More Comprehensive Vibration Limits for Rotating Machinery

Vibrations are often found to be the cause of rotating machinery failures. To minimize these outages a large number of vibration criteria have been introduced by technical societies, equipment manufacturers, and experienced individuals. While useful, these vibration criteria have often been found to be contradictory and restricted to particular transducer types, machine design, or failure mechanisms. Based on this work and adding the experience accumulated by SwRI with various types of rotating equipment, more comprehensive combined vibration severity limits are established. These limits are divided into several severity regions, and cover filtered and unfiltered vibration. The appropriate correction factors are also introduced to equitably accommodate different machine designs, installations, and vibration problems. Vibration severity limits are provided for relative shaft displacement, for shaft displacement with respect to bearing clearance, and for vibration measurements taken on machine casing or bearing housing. The use of these limits is clarified by reviewing the results obtained from five field studies of actual operating equipment. Advantages, disadvantages, and use of various transducer types (proximity probes, velocity pickups, accelerometers, dual probes), as well as sources of machinery vibration (subsynchronous instabilities, resonance, imbalance, misalignment, etc.) are analyzed to assure proper application of the vibration limits.