Hydraulic gear pumps
Hydraulic Gear Pumps
Hydraulic gear pumps are among the most commonly used types of positive displacement pumps in hydraulic systems. Their operation is based on the volumetric displacement principle by two intermeshing gears rotating in the same direction inside a sealed housing. During the rotation of the gears, a vacuum is created in the spaces between the teeth, causing fluid to be drawn from the suction port. The fluid then moves around the housing’s perimeter to the discharge side, where the meshing of the gears pushes the fluid into the hydraulic system. The fluid movement is continuous, and thanks to the compact design and a small number of moving parts, these pumps are highly durable and reliable.
Construction of Hydraulic Gear Pumps
The basic components of hydraulic gear pumps are:
- Gears – one is driven directly by the motor (drive gear), while the other rotates idly (idler gear). The gear teeth are designed to ensure continuous sealing of the working spaces and prevent fluid backflow.
- Pump housing – usually made of cast iron or aluminum alloys, it serves as the enclosure for the gear mechanism and ensures the overall system’s tightness. Inside the housing, there are suction and discharge channels.
- Bearings and bushings – used to guide and stabilize the gear shafts. They must have high wear resistance and maintain minimal operational clearances.
- Seals – mounted around the shaft and housing joints, they prevent fluid leaks and protect the system from external contaminants.
A key design aspect of hydraulic gear pumps is maintaining minimal clearances between the working parts, especially between the gear tooth sides and the housing. Excessive clearances cause internal leakage, significantly reducing the volumetric efficiency of the pump.
Technical Parameters and Performance Characteristics of Hydraulic Gear Pumps for Oil
Hydraulic gear pumps feature a simple, compact design and can operate over a wide range of parameters. The typical geometric displacement ranges from 0.2 cm3/rev to over 200 cm3/rev, with maximum operating pressures reaching up to 300 bar. Depending on the model, operating speeds range from 1000 to 4000 rpm. The nominal flow rates of hydraulic gear pumps can vary from a few to several hundred liters per minute.
The volumetric efficiency of these pumps often exceeds 90%, provided that the hydraulic fluid cleanliness is maintained and internal leakage is minimized. Due to the lack of control elements, hydraulic gear pumps deliver a constant flow rate at a given rotational speed, making them particularly useful in systems with stable operating parameters.
Design Variants of Hydraulic Gear Pumps
In hydraulic systems, two primary types of hydraulic gear pumps are used:
- External gear pumps – the most common type, characterized by a simple design and low manufacturing cost. The gears are mounted externally relative to the pump’s axis. These pumps tend to be relatively noisy but are highly resistant to contamination.
- Internal gear pumps – feature internal meshing, resulting in quieter and smoother operation. They are suitable for applications requiring low noise levels and precise flow.
There are also dual-flow hydraulic gear pumps and split-housing versions designed for special applications, such as systems with multiple working circuits.
