What is a condition monitoring system?
Condition monitoring systems are used in industry as a maintenance approach to detect developing machine failures. They combine data from sensors, which measure various equipment parameters, monitoring software and algorithms, which analyze this data. Each system monitors and checks a certain condition of the equipment and can, by identifying abnormal changes in the collected data, predict upcoming failures on the machinery.
This ability to predict machine fault by observing variations in parameters is called predictive maintenance. When a problem is detected, the system sends an alert to allow maintenance technicians to assess the situation, plan a maintenance schedule and repair at the most appropriate time. By managing equipment failures, it becomes possible to reduce unplanned downtime and increase machinery life span. This results in a gain of time and money. These health monitoring systems, with their proactive approach to plant maintenance, often have a high ROI. By investing in these monitoring devices, you will avoid extremely costly downtime.
Most solutions allow remote-monitoring and real-time monitoring of industrial assets. Condition monitoring devices can include, but are not limited to, the monitoring of rotating equipment. Those systems can perform machine health diagnosis on pumps, compressors, blowers, turbines and many other.
The most famous are vibration monitoring systems, because they dominated the market for many years. There has been a lot of innovation in this area so are vibration monitoring systems still the best?
We will review and compare here the 5 main methods: vibration, electrical signature, temperature, acoustic and oil analysis. Each of these condition monitoring techniques have pros and cons so which one is the best condition monitoring system?
Let’s start with the one that is probably the best known but is the vibration monitoring system actually the best condition monitoring system?
The machine vibration monitoring system is based on the idea that by measuring the level and frequency of vibration of an industrial equipment, we can observe its operating condition. Vibration sensors are placed directly on the machines to record the data and remotly monitor machine health. Degradation is then indicated by changes in vibration frequency. Unusual vibration patterns can help identify faults and developing failures.
Advantages of vibration analysis
- Vibration monitoring devices have been in the market for some time. Therefore, they have had time to adapt and improve to meet industrial needs. These systems are helpful in detecting a wide variety of mechanical failures.
- This method is effective in detecting problems such as misalignments, bearing failures, imbalances, etc.
- It always depends on the nature of the failure and the solution chosen, but vibration monitoring is often a fairly early indicator of machine defects.
Disadvantages of vibration analysis
- Vibration measurement requires more than one sensor per equipment in order to monitor the whole drive train.
- Since the sensors must be placed directly on the machines, this can be a problem when the equipment is located in hard-to-reach hazardous areas such as ATEX zones or submerged equipment.
- It usually doesn’t detect any electrical problem.
- They are usually on batteries so they run out of power after a while.
Oil analysis – Lubricant
With this method it can be verified that lubricated machines are working properly. An oil analysis allows to identify abnormal parameters in oil contamination and in lubricant chemistry and can identify the presence of wear debris in lubricant fluid. Anomalies in lubricating oils are signs machine defects.
When a machine degrades, it loses small wear debris that are deposited in the equipment’s lubricant. Thanks to oil condition monitoring, we can find the presence of debris and determine where the problem comes from and how long it remains before the machine breakdown.
Advantages of oil analysis
- Highly effective in predicting certain mechanical failures such as bearing failures. It would detect the problem before other systems. For example, the temperature will only be affected when the viscosity of the oil has strongly degraded.
Disadvantages of oil analysis
- Except for those specific mechanical failures mentionned above, lubricant analysis is often a late indicator.
- Innovations are gradually making these analyses more autonomous. But a reliable diagnosis is still complicated to obtain and generally requires the intervention of experts, which prevents continuous and real-time monitoring and can be more costly.
Infrared thermography – temperature analysis
Machine health can also be evaluated by analyzing temperature and radiations changes. Each equipment part emits infrared radiations. The higher the temperature, the more radiation it emits. Indeed, some change in heat signature may suggest some change in the condition of the machine. It becomes possible to detect abnormal heat pattern to identify failure in machinery. Thermal data is analyzed to define thermal radiation patterns, and thermography analysis can be used to identify deviations from this pattern and thus determine upcoming failures.
Advantages of thermography
- This system monitors electrical and mechanical faults. Localized unusual thermal changes occur as a result of various development faults such as electrical overheating, misalignment, etc.
- A single infrared camera can analyze more than one machine at a time by observing an entire area.
Disadvantages of thermography
- Infrared thermography is often a fairly late indicator of defects. For example, it may indicate lubrication problems, but machines will start to produce heat once the problem is well established.
- The quality of the analysis is affected by environmental parameters such as ambient temperature or air currents.
- Sensors are sometimes on batteries that can run out of power after a while. Moreover, this is not always an automated process and many of these temperature analysis systems require human action.
Acoustic emissions – ultrasonic monitoring
All machinery emits a sound relating to its nature. A change in the sound produced by the equipment suggests an operating fault. This method monitors high-frequency sound waves, to as soon as a change appears, be able to identify which fault is being developed. Stress waves are produced when machinery failure appear.
Advantages of acoustic analysis
- There is a good return between price and effectiveness in detecting mechanical defects.
- It is quite accurate in some cases, allowing the detection of small changes that could be missed with other techniques. It is for example effective in locating leaks or cavities.
- Can detect some basic electrical problems like the presence of arcing or tracking.
Disadvantages OF ACOUSTIC ANALYSIS
- Acoustic analysis is efficient for high frequency problems (e.g. gear problems, lubrication issues, cavitation) but useless for low frequency problems (e.g. misalignement, imbalance, looseness, ..)
- To detect the source of the problem, you will need many sensors.
- This method seems to us to be a good complement but is not sufficient on its own.
Motor current signature analysis - MCSA
Unlike the motor circuit analysis, which can only be performed when the machine is turned off, the motor current signature analysis allows the electrical signatures to be analyzed in real time and remotely. It is therefore possible to determine the operating status of the equipment without having to shut it down.
With electrical signature analysis, it becomes possible to obtain machine health information concerning the whole drive train by measuring current and voltage of a running AC motor. Once connected to rotating equipment, those systems analyse data and detect deviations from normal patterns to identify the source of developing failure.
Advantages of electrical signals analysis
- The sensors are located in the motor control cabinet. This makes a big difference when the equipment is placed in hard-to-reach or dangerous areas. The sensors are located in a secure environment and allow for easy monitoring of equipment regardless of location. Only one sensor will be needed for the whole drive train.
- MCSA is often an early indicator of machine faults. It usually detects failures at early stage before apparent symptoms such as overheating or wear debris in lubricants. It detects mechanical and electrical problems as well as problems with the motor power supply.
- In addition to current and voltage measurements being useful for predictive maintenance analysis, this same data can be used for energy analysis of your machines. This data can help identify energy inefficiencies and allow you to think about energy optimization of your assets.
- Installation is very easy, with no need for expertise or downtime.
Disadvantages OF ELECTRICAL SIGNALS ANALYSIS
- This system can only be applied to AC motors
- Because their is only one sensor in the whole drive train, the further away the fault is initiated from the MCC, the more difficult it becomes to detect the source of the problem with high accuracy.
Discover more about the motor current signature analysis!
In conclusion, there is not really one system that is better than the others in all situations. All these systems help to proactively manage equipment failure and therefore avoid catastrophic failures, eleminate unscheduled downtime and improve machinery uptime. It is up to you to take into account different factors and choose the sensor that best suits your situation. Think about:
- the environment in which your equipment is located,
- what are the most likely failures, the most costly, etc.,
- your desire to improve your energy consumption,
At Insens, we developed a cutting-edge MCSA solution (motor current signature analysis). If you are interested in this condition monitoring system, come check what we offer.
why is our solution a powerful machine monitoring system?
RED is more than just a predictive maintenance system. Most condition monitoring solutions focus only on machine health diagnosis and detecting upcoming failures (e.g. thanks to vibration analysis, lubricant analysis or infrared thermography). Our cutting-edge technology allows us, with the same solution, to provide predictive maintenance diagnostics with high reliability but also to monitor energy consumption, offer optimization suggestions and report the savings made.
We help you through your transition to a more sustainable approach. We can measure and quantify your efforts and therefore help you demonstrate them to your customers.