P08 P16 P22 P36 P46 P70 HHPC Piston Pump 8-70cc 255Bar

Product Overview

The P08, P16, P22, P36, P46, and P70 belong to the HHPC (Hsu Hung) / OMAX P Series of pressure-compensated variable displacement axial piston pumps, covering displacements from 8 cm³/rev to 70 cm³/rev for medium-to-high pressure open-circuit hydraulic systems. The series features swashplate design with an integrated pressure compensator that automatically destokes the swashplate as outlet pressure approaches the setpoint, reducing flow to the minimum required to maintain set pressure — fundamentally eliminating relief losses. All models feature SAE J744 two-bolt mounting flanges with parallel key shafts: P08/P16/P22 use SAE A or B flanges, P36/P46 use SAE-C two-bolt flanges, and P70 uses an SAE-C four-bolt flange.

Manufactured to original technical specifications with full drop-in interchangeability, directly replacing HHPC, OMAX, and equivalent industrial hydraulic pumps. The A0/A1/A2/A3 suffix in each model code corresponds to different pressure adjustment ranges, allowing users to select the optimal configuration for their system requirements. Every pump undergoes 100% simulated load testing at the factory, covering pressure hold, flow response, and pressure compensator dynamics for seamless replacement in injection molding machines, presses, and machine tool hydraulic systems.

Technical Specifications 

• Series: HHPC / OMAX P Series

• Design: Swashplate axial piston variable pump, pressure compensated, open circuit

• Displacement: 8.0 cm³/rev (P08) / 16.5 cm³/rev (P16) / 22.0 cm³/rev (P22) / 36.0 cm³/rev (P36) / 46.0 cm³/rev (P46) / 70.0 cm³/rev (P70)

• Pressure Adjustment Range (A0/A1/A2/A3 Suffix): A0: 15–45 bar / A1: 20–75 bar / A2: 25–150 bar / A3: 30–255 bar (P70 A4: 30–286 bar)

• Maximum Setting Pressure: 255 bar (P08/P16/P22/P36/P46-A3); 286 bar (P70-A4)

• Maximum Speed: 2,000 rpm (P08–P46); 1,800 rpm (P70)

• Minimum Speed: 500 rpm (P08–P46); 300 rpm (P70)

• Theoretical Flow @ 1,500 rpm: 12 L/min (P08) / 24.7 L/min (P16) / 33 L/min (P22) / 54 L/min (P36) / 69 L/min (P46) / 105 L/min (P70)

• Control Type: Pressure compensation (Type A), manual pressure adjustment

• Mounting Flange: SAE A/B two-bolt (P08/P16/P22); SAE-C two-bolt (P36/P46); SAE-C four-bolt (P70)

• Shaft End: Parallel key cylindrical shaft, per SAE J744

• Direction of Rotation: Clockwise (viewed from shaft end, R standard); counterclockwise (L optional)

• Housing Material: High-strength cast iron

• Weight: 9 kg (P08) / 13 kg (P16) / 13 kg (P22) / 21–24 kg (P36) / 23–24 kg (P46) / 43 kg (P70)

Model Code Interpretation (Examples):

• P08-A3-F-R-01: P08 pump size, A3 for 30–255 bar pressure adjustment range, F for flange mounting, R for clockwise rotation, 01 design number. Suitable for industrial hydraulic power units and press systems requiring 255 bar high-pressure output.

• P08-A2-F-R-01: P08 pump size, A2 for 25–150 bar pressure adjustment range, F for flange mounting, R for clockwise rotation, 01 design number. Suitable for medium-pressure injection molding machines and machine tool hydraulic systems with high flow control precision.

• P16-A3-F-R-01: P16 pump size, A3 for 30–255 bar, flange mounting, clockwise rotation, design number 01. Compatible with injection molding machine high-pressure injection circuits and hydraulic clamping systems.

Data based on HHPC/OMAX P Series technical documentation.

Key Technical Advantages

1. Pressure Compensation Control — Constant Pressure Output, Zero Relief Loss

The defining engineering feature of the P Series is its integrated pressure compensation control mechanism. As outlet pressure approaches the setpoint, the compensator strokes the swashplate back toward neutral, reducing displacement to the minimum flow required to maintain set pressure (theoretically approaching zero). This fundamentally eliminates the energy losses inherent in fixed-displacement pumps relying on relief valves for pressure regulation. Measured data shows pressure compensation reduces system energy consumption by over 30% in holding conditions, while significantly reducing hydraulic oil heat generation and extending seal and fluid service life. Pressure setting is accomplished via a manual adjustment screw with high precision and repeatability. The wide A0 through A3 pressure adjustment options allow the same pump body to serve applications ranging from 15 bar low-pressure to 255 bar high-pressure systems.

2. Series Design — Single Platform Covers Full Displacement Range

The P Series spans six displacement sizes from 8 cm³/rev to 70 cm³/rev, sharing identical design architecture and control principles. Users can select within the series based on system flow requirements without changing control systems or mounting interface specifications. All models use SAE J744 standard flanges, with P08–P46 shaft ends and mounting dimensions designed for consistency, facilitating pump upgrades or downgrades within the series. This series design significantly reduces hydraulic system design complexity and spare parts inventory variety.

3. Precision Piston Pairs and High Volumetric Efficiency

Piston pairs are manufactured from high-strength alloy steel with precision-honed cylinder bores, with cylindricity controlled to micron-level tolerance. A hydrodynamic oil film forms between the swashplate and slippers, reducing metal-to-metal wear and extending critical friction pair life. Volumetric efficiency is maintained above 90% at 255 bar continuous pressure. The port plate is hydrodynamically optimized to reduce pressure pulsation and flow fluctuation, ensuring output stability in precision applications such as injection molding machine holding and press compaction.

4. Compact Cast Iron Housing and Wide Speed Range

The pump body features a compact cast iron housing delivering high power density while maintaining structural rigidity. The P08 pump body weighs only 9 kg for easy installation in space-constrained equipment. The full series supports a 500–2,000 rpm wide speed range (300–1,800 rpm for P70), adapting to both electric motor and engine-driven applications. The 500 rpm minimum speed enables stable operation at low speeds for industrial applications requiring high torque at low flow.

Application Areas

• Injection Molding Machine Hydraulics: Clamp circuits, injection circuits, holding circuits — pressure compensation ensures zero flow during holding, eliminating relief heat

• Hydraulic Presses: Main cylinder pressurization and holding circuits, hydraulic clamping systems — high-pressure output with precise pressure setting

• Machine Tool Hydraulic Power Units: Grinding, milling, and machining center hydraulic power packs — compact design fits within machine tool envelopes

• Industrial Hydraulic Power Units: General hydraulic station main pumps, accumulator charging circuits — series selection matches varying flow requirements

• Tube Bending and Pipe Processing Equipment: Tube bender oil pumps (P08-A0-F-R-01 typical application) — flexible switching between low-pressure high-flow and medium-pressure output

• Test Equipment: Hydraulic test bench power sources, pressure test pumps — wide pressure adjustment range meets multiple testing standards

Expert Maintenance Tips

Pre-Installation Cleanliness Control: Before installing P Series pumps, verify hydraulic system cleanliness meets ISO 4406 18/16/13 or better. Port plugs should be removed and piping connected immediately after unboxing — environmental exposure should not exceed 15 minutes. Before first start, fill the pump case with clean hydraulic oil to the maximum allowable level. Dry-start is strictly prohibited. Ensure concentricity between the drive shaft and pump shaft is maintained within 0.05 mm, and use a flexible coupling to avoid additional radial loads.

Pressure Compensator Calibration: The P Series pressure compensation setpoint is manually adjusted via a screw on the housing. Turn clockwise to increase set pressure, counterclockwise to decrease. Monitor outlet pressure with a gauge of at least 1.6 accuracy class (0–300 bar range) during adjustment. Perform adjustments with the system unloaded, in increments not exceeding half a turn per step, allowing the system to stabilize before further fine-tuning. The pressure range indicated by the A0/A1/A2/A3 suffix represents the span the adjustment screw can cover; the setpoint should maintain 10%–15% margin to avoid frequent compensator cycling.

Operating Oil Temperature Management: The P Series recommended fluid temperature range is -10°C to +70°C, with ambient temperature -10°C to +50°C. When starting with oil temperature below 15°C, warm the hydraulic oil or run at low speed and no load until oil temperature reaches 15°C before applying load. Prolonged operation above 60°C accelerates seal aging and fluid degradation — inspect the cooling system if oil temperature consistently exceeds this threshold. VG 32–46 mineral hydraulic oil is recommended.

Oil Maintenance Schedule: Replace hydraulic oil and filter after the first 500 hours of operation. Thereafter, replace every 2,000 hours or 12 months, whichever comes first. If the system is equipped with an online particle counter, replace oil and inspect filter differential pressure immediately when cleanliness drops to ISO 4406 20/18/15. Pressure-compensated pumps are sensitive to fluid contamination — contaminant particles can jam the compensator spool, causing setpoint drift. Maintain return filter efficiency at 10 μm or finer.

Long-Term Storage Protection: For pumps stored over 3 months, drain case oil, fill with rust-preventive oil, and plug all ports. Before recommissioning, flush with flushing oil for 30 minutes and confirm flushing oil cleanliness meets specification before connecting to the system. Always refill the case to the maximum allowable level before restart.