Let’s start by briefly defining what a hydraulic pump is. A hydraulic pump is a system component that converts mechanical energy into hydraulic energy. It uses the rotational motion from an electric motor or an internal combustion engine to draw fluid from a reservoir according to the principle of increasing or decreasing volume and then delivers it to the system. Many people assume that hydraulic pumps generate pressure; it is commonly believed that they operate under the pressure they create. However, hydraulic pumps do not generate pressure themselves. Pressure arises due to the resistance against the fluid flow. In short, pumps do not create pressure—any pressure observed depends on the resistance in the system.
Hydraulic pumps serve as a power source for many dynamic machines. They are capable of delivering large volumes of oil to hydraulic cylinders or hydraulic motors, converting the driver’s mechanical energy into hydrostatic energy. Hydraulic machines equipped with pumps can perform various tasks such as lifting, lowering, opening, closing, or rotating components. Depending on the application and system requirements, different types of hydraulic pumps are used. Before discussing the types, let’s briefly explain how a hydraulic pump works.
Working Principle of Hydraulic Pumps
Hydraulic pumps operate on the principle of displacement and have two primary functions. First, they create suction. By generating a pressure difference, the pump creates a vacuum effect on the hydraulic oil in the tank. This causes the hydraulic oil to be drawn into the pump and trapped between its components, increasing pressure. Hydraulic pump manufacturers design pumps based on functional and system requirements such as operating environment, required pressure range, and drive type. There are various design principles and configurations for hydraulic pumps, and no single pump meets all needs. That’s why three main types exist: gear pumps, vane pumps, and piston pumps. Let’s examine these types in detail.
Types of Hydraulic Pumps
Gear Pumps
Gear pumps are classified as external or internal gear pumps. Their structure is simple, consisting of two meshing gears. Oil is drawn from the suction line, trapped between the gears, and pushed into the pressure line. They can reach pressures up to 200 bar. Gear pumps are widely available and economical, but they may show lower efficiency at high pressures and have shorter service life. They also tend to generate high noise levels.
Vane Pumps
Vane pumps are variable displacement pumps and can reach pressures up to 100 bar. Another type is the rotary vane pump, commonly referred to as a vane pump in the market. They are preferred in hydraulic circuits of machine tools and enclosed spaces. Unlike gear pumps, vane pumps operate with lower noise levels, which makes them highly favored. However, their suction performance is lower compared to other pump types.
Piston Pumps
Piston pumps are the most efficient type of hydraulic pump and are capable of generating the highest pressures. They come in various designs such as axial, radial, fixed displacement, variable displacement, and constant flow types.
Common Hydraulic Pump Failures
Regardless of type, every pump requires specific maintenance. Regular maintenance not only improves operational efficiency but also extends the pump’s service life. Common issues in hydraulic pumps include:
- Contamination of the hydraulic fluid
- Cavitation problems
- Faults due to incorrect oil selection
- Installation errors
- Problems during system commissioning