industrial//rotating machinery

Rotating machinery is the class of machines built around a shaft turning in bearings (pumps, fans, compressors, electric motors, gearboxes, turbines), and it is most of what an industrial plant's maintenance and condition monitoring watch, because it moves every fluid, every belt and every generator, and because its faults announce themselves in vibration, temperature and current long before it stops. A refinery may run thousands of pumps and motors, a water utility hundreds of pumping stations, and each is a candidate for a sensor and a limit.

Rotating machinery is the class of machines built around a shaft turning in bearings (pumps, fans, compressors, electric motors, gearboxes, turbines), and it is most of what an industrial plant's maintenance and condition monitoring watch, because it moves every fluid, every belt and every generator, and because its faults announce themselves in vibration, temperature and current long before it stops. A refinery may run thousands of pumps and motors, a water utility hundreds of pumping stations, and each is a candidate for a sensor and a limit.

What the members share is a physics that makes diagnosis possible. Everything that happens in them is tied to the shaft speed: imbalance shakes at once per revolution, misalignment at twice, a damaged gear tooth at the mesh frequency, a bearing defect at a rate set by its geometry, so defects can be told apart by the orders of shaft speed at which they appear (vibration analysis, bearing defect frequency). Turbomachines (pumps, fans, compressors) add a second law, the operating point where the machine's characteristic curve meets the curve of the system it drives, and the affinity laws that scale flow, head and power with speed; these give the physical features and the model-based residuals that diagnosis uses (centrifugal pump).

Speed is usually set by a VFD, which saves energy (a fan at 80 % speed draws about half the power) and complicates monitoring, since every feature must be normalized by the speed before two readings can be compared.

A compressor pushed below a critical flow loses stable operation and enters surge, violent oscillations of flow and pressure that can destroy it in seconds; it is an industrial instance of a bifurcation, and anti-surge control keeps the operating point away from that line.

Motors are diagnosed through their own current as well as their vibration, which lets a drive watch the load it turns without a single extra sensor (condition monitoring).