Water hydraulics
The water medium has no pollution, low cost, good flame retardancy and safety. The system with water as the medium has good dynamic characteristics and small temperature rise, which makes the water hydraulic system have incomparable advantages over the hydraulic oil system in some specific applications. However, the physical and chemical characteristics of the water medium, such as low viscosity, poor lubricity, strong corrosion, and high saturated vapor pressure, bring many problems such as sealing, lubrication, friction, wear, corrosion, and cavitation to water hydraulic components, which affect the service life and limit development.
The situation of water hydraulic components
1. Water pump
1.1 Plunger pump
Mainly swash plate structure as follows
The working pressure is generally less than 20MPa, and the flow rate can reach 150L/min.
Another type of plunger pump is a 3-cylinder plunger pump
This plunger pump is currently the mainstream product on the market, with a pressure output of up to 400 MPa and a flow output of hundreds of cubic meters per hour.
1.2 Gear pump
For the application of small pressure, some domestic companies have also carried out research on gear pumps. However, with the continuous development of the application range and product line of plunger pumps, there are almost no gear pump products on the line.
2. Valves
At present, HAUHINCO in Germany provides various types of proportional relief valves, reversing valves, pressure regulating valves, etc. with a pressure of 800bar and a flow rate of 3000L/min. The proportional reversing valve developed by Japan KYB Company has a rated working pressure of 14MPa and a flow rate of 20L/min. The French CEA LIST company has developed a servo valve applied to manipulators, with a pressure of 21MPa, a working frequency of 20hz, and a flow rate of 10L/min. Commonly used needle valves, ball valves, etc. are also used in water hydraulic systems.