For rotating equipment, there are various forms of maintenance available, each with its own pros and cons. These include reactive maintenance, periodic maintenance, preventive maintenance, and finally predictive maintenance, also known as condition-dependent maintenance (CDM).
In this form of maintenance, the status of a machine is measured during operation. The goal is to visualize and determine when critical parts need to be replaced. Parts that are still in good condition do not need to be included in the maintenance, and parts that are known to cause problems soon will be replaced at the next opportunity or during a turn-around.
This form of maintenance is a type of Condition Monitoring and is also known as predictive maintenance. There are several measurement methods to gain insights into the condition of a machine so that condition-dependent maintenance can be implemented:
- Vibration measurements
- Thermography / Infrared measurements
- Oil analysis
Vibration measurements as a form of condition monitoring
Vibrations in a machine provide insight into the status of a machine. They can indicate imbalance, alignment errors, bearing damage, gearbox problems, etc. As long as these vibrations remain within predetermined limits, there is nothing to worry about, but when vibrations become too intense, they can lead to severe damage and dangerous situations. Therefore, it is important to properly map out at which frequencies vibrations occur. With the help of continuous vibration measurements or periodic condition monitoring, a trend analysis can be made after which a specialist can predict when critical parts need to be replaced.
Infrared measurements
Information about the status of a machine can also be obtained through thermography. This method uses infrared measurements to make the heat (infrared radiation) from materials and objects visible. This form of radiation is not visible to the human eye.
If a part of a machine is subject to friction, heat is generated, and thermography quickly makes this visible. In addition to friction, alignment errors, leaks, and heat losses can also be detected.
Oil analysis
Analyzing (lubricating) oil can provide insights into the status of a machine and contribute to preventive maintenance. By taking oil samples from lubricating oil, wear, contamination, oxidation, water contamination, or combustion residues can be detected. For example, if steel particles are noticed in the oil sample, it indicates wear. Another finding from an oil analysis might be the presence of soot particles in the oil, indicating an excess of lubricant in the bearing housing, causing the temperature to become so high that the grease burns.