Piston Rings for Bent Axis Pumps and Motors
Piston rings for A2F A2FO A2FM A6V A6VM A7V A7VO and A8VO bent axis pumps and motors, ground and gap checked by size group.
Product Overview
Bent axis pumps and motors seal the piston in the bore with a ring rather than a close fit. The ring is small, inexpensive and the first thing to wear, and a worn ring set shows up as lost efficiency and a hot case drain long before anything else in the unit is worn out. Replacing rings is often the cheapest repair available on this family.
| A2F and A2FO groups | 10 12 16 23 28 32 45 56 63 80 107 125 160 180 200 225 250 500 1000 |
|---|---|
| A2FM groups | 10 12 16 23 28 32 45 56 63 80 90 107 125 160 180 200 225 250 500 1000 |
| Other families | A6V A6VM A7V A7VO A8VO ring sets |
Key Benefits
- Cheapest single repair that restores lost efficiency on a bent axis unit
- Ground and gap checked by size group
- Sold as a complete set for one unit so all bores seal the same
- In stock for the common size groups
Application Scenarios
- Winch and drum motor overhaul
- Excavator main pump refresh where the block is still good
- Fixed displacement power take off pump repair
- Preventive replacement during a scheduled overhaul
Who It Is For
- Rebuild shops
- Fleet and plant maintenance
- Distributors
- Marine and crane service engineers
Problems It Solves
- The unit has lost efficiency but the block and shoes still measure within limits
- Case drain is hot and flow has risen
- A full rotary group is not justified for the loss of performance seen
- Rings for an older size group are no longer offered locally
Technical Features
- Ground on the running face and the sides
- Gap checked against the bore size group
- Supplied as a complete set for one unit
- Covers A2F A2FO A2FM A6V A6VM A7V A7VO and A8VO families
- Individually packed by size group
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.
| Supply | Complete set for one unit |
|---|---|
| Finish | Ground running face and sides |
| Gap | Checked against the bore size group |
| Families | A2F A2FO A2FM A6V A6VM A7V A7VO A8VO |
| Packing | Oiled and packed by size group |
| Lead time | From stock for the common groups |
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 | Piston Ring Set | Piston and Shoe Set | Complete Rotary Group |
|---|---|---|---|
| Cost | Lowest | Middle | Highest |
| When it works | Bores and shoes measure good | Shoes worn or scored | Block face also worn |
| Downtime | Shortest | Short | Longest |
| Efficiency restored | Most of it if nothing else is worn | Most of it | Fully |
Use Guide
- Measure the bore before fitting so the ring group is correct.
- Check the ring gap in the bore before assembly.
- Fit rings dry into the groove, then oil the piston before entering the bore.
- Do not reuse old rings with new pistons.
- Run in at low pressure and check case drain temperature.
Product Photographs
Related Products
Cylinder Blocks
Cylinder blocks for axial and bent axis piston pumps with sintered bronze running faces bonded and machined after sintering then lapped flat.
View Series and Sizes
Piston and Shoe Assemblies
Piston and shoe assemblies for axial piston pumps, swaged and checked for shoe clearance with hydrostatically balanced bronze shoe faces.
View Series and Sizes
Valve Plates and Swash Plates
Valve plates swash plates cradles retainer plates and ball guides for axial and bent axis piston pumps lapped and ground to the original drawing.
View Series and Sizes
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Frequently Asked Questions
Will new rings alone restore my motor?
Often yes, if the block face, shoes and valve plate still measure within limits. Rings usually wear first.
How do I identify the ring group?
By the unit size code such as A2FM107. Send the code and we will identify the set.
Do you sell rings singly?
They are supplied as a complete set for one unit so every bore seals the same.
What causes rings to wear quickly?
Contaminated oil and running the unit hot. Check the cooler and the filters when you fit new rings.
Are rings held in stock?
Yes for the common size groups, and they ship the same day in most cases.
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.