PVD-1B-32P PVD-1B-34P Hydraulic Pump | Excavator 303C Nachi Replacement

Genlu Hydraulic proudly introduces our PVD Series (PVD-0B / PVD-1B / PVD-2B / PVD-3B) heavy-duty axial piston variable displacement hydraulic main pumps engineered specifically for compact and mini-excavators. Integrating two separate high-pressure axial piston variable streams and an auxiliary fixed gear charging unit onto a single direct drive shaft, this line serves as the operational “power heart” for heavy-duty tracked mini-diggers—most notably the classic Caterpillar (Cat) 303C, 303.5C CR, and equivalent small-footprint Komatsu or Hitachi platforms. This series provides a precision-manufactured, drop-in replacement for the classic Nichi (Nachi) PVD multi-stream aggregate frameworks. We specialize in supplying standard and custom build configurations, prominently the PVD-1B-31BP-8AG5-4901B and PVD-1B-34P-11G5-4665B designations, along with comprehensive support for the full PVD core rotary group matrix.

Mini-excavators must smoothly perform multi-axis synchronized gestures (such as simultaneous tracking, cabin swinging, and boom hoisting) within confined urban workspaces. This places rigorous constraints on the main pump’s structural envelope and volumetric response profile. Genlu’s PVD replacement line conforms strictly to original space-saving cast flow channel matrices. We guarantee 100% Drop-in Interchangeability across standard compact mounting options (specialized 2-bolt/4-bolt mini-excavator pilot flanges), standard input drive splines (including standard 10-tooth and 13-tooth configurations), multi-angle side/rear port arrangements, and the exact reactive curves of the built-in total-power constant control regulator blocks. Prior to final validation, each PVD pump assembly undergoes 100% full-load cross-circuit power synchronization, multi-spool simulator valve bank load sweeps, and low-idle bypass leakage audits to ensure no engine stalling and uncompromised productivity on the job site.

Technical Specifications 

• Product Line: PVD Series Compact Axial Piston Variable Multi-Stream Main Pump for Mini-Excavators

• Core Covered Designation Formats:

  • PVD-1B-34P-11G5-4665B (Standard specification replacement for Cat 303C main pump aggregate)

  • PVD-1B-31BP-8AG5-4901B (Dual variable piston streams coupled with integrated rear gear charging configuration)

• Internal Component Array: Dual-stream variable piston rotary groups + Single fixed displacement gear charge pump (Driven via a single common shaft)

• Variable Piston Pump Displacement Envelopes:

  • PVD-0B Frame: Approx. 8.0 to 10.5 $cc/rev \times 2$

  • PVD-1B Frame: Approx. 14.0 to 16.5 $cc/rev \times 2$

  • PVD-2B Frame: Approx. 18.0 to 22.0 $cc/rev \times 2$

  • PVD-3B Frame: Approx. 26.0 to 29.0 $cc/rev \times 2$

• Rear Pilot / Gear Charge Pump Displacement: Approx. 4.5 to 6.5 $cc/rev$

• Continuous Rated Operating Pressure (Piston Elements): 21.0 MPa (210 bar / 3045 psi)

• Maximum Intermittent Peak Pressure (System Relief Threshold): 24.5 MPa (245 bar / 3553 psi)

• Auxiliary Gear Charge Pump Maximum Working Boundary: 4.9 MPa (49 bar)

• Maximum Allowable Input Shaft Rotation Speed: 2200 rpm to 2600 rpm

• Regulator Valve Logic Class: Total-Power Cross-Sensing Constant Torque Control + Pressure Cut-off Limiters (Prevents prime mover drop-stalling under sudden high loads)

Key Technical Advantages:

• Ultra-Compact Single-Shaft Power Integration Layout: The PVD design arranges two variable piston groups and a high-efficiency pilot gear pump onto a single shared input shaft. By eliminating the heavy internal distribution gearboxes used on larger excavator pumps, this setup shortens the axial length by 40% and reduces unit weight, making it a perfect fit for the tight engine bays of mini-excavators like the Cat 303C.

• Cross-Sensing Total Power Control to Prevent Engine Stalling: Equipped with an internal, highly responsive total-power regulator valve network. The valve monitors the combined operational pressures of both main piston circuits. If digging resistance climbs and the total load approaches the engine’s power limits, the regulator cuts swashplate stroke angles within 30 milliseconds. This reduces flow output and keeps the engine running smoothly through heavy clay or rock clearing.

• Bimetallic Fused Cylinder Block with 9-Piston Micro-Arrangement: The heart of the rotating group pairs a high-tensile nodular iron barrel with a bimetallic friction layer made of fine-grain copper alloy, permanently sintered onto the face plate. This 9-piston assembly delivers high volumetric efficiency at continuous 21 MPa loads, helping protect against slipper delamination or barrel scoring caused by heat buildup in compact pump housings.

• Integrated Multi-Passage Monoblock Valve Head Porting: All discharge outlets, internal suctions, and pilot routing orifices are integrated into a single, three-dimensionally cast fluid distribution block. This design replaces extensive external high-pressure hosing, reducing the risk of line leaks or bursts from machine vibration while smoothing out fluid intake to improve cavitation resistance at high shaft speeds.

Application Areas:

• Miniature & Compact Tracked Excavators: Direct replacement for main hydraulic assemblies on 3-ton to 4.5-ton crawler excavators, including Caterpillar (Cat 303C, 303.5C, 304C), Kubota, Nachi-equipped systems, and Kobelco machines.

• Compact Multi-Purpose Tracked Skid-Steer Loaders: Main hydraulic power systems for orchard management vehicles and compact municipal utility machinery working in tight spaces.

• Compact Piling & Trenchless Horizontal Boring Rigs: Primary hydraulic source for urban micro-tunneling units and compact utility foundation drilling systems.

Expert Maintenance Tips:

• Mandatory Priming of the Pump Case Prior to Initial Engine Crack: Compact, high-speed PVD series pumps rely entirely on free case fluid to lubricate the sliding piston slipper faces and cradle swashplate. After bolting the replacement pump in place, fill the internal casing through the top-most drain port with clean, filtered hydraulic oil before starting the engine. Turning the pump dry will destroy the precision hydrodynamic oil film between the slippers and the swashplate within the first few seconds of operation.

• Inspect Inlet Suction Hose Integrity and Screen Restrictions: On older excavators, aging rubber suction hoses can degrade and collapse internally under high suction loads. This restriction creates a local vacuum that induces severe cavitation, causing a loud buzzing noise and high vibration in the main pump. When replacing a pump, always inspect or replace the intake line and clean out any sludge on the reservoir’s internal suction screen.

• Verify and Reset Main Relief Valve Tolerances After Pump Replacement: During an excavator’s service life, mechanics may turn up the main relief valves on the control block to try to restore lost digging force on a worn pump. Installing a new pump without checking these settings can expose the compact PVD housing to pressures over 25 MPa, causing premature structural fatigue and shortening the service life of the new unit.