A4VSO Series Rotary Groups and Spare Parts
A4VSO and A4V rotary groups and spare parts in sizes 28 to 500, supplied as matched sets with cylinder block pistons valve plate and swash plate.
Product Overview
A4VSO is the variable displacement axial piston pump used on industrial power units, test benches and press circuits that run at high pressure for long hours. We machine the complete rotary group and every part inside it in sizes 28 through 500, plus the related A4V frames. The set is lapped and matched before packing so the block, shoes and valve plate bed in as one group rather than three separate parts.
| A4VSO | 28 40 50 56 71 90 125 180 250 355 500 |
|---|---|
| A4V | 40 56 71 90 125 180 250 355 500 |
Key Benefits
- Supplied as a matched set so the block, shoes and valve plate run in together
- Same envelope and spline as the original, so the pump goes back on the machine unchanged
- Available for frames the original maker has moved off its list
- Twelve month warranty on the same terms as a new original part
Application Scenarios
- Industrial power units on presses and forming machines
- Test benches and simulation rigs holding high pressure
- Steel mill and heavy plant hydraulics
- Marine deck machinery and offshore power packs
Who It Is For
- Pump rebuild shops working to a customer deadline
- Plant and fleet maintenance teams
- Distributors carrying rotary group stock for local machines
- Machine builders needing a second source
Problems It Solves
- The pump has lost pressure and a strip has found scored shoes and a worn block
- The original rotary group has a long lead time and the rig is out of service
- Individual parts sourced separately do not bed in and the pump fails again
- The machine is old but sound and a full pump replacement is not justified
Technical Features
- Cylinder block with sintered bronze running face bonded and machined after sintering
- Piston and shoe assemblies swaged and checked for shoe clearance
- Valve plate lapped to a mirror finish so the pair seals under pressure
- Retainer plate and ball guide matched to the block
- Splines and bearing seats ground after heat treatment
Specifications
Performance figures depend on the exact variant, so we confirm them against your model code rather than publishing a number that may not apply to your pump.
| Set contents | Cylinder block, pistons with shoes, retainer plate, ball guide, valve plate and spring set |
|---|---|
| Matching | Parts lapped and matched as one running set |
| Spline | To the original pattern, checked over pins |
| Marking | Neutral or your own part number on request |
| Packing | Oiled and vacuum sealed, boxed per set |
| Performance data | Confirmed against the full model code on your unit before quotation |
Materials
| Cylinder blocks | Case hardening steel with a sintered bronze running face, bonded and machined after sintering |
|---|---|
| Pistons and shoes | Case hardening steel with a bronze shoe face, swaged and hydrostatically balanced |
| Valve plates | Bearing steel or bronze faced steel depending on the frame, lapped to a mirror finish |
| Drive shafts | Alloy steel, carburised and hardened on the spline and bearing seats, ground on centres |
| Vanes and rotors | High speed tool steel and case hardening steel, hardened and ground on all working faces |
| Cam rings | Bearing quality alloy steel, through hardened then profile ground |
| Seals | Nitrile as standard, fluorocarbon or polyurethane on request for hot or fire resistant fluid duty |
Manufacturing Process
- Turning and millingBlanks are turned and milled from certified bar and forging stock on CNC machines.
- Heat treatmentCarburising, quenching, tempering or nitriding to the route the original part uses.
- GrindingBores, spline seats and running faces are ground after heat treatment so distortion is removed.
- Lapping and superfinishingValve plates, shoe faces and block faces are lapped so the pair seals under pressure.
- InspectionDimensions, hardness and surface finish are recorded against the drawing on a sampling plan.
- Assembly and testComplete pumps are built, run in and tested for efficiency, leakage and noise before packing.
Quality Control
- Incoming material certificates are checked against the grade called for on the drawing.
- Hardness is measured after heat treatment on every batch and recorded on the batch card.
- Critical bores and running faces are gauged against the drawing tolerance, not against a sample part.
- Mating parts are matched as a set so the block, shoes and valve plate run in together.
- Rebuilt pumps are bench tested for volumetric efficiency, external leakage and sound level.
- Parts are cleaned, oiled and vacuum sealed so they arrive without surface rust.
Certifications and Documentation
Supplied on request with an order. We do not claim approvals we cannot evidence.
| Material certificate | Mill certificate for the steel grade used in the batch |
|---|---|
| Hardness report | Surface and core hardness readings after heat treatment |
| Dimensional report | Measured values for the critical features named on the drawing |
| Test bench report | Flow, efficiency, leakage and sound readings for a rebuilt pump |
| Packing list and photographs | Carton contents and photographs of the packed goods before shipment |
Customization Options
- Shaft and splineKeyed, straight or splined shaft ends built to your sample or drawing.
- Port and mountingFlange, thread and mounting pattern matched to the pump already on the machine.
- Seal materialNitrile, fluorocarbon or polyurethane for hot oil, fire resistant fluid or low temperature duty.
- Rotation and displacementLeft or right hand rotation and the displacement code your circuit was set up for.
- Marking and packingNeutral packing, your own carton artwork and your own part number laser marked on the part.
Comparison With Other Products
| Point | A4VSO | A4VG | A10VO |
|---|---|---|---|
| Circuit | Open circuit industrial | Closed circuit mobile | Open circuit mobile and industrial |
| Sizes we build | 28 to 500 | 28 to 500 | 16 to 140 |
| Typical machine | Press and test bench | Self propelled machine drive | Compact excavator and power unit |
| Control | Variable displacement | Variable displacement with charge pump | Variable displacement |
Use Guide
- Record the full model code and the serial plate before stripping the unit.
- Measure the housing bore and bearing seats. A worn housing will kill a new rotary group.
- Fit the set complete rather than mixing new and used running faces.
- Renew the seal kit and the shaft bearing at the same time.
- Flush the circuit, prime the case with clean oil and run in at low pressure.
Product Photographs
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Frequently Asked Questions
Do you supply the rotary group only or single parts as well?
Both. You can order the complete matched set, or a single cylinder block, piston shoe set, valve plate or swash plate.
Which sizes are held in stock?
The 71, 90, 125 and 180 sizes move fastest and are normally on the shelf. Ask on WhatsApp and we will confirm before you order.
Will a new rotary group fix a pump with a worn housing?
No. Measure the housing bore and bearing seats first. If they are worn the housing needs attention or the new set will fail early.
Are the parts interchangeable with the original?
They are machined to the original dimensions and spline pattern so they fit the original housing. Send the model code and we will confirm the variant.
What documentation comes with the order?
Material certificate, hardness report and dimensional report on request, plus photographs of the packed goods.
Send Us the Model Code and We Will Quote
Tell us the model code stamped on the pump, the quantity and your delivery port. A quotation with lead time usually comes back within one working day.