Vibration Patrol Monitoring

| Environmental Testing

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Jonathan Newell looks at patrol sampling machinery with vibration measuring equipment to avoid costly downtime.

Decades ago, an older colleague told me a noisy pump was down to a defective bearing and when asked how he knew, he produced a large screwdriver, placed the blunt end to his ear and the other end against the pump casing. “Listen to that, definitely the bearing,” he said. For me it was like holding a conch shell to my ear and expecting to hear a passing trawler; he clearly had the ear for it and I didn’t.

Years of dealing with plant maintenance had tuned his ears to the point where he could make a good assessment of the defect and confidently instigate the correct maintenance procedure.

Now, there are more repeatable and reliable options for assessing machinery vibration and analysing defects using accelerometers connected to instruments, which gather the data to be analysed by software that’s able to identify defects and highlight trends.

Handheld vibration sampling

One such instrument is Schaeffler’s FAG Detector III handheld vibration monitoring device. With its free of charge Trendline software, the device enables the user to collect, store and analyse vibration measurement data, based on a database of over 20,000 different bearing products from a range of suppliers.

The FAG Detector III is frequently used in patrol monitoring, a routine in which maintenance engineers can sample vibration data from equipment in a number of installations sited along a patrol route around the facility.

Vibration data is measured and recorded at each sampling point and the data analysed against three parameters, including velocity, acceleration and enveloped acceleration.

Velocity is used to indicate any mechanical issues such as imbalance, misalignment or looseness. Acceleration is typically used to monitor gear defects and progressing bearing defects whilst enveloped acceleration (or demodulation) is a measure of high frequency impact type events, typified by early bearing or gear faults.

Identifying trends

Explaining the Trendline software that comes with the instrument in more detail, Schaeffler Service Engineer, Ian Pledger told me that it identifies trends in the data, can characterise the cause of the failure and the kind of maintenance that’s likely to be required.

The software enables the user to analyse the vibration trends over time and to suggest when and where a failure on a motor, pump or fan is likely to occur. This allows maintenance to be planned, and carried out at a time, which is convenient to the user rather than experiencing unplanned downtime in the middle of a production run

“In the hands of an experienced user, the FAG Detector III is a very powerful predictive maintenance aid. But it can also be used by an inexperienced engineer to patrol monitor and identify increasing trends,” he explains.

Such trend analysis is an important part of keeping equipment well utilised and preventing costly, unplanned outages and maintenance. Pledger went on to explain that Patrol monitoring is ideal for many companies that have a high number of assets or machines that are critical to their production process but which may have limited maintenance budgets.

Vibration monitoring is relevant to all industry sectors, in fact anywhere where rotating equipment and machines are present. Any plant that utilises electric motors, gearboxes, air compressors, fans, conveyors or pumps can benefit from vibration monitoring of this kind.

When asked for examples of the industries in which patrol monitoring is performed, Pledger told me, “Schaeffler has customers in the process industries such as food and beverage, chemicals, metal processing, quarrying and cement, but also in discrete manufacturing such as automotive and aerospace, as well as the rail industry. In recent years, Schaeffler has provided vibration monitoring services to the pharmaceuticals industry, which monitor the condition of very large air handling systems that must remain operational at all times in order to keep drugs production at a certain positive atmospheric pressure. Schaeffler has also provided vibration monitoring services to the Health sector where HVAC systems in blood storage facilities need to be monitored continuously.“

Sensor placement

With such a wide variety of industrial applications, the measuring device needs to have the flexibility to deal with different modes of usage. There will be times when different transducers are required for different measurement points as well as occasions when accelerometers are fixed in place as part of the installation.

I asked Pledger if the preferred option is for permanently fixed transducers, into which the technician plugs the instrument to ensure repeatability between measurement. He explained that the FAG Detector III is supplied with the full range of accessories required to carry out vibration monitoring, including a portable sensor and magnetic holder.

“On a patrol monitoring route where sensors do not need to be permanently fixed to the machines/equipment, the portable sensor allows the engineer to move from one asset to another, taking vibration measurements at the pre-planned positions on the assets,“ he says.

Alternatively, the factory may have installed permanent sensors on some assets, particularly those that are difficult to access or dangerous to be around, eg a saw in a saw mill.

“In this scenario, it is safer to install fixed sensors on the saw and run cabling away from the sensor to a junction box in a safe area, where the maintenance engineer can plug-in the FAG Detector III to take vibration measurements,“ continues Pledger.

Generally, defining sensor positions does require some careful consideration, some experience of vibration monitoring techniques and a good knowledge of the machine to be monitored. In particular, knowledge of how vibration is transmitted through the machine will help define sensor positions. From a well-positioned measuring point on a machine.

“Placing vibration sensors in the correct location on a motor, belt drive and fan arrangement, for example, can provide measurement data that can help determine whether the fault is likely to be a bearing defect, fan imbalance or belt misalignment,“ explains Pledger.

The right skills

With so many options and the potential for making mistakes, the role of patrol monitoring requires some skill and an understanding of vibration analysis. I asked if the those skills generally exist in Schaeffler’s target industries.

“Many of Schaeffler’s customers don‘t have the knowledge or the required maintenance resources in-house to do this type of vibration monitoring themselves. Other customers do the patrol monitoring part and then send the vibration measurement data to an expert at Schaeffler, who can then analyse it,“ he told me.

Schaeffler also provides training courses and can help mentor maintenance engineers at the customer’s site until they are confident in using the vibration monitoring hardware and software themselves.

Patrol monitoring at EFW facility

Schaeffler performing patrol monitoring and vibration analysis for an energy-from-waste (EFW) facility, where the company is able to detect damage to components such as bearings and gears early and prolonging the life of fan, conveyor and pump motors and gearboxes.

60-70 items of equipment are analysed on each visit critical equipment on separate furnace feed lines. Using the output from the Trendline software, Schaeffler reports on all the items of equipment and recommends any repairs or remedial action that is required.

The resulting action plan isn’t just the replacement of bearings. An example cited by Schaeffler is recent advice it gave to the EFW to inspect, clean and rebalance some fan blades on a large primary air fan. Over a period of several months, vibration data collected from the fan’s non-drive end motor showed a slowly increasing velocity trend, which suggested a minor issue was developing. The customer took the fan offline to steam clean the blades in the workshop and after refitting it, the fan vibration and noise levels returned to their normal state.”

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