Shake-up in vibration

Until recently, the cost for a vibration monitoring system was so high that only the most costly assets could justify the technology. However, downsizing and cost reductions by the major suppliers mean it is now affordable on lower cost assets, said Tim Shaw, chief technology officer at Swantech, based in Fort Lauderdale, Florida. Companies investing in predictive maintenance technology need a clear strategy to maximise the benefits of reduced maintenance spend, increased productivity and reduced plant failures, according to John Rouse, AVT development manager.

Predictive maintenance is well established in some industries, for instance oil & gas, pulp & paper and some areas of the chemicals industry. This, said Rouse, reflects "the cost and criticality of the process and products in these industries; they can't afford to have a failure."

The food & beverage industry, however, represents the key growing market for this technology, which is finding increasing use for critical processes, for example with high value or perishable products.

This trend is in part being driven by the competitive nature of the food & beverage industry, according to Rouse. "Plants have become leaner due to consolidation of production at larger facilities, thereby increasing the criticality of the processes."

However, these trends are not universal across the food & beverage sector, Rouse commenting: "Surprisingly, we are working with some big boys and they have not done it [started down the preventative maintenance route] yet."

Manufacturers adopting predictive maintenance tend first to move from fire-fighting to planned maintenance involving lots of continual checks and labour-intensive operations. They then adjust their strategies to encompass preventive maintenance, said Rouse.

Preventive maintenance technology comes into its own on continuous dedicated processes, rather than for batch processes or where it is possible to shift from one continuous line to another, Rouse continued.

"When companies start to think of the hardware spend and the thousands of pounds involved, the process guys tend to identify, for example, the two or three lines in a bottling plant that are most critical to the operation," he said.

The cost of implementing the technology often depends on access, noted the AVT man. "If a bottle filling line's critical parts such as the drive motor are hidden right in the guts of the machine, it can be much more difficult and costly to put the hardware in and get the wires out to collect the data."



When to outsource

Another consideration for companies adopting CM concerns the balance between outsourcing and in-house services relating to predictive maintenance.

"Many companies introduce the technique by outsourcing, then move the programmme in-house. Others tend to buy kits and it is left to us to pick up the pieces when they recognise that they can't use the technology with their in-house resources. The use-it-yourself concept is being oversold," said Rouse.

Higher-end users require far more sophisticated and expensive equipment for dedicated failure prediction, continued Rouse. "Companies that really take it on board and get the most out of it tend to invest in outsourcing and training."

According to Rouse, vibration analysis (see panel p27) continues to be the main condition monitoring technique, followed by thermography, oil analysis and ultrasonic testing — in that order. "Vibration is still the dominant technique, especially for companies taking up CM for the first time as it is a familiar technology that people have heard of."

Thermography was traditionally used in electric panels to identify circuit failures but has also become established in areas such as monitoring heat losses from furnaces or bearing friction in motors.

"Costs are falling, though often if a company invests £3,000 or £5,000 in a thermography unit, it will still only do so much," Rouse concluded.

QAQAQAWhat is Unilever's strategy towards optimising the overall maintenance regime?



The aim is to use common processes across all categories and sites. Unilever in the UK is fully committed to implementing TPM (Total Productive Maintenance) in our sites. Effective maintenance is a key pillar of TPM.



What is the company's overall strategy for introducing and expanding predictive maintenance throughout its UK activities?



The use of predictive maintenance techniques, such as thermography and vibration monitoring, generally depends upon the consequence of equipment failure. If this is high then we tend to use such techniques. However, we do insist that basic maintenance practices are in place and delivering before we consider predictive maintenance techniques.



How is the typical split between the spend on corrective, preventive and predictive maintenance (at the operations where predictive maintenance is applied) developing?



Previous 2006 2010



Corrective 60 40 <20

Preventive 30 40 50

Predictive 10 20 30QAQAQAWhat is the company's strategy with regard to outsourcing and in-house services relating to predictive maintenance?



The strategy is to develop such skills in-house by initially using third-parties for training. This approach is fully consistent with our ambition to up-skill the technical workforce. For specialised areas such as ferrography we would always use third-parties.



What are the main achievements from Unilever's predictive maintenance activities to date?



Marked improvement in technical skills; considerable improvement in machine uptime (usually measured via OEE improvement); reduction in spare part costs; improvement to machine designs by using the actual data trending from the predictive maintenance systems; more effective use of the technical workforce.



What advances would you like to see from suppliers/developers of predictive maintenance equipment?



Predictive maintenance systems for high speed packing machinery; more use of telemetry; standardisation of approaches.



"Of course the essential insensitivity and complex interpretation issues [related to vibration monitoring] still remain, no matter how low the cost becomes," the Swantech CTO commented.

In the past, continued Shaw, vibration analysis and debris analysis were done every few weeks or months, rather than continuously. "Since a lot of things can (and do) happen in that amount of time, plants have been going to continuous monitoring, even linking the monitoring systems into their plant control systems for trending and alarming purposes."

Continuous monitoring systems are now being linked to plant automation and control systems to receive related operational measurements — those that relate directly to the load/speed/stress being experienced by a machine — and to supply asset condition information, noted Shaw.

Operational data, he said, can be correlated with the stress wave readings for the machine to generate a "profile" that shows both what is 'normal' for the machine and identifies where an asset is experiencing high stress. This information enables users to avoid operating levels that can damage an asset.

Stress wave analysis, said Shaw, can also identify friction-related problems, such as lubrication (in)effectiveness, and shock-related problems, such as imbalance, cracks and other physical damage, well before vibration systems can detect the damage.