FEATURE Drives, Controls & Motors
Don’t let the vibration of that motor take you down
Cliff Ortmeyer, Global Head of Technical Marketing at Farnell states that cost reductions mean companies should deploy vibration analysis now
M
any industries rely on continuous operation of critical assets like motors and pumps. These devices
must work properly to ensure customers get the products and services they require. To do so, and with the help of advances in technology, companies are increasingly turning to predictive maintenance programmes, which can eliminate unexpected failures and unplanned downtime. These programmes monitor the health and performance of machines to assess which ones are more likely to fail and when. Armed with this information, maintenance staff can investigate a machine’s condition more eff ectively, schedule maintenance tasks to fi t production schedules and conduct repairs before a machine fails. Benefi ts include: • Maintenance costs: down by 50%; • Unexpected failures: reduced by 55%; • Repair and overhaul time: down by 60%;
• Spare parts inventory: reduced by 30%;
• Mean Time Between Failures (MTBF): increased by 30%;
• Uptime: increased by 30%. According to the Plant Engineer’s Handbook (2001), a 10% reduction in
12 March 2023 | Automation
maintenance costs can produce the same fi nancial benefi t as a 40% increase in sales for a typical manufacturing plant.
Vibration analysis
One of the major tools that can provide data for a predictive maintenance programme is vibration analysis. The most common type of vibration sensors are accelerometers, which must be in direct contact with the measured machine or component. Piezoelectric accelerometers are the most widely used type. They are popular because they produce a strong, clear signal at most frequencies, although piezoresistive accelerometers, which produce resistance changes, are also becoming increasingly common. Microphone sensors are also popular. They can detect changes in high- frequency sounds and cost eff ectively provide basic information; they are often used alongside accelerometers. Strain gauges work through an electrically-conductive grid, which deforms as a component experiences vibration. These deformations change the electric resistance of the grid and, by reading the time taken for an electric current to pass through it, the vibration of
the object can be assessed. Non-contact techniques such as eddy
current and laser displacement can also be used. As they don’t need to contact the equipment, they are ideal for delicate assets. There are also well-established vibration analysis techniques that can be used in predictive maintenance, such as maximum acceleration analysis, frequency analysis and artifi cial intelligence techniques. Some vendors off er compact vibration analysis equipment that can provide indications of vibration problems in motors, hydraulic components and other machinery.
Popular misconceptions There are several misconceptions and misunderstandings about vibration analysis and its role in predictive maintenance programmes. These include:
1. “Our machines don’t vibrate, so we don’t expect them to fail soon.” All machines vibrate and while it is normal for motors to generate small vibrations, large vibrations or any changes in a motor’s pattern of vibration could indicate problems. One of the prime causes of vibration is imbalance in
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