Machine condition monitoring is the process of monitoring the condition of a machine with the intent to predict mechanical wear and failure. Vibration, noise, and temperature measurements are often used as key indicators of the state of the machine. Trends in the data provide health information about the machine and help detect machine faults early, which prevents unexpected failure and costly repair.
2. Understanding Machine Condition Monitoring
Machine condition monitoring is important because it provides information about the health of a machine. You can use this information to detect warning signs early and help your organization stop unscheduled outages, optimize machine performance, and reduce repair time and maintenance costs. Figure 1 shows a typical machine failure example and the warning signs.
Figure 1. The warning signs of machine failure: Using a machine condition monitoring system, you can detect failure signs months before repair is required, allowing for proper maintenance scheduling and shutdown.
As shown in Figure 1, vibrations are the first warning sign that a machine is prone to failure. This warning sign can provide three months of lead time before the actual failure date. Monitoring this data with vibration analysis hardware and software helps you predict this failure early and schedule proper maintenance.
Types of Machine Condition Monitoring
Each of the five main varieties of machine condition monitoring serves a different role.
- Route-Based Monitoring
Route-based monitoring involves a technician recording data intermittently with a handheld instrument. This data is then used for trending to determine if more advanced analysis is needed.
- Portable Machine Diagnostics
Portable machine diagnostics is the process of using portable equipment to monitor the health of machinery. Sensors are typically permanently attached to a machine and portable data acquisition equipment is used to read the data.
- Factory Assurance Test
Factory assurance test is used to verify that a finished product meets its design specifications and to determine possible failure modes of the device.
- Online Machine Monitoring
Online machine monitoring is the process of monitoring equipment as it runs. Data is acquired by an embedded device and transmitted to a main server for data analysis and maintenance scheduling.
- Online Machine Protection
Online machine protection is the process of actively monitoring equipment as it runs. Data is acquired and analyzed by an embedded device. Limit settings can then be used to control turning on and off machinery.
Condition monitoring is used in a wide variety of industries. The following is a brief overview of how it works in just a few of them. Certainly condition monitoring can play an important role in any machine with vibrations.
|To be competitive in the energy market, wind turbines must be operated as cheaply as possible. Maintenance costs for their often remote locations are typically quite high, so route-based monitoring or portable diagnostics systems often don't make sense.|
Online machine monitoring is often used to monitor wind turbines online from a central location. Technicians can then be deployed to the remote wind farm locations only when maintenance is actually needed.
Additionally, as companies design larger and more efficient direct-drive turbines, the need for more advanced factory assurance tests becomes increasingly important. Large test cells will need to be built that can monitor turbine designs for up to weeks at a time to verify new multimegawatt designs.
Wind Energy Resources
Oil and Gas
|As the cost of reaching oil and gas reserves increases, reducing the operating and maintenance costs of oil and gas assets grows increasingly important. Pumps and drills are often in remote locations where technician expenses are high.|
Using online condition monitoring techniques, you can monitor pumps, wells, and refineries from a central location and only deploy maintenance personnel when necessary, saving operating and maintenance costs.
The oil and gas industry is also increasingly under pressure for improved safety and oversight. Condition monitoring offers the opportunity to discover possible defects weeks before a technician may find them, and it provides advantages over performing maintenance at only manufacturer-recommended intervals, which may not be early enough to prevent a catastrophic failure.
Oil and Gas Resources
3. Sensors and Signals
Machine condition monitoring is dominated by three different types of sensors: accelerometers, tachometers, and proximity probes. Accelerometers are used to monitor the vibrations of a machine. Tachometers are used to determine the rotational speed of a shaft to provide phase information for the vibration data. Proximity probes are used to monitor the movement of a shaft.
Accelerometers are transducers for measuring the dynamic acceleration of a physical device. They are important to machine monitoring because they monitor system vibrations. You can use these vibrations to predict the life cycles of parts and to detect faults in machinery. Piezoelectric accelerometers are the most common.
A proximity probe is a transducer for measuring the displacement of a physical device. They are important to machine monitoring because they monitor the movement of a rotating shaft. Proximity probes are usually found in 90-degree offset pairs to map an X-Y plot of the shaft movement. Then you can detect imperfections such as misalignment of the shaft, faulty bearings, or other external factors preventing perfect rotation.
A tachometer is a transducer for measuring the rotational speed of a physical device. They are important to machine monitoring because they provide rotational speed as well as phase information, so you can match frequency components to shaft speed and position.
4. Signal Processing and Machine Condition Monitoring Software
Discover how orbit plots, waterfall plots, and order analysis can help you effectively monitor your machine.