Experience with shaft vibration readings on turbines

In the operational supervision of turbines, vibration readings have two functions to fulfill - firstly, in indicating critical vibration for the purposes of damage prevention and, secondly, in assessing the mechanical condition of the rotor and bearings (damage diagnosis). Direct measuring of the shaft undulation is the most indicative method. Several manufacturers of measuring devices offer highly developed shaft vibration reading systems. On the basis of examples drawn from actual turbine operations - and, in particular, on the basis of damage incidents - the authors show the possibilities and limitations of shaft vibration readings. Qualitative assessment criteria rank in the foreground. The problem of furnishing boundary values is also dealt with. Measuring equipment serving the protection of a turbo-set by indicating critical vibration for the purposes of damage prevention incurs little expense in relation to the value of the machinery itself. The equipment for assessing the mechanical condition of the rotor and bearings, on the other hand, incurs greater financical outlay, but is in the majority of cases justified in view of the cost of operational interruptions caused by unscheduled, forced shut-downs, as well as in view of the availability factor involved. By means of ambulant vibration analyses carried out by a specially trained team of experts at regular intervals, in the case of breakdowns and prior to and following inspections, gaps in the monitoring system can be closed to a certain degree. Details are furnished on the conducting of such measurement readings by the Allianz Centre for Technology and on initial results. (orig.)