In the past, manufacturers generally relied on their experienced technicians to manually check the health of all their equipment during routine maintenance. However, such a practice faces problems.
First of all, labor shortage may affect the frequency and efficiency of the routine maintenance. Second, novice technicians may have limited experience working with the multitude of sophisticated equipment, which could compromise inspection reliability. There could even be safety risks in potentially dangerous work environments. Furthermore, with time-based maintenance, manufacturers have difficulty grasping real-time operating conditions of their equipment and they generally are more cost-conscious especially with high-precision and high-cost production equipment.
Manufacturers could encounter two situations. One is early replacement of equipment before the end of its useful service life. This unnecessarily increases operating costs if expensive equipment is replaced. The other situation is that manufacturers have no knowledge of equipment irregularity when it starts to happen but the equipment is not yet due for maintenance or replacement. This could result in even more serious consequences.
Sheng-Wei Wu, product manager, Industrial IoT Group, Advantech, commented if equipment operates under irregular conditions or outside of tolerance, the production line will have a lower yield. In the case of continuing operation without timely detection of the irregularity, manufacturers face the risks of unexpected downtime and possible damage to peripheral components resulting in extensive loss. The root of these problems that give manufacturers a headache lies in their inability to stay on top of equipment conditions at all times. Traditional time-based maintenance falls short of expectations. By introducing equipment monitoring systems, manufacturers can instead take a proactive approach to use machines rather than manual labor, and scientific methods rather than experience to build up their ability in predictive and preventive maintenance.
Equipment health data: physical signals
In general, equipment monitoring can be divided into a few aspects (or steps). First of all, it is fundamental to have sensing capability on the equipment in order to gain an understanding of its operating condition. This is achievable through today's sensor technologies which can collect physical signals from the equipment in operation. These physical signals which are the equipment's health data serve as the basis for the determination on whether the equipment is maintaining normal operation or the prediction of when a failure might occur.
Various types of sensors can be used to detect changes in the equipment's components. Vibration sensors and electric current sensors are more common. As motors are the core components driving equipment operation, the changes in motor electric current are usually the most important factor to equipment monitoring as basis for making judgements. When the equipment is not operating smoothly, more driving power is needed and the electric current will therefore increase. Accordingly, in the case of sudden electric current surge, it could mean the motor is not operating normally.
However, when the electric current shows an irregular increase, the equipment may already be on the brink of a failure. Vibration is another physical signal indicating possible equipment malfunction. Vibration detection can enable early discovery of signs of mechanical aging or damage. Wu indicated vibration monitoring allows the detection of even a slight displacement of components in the equipment so that manufacturers have ample time to deal with aging or malfunctioning parts before potential failure actually happens.
In addition to the common electric current and vibration signals, there are other sensing mechanisms available for detecting changes in equipment components. For example, thermal sensing can be used to measure heat generated from equipment movement, such as friction caused by machining. Detections of noise, pressure and spindle speed are other sensing technologies useful to equipment monitoring.
Different types of equipment may have different failure modes, which may manifest themselves with various physical indications. Wei-Han Wu, engineering marketing manager, National Instrument, drew an analogy between equipment monitoring and medical diagnosis. A doctor considers various measurements such as heart rate, blood pressure, pulse and breathing and then arrives at a diagnostic decision. Equipment maintenance experts also conduct health evaluations on machinery based on various physical information.
On-site experts are indispensable
After the various types of sensors gather physical signals from the equipment in operation, the next step will be for the signal capture module of the equipment monitoring system to collect and report the signals back to the system host. Further analyses and processing by inspection software can determine whether equipment components are working normally. For a large-scale manufacturer operating on a multi-site or multi-national basis, remote monitoring is also feasible with cloud-based signal communication.
Before introducing an equipment monitoring system, the manufacturer should first evaluate its factory environment for considerations such as hardware wiring. As the equipment chassis may have limited space to accommodate monitoring devices, along with the wiring, space arrangement may become challenging. Maintenance and management difficulty could also be an issue.
The first and foremost benefit of equipment monitoring is that manufacturers can stay aware of equipment's operating conditions and life cycle through real-time physical data gathered during operation. General IT employees at factories are not trained to deal with the sophisticated and specialized data collected from the equipment. Therefore, on-site experts (or equipment service experts) skilled with various types of machinery play an important part in the buildup of equipment monitoring systems.
Wu said on-site experts with comprehensive knowledge on structures and operations of various machinery can further help factory management raise efficiency when putting equipment monitoring systems in place and make accurate decisions on the basis of data analyses.
For example, on-site experts with their know-how on the machinery have better knowledge than anyone else about where the equipment may go wrong. They can therefore help factory management put sensors at the right places to ensure they accurately and effectively collect signals during equipment operation.
In addition, on-site experts also serve as a bridge between factory equipment and back-end IT professionals to help them convert the collected raw data into useful information facilitating the determination of normal operation.