Downtime is expensive. While the cost varies depending on the incident and the plant, it can quickly mount up. Because lubrication is the most prevalent cause of bearing failure, it's evident that lubrication is a significant business.
While most people find lubrication easy and think that all you need to do is apply the proper lubricant with the correct amount and at the right time, but the truth is, that is not always true. You need condition-based monitoring technologies to monitor your lubrication program to confirm whether you are succeeding or not.
Vibration analysis, infrared imaging, and other technologies have been used for condition monitoring and predictive maintenance. Another CBM technology you can utilize is Airborne ultrasound technology which is a great solution for businesses with few resources. For rotary equipment, vibration analysis is a wonderful complement to oil analysis. A monitoring strategy that combines both tactics may be able to detect problems in the oil, as well, as failures caused by the machine's operation or condition. Oil analysis, on the other hand, is frequently chosen to aid in the early identification of oil-related failure modes, whereas vibration analysis is frequently chosen to aid in the detection of failure modes related to misalignment.
While ultrasonic technology is oftentimes used to detect a leak, it can also be applied to detect lubrication-related failures. Lubrication issues such as under-lubrication, over-lubrication, and incipient wear all produce sounds that ultrasonic tools can easily detect.
Friction, impact, turbulence, and electrical discharge cause ultrasound. Mechanical equipment produces friction and impact as by-products. As the shaft and balls rotate around the center of a roller bearing, for example, friction is created. If there is too much friction, however, difficulties arise on the equipment owing to unbalance, or the bearing may seize, causing the machine to shut down completely.
Advantages of Airborne Ultrasound
Ultrasonic equipment detects ultrasounds in the air and on structures that are usually beyond the capacity of the human ear to detect. After detection, the ultrasounds are electronically converted into audible signals that a technician can hear through headphones and see on a display panel as decibel (dB) levels. The received sound can also be seen on a spectrum analysis screen in some equipment. Here are numerous advantages of using ultrasound technology:
1. They are straightforward and simple to find.
2. Many issues can only be detected via ultrasonic technology.
3. The capacity to locate is made more selective by ignoring acoustic noise. As a result, they are better at identifying incipient failures.
4. They can be used to find leaks and circumstances that could lead to an electric failure.
5. Instruments can be employed in noisy, loud situations.
6. They can complement and improve other predictive maintenance (PdM) technologies, or they can stand alone in a maintenance program.
7. Inferring a diagnosis is immediate for them.
8. Ultrasound is more adaptable because it can be utilized for a variety of purposes.
9. Ultrasonic devices are non-destructive, meaning they don't harm, open, or interfere with the component being tested.
10. Ultrasonic testing can be done while the machine is running.
11. This equipment is simple to use for maintenance personnel who are already utilizing Infrared Inspection.
12. Even airborne sound waves from the apparatus and several motor NDE bearings can be detected.
While running properly, mechanical equipment emits a "normal" sound characteristic. When components start to deteriorate, the original sound signature changes. “Ultrasonic monitoring of bearings offers the earliest warning of bearing failure,” according to NASA research. They discovered that a 12-decibel rise in the amplitude of a monitored ultrasonic frequency over baseline indicated the beginning stages of bearing failure. This shift is sensed long before vibration or temperature changes show it.” Cavitation in pumps, compressor valve leakage, broken gears, excessive friction, and bad connections are just a few examples of ultrasonic mechanical inspection opportunities.
Three scenarios can be regarded as good, better, and best when it comes to lubricating methods in plants. Following the manufacturer's instructions for the frequency, kind of oil, and amount of lubricant to be applied to a certain piece of equipment is a good scenario.
A preferable scenario would be to continue to use the timed interval, but instead of using a grease gun to lubricate, you can use ultrasonic equipment. At the very least, the lube techs will be able to tell when they have applied enough grease or when they have applied too much grease. Another advantage is that the person lubricating the equipment can listen to it while doing so. This allows the tester to hear if there are any other bearing issues that lubrication won't fix. The lubricators, in a way, become fault finders. If a bearing does not sound normal or has a high decibel level, it should be noted. Additional vibration or ultrasound data can be acquired to figure out what the problem/defect is.
Finally, the optimal case is to establish routes using an ultrasound device and data storage and administration software. Periodically, data such as decibel levels and sound files can be recorded. The frequency with which the readings are obtained should be determined by the asset's criticality.
If proper lubrication does not solve the problem, a more thorough examination is needed to pinpoint the precise flaw, such as an inner or outer race-bearing fault. An inspector can travel to a place along a route that has been determined to be low in lubrication and apply the oil until the decibel level decreases down to the baseline level.
How Ultrasound Improves Lubrication Techniques
Ultrasonic technology aids lubricant technicians in removing much of the guesswork from lubrication. Because ultrasound is a confined signal, when a sensing probe is placed on a bearing, it will not be influenced by "crosstalk," allowing the technician to hear and monitor the condition of each bearing. Ultrasound examines each bearing separately, similar to how medical ultrasound can determine which artery or vein is congested or leaking.
In terms of lubrication, how does ultrasound work? The initial step is to establish a decibel level baseline as well as a sound sample. When going along a route for the first time, this is best accomplished by comparing the dB levels and sound quality of similar bearings. Anomalies will be easy to spot. After establishing baselines, each bearing can be trended over time to detect any changes in amplitude or sound quality. The bearing should be lubricated when the amplitude of the bearing exceeds 8 dB and there is no variation in the sound quality established at the baseline.
To increase efficiency, the technician should keep track of when the equipment was last lubricated and how much grease was applied, so that he or she can estimate how much lubricant is needed every week.
By lubricating with ultrasound every time, the technician creates historical data that can be used as a guide to see if the lubrication schedule can be changed to save man-hours and if the manufacturer's recommended lubricant amount is correct. There is potential for cost savings if less is required.
Maximizing The Use of Ultrasound Technology
Making a new technological investment is always a risky undertaking. Is it going to pay off? Is it going to be simple for your employees to use? Is it a one-hit-wonder or a tried-and-true method that will endure the test of time?
Despite the fact that more plants are using ultrasound technology and adopting a predictive or proactive rather than reactive perspective, many still rely on crystal balls and outmoded approaches which leads to poor and wasted man-hours, downtime, and lost production and profit. While ultrasound cannot cure all reliability issues, it has proven to be a helpful and strong diagnostic tool in a variety of scenarios, and technicians should include it in their toolkits.