Directional valves for central lubrication systems
Central lubrication systems such as single-line systems or progressive systems work with a large number of different media flows to supply up to 150 lubrication points. Directional valves are used so that these lubricant flows can be controlled according to the specifications. Directional control valves can divide material flows with oil or grease, for example, in order to control several lubrication circuits zonally. In this way, it is possible to decouple lubrication circuits with different clock, volume flow or pressure requirements.
Directional valves are used in single-line systems with piston metering devices up to a pressure of 45 bar. In progressive systems with significantly higher pressures, the valves can even achieve values of 300 or 500 bar. When selecting a directional valve for central lubrication systems, however, not only the pressure has to be taken into account. The number of flow paths is of primary importance. Directional valves are classified in terms of flow paths based on the number of switch positions and the connections per switch position. For example, a 4/2-way valve is equipped with four connections and two switching positions, while a 2/2-way valve has two connections and two switching positions.
Technical details on directional valves from SKF
Using the switch positions, the path for the lubricant in the hydraulic system can be released or blocked. Changes of direction are also possible. In addition to the connections and switching positions, when selecting the directional control valve, it is also important to consider how large the amount of lubricant flowing through is. The medium is also crucial: directional valves are generally used for oils and greases up to NLGI class 2.
The model 161-110-018 is, for example, a 2/2-way valve with a KV value of 0.8 and a maximum pressure of 50 bar. The directional control valve can be used excellently for single-line systems and can be used at media temperatures from -10 to +80°C. The sister model of type 161-110-031 even realizes pressures of up to 500 bar using a ball seat valve and is therefore predestined for use in progressive systems. While the directional control valve is used for single-line systems with viscosities of up to 21 mm²/s, the model is suitable for progressive systems for viscosities between 4 and 1,500 mm²/s.
The 4/2-way valve type 161-140-050 works as a slide and is designed for maximum pressures of 320 bar. At temperatures from -25 to +75 ° C the valve can be used in connection with oils in a range from 20 to 1000 mm²/s. Further important hydraulic and mechanical parameters as well as electrical values can be found in the corresponding product data sheets.