Gear pumps for the highest demands – powerful, compact, and versatile

HM gear pumps are used in a wide range of hydraulic applications:

• Hydraulic systems and power units
• Agricultural vehicles: Tractors, harvesters, combines
• Construction machinery: Excavators, loaders, cranes
• Machine tools: Industrial manufacturing systems
• Heavy-duty equipment: Various industrial applications

Applications include industry, agriculture, and construction.

HM gear pumps are classified into five frame sizes (HM1, HM2, HM3, HM4, HM5 / Group I–V). They are available as single, double, or multiple pumps, with fixed rotation (clockwise or counterclockwise) or bidirectional operation.

• HM1 (Group 01/I): Rated pressure 170–250 bar, rated speed 700–3500 rpm, displacement 1–7.9 cm³
• HM2 (Group 02/II): Rated pressure 160–250 bar, rated speed 700–3500 rpm, displacement 4–32 cm³
• HM3 (Group 03/III): Rated pressure 160–250 bar, rated speed 700–2500 rpm, displacement 20–63 cm³

It is important to note that rated pressure and speed depend on the displacement.

For optimal operation, the following parameters should be observed:

• Maximum inlet velocity: 2.5 m/s
• Inlet pressure: Between -0.2 and 0.5 bar
• Hydraulic fluid viscosity: Recommended 20–60 mm²/s (allowable: 6–200 mm²/s)
• Operating temperature: Between -25°C and +80°C (recommended: 30–50°C)

Under these conditions, all pumps can operate continuously and reach the outlet pressure specified in the catalog.

The ordering codes include a variety of shaft and flange options:

HM1:

• Tapered shafts 1:8
• Plessey flanges

HM2:

• Tapered shafts 1:8, splined shafts 9T.16/32, tapered shafts 1:5
• Flange types: European (4xØ9), SAE A, DIN 60x60

HM3:

• Tapered shafts 1:8, splined shafts 13T 16/32
• Flange types: Plessey (4xØ11), Oval SAE B, Plessey (4xØ9)

This variety allows for customization to different system requirements.

Tandem (dual) or triple gear pumps are configurations where multiple pump units are combined. These multiple pumps are subject to important limitations:

• The maximum speed is determined by the pump unit with the lowest maximum speed
• The technical data of the individual pumps also apply to tandem and triple pumps, provided that only one pump operates at rated pressure while the others are unloaded
• The total performance is not simply the sum of the individual units under all conditions

Yes, specific guidelines are essential to ensure reliable operation and long service life of gear pumps:

• Stress-free installation: Power transmission from the motor to the pump must occur without radial or axial forces on the pump shaft
• Accessories: On request, we offer elbows, couplings, and seals
• Quality assurance: All hydraulic products undergo production testing

Failure to follow these recommendations may impair reliability or reduce service life.

HM gear pumps offer several key advantages:

• Simple design: Few moving parts mean low maintenance
• Cost efficiency: Low acquisition and operating costs
• Ruggedness: Reliable operation even under harsh conditions
• Versatility: Wide range of sizes and configurations
• Constant flow rate: Steady oil delivery at constant speed
• Compact design: Space-saving installation possible

Selection depends on several key criteria:

• Displacement: Determined by the required flow rate of your application
• Operating pressure: Must be within the rated pressure range of the selected group
• Speed: Drive speed must be within the rated speed range
• Connection type: Compatible with your hydraulic system
• Shaft/flange type: Depending on the drive unit and mounting situation
• Rotation direction: Clockwise, counterclockwise, or bidirectional
• Additional functions: Pressure or priority flow regulators if needed

These designations correspond to international standards and define performance classes:

• HM1 (Group I): Smallest size for low flow rates and precision applications
• HM2 (Group II): Medium size for standard hydraulic applications
• HM3 (Group III): Larger size for higher flow rates in heavy-duty applications
• HM4/HM5 (Group IV/V): Largest sizes for high-performance applications

This classification facilitates international compatibility and spare parts procurement.