Vane Pump

A vane pump is a positive displacement pump in which radially movable vanes rotate within a stator arranged eccentrically relative to the rotor, alternately enlarging and reducing the volume of the chambers. This principle generates the flow required for hydraulic systems at operating pressures up to approximately 150 bar and is characterized by low pulsation and low noise levels.

Basics and Operating Principle of the Vane Pump

The vane pump, also referred to as a rotary vane pump in the technical literature, belongs to the family of positive displacement pumps. Its operating principle is based on the change in volume of chambers formed between the vanes of the rotor and the inner wall of the stator. Due to the eccentric arrangement of the rotor and stator, these chambers change their volume during each revolution, which drives the pumping process.

The pumping principle in detail

The pumping process of a vane pump can be divided into four phases. During suction, the rotor rotates, and the cells expand on the suction side, causing hydraulic fluid to flow in through the suction channel. On the opposite side, the cells contract again, the fluid is compressed, and expelled through the discharge channel. The pressure change occurs at the transition between the suction and discharge sides. The vanes are pressed against the housing wall by centrifugal force, hydraulic pressure, or mechanical push rods, thereby forming reliably sealed pumping chambers.

Structure and Design Features

The core of a vane pump consists of a few, precisely matched components. The rotor accommodates the radially movable vanes and rotates within the stator, which is designed as a hollow cylinder with an eccentric inner contour. Side plates and a cover ensure the axial sealing of the pumping chambers. In many industrial designs, the rotor, vanes, and impeller are combined into a replaceable insert assembly, which significantly simplifies maintenance and repair.

Types of Vane Pumps

Vane pumps are available in various designs that differ in terms of flow characteristics, pressure rating, and adjustability. The selection of the appropriate design depends on the specific requirements of the hydraulic system.

Vane pump with constant flow rate

The simplest and most widely used design delivers a constant flow rate at a constant speed. Typical displacement volumes in industrial applications range from 10 to 25 cm³ per revolution; at nominal speeds of around 1500 min⁻¹, flow rates in the range of approximately 60 to 70 l/min result. This design is suitable for applications requiring a continuous, low-pulsation flow rate.

Double vane pump

Double vane pumps combine two pump stages in a single housing. Each stage can have a different displacement volume, allowing two independent pressure circuits to be supplied from a single drive. In practice, combinations of vane and axial piston pumps are used, delivering flow rates of approximately 62 to 69 l/min at operating pressures up to 150 bar. This design reduces the required installation space and simplifies the system structure.

Variable-displacement vane pump

Variable-displacement vane pumps allow the flow rate to be adjusted to current demand. The adjustment is performed via a mechanical pressure compensator, which reduces the flow rate when the set target pressure is reached. In medium-stroke operation, the pump delivers only the amount actually required, which significantly reduces energy consumption. Series such as the PV7 series or the PVD series implement this principle and are suitable for applications with highly fluctuating flow rate requirements.

Technical Characteristics and Operating Limits

Vane pumps operate within a defined operating range that distinguishes them from other pump types. Knowledge of these parameters is essential for the correct design of hydraulic systems.

Operating pressure and flow rate

The typical operating pressure of a vane pump ranges from 100 to 150 bar, although some models can handle up to 160 bar for short periods. For higher pressures starting at 200 bar, axial piston or radial piston pumps are the better choice. The flow rate depends directly on speed and displacement volume. At rated speeds of 1500 rpm and viscosities around 24 mm²/s, industrial pumps achieve effective flow rates of 62 to 64 l/min at a system pressure of 150 bar.

Efficiency and Noise Level

Vane pumps achieve good volumetric and mechanical efficiencies because the vanes are pressed against the stator wall by centrifugal force and hydraulic pressure, thereby self-adjusting. Wear is partially compensated for by this self-adjusting effect, which keeps efficiency stable over the pump’s service life. Another advantage is the low noise level, which makes vane pumps ideal for use in noise-sensitive environments.

Vane Pumps Compared to Other Pump Designs

In practice, the decision for or against a vane pump is often made in comparison with gear and piston pumps. Each design has its strengths and weaknesses.

Compared to gear pumps, the vane pump offers better suction characteristics and lower pulsation. Compared to piston pumps, it stands out for its more compact design, lower noise level, and more affordable price for medium-pressure applications. However, piston pumps are preferable for abrasive or highly viscous fluids.

Applications in industrial hydraulics

Vane pumps are found in numerous industrial applications that require a low-pulsation flow at medium pressures. Typical areas of application include machine tools, injection molding machines, presses, and test benches. In mobile hydraulics, they are used in systems where low noise levels and a compact design are required, such as in lifting platforms or small wheel loaders. Their suitability for mineral oils in viscosity classes ISO VG 32, 46, and 68, as well as for flame-resistant fluids in classes HFC and HFD, extends their application range to safety-critical systems.

Standards for Vane Pumps

The design and testing of vane pumps are governed by several standards. DIN 51389 defines the testing of the wear behavior of hydraulic fluids in vane pumps. DIN EN ISO 20763 regulates the testing of hydraulic fluids with regard to their wear protection. The safety requirements for hydraulic systems with vane pumps are covered by DIN EN ISO 4413. Hydraulic oils must meet the requirements of DIN 51524, and the filterability of the lubricant is evaluated according to DIN ISO 13357-2. The symbols for pumps in circuit diagrams are based on DIN ISO 1219.

Maintenance and Servicing

Regular maintenance of a vane pump ensures its proper functioning and extends its service life. Since the main wear parts—namely the vanes, impeller, rotor, side bushings, and control plates—are combined into a replaceable insert assembly, signs of wear can be remedied by replacing the entire unit. Wear is determined during test operation over 250 hours under defined conditions, with mass loss on the vanes and impeller ring as well as the decrease in flow rate serving as evaluation criteria.

Importance of Oil Quality and Filtration

The cleanliness of the hydraulic fluid has a decisive influence on the service life of a vane pump. Filters with a nominal mesh size of 25 µm or finer, with a filtration ratio ß10 ≥ 100, are required to comply with the cleanliness class according to ISO 4406. Adherence to the oil change intervals specified by the manufacturer and regular monitoring of oil quality in accordance with DIN 51524 prevent premature wear on the sliding surfaces.

Typical signs of wear

Wear on the vanes manifests as a decrease in flow rate and increased leakage. Scoring or pitting on the raceway indicates insufficient lubrication or contaminated oil. Bearing and seal damage is noticeable through increased noise, rising temperatures, or visible leaks. Early detection of these symptoms enables scheduled maintenance and helps avoid unplanned downtime.

Future Developments

The development of vane pumps is focused on higher pressure ratings, improved energy efficiency, and the integration of intelligent control systems. Manufacturers are working on series that cover pressures up to SAE 3000 PSI while maintaining a compact design and low noise level. The integration of sensors to measure pressure, temperature, and flow rate directly at the pump enables condition-based maintenance concepts and adaptive control of the flow volume. Advances in materials science are contributing to more wear-resistant coatings and longer maintenance intervals. The growing importance of energy-efficient hydraulic systems will further increase demand for variable-displacement vane pumps, as these significantly reduce energy consumption during partial-load operation.