Within the HMLIFT gear pump product range, Group 30 and Group 40 are the two main classes most frequently compared and specified for industrial vehicle-mounted applications. Although both pump groups share high material quality and field-proven durability standards, they differ clearly in volumetric displacement capacities, pressure limits, physical dimensions and the structural solutions they offer to the system architecture. Correct analysis of these technical differences enables the optimum selection to be made during system design.

Engineering Meaning of Group Classification

In gear pumps, the term “group” is an industry metric that describes the geometric dimensions and tooth geometry of the gears inside the pump housing and, consequently, the volume of fluid transferred during each shaft revolution (cm³/rev). As the group number increases, the pump’s internal volume and therefore the total flow capacity it can produce at the same rotational speed also increase.

Profile of Group 30 Gear Pumps

Group 30 pumps generally provide balanced solutions for medium-duty tipper systems, agricultural trailers and compact vehicle-mounted hydraulic applications. They are available with displacement options such as 55, 61, 65 and 82 cm³/rev.

• Pressure and Speed Ratings: Depending on the model, continuous operating pressures are optimised between 180 and 220 bar. Maximum continuous speed limits are up to 1,700 rpm.
• Configuration Flexibility: Bidirectional (PDCD), unidirectional (PDTD) and DPK-series (PDTDK) options are available. Their structurally compact design offers a significant packaging advantage on chassis with limited installation space.

Profile of Group 40 Gear Pumps

Group 40 pumps are designed for heavy-duty series, semi-trailer applications, high-tonnage tippers and complex systems in which multiple hydraulic functions must be supplied. In the unidirectional configuration, they are available with displacement options of 87, 109, 133 and 151 cm³/rev.

• Pressure and Power Characteristics: In unidirectional models, continuous operating pressures are balanced within the 170-220 bar range. Because of their higher displacement values, the torque and power they draw from the PTO shaft at the same pressure are greater than those of Group 30 pumps; the vehicle platform must therefore be capable of carrying this mechanical load.
• Tandem Capability: One of the most important engineering differences distinguishing Group 40 from Group 30 is the availability of a Tandem (PDTDT-40) configuration, in which two pump housings are combined on a single shaft. Tandem models operate in the 200-250 bar continuous-pressure range with displacement options of 63, 73, 87, 109 and 133 cm³/rev. This arrangement allows two independent hydraulic circuits to be supplied from a single power take-off.

Side-by-Side Technical Comparison

Key Criteria in the Selection Process

The choice between the two groups is derived from the volume of the telescopic cylinder and the targeted lifting speed. Extending a large-diameter, long-stroke cylinder within a reasonable time requires a high oil volume, which may direct the design towards Group 40. In projects where installation space is limited, torque limits are restrictive or the required flow remains below 82 L/min, the compact structure of Group 30 provides a suitable engineering solution. For both groups, it should be remembered that the flange and shaft types (DIN 5462 for ISO and DIN 5463 for UNI) must be matched to the vehicle PTO configuration before ordering.