If your excavator, loader or crane runs on a piston-type hydraulic pump, you’re already in the “high-performance” tier of hydraulics. Compared with gear and vane pumps, piston pumps deliver higher pressure, better efficiency, and more precise control – which is exactly why they’re used as main pumps in modern excavators and other heavy equipment.
1. Piston pumps in excavator hydraulic systems
In an excavator, the main pump converts engine power into oil flow and pressure for the boom, arm, bucket, swing and travel circuits. For 4–40 ton machines (roughly the PC40–PC400 class), this main pump is almost always an axial piston pump mounted on the engine PTO.
Other pump types still exist in the system:
Gear pumps – often used for pilot control or simple auxiliary functions.
Vane pumps – more common in industrial machines than in excavators.
Piston pumps – used where high pressure, high efficiency and fine control are required.
Typical rated pressure ranges are:
Axial piston pumps for mobile equipment: nominal 250–350 bar, some families up to 420 bar [1][2]
Radial piston pumps for high-pressure units: up to 700–1,000 bar in specialised series [3]
For excavators, this means: axial piston pumps cover almost all main-pump duties, while radial piston pumps are reserved for special ultra-high-pressure systems.
Topvelsun supplies excavator hydraulic pumps and related parts that cover most 4–40 ton excavator models used in construction, mining and quarry applications.
2. Radial piston pumps – ultra-high-pressure specialists
A radial piston pump arranges several small pistons like spokes around a shaft. An eccentric ring or cam makes each piston move in and out of its bore:
When the piston moves outward, chamber volume increases and oil is drawn in through an inlet check valve.
When the piston moves inward, volume decreases and oil is pushed out through an outlet check valve.
With several pistons working in sequence, the flow is smooth and the volumetric efficiency is very high, even at extreme pressure. In modern designs, continuous working pressures up to 700–1,000 bar are possible [3].
Main characteristics of radial piston pumps
Very high continuous working pressure (700–1,000 bar, depending on series).
High volumetric efficiency and low flow ripple at low speed.
“Short and fat” body: larger diameter but shorter axial length.
Best suited to industrial presses, test rigs and custom power packs.
For typical excavators in the 40–400 machine number range, there is rarely enough added benefit to justify a radial piston pump as the main pump. It is more common in stationary high-pressure units than on mobile machinery.
3. Axial piston pumps – the standard excavator main pump
In an axial piston pump, several pistons are arranged parallel to the drive shaft inside a rotating cylinder block. The pistons run against a swashplate that is set at an angle to the shaft:
As the block rotates, each piston follows the inclined swashplate.
Moving away from the valve plate creates a suction stroke; moving towards it creates a discharge stroke.
On variable pumps, changing the swashplate angle changes piston stroke and therefore the pump displacement and flow.
This swashplate axial piston pump is the standard design used by major manufacturers such as Bosch Rexroth and Parker for mobile machinery [1][2].
OEM excavators adopt this design for their main pumps.
Key features for excavator use
High working pressure – typically 280–350 bar nominal, with peak pressures up to around 420 bar in some families [1][2].
Compact layout – slim, inline body that fits on the engine PTO and leaves space for hoses and valves in a crowded upper-structure.
Flexible control options – load-sensing, constant pressure, constant power, torque limiting and electro-proportional controls for smooth, efficient operation.
Good efficiency – lower fuel consumption and heat generation compared with gear pumps at similar pressure.
When an excavator main pump wears out or is damaged, owners usually replace it with an OEM-equivalent or upgraded axial piston pump, such as:
These concrete model numbers help keep your content tightly aligned with excavator users searching for replacement hydraulic main pumps.
For a wider overview of pump types, displacement and pressure selection, you can cross-link to your general article: Hydraulic Pump Buying Guide: How to Choose Type, Displacement and Pressure?
4. Radial vs axial piston pumps in real excavator fleets
From an excavator owner’s point of view, the practical comparison looks like this:
Pressure capability
Axial piston pump: high pressure suitable for digging, lifting and breaker work (280–350 bar nominal, up to ~420 bar peak in some series).
Radial piston pump: ultra-high pressure for special tools, presses or testing systems (up to ~1,000 bar).
Size and installation
Axial: compact, inline layout; easy to mount directly on the engine with through-drive options for tandem pumps.
Radial: larger diameter; better suited where space in front of the drive shaft is available, typically on stationary power units.
Control and integration
Axial: many variable-displacement controls for excavator work modes (e.g. power, economy, fine control).
Radial: some variable designs exist, but with fewer control variants and less focus on excavator-style load-sensing systems.
In other words:
Use axial piston pumps for almost all excavator main pump applications in the 40–400 machine class.
Reserve radial piston pumps for separate high-pressure circuits where unusually high pressures are required and space is not a limitation.
5. Common excavator piston-pump symptoms
Most field issues on excavators involve axial piston main pumps. Typical symptoms include:
Increased noise and vibration
Often linked to misalignment, worn couplings or bearings, suction restrictions, low oil level or air leaks on the suction side. Cavitation and aeration are common root causes.
High oil temperature
Can be caused by internal leakage due to wear, wrong control settings (pump held on high pressure with low flow), or blocked return filters and coolers [2][4].
Slow or jerky boom / arm / travel
May indicate wear between the cylinder block and valve plate, or sticking swashplate control pistons due to contamination [2].
Broken feedback springs or blocked damping orifices can also cause unstable pressure and flow.
Loss of power or low flow
Often starts with low oil level, a clogged suction strainer, a collapsed suction hose or a pump that is simply at the end of its service life.
Once simple external issues (oil level, filters, hoses) are ruled out, replacing the main pump with a correctly matched axial piston unit is usually more cost-effective than trying to repair a heavily worn pump.
6. Maintenance habits that extend pump life
Whether the system uses a radial or axial piston pump, a few simple habits can significantly extend service life:
Control oil cleanliness
Follow cleanliness levels suitable for piston pumps (commonly specified using ISO 4406 particle codes) and change filters on schedule [4].
Keep temperature in a healthy range
Many OEMs expect normal operation around 40–60 °C. Long-term operation at very high oil temperature accelerates wear, oxidation and leakage [2][4].
Use the correct fluid and viscosity
Follow pump and machine manuals for oil type and viscosity range. When changing oil type (for example to a fire-resistant fluid), flush the system instead of only topping up [1][2][4].
Respect start-up procedures
After replacing a pump or after long downtime, pre-fill the housing, bleed air and run at low speed without load before returning the machine to full operation [2][4].
With these practices plus high-quality axial piston main pumps for 4–40 ton excavators, your machines can achieve stable performance and long service life even in demanding construction, mining and quarry conditions.
References
Bosch Rexroth – A10VO Series 52/53 axial piston variable pump data sheet (RE 92703) and A11V(L)O Series 40 axial piston variable pump data sheet (RE 92510).
Parker Hannifin – P1/PD Series Medium Pressure Axial Piston Pumps catalog HY28-2665 and PVplus axial piston pumps product overview.
Bieri Hydraulik – Radial piston pumps BRK11/12 heavy-duty series – up to 1000 bar.
ISO – ISO 4413:2010 – Hydraulic fluid power — General rules and safety requirements for systems and their components.
