QX41-040/31-025R Bucher Internal Gear Pump | 40.6+?cc 160 bar

Product Overview

The QX41-040/31-025R is a tandem high-pressure internal gear pump from the Bucher Hydraulics QX series, the fifth generation of Bucher’s renowned internal gear pump technology. This tandem configuration combines a QX41 series main pump with a QX31 series secondary pump, featuring a main pump displacement of 40.6 cc/rev and a secondary pump displacement of 24.5 cc/rev (based on QX31-025R specification), for a total displacement of approximately 65.1 cc/rev.

The QX series represents over thirty years of proven global service, with the fifth generation incorporating numerous improvements to an already straightforward and rugged design. Featuring a new tooth profile conceived and optimized with CAE, combined with an optimized hydrodynamic lubrication film, the series delivers extremely low noise levels (< 75 dB(A)) and minimal flow and pressure pulsation. Volumetric efficiency reaches up to 98%, ensuring consistently high performance throughout the pump’s service life.

Engineered as a direct OEM-replacement solution, the QX41-040/31-025R fully complies with Bucher original design standards and SAE/ISO mounting interface specifications, offering 100% direct interchangeability with OEM pumps. Every unit undergoes 100% workload simulation testing prior to shipment, rigorously validating pressure retention, volumetric efficiency, and internal leakage performance to meet or exceed OEM standards.

Model Code Breakdown (Bulleted List) :

• QX — Series: Bucher Internal Gear Pump

• 41 — Main pump frame size: QX4 series (displacement range 20.4 – 64.7 cc/rev)

• 040 — Main pump displacement code: 40.6 cc/rev

• / — Separator between main pump and secondary pump

• 31 — Secondary pump frame size: QX3 series (displacement range 10.0 – 31.2 cc/rev)

• 025 — Secondary pump displacement code: approx. 24.5 – 25.1 cc/rev

• R — Rotation direction: R = Right-hand (clockwise)

Note: The QX41-040/31-025R is a tandem pump configuration, with two pump stages (QX41 + QX31) driven by a common input shaft, enabling simultaneous oil supply to two independent hydraulic circuits or flow combination for greater total output.

Technical Specifications 

QX41-040 Main Pump Specifications

• Model: QX41-040R (Bucher Part No. 100017834)

• Displacement: 40.6 cc/rev

• Rated Pressure (Continuous): 160 bar

• Peak Pressure: 210 bar

• Maximum Speed: 3000 rpm

• Shaft Type: 32 mm

• Mounting Flange: SAE B 2-bolt flange

• Weight: Approx. 8 kg

QX31-025 Secondary Pump Specifications

• Model: QX31-025R (or QX31-025R29)

• Displacement: Approx. 24.5 – 25.1 cc/rev

• Rated Pressure (Continuous): 160 – 210 bar

• Maximum Speed: 3200 rpm

QX Series General Specifications

• Series: Bucher QX 5th Generation Internal Gear Pump

• Pump Type: Fixed Displacement Internal Gear Pump

• Maximum Operating Pressure (Open Circuit): 400 bar

• Displacement Range: 3.3 – 500 cc/rev

• Volumetric Efficiency: ≥ 95% (up to 98%)

• Noise Level: < 75 dB(A)

• Compatible Fluids: Mineral oil, HFB/HFC/HFD fire-resistant fluids, fuels, biodegradable and low-viscosity fluids

• Certifications: ATEX 2, ABS, DNV, GL, LR, NK, etc.

• Housing Material: High-strength cast iron

• Operating Temperature Range: -20℃ to +80℃

Key Technical Advantages

1. 5th Generation Internal Gear Technology with 98% Volumetric Efficiency
The QX series represents Bucher’s fifth-generation internal gear pump technology, proven over thirty years of global service. Featuring a CAE-optimized tooth profile and large sealing areas that effectively reduce internal leakage, volumetric efficiency reaches up to 98%. Consistently high performance is maintained throughout the pump’s service life, significantly reducing energy losses and system temperature rise.

2. Extremely Low Noise and Pulsation – < 75 dB(A)
The CAE-optimized tooth profile, combined with an optimized hydrodynamic lubrication film, delivers exceptionally low noise levels (< 75 dB(A)) and minimal flow and pressure pulsation. This not only improves operator working conditions but also significantly reduces system piping vibration and noise radiation.

3. Superior Pressure Capability – Peak 400 bar
The QX series delivers up to 400 bar maximum working pressure in open circuits. The QX41 series main pump offers 160 bar continuous pressure with 210 bar peak capability. The high-strength cast iron housing provides excellent fatigue strength and dimensional stability for long-term reliability under high-pressure conditions.

4. Flexible Configuration and Combination Capability
The QX series supports single, tandem, and triple pump configurations, with over 1000 variants available worldwide. The QX41-040/31-025R combines QX41 and QX31 stages in a tandem configuration, with both stages driven by a common input shaft for simultaneous oil supply to two independent circuits. Bucher also offers a wide range of mounting flange (SAE A/B, ISO), shaft, and port options.

5. Wide Fluid Compatibility
QX series pumps can operate with a wide range of fluids, including mineral oil, HFB/HFC/HFD fire-resistant fluids, fuels, biodegradable fluids, and low-viscosity fluids. For low-viscosity applications, Bucher offers the dedicated QXV series.

6. Comprehensive International Certifications
QX series pumps carry ATEX 2 explosion protection certification, along with ABS, DNV, GL, LR, NK, and other international marine classification society certifications, making them suitable for industries with stringent safety and reliability requirements.

7. 100% Factory Tested & Direct Interchangeability
Every unit undergoes 100% workload simulation testing prior to shipment, covering pressure retention verification, internal leakage detection, and flow validation. Fully compliant with Bucher original design standards, with flange dimensions, shaft specifications, and mounting interfaces identical to OEM pumps—direct drop-in replacement with zero modifications required.

Application Areas

The QX41-040/31-025R tandem internal gear pump is widely used in the hydraulic systems of the following equipment:

• Injection Molding Machines: Precise, stable hydraulic power for injection, clamping, and other processes

• Die Casting Machines: High-pressure, high-flow hydraulic systems

• Hydraulic Presses: Precise pressure and speed control

• Hydraulic Power Units (HPU): Core power elements for industrial hydraulic stations

• Material Handling Equipment: Forklifts, lifting platforms

• Waste Compactors: Municipal and sanitation equipment

• Machine Tools: Hydraulic systems for metal cutting and forming machinery

• Lift and Elevator Drives: Hydraulic drives for vertical transportation

Expert Maintenance Tips

1. Rotation Direction Confirmation
The “R” suffix in the model designation indicates right-hand (clockwise) rotation. Before installation, always verify that the PTO rotation direction of the host machine matches the pump’s rotation direction—incorrect rotation will result in pump failure to prime and may cause severe damage to internal components within a short period.

2. Tandem Pump Installation Precautions

• The QX41-040/31-025R is a tandem pump configuration—both stages share a common drive shaft. Pay special attention to axial alignment accuracy during installation

• Thoroughly clean the mounting flange (SAE B 2-bolt)and 32 mm shaft mating surfacesbefore installation to ensure no debris remains

• Use Bucher-specified torque values for mounting bolts—avoid over-tightening which may cause housing distortion

• Ensure correct connection of inlet and outlet ports for both stages—do not interchange

3. First Start-Up and Bleeding

• Before first start-up, must fill the pump with hydraulic oil through the inlet port—never start dry

• After start-up, run at low speed with no load for 2–3 minutes to ensure complete air evacuation from the system

• Check for abnormal noise or leakage—internal gear pumps are particularly sensitive to cavitation

4. Fluid and Filtration

• Use high-quality anti-wear hydraulic oil compliant with DIN 51524 standards

• Maintain system oil cleanliness to ISO 4406 18/15 or better

• QX series pumps have high cleanliness requirements—install a high-quality filter in the inlet line

• Operating temperature should be maintained within -20℃ to +80℃

5. Periodic Maintenance

• Check mounting bolt torque every 1,000 operating hours

• Regularly monitor system operating pressure to ensure the main pump does not exceed 160 bar rated pressure (210 bar peak)

• QX series pumps are known for long service life and low maintenance requirements—nevertheless, regularly inspect shaft seals to prevent leakage

• If flow output decreases, noise levels increase abnormally, or system temperature rises excessively, inspect and replace worn components promptly