ALP Series Hydraulic Gear Pump Replacement | ALP1 ALP2 ALP4

The ALP Series High-Pressure External Gear Pumps by Chengyuan Hydraulic—encompassing Group 1, Group 2, and Group 4 frames, including standard models ALP1-D-13, ALP1-D-16, ALP2-D-34, ALP2-D-50, and ALP4-D-300—are premium industrial-grade fluid components engineered for 100% direct drop-in interchangeability with the original Marzocchi Pompe ALP series. Manufactured strictly to global European installation footprints, these gear pumps precisely match the original mounting flanges, drive shafts, and port configurations, allowing immediate, hassle-free field replacement in existing systems without modification to structural frames or plumbing layouts.

Featuring a high-strength extruded aluminum alloy body coupled with premium cast iron front flanges and rear covers, the ALP series delivers rigid mechanical resistance against housing deflection under continuous pressure cycles. As the primary hydraulic power unit across mobile and industrial sectors, this series is globally acclaimed for its high speed tolerance, quiet acoustics, and cost efficiency. At Chengyuan, every single ALP pump undergoes 100% rigorous dynamic simulation testing before dispatch. We closely log volumetric efficiency and thermal spikes under full load to ensure that every delivered pump provides zero-defect performance in demanding fields.

Technical Specifications

• Product Series: ALP Frame Classification (Group 1, Group 2, Group 4 External Gear Pumps)

• Direction of Rotation: D (Clockwise rotation, viewed from the drive shaft end)

• Material Matrix: Premium extruded aluminum alloy housing + high-grade cast iron front flange and rear end-cover

• Specific Model Parameters:

  • ALP1-D-13: Displacement 9.3 cc/rev ($cm^3/rev$); Nominal Continuous Pressure 220 bar (22 MPa); Maximum Peak Pressure 240 bar; Maximum Continuous Speed 3000 rpm; Approximate Net Weight 1.2 kg.

  • ALP1-D-16: Displacement 11.0 cc/rev ($cm^3/rev$); Nominal Continuous Pressure 200 bar (20 MPa); Maximum Peak Pressure 220 bar; Maximum Continuous Speed 3000 rpm; Approximate Net Weight 1.3 kg.

  • ALP2-D-34: Displacement 23.7 cc/rev ($cm^3/rev$); Nominal Continuous Pressure 210 bar (21 MPa); Maximum Peak Pressure 230 bar; Maximum Continuous Speed 2500 rpm; Approximate Net Weight 3.2 kg.

  • ALP2-D-50: Displacement 35.2 cc/rev ($cm^3/rev$); Nominal Continuous Pressure 140 bar (14 MPa); Maximum Peak Pressure 160 bar; Maximum Continuous Speed 2200 rpm; Approximate Net Weight 3.8 kg.

  • ALP4-D-300: Displacement 201.0 cc/rev ($cm^3/rev$); Nominal Continuous Pressure 180 bar (18 MPa); Maximum Peak Pressure 200 bar; Maximum Continuous Speed 1800 rpm; Approximate Net Weight 17.5 kg.

• Recommended Hydraulic Fluid: Mineral-based hydraulic oils (Viscosity spectrum: 10 to 500 $mm^2/s$)

• Fluid Operating Temperature Range: -15°C to +80°C

Key Technical Advantages

• Automatic Axial Clearance Hydraulic Balancing: The internal architecture incorporates optimized thrust plates and specialized Teflon-coated anti-extrusion seals. As working pressure scales up, a dedicated hydraulic balance zone directs pilot fluid behind the thrust plates, keeping them tightly flush against the gear faces. This permanently compensates for long-term wear and secures a volumetric efficiency above 95% at 200 bar pressures.

• Precision-Ground High-Hardness 12-Tooth Gearsets: The internal driven and driving gears are machined from high-grade carbon steel, case-hardened via advanced carburizing treatments, and CNC-ground to mirror finishes. This asymmetric 12-tooth profile heavily reduces trapped fluid oil volumes and fluid pulsations, keeping overall noise levels 4 to 6 dB(A) lower than entry-level market substitutes.

• Heavy-Duty Self-Lubricating DU Bushings: Replacing traditional fragile needle bearings, our ALP series implements high-load DU composite journal bearings with excellent anti-seizure matrices. This bushing assembly accommodates micro-particulate pollution inside the fluid and absorbs radial shaft overhung loads, multiplying the structural fatigue life of large sizes like ALP2 and ALP4.

• 100% Full-Load Factory Simulation Benchmarks: Every Chengyuan ALP gear pump must clear our stringent test bench validation prior to boxing. The testing routine registers transient overpressure shock profiles, full-RPM flow tracking, and shaft lip seal integrity under heat, ensuring absolute reliability right out of the crate.

Application Areas

Thanks to its flexible, lightweight design and high speed ranges, the ALP series is widely integrated into space-confined hydraulic modules:

• Miniature Hydraulic Power Units (HPUs): Automotive workshop two-post lifts, commercial vehicle hydraulic tailgates, and electric pallet jack lift manifolds (primarily size ALP1-D-13 / 16).

• Agricultural & Off-Highway Assets: Tractor auxiliary hydrostatic power steering systems, combine harvester header control loops, skid steer loaders, and industrial turf mowers (primarily size ALP2-D-34 / 50).

• Industrial Plants & Automated Machinery: Blow molding equipment, light-duty machine tool power packs, textile processing arrays, and low-pressure lubrication offline cooling filtration systems (primarily size ALP2 and large-scale ALP4-D-300 loops).

Expert Maintenance Tips

• Shaft Alignment Rigidity & Flexible Couplings: When mounting the ALP gear pump, verify precision axial alignment between the pump shaft and prime mover ($\le 0.1mm$ alignment variance). Use premium jaw-type or elastomeric pin flexible couplings; never hammer couplings directly onto the shaft woodruff key, as this shatters internal thrust balances and causes premature shaft seal failure.

• Pre-Commissioning Priming & Air Evacuation: Prior to initial startup or system resetting, manually pre-fill the pump intake port with filtered oil. During the first electrical jogging sequence, run the pump under zero-pressure idle conditions for 1 to 2 minutes to completely purge trapped air. Avoid intake starvation or dry running.

• Rigid Fluid Cleanliness Enforcement: Aluminum body pumps are highly sensitive to abrasive micro-contaminants. System oil must be managed to meet or exceed ISO 4406 20/18/15 (NAS Class 9). We strongly recommend setting up a $60 – 90 \mu m$ strainer on the suction line and an absolute filtration rating of $\le 25 \mu m$ in the main return circuit.