Rotating machines have the ability to bring production to a grinding halt – is your plant really protected? Susan Fearn Ringsell reports.
“It sounds simple – routine monitoring of your rotating equipment results in data necessary for deriving information about the condition of your equipment. But if the data isn’t accurate, your analysis won’t be either.” So says Michael Whittaker (reliability solutions consulting Europe) at Emerson Automation Solutions.
Customers need to have a clear understanding of the criticality of rotating equipment and the associated consequences of its failure, explains Whittaker, so they must ask themselves three important questions:
- Has a failure mode effects analysis (FMEA) been conducted to identify the appropriate failure mitigation controls?
- Is there an in-house capability to conduct both data collection and analysis – in other words diagnostics and prognostics?
- How does the condition management of rotating equipment feed into work management processes?
George Perkins, marketing director at Turck Banner, agrees that data is a key consideration: “Accuracy of the data gathered is paramount, which is why sensor manufacturers are constantly striving to develop and improve input devices such as encoders and vibration monitors [see below] to ensure reliable data input.”
For Sally Sillis, industrial services and MRO manager at Schaeffler UK, it is important that customers ask whether the benefits of monitoring an asset are greater than the cost to install and maintain the monitoring regime.
They should also find out what the failure modes of the chosen equipment are and therefore which monitoring technique should be used.
In addition, it is worth investigating whether there are necessary skills and knowledge available in-house to implement the chosen regime, or if it is necessary to use external consulting services.
Whittaker adds: “For rotating machines such as turbines, compressors and pumps, digital overspeed protection systems provide speed measurement and detection of rotational direction.”
These systems protect equipment against overspeed conditions and detect incorrect rotation at start up.
In addition to overspeed, an online machinery protection system can provide a wide range of protection measurements, including case expansion, thrust position, and relative and absolute radial shaft vibration.
“Once the shutdown occurs, your protection system provides little insight to the cause of the problem,” explains Whittaker. “By adding condition monitoring to your system, you gain the predictive intelligence necessary to identify developing faults, schedule maintenance, and minimise the impact to production schedules.”
By adding condition monitoring to your system, you gain the predictive intelligence necessary to identify developing faults, schedule maintenance, and minimise the impact to production schedules
Michael Whittaker, Emerson Automation Solutions
Emerson’s online machinery monitoring solutions combine API 670 protection with prediction and performance monitoring. This is integrated with a process automation system to deliver a complete solution for managing both fixed and rotating assets.
“Prediction based on the periodic gathering of vibration data with a handheld analyser is used to identify potential problems, typically with the balance of plant equipment,” says Whittaker.
This can be used as part of an asset management programme, but not as a protection solution, because incidents requiring a machine to be brought safely offline may occur in between the manual rounds.
The advent of wireless communication systems in plants and factories has allowed for the reliable monitoring of difficult-to-access rotating equipment such as roof-mounted ventilation and heating fans.
“Contactless encoders, as the name suggests, have no moving parts,” explains Perkins. “In these the development of inductive resonance coupling circuits that utilise emitter and receiver coils, manufactured as printed circuit boards, offer exceptional precision.”
Good to share
To date, most systems have predominantly been used as local systems, collecting vibration data from machines and using analysis algorithms and a rolling bearing database to check for signs of wear, defects or other unusual behaviour.
Sillis says: “While this works very well for many companies, imagine the added value of being able to share and compare your local machine condition data, via the cloud, with other similar items of equipment across your plant, or better still, with other equipment at multiple plants within your business, wherever they are located in the world.”
Vibration analysis is one of the more successful techniques for monitoring the condition of rotating equipment.
Whittaker says: “Peak value analysis (PeakVue) and auto correlation enables the vibration data to be presented in a way that makes it much easier to interpret, enabling operators with no special training to determine both when a piece of rotating equipment is healthy and when an abnormal situation is present.”
Auto correlation is a time domain analysis that is useful for determining the periodicity or repeating patterns of a vibration signal. “The autocorrelated waveform can be presented in a circular format, which makes interpretation of the data much more straightforward,” adds Whittaker.
The latest condition monitoring (CM) systems are quick and easy to install and set up, with the user requiring no specific skills or knowledge of vibration diagnosis
Sally Sillis, industrial services and MRO manager, Schaeffler UK
Before any meaningful analysis can be gleaned from the data produced a certainty of the accuracy of said data must be assured.
Vibration and temperature monitoring of heavy-duty motors are already proving invaluable in detecting bearing wear.
“This early warning indication facilitates predictive maintenance and avoids costly shutdowns,” says Perkins.
Performance trends leading up to a particular incident can also be analysed to understand and remedy system problems.
Current cloud-based condition monitoring systems offer a suitable platform for managing and processing Big Data.
“The latest condition monitoring (CM) systems are quick and easy to install and set up, with the user requiring no specific skills or knowledge of vibration diagnosis,” says Sillis.
When changes occur in the condition of the equipment, the CM system automatically generates plain text messages on a display, providing the user with clear instructions for action, enabling any corrective maintenance work to be undertaken and any replacement parts to be ordered if required.
“These automatic fault assessment systems are truly groundbreaking, as they help to minimise the skills, knowledge and experience required of maintenance staff or operators of the equipment,” says Sillis.
Global solution
The benefits include analysis that can be carried out anywhere at any time – experts can be anywhere in the world within an organisation or even external.
Similar equipment can be compared across global manufacturing facilities, to compare and develop trends.
Although many think the price of equipment itself is the biggest outlay a business faces, studies have found that it makes up a small percentage of its life cycle cost. In other words, it makes sense to look after rotating assets.
