically for stacking a second pump on the same input shaft.

Q3: How to purchase an A10VSO28 hydraulic pump?

A3: You can visit https://www.baolilaihydraulic.com/contact/ to contact us and purchase our products through various methods.

Q4: What is the price and delivery time of the A10VSO28 hydraulic pump?

A4: The specific price and delivery time will be provided based on the specific model you provide.