Getting the right vibe
Anybody who has ever driven a car knows that vibration can be a common sign of a malfunction. Whether it’s an unfamiliar noise, shaking or rattling, it can indicate that something is not quite right and that you need to consult a mechanic. The same holds true for industrial machinery, where unusual vibration can be an important red flag.
Vibration analysis involves measuring the vibration levels and frequencies of rotating equipment and then using that information to determine the conditions of a machine and its components. The principle behind it is simple ─ the rotating elements of every machine generate vibrations at specific frequencies, which can be measured using a device called an accelerometer.
The accelerometer will output a voltage signal proportional to the amount and frequency of the vibration; this signal is then fed into a data collector which records it as either a time waveform (amplitude vs. time), a Fast Fourier Transform (amplitude vs. frequency), or both. The result is then analysed by a vibration analyst or by a smart algorithm and compared with the parameters provided by the original equipment manufacturer (OEM). An increase in vibration amplitude signals a problem in the rotational elements of the machine.
Vibration analysis can be applied to a variety of machines and tools that have rotational elements — motors, pumps, compressors, turbines and many more — and the collected data can detect faults such as misalignment, loose bolting, bent shafts and insufficient lubrication. As a consequence, vibration analysis can be extremely useful in predicting breakage, planning appropriate repair and substituting damaged parts before disaster strikes. But how can we get the most out of this technology?
Collecting thorough data
First things first, we need to to choose the right accelerometer and mount it correctly. Accelerometers are fixed to a machine using bolts or a magnet ─ it is essential to choose the correct sensor, cable, connector and mounting technique for each piece of equipment. For example, in certain cases sensors and connectors have to be able to withstand harsh industrial environments to measure vibrations accurately and provide reliable data.
In addition, it is always important to obtain a full-spectrum vibration signature in all three axes horizontal, vertical and axial — on both ends of the machine and driven equipment. Sometimes maintenance personnel fail to do so, but this may mean the manufacturer cannot detect technical issues that only show up in one axis. Consequently, it is paramount to check all three to spot the one that signals the problem.
Relying on qualified personnel
In the past, vibration analysts had to scan the full vibration spectrum of a machine to identify frequencies at which vibration was higher and then consult a chart that matched vibration peaks with their most likely causes. Over time, this procedure allowed analysts to develop a sense of how the machine was supposed to vibrate when functioning correctly.
The latest accelerometers have more automated functions, which makes vibration analysis faster and more precise. However, you still need a trained technician or an engineer competent in rotating machinery vibration to make sense of the data that the accelerometer provides. Once the operator interprets the data correctly and identifies the problem, you can order the spare parts you need by contacting an automation parts supplier and then scheduling the necessary repairs.
In our cars, strange sounds or unfamiliar vibration can indicate a problem, but if we spot it in time we can intervene, minimising damage to the car and maybe even preventing an accident. Similarly, vibration analysis can help manufacturers understand when a machine is deteriorating, so that they can take immediate action. If that action involves ordering spare parts, we are always here to help.