scope:

The present guideline provides an overview of the specific vibration problems occurring with fans and blowers for gases which are used in installations and equipment. These fans and blowers may have drive power levels in the kilowatt to megawatt range and the external diameter of their impellers may exceed 100 mm. General information about the measurement and analysis of machine vibrations and the vibration problems which can arise in all rotating machines is given in VDI 3839 Part 1 and Part 2 and forms the basis for Part 4. This general information will not be repeated here unless this is necessary in describing the special features of fans and blowers.

Many of the phenomena described here can also occur with other fluid kinetic machines, such as, for example, turbo-compressors. These are to be dealt with in the scheduled guideline VDI 3839 Part 3. Screw and piston compressors are not covered here since they work on different principles and have a different type of mechanical design. Specific information about this may be found in VDI 3836 and VDI 3838.

This guideline is intended to provide the machine manufacturer, the plant engineer and the operator with information on identifying the causes of troublesome vibrations and on remedial measures. In many cases problematic vibrations do not occur until the machine is actually operating in its intended location and need to be analysed quickly in order to prevent operational disturbances. In most cases the problematic vibrations can be traced back to just a few typical causes. Imbalance, misalignments and roller bearing damage are by far and away the commonest although natural vibrations and aerodynamic excitations are relatively frequent causes. On the other hand, a wide variety of other causes is found in the less common special cases. Both the typical and also the special vibration problems found in practice will be explained below with the aid of examples, and their manifestations and causes will be systematically presented.