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Condition Monitoring/Predictive Maintenance

Advanced Rotorbar Analysis – False Positives: Spiders / Axial Cooling Vents

whitelegg pic 3Ernesto Wiedenbrug, Ph.D., SM IEEE,
Virtually all rotors of motors above 100kW are designed with axial  cooling vents, potentially causing false positives for both prevalent  diagnostic technologies, vibration and MCSA. Fig 1 shows the rotor  with 8 spider-legs of a 2.4MW 6.6kV motor that was pulled out of  service due to such a vibration and MCSA false positive.
 This paper explains how to recognize problematic motors, the reason for these false positives, how these motors react, and how  to deal with them.
To continue reading the full case study, with images, please download the free PDF file here.
To contact Whitelegg direct please visit  

Advanced Rotorbar Analysis – False Negatives: Dual Cage Rotors

 advance rotobar-20022Ernesto J. Wiedenbrug, Ph.D., SM IEEE
Some squirrel-cage motors designed for high start-up torque may get weaker over time, needing longer startup times and may perhaps even trip during line-start – but never show big problems in vibration or MCSA. This paper  explains what gives high startup torque motors their  special capabilities, describes a common failure mode  making it nearly impossible to find the issue using MCSA or  vibration, and diagnostic alternatives for these problems.

To continue reading the full case study, with images, please download the free PDF file here.
To contact Whitelegg direct please visit  


art-feb-2013Artesis has recently proved to regional water and sewerage treatment business Wessex Water, its ability to diagnose equipment problems and anomalies accurately and reliably, after a pump failure occurred at one of the company’s pumping station near Yeovil, within days of the date predicted by the Artesis team.

Details of the application

Wessex Water, which serves areas within the South West of England, invested in the new maintenance technology from Artesis to optimize the effi ciency and performance of its pumping equipment.



art-feb-2013-2Artesis has completed an installation trial of its Motor Condition Monitoring (MCM) technology for BP Shipping, the global centre of marine expertise for the BP Group; fitting two MCM units to two seawater pumps aboard a LNG carrier.


“As with all new technology in the marketplace there is a degree of scepticism when embarking on an initial R&D and trial period. To prove a useful and worthwhile tool we needed to determine whether the MCM unit could accurately detect a fault prior to catastrophic failure and ultimately, provide us with a non-intrusive monitoring process with cost saving benefi ts,” said Mark Pellow, engineering superintendent for BP Shipping.

In addition, the trial aimed to validate the Artesis condition monitoring application technique when compared to the more traditional technique of vibration monitoring.

BP Shipping – Worldwide Fleet With over 50 ships in its worldwide fleet, BP Shipping is very much aware of the benefi ts of condition monitoring and runs a successful global initiative, adopting CM technologies and programmes throughout its fl eet. MCM has the ability to monitor equipment that is currently outside of the BP CM programme, where kit may be inaccessible or in a hazardous location.


Device enables fast, easy alignment of rotating plant

scheaffler-204A new handheld laser optical alignment device has been launched that enables faster, easier alignment of shafts in rotating equipment such as fans, motors, pumps, gearboxes, ventilators and compressors.

On show for the first time in the UK at MAINTEC 2013, Schaeffler’s FAG Top-Laser EQUILIGN is a compact, robust, easy-to-use device that guides the user step-by-step through the measurement process until correct shaft alignment is achieved. Graphical operating instructions and an intuitive autoflow function ensure that all maintenance technicians can use the device, regardless of their skills or experience.

The correct alignment of coupled and uncoupled shafts is critical in order to achieve high efficiency and reliability of rotating equipment. Approximately 20% of rotating equipment is incorrectly aligned. A correctly aligned shaft means less friction and vibration are generated by the drive system, which means less wear on belts, pulleys, bearings and seals. This means the running time and reliability of rotating machinery is increased, energy costs are kept to a minimum and overall plant efficiency is improved.

Read more: Device enables fast, easy alignment of rotating plant

Who monitors the monitoring system?

scheaffler-200Condition monitoring (CM) has been used in the marine industry for many years, typically using data collectors operated by ship's staff. However, with the advent of larger, more complex machinery, particularly on vessels such as large LNG carriers, automated online CM systems have become more popular.

The use of online CM systems has a major advantage in that remote monitoring and advice can be readily provided by fleet technical management, OEMs or shore-based CM specialists. Higher workloads and the reducing number of staff on modern ships also make remote monitoring more attractive. In the event of an alarm condition, an automated monitoring system will typically provide alarm text for the duty engineer in the ECR and an automatic notification to the remote monitoring facility. Trend and analysis data would also be transferred ashore for diagnostic purposes.

Read more: Who monitors the monitoring system?

Advanced Rotorbar Analysis – Cage Damage vs. Porosity

pdf-fig1Manufactured vs. Die-Cast Rotors
Squirrel Cage Induction Motors are of either a manufactured, or a die-cast design. Larger motors (above 300 to 500hp) will tend to be of the manufactured kind, being produced by inserting the rotorbars into the rotor slots first, and then connecting the bars to the end-rings. Copper is the most common material for such squirrel cages, but they can also be made of Aluminum, or even Brass in the case of the outer cage of a Dual-Cage rotor design. The squirrel cage of die-cast motors is typically aluminum, and in a few cases made of copper. Fig. 1 shows an example of a manufactured rotor and a die-cast rotor.

Read more: Advanced Rotorbar Analysis – Cage Damage vs. Porosity

Monitran’s new website gives engineers easy access to product

Monitran PRMonitran, a world-leader in the development and manufacture of transducers for the measurement of vibration, proximity and displacement, has revamped its website.

Designed with ease-of-navigation for sensor identification and selection in mind, details Monitran's extensive range of products and the company's value-added services.

The site includes; product selection guidelines, installation and maintenance tips, frequently asked questions (FAQs) and pages devoted to specific industries, including wind energy, mining and paper.

Read more: Monitran’s new website gives engineers easy access to product

Monitran launches the MTN/5000-16 microcontroller-based condition monitoring system.

Monitran PR3Monitran - a world-leader in the development and manufacture of transducers for the measurement of vibration, proximity and displacement – has launched the MTN/5000-16; a robust and reliable microcontroller-based condition monitoring system.

The MTN/5000-16 contains up to 16 Monitran g-mac signal conditioning units and features a 2.8 inch TFT touchscreen with an easy-to-navigate menu that enables users to set data sampling periods, ranges and accuracy levels plus vibration threshold (alarm) levels; on a channel-by-channel basis or across all channels. In addition, the system has 20 digital I/O channels, enabling the MTN/5000-16 to be integrated with other systems.

Read more: Monitran launches the MTN/5000-16 microcontroller-based condition monitoring system.