Pressure gauge for monitoring the pressure in lubrication systems
Pressure gauges are used to monitor and display the pressure in hydraulic systems and are also used in central lubrication systems such as single-line lubrication systems or progressive lubrication systems. In central lubrication systems, it is necessary to continuously monitor the specified thermodynamic variables such as pressure, temperature and volume flow in order to be able to react to deviations. If, for example, the pressure does not correspond to the specified operating pressure, there may be deviations in the amount of lubricant at the lubrication points. As a result, lubrication points are under- or over-supplied and the system may wear out faster. In addition to conventional pressure gauges, special glycerine pressure gauges and pressure gauges with visualization are used in central lubrication systems.
This is how pressure gauges work
Various techniques are used to monitor the pressure in hydraulic systems. The classic pressure gauge is equipped with a tube spring and takes advantage of the pressure-proportional change in length of the spring when pressure is applied. The tube spring inside the housing is usually realized with a circular or helical metal tube. This metal tube bends when subjected to pressure and transmits its change in length to the measuring mechanism via a pull rod. The measuring mechanism in turn translates the change in length into a rotation of the pointer axis, so that the pressure in the system can be easily read from the outside.
The decisive factor when choosing a pressure gauge is the pressure range in which the device is to be used. The pressure range must cover the entire operating pressure range of the central lubrication system. Excessively high pressures can lead to the tube spring of the pressure gauge deforming plastically and not fully relaxing after the expansion. Generally, central lubrication systems from SKF have pressure gauges with a display range from 0 to 400 bar. The measuring devices can measure the pressure for oil and fluid grease as well as for grease.
Pressure gauges from SKF
The classic pressure gauge from SKF is attached to the pressure pipe using a double tapered ring and a union screw. The type 248-602.25 manometer, for example, is suitable for a pressure range from 0 to 10 bar, while the model 169-106-004 can even record pressures of up to 60 bar. Alternatively, pressure gauges with a sealing ring are available. These can measure much higher pressures of up to 250 bar without compromising accuracy.
So-called glycerine pressure gauges are available for special applications. These are used at measuring points with particularly high dynamic alternating loads in order to protect the pointer mechanism and to give the pressure gauge greater resistance to wear. Thanks to the inertia of the system, the position of the hands on a glycerine manometer can be read much more easily. With the Model 169-110-010, SKF offers, for example, a glycerine pressure gauge with a pressure range from 0 to 100 bar. This range corresponds to 0 to 10 MPa and is sufficient for most central lubrication systems. In the pressure gauge with visualization section, measuring devices with a pressure range of up to 100 bar are also available.