top of page

Hydraulic Power Unit (HPU)

ARS has invested many years in the design and development of heavy duty HPUs for the construction industry and custom hydraulic manifold design, and would be open to offers from a manufacturer to either transfer or outright sell the technology.

ARS would work with the manufacturer and would be able to provide the following services:

  • Conceptual design for hydraulic system and manifolds

  • Conceptual design for mechanical structures including hydraulic tank

  • Electrical and programming statement of work (SOW)

  • Autodesk® Inventor Pro 3D drawings for all mechanical assemblies, machining, profile cutting and parts manuals

  • Hydraulic schematics

  • Supervision of assembly, testing and setup

  • Training of manufacturer's personnel and customers

The unit shown below in the images and video was designed to power the following:

  • Casing oscillators (Bauer and Leffer)

  • Crane mounted vibro-hammers

  • Hydraulic motors (crane mounted top drive CFA systems)

  • Hydraulic rams (equipment repair, field load testing) 

  • Test Stand for testing drill rig casing drive units (Bauer KDK)

  • Hydraulic chain saws


The HPU features a programmable control module that monitors and controls all engine and hydraulic functions.

A programmable Mobile Machine Display with high resolution TFT display (400 x 200 pixels, 18-bit color with ingress protection of IP67) is used for selecting various hydraulic programs, controlling operational functions, monitoring systems operations and displaying system warnings.  

The HPU is controlled by the Mobile Machine Display, or remotely by wireless transceiver.

The belly-box transmitter is generally worn by an on-the-ground operator and is preferred when operating a casing oscillator (please see video below) and the KDK test stand. 

Specifications and features:

  • Caterpillar industrial engine rated at 440 BHP @ 1800 to 2100 RPM

  • Programmed engine speed of 1800 RPM used for low to medium flow hydraulic attachments

  • Programmed engine speed of 2100 RPM used for high flow applications such as the KDK Test Stand, crane mounted vibro-hammers, oscillators and top-head CFA drills

  • Engine’s speed reduced to Low Idle (800 RPM) automatically (10 second delay) when hydraulic flow is not required. This feature reduces fuel consumption, mechanical wear and noise.

  • Noise and vibration reduced by flexibly engine mounts located between the engine and the base frame/fuel tank

  • Multiple, individual hydraulic flows provided by three Rexroth axial piston pumps (P1, P2 and P3). Each of the pump’s output flow is filtered by a full flow, high pressure filter.

  • Hydraulic oil flow from pumps P1 and P2  supplied to an ARS designed and Rexroth built custom manifold where the pump’s flows can remain separated and reversed, or combined and reversed at the work ports.

  • Hydraulic pump P3 supplying hydraulic oil to a four section valve group (two large flow sections, two small flow sections).  Flow from each of the four sections is infinitely variable (electronically controlled) and reversible. The two small flow sections are for hydraulic circuits requiring low flow and high pressures such as a vibro-hammer’s clamp circuit.

  • The three pumps mounted on to a 3-position pump drive and attached to the rear of the Caterpillar engine. All three pumps are open circuit and feature power control with pressure cut-off and load sensing. Nominal operational pressure for each pump is 350 Bar. (5075 psi), while maximum flow is 272 liters (72 GPM) at an engine speed of 2100 RPM. Very little hydraulic oil is flowing when the three pumps are at their standby pressures, resulting in less heat buildup and reduced engine fuel consumption.

  • As mentioned above, individual hydraulic oil flowing from pumps P1 and P2 (up to 72 GPM per pump) supply the ARS manifold and is primarily used to operate large attachments. In the case of the Bauer BV1320 oscillator (shown working in video below), pump P1 supplies hydraulic oil to the oscillating and retaining cylinders, while pump P2 supplies hydraulic oil to the lifting cylinders. Pump P3 supplies hydraulic oil to the four section valve group which supplies hydraulic oil to the oscillator’s clamping cylinders.

  • The ARS manifold also allows pumps P1 and P2 to combine their flows (144 GPM) when operating top drive CFA drill heads and vibro-hammers. The manifold features an automatic retardation  circuit when using vibro-hammers. 

  • The hydraulic system module comprised of a main hydraulic tank, high pressure in-line pump filters, medium pressure return filters, ARS custom  manifolds, four section valve group and the attachment’s hydraulic quick couplers. All are attached to a quick detachable mounting frame (hydraulic module) that locks into the HPU’s lower main frame/diesel tank.

  • A main hydraulic tank supplying oil to the three axial piston pumps. A separate fill oil tank holds additional oil for the main tank. Oil is pumped into the main tank from the separate fill tank by a hydraulic pump driven by a 24Vdc motor. Oil is filtered before entering the main hydraulic tank. Hydraulic oil level and temperature are monitored electronically. If the oil level drops to an unsafe level (3rd level switch), the engine will automatically shut down. Oil temperature is used to determine oil cooler bypass operation, filter restriction readings and hydraulic system shutdown (nearing overheating). The operator will be warned of high oil temperature, and hydraulic oil flow to any attachment(s) being operated will eventually be shut down. All return oil to the tank is filtered by high capacity return filters.

  • The base/fuel tank (US 180 gal.) featuring two cleanout inspection ports, a fill port on both sides and a wear resistant bottom plate

  • The quick detachable top frame attached to the Base/fuel tank by 8 bolts, being the main lifting point for the HPU

  • The HPU in this configuration being compact by design, allowing it to be mounted on the rear of a service crane when using a vibro-hammer or top mounted CFA drill.


ARS Hydraulic Power Units (HPU) shown with the top cover/lifting assembly disconnected  from the base/fuel tank by removing 8 bolts and detaching the exhaust and air cleaner connections.


ARS Hydraulic Power Unit (HPU) showing  the hydraulic module, Caterpillar engine and high ambient temperature cooling package. The Espar diesel fired coolant heater is for heating the engine coolant and hydraulic oil (heat exchanger in the hydraulic tank). A high capacity hydraulic oil cooler is mounted on the front of the radiator assembly. Notice the compact design as this unit was designed to fit on the back of a service crane to run a vibro-hammer. All service items are easily accessed, even with the top cover/lifting assembly installed.


ARS custom designed manifold (designed by ARS and built by Rexroth). Hydraulic manifolds use reliable industrial logic elements and reduce space requirements by reducing the number of hydraulic hoses.


ARS Hydraulic Power Unit (HPU) showing the custom manifold, CAT engine monitoring panel. The Sauer Danfoss programmable Mobile Machine Display and programmable control module (top left, cover removed) are also shown.

ARS Hydraulic Power Unit (HPU) is shown working with a Bauer BV 1320 casing oscillator. The HPU is being controlled by remote wireless control by the operator on the far left. 

bottom of page