FEATURE Drives, Controls & Motors
a motor, i.e., a spot where an unbalanced weight moves around the machine’s axis, causing the rotating components to vibrate. These types of imbalances can be caused by casting fl aws, machining errors or even maintenance issues, such as dirty fan blades.
The total vibration experienced by a motor can be down to many elements. Knowing what the possible causes of vibration are allows a better diagnosis of what is happening to the motor. Bearings also cause vibrations that can easily spread to other components. Lack of lubrication, poor insulation or contamination can wear out bearing components quickly, while a rutted roller bearing race can create movement each time a bearing travels over the damaged area.
Misaligned gears are also a source of vibration, and so are worn or broken gear teeth that can grind against each other.
2. “We don’t need vibration analysis; if our machines run hot or make unusual noises, we can investigate them then.” Waiting until there are obvious signs of imminent failure is false economy. By then, a catastrophic failure could be only days or hours away. If monitored closely, changes in a component’s or machine’s vibration profi le can be detected many months before a failure might occur.
3. “Vibration analysis is too difficult and expensive.” Analysing vibration data requires software, hardware, training, signifi cant asset information infrastructure and a disciplined schedule. Although the most complex analysis of vibration signatures with multiple causes might be best left to specialist vibration analysts, there is much that can be done to detect basic issues with relatively inexpensive equipment. One example is the Fluke 805 Vibration Meter, an easy-to-use instrument that provides accurate, repeatable readings. This meter has a four-level severity scale and an onboard processor that calculates bearing condition and overall vibration using equally easy-to-understand textual alerts. Its sensors can read a wide range of frequencies, from 10Hz to 20,000Hz, wide enough to cover the vibration profi les of most machines and components. The 805 has a straightforward user interface that only requires the user to
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maintenance programmes, according to Reliable Plant.
4. “We don’t have the staff to perform vibration analysis.” If an organisation is large enough to have a dedicated reliability team, then vibration monitoring and analysis should be part of the responsibilities of that team. Maintenance technicians can be trained via online courses to ISO 18436 standard, for only a few hundred pounds. One of the advantages of maintaining an in-house vibration analysis programme is the opportunity to assess trends in the machines. In-house staff know the machines, processes, conditions and history, and can use that knowledge to supplement information received from their monitoring tools.
input RPM range and equipment type. Fluke also off ers the 810 Vibration Tester, a more advanced instrument with a diagnostic engine that uses a database of real-world vibration data. Although there is some expense
required to set up a vibration analysis programme, the costs of not having one can be signifi cantly greater. For example, an analysis by ABB Motors outlined the potential costs caused by a motor fail. The analysis looked at a 315kW motor with a 95.5% effi ciency, used continuously. At an energy cost of 11p/ kWh and with the motor running for 8,400 hours per year, the cost of running the motor over a 20-year lifetime exceeds £6m – which is extremely high compared to the typical purchase price of £18,000 for a vibration analysis programme. Yet the cost of not running the motor is equally signifi cant. The analysis cited an example of a motor used in the oil and gas industry where a single failure can lead to losses of £220,000 an hour. Just one 10-hour failure over a motor’s 20-year lifespan could amount to losses of £2.2m.
Losses can be experienced in any industry – automotive, metal casting, food and beverage, and so on. The potential losses from unscheduled downtime has led more than 70% of motor users to cite reliability as the number one priority of their motor
5. “Sourcing vibration analysis equipment is too time consuming and difficult.” A growing number of vendors provide specialist monitoring and analysis equipment, which is helping vibration analysis become more mainstream by increasing the awareness of its benefi ts. Farnell provides solutions from a range of suppliers, including Fluke, Kemet, Omron, Murata, Amphenol Wilcoxon, TE Connectivity and Rohm, several of which provide online resources to assess vibration analysis and its practical application.
6. “Our plant experiences harsh conditions not suitable for delicate vibration sensors.” Industries with harsh environments, such as industrial, automotive and aerospace, already use vibration sensors widely. Although these are challenging industries, careful consideration of issues such as casing/connector structure, sensing element material, signal conditioning and cabling has shown that the challenges are not insurmountable. Reputable manufacturers can advise on suitable solutions for the majority of applications. In fact, demand for sophisticated sensors that are also resistant to severe weather conditions, such as MEMS, ultrasonic, wireless and fi bre-optic sensors, is growing.
https://uk.farnell.com/ CONTACT:
Farnell
Automation | March 2023
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