PVD-15B-37P-9AG5-5599B Nachi Excavator Pump 38cc 24.5MPa

Product Overview

The PVD-15B-37P-9AG5-5599B is a dual-circuit variable displacement pump from the Nachi PVD series, engineered as the primary hydraulic power source for mini excavators up to the 4-ton class. With a single-circuit displacement of 19 cm³/rev and a combined dual-circuit displacement of 38 cm³/rev, the pump delivers rated continuous pressure of 21 MPa and intermittent peak pressure of 24.5 MPa. The two circuits maintain a flow deviation of less than 1%, ensuring precise straight-line travel and smooth combined-operation performance.

The PVD-15B series features standard constant horsepower control (Total Horsepower Control), which automatically adjusts displacement in response to load demand, keeping pump drive power within the engine’s capability envelope and eliminating stall risk. The pump utilizes an internal drain architecture — case leakage returns to the suction side through internal passages — requiring no external drain line. This simplifies vehicle hydraulic plumbing and removes the risk of shaft seal damage from excessive drain-line back pressure. The suffix code -37P-9AG5-5599B indicates the integration of power-shift control (P) and a pilot gear pump (9AG5) for direct supply of pilot oil to the machine’s valve block.

Every PVD-15B-37P-9AG5-5599B unit we supply is manufactured to original Nachi drawing tolerances. Mounting flange, shaft spline, port positions, and control logic are dimensionally identical to the genuine article — delivering true drop-in interchangeability. Each pump undergoes 100% simulated load testing across the full pressure range from rated to peak before shipment.

Technical Specifications

• Model: PVD-15B-37P-9AG5-5599B

• Series: Nachi PVD Series Dual-Circuit Variable Displacement Pump

• Pump Type: Dual-circuit variable pump (coaxial equal-flow output)

• Single-Circuit Displacement: 19 cm³/rev

• Combined Displacement: 38 cm³/rev

• Rated Continuous Pressure: 21 MPa

• Maximum Intermittent Peak Pressure: 24.5 MPa

• Maximum Speed: 2,600 rpm

• Rated Speed: 2,400 rpm

• Minimum Speed: approximately 900 rpm

• Flow Deviation Between Circuits: ≤ 1%

• Control Type: Constant horsepower control (standard) + power shift control (optional, included in this model)

• Integrated Options: Pilot gear pump (included per 9AG5 configuration code)

• Drain Configuration: Internal drain, no external drain line required

• Applicable Excavator Class: ≤ 4.0 t

• Base Pump Weight (reference): approximately 38 kg (increases to 41–46 kg with integrated components)

• Recommended Hydraulic Fluid: ISO VG32 / VG46 anti-wear hydraulic oil

Specifications compiled from Nachi PVD series technical data and published engineering resources for equivalent configurations.

Key Technical Advantages

Coaxial Dual-Circuit Equal-Flow Output & Travel Straightness. The PVD-15B-37P-9AG5-5599B replaces the conventional two-pump configuration with a single housing driving two rotary groups on a common shaft. Flow deviation between the two circuits is held below 1%, ensuring equal oil delivery to left and right travel motors for precise straight-line tracking. During combined operations (travel + swing + boom lift), stable flow distribution between circuits directly determines machine controllability — this design eliminates hydraulic-induced travel drift at the source.

Constant Horsepower Control & Anti-Stall Protection. The standard constant horsepower control mechanism continuously monitors load pressure and automatically adjusts the displacement mechanism to keep pump input power within the engine’s output curve. When system pressure rises under heavy digging loads, pump displacement reduces automatically, preventing engine stall. This feature is particularly valuable for small displacement diesel engines without turbocharging, significantly reducing operator fatigue.

Internal Drain Architecture & Compact Engine Bay Fitment. The PVD series employs an internal drain design in which case leakage returns to the suction side through internal passages. This eliminates external drain lines, reducing fittings and potential leak points, and minimizes the pump’s axial installation length for effortless fitment in confined mini excavator engine bays. It also removes the risk of shaft seal damage from drain-line back pressure.

Integrated Pilot Gear Pump & Modular Expansion. This configuration (9AG5 code) integrates a pilot gear pump driven directly from the main pump shaft, supplying pilot oil to the machine’s directional control valve. This modular design eliminates the need for a separate pilot pump and its drive gearing, reducing component count and installation space. The PVD series further supports rear-mounted integration of a high-pressure auxiliary gear pump for breaker, quick-coupler, or other attachment circuits, extending the host machine’s multifunction capability.

Application Areas

The PVD-15B-37P-9AG5-5599B is specified for the following compact construction machinery hydraulic systems:

• Mini Excavators: Kubota U30-6, U35 series; Takeuchi TB135, TB235 series; Yanmar VIO27-5B series; Kobelco SK75 series and equivalent sub-4-ton models

• Municipal Machinery: Micro street sweepers, compact loader work circuits

• Agricultural Machinery: Compact tractor auxiliary hydraulic systems

• Material Handling: Micro telehandler main hydraulic circuits

• Interchange Compatibility: Fits mounting positions of equivalent Uchida and Nachi OEM pumps in the same tonnage class

Expert Maintenance Tips

Pre-Installation Checks. Verify that the pump shaft spline matches the engine flywheel housing PTO specification. The suction line diameter must support self-priming at the 2,400 rpm rated speed (38 L/min combined flow). Use a suction filter rated at 10 μm or finer. Because the pump uses an internal drain design, no case drain line connection is required — however, ensure the mounting flange face and engine flywheel housing mating surface are free of oil, debris, and burrs, and that the O-ring seal is intact.

First Start-Up. Fill the pump housing with clean hydraulic oil (ISO VG32 or VG46, cleanliness ISO 18/16/13) before initial start. Jog the starter 2–3 times to confirm rotation direction (standard: clockwise / right-hand, viewed from shaft end). Run unloaded for 5 minutes, then ramp to operating pressure gradually. The power-shift control mechanism is factory-set. To switch between light- and heavy-duty power curves, refer to the Nachi PVD series operation manual and tighten the locknut after adjustment.

Routine Maintenance. Inspect pump operating condition every 1,000–3,000 hours or six months, focusing on oil temperature, pressure, flow rate, and vibration. Check the constant horsepower control mechanism for proper response — abnormally large engine speed fluctuation under changing loads may indicate compensator spring fatigue or spool sticking. Replace suction and return filter elements every 2,000 hours. Maintain oil cleanliness at ISO 18/16/13 or better and keep oil temperature below 80°C. After extended storage, circulate unloaded for 30 minutes before applying load.