The cartridge bearing
Bearing and basket/rotor together form the heart of the machine. From Krettek’s point of view service life, high reliability and an economical replacement are the significant aims of the design of these components. An easy replacement of the bearing system will be provided by fixing of the bearing in a cartridge, which can be moved back into the machine room.
To guarantee furthermore a long availability of the cartridge bearing the decisive system components like shaft, bearing and bearing sleeve are consciously overdmensioned. By the achieved rigidity of these components on the one hand high production accuracy exactness can be reached by the reduced deformation of components, on the other hand the inclination of the bearing as a result of shaft deformation resp. deformation of the bearing sleeve. Both consequential effects together guarantee a low-vibration and smooth operation of the system and contribute to a high reliability of the bearing.
The lubrication for high-speed centrifuge systems is made by oil for the purpose of selective heat dissipation. Oil circulation lubrication systems will be used whereas the recirculated quantity is adjusted to the respectively expected operation conditions. By request the operating temperature of the oil can be reduced due to high stress by integration of an oil cooling system into the oil circulation system to guarantee an adequate kinematic viscosity of the lubricating film.
For a fully automatic monitoring of the permitted operating temperature the bearing positions will be equipped with temperature sensors, type PT 100.
The sealing of the bearings is designed in such way that apart from the standard choosen multiple radial shaft seal also a huge number of varied special solutions with the same outside diameters of the cartridge bearing are possible, on operator’s option. So a high flexibility is given at altered operator requirements. The type diversity includes medium wetting bearing chambers for e.g. sealing liquid, rinse or also cooling liquid, especially for the processing of temperature sensitive products. Furthermore also the installation of axial seal rings or a special labyrinth design is possible.
As standard solution a triple sealing by means of radial shaft seals is favoured on process room side. These are running on a special covered shaft protection sleeve , which on the other hand will be statically sealed to the adjacent components by means of O-rings. Following the philosophy to offer a maximum of process security the following design will be ensured. At product side a chamber is generated by two special radial shaft seals face each other. This chamber can be inertized with e.g. nitrogen by means of an external connection. Opposite to the process room a leakage collecting room follows. It is designed in such way that penetrated product and/or lubricant will be collected and discharged by a hose pipe into a transparent leakage bottle which is positioned at a well visible place. So a simple visual control of the sealing system is guaranteed. The sealing at bearing side is made by approved radial shaft seals on both sides which again have prepended a decompression room. So a reliable sealing of the cartridge bearing is guaranteed which meet all the requirements of the high-speed centrifuge systems.