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Good vibrations: monitoring machines with accelerometers

Accelerometers are an important part of condition monitoring and preventative maintenance in industrial settings. PACE talks with Mitch Callon from Metromatics to find out more.

Manufacturing production lines often rely on highly complex automated processes and systems, with machinery and moving parts often put under immense pressure and strain from constant use. In these circumstances, condition monitoring to identify changes and potential or existing issues and problems for these processes is a necessity to avoid significant failure and damage to equipment.

Accelerometers form a central part of this process. Accelerometers are devices that measure vibrations and acceleration of machinery and industrial structures, providing crucial reporting on changes and fluctuations in equipment such as turbines, pumps, fans, rollers and compressors.

A provider of accelerometers is Dytran Instruments, a company based in Chatsworth, California. Formed in 1980, the company has been producing accelerometers and force and pressure sensors for over three decades. While initially the company’s output was based on piezoelectric technology, its offerings now include DC-MEMS-based accelerometers, digital output, and USB-powered triaxial accelerometers.

Brisbane-based technology solutions company, Metromatics, has been a long-time supplier of Dytran products in Australia and New Zealand. Recently, Dytran made Metromatics its sole distributer for Australia and New Zealand.

According to Mitch Callon, technical sales manager at Metromatics, Dytran’s accelerometers and sensors are the go-to for manufacturers looking to carry out effective condition monitoring and preventative maintenance.

“While we at Metromatics don’t actually provide a full engineering solution for process lines, if an engineering or manufacturing firm or client comes to us for preventative maintenance solutions, we’ll be frequently recommending that they apply Dytran accelerometers,” Callon said.

Paper mill recycling plants are a perfect example of where pressure sensors are used on pipelines and accelerometers are used on drying drums and other machinery for watching for potential pending failures of bearings or pumps.

These are able to provide advanced warning of failure to the maintenance team, letting them know that a shutdown may be needed to carry out preventative maintenance before issues with the machinery become more serious. It also prevents unnecessary downtime, Callon said.

“As you can imagine, it’s not a simple task to shut down a whole production line. The accelerometers enable maintenance to be carried out when it’s needed and not before that point,” he said.

“The accelerometers measure changes against baseline vibrations.
In other words, if we know that this vibration should be at a particular frequency at this particular g-force, and if the equipment exceeds those parameters, then the accelerometer end controller can generate an alarm.

“Additionally, you can actually have a vibration specialist who comes in once a month and measures it with an instrument against the known good baseline vibration figures and says, ‘This is exceeding the baseline target; we to have a maintenance shutdown before there is a catastrophic failure event’.”

When supplying customers with Dytran accelerometers, Metromatics will generally recommend they are used with DEWESoft. “It’s a high- speed data acquisition hardware and software analysis solution that provides users with all the logging, triggering and maths that you apply to the accelerometers to get your known outputs,” Callon said.

Power stations use accelerometers in much the same way a process line in a manufacturing plant does but on turbines where they can monitor turbine vibrations. “We supply data acquisition systems and accelerometers to a power plant where they are used to make sure that when the generator is running up and down that it is not left in a resonant frequency zone,” Callon said. “Otherwise the generator will blow itself apart.”

He said that for some processes, such as those that involve high- pressure pipes channelling liquids, accelerometers can be coupled with Dytran pressure transducers. These can be placed at every juncture along a pipeline to monitor blockages or other issues by indicating fluctuations in pressure.

“And this is exactly what one of our customers, a paper mill based in Auckland, New Zealand, has been doing. They are using approximately 40 Dytran pressure sensors for this application in their pressure pipes,” Callon said. “They’ve been using them for around 10 years without failure.”

According to Callon, one of the salient features of Dytran’s accelerometers is their versatility: they can be used in a variety of industrial applications and in a range of conditions.

“They can be used in environments from low temperature to high temperature. In fact, Dytran is developing some sensors now that will operate in up to 600-800 degrees Celsius without failure,” said Callon. “They provide a silver hermetic seal on the sensor, which allows oxygen from the external environment to enter into the sensor by diffusion and which compensate for the oxygen depletion encountered when operating at elevated temperatures.”

This accelerometer range spans from general-purpose industrial accelerometers to seismic accelerometers, which are used to monitor construction activity, volcanoes and earthquakes. The company also has a range of accelerometers that are geared for aerospace – specifically aircraft and helicopters – or for monitoring vibration through flight (known as HUMS accelerometers).

“The kind of accelerometer and its features depend on the application they are geared towards,” Callon said. “For seismic applications, or aircraft applications, what you’re looking for are accelerometers that can work with very low frequencies – 0 hertz up to 3000 hertz. However, if you’re looking at something like a turbine, where it’s spinning at 3000 rpm, then you need an accelerometer that’s got a frequency range of around 1000 to 20,000 kilohertz, and it has to be able to withstand any shock and vibration.”

Dytran is also at the cutting edge of the industry, supplying accelerometers to commercial; space companies, where they are being used for engine testing. The company is also leading the way in miniaturising accelerometers – their smallest one, the 3224 Series, is only 3.5mm x 5mm in size. These are used for drone testing or for autonomous vehicles, where weight and size is a factor.

“That’s the strength of Dytran’s accelerometers,” Callon said. “They have such a diversity of applications and an ability to be used to such a wide variety of environments and situations – from industrial process lines to rocket testing.

“In many cases, they are essential for effective condition monitoring. They can prevent unnecessary maintenance and help stop catastrophic failure in industrial equipment. They’re a fantastic product.”

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