Engineer develops new method to measure lagging Thursday, 16 June 2016

Conveyors are important for a multitude of projects, from transporting iron ore around a mining site, to ensuring the manufacturing process runs smoothly as goods are handled along a production line.

But one rarely thought-about aspect of conveyors is the lagging friction, which can have a significant impact.

Brett DeVries is looking to change that, and even has the data to back it up.

DeVries is a staff engineer of research and development at Flexco, a US-based company that specialises in how to maximise belt conveyor productivity.

When DeVries started researching lagging friction coefficients, he was unable to find any literature on the best practice for how to measure it.

“We have long believed and advertised and really got support from the industry that the full ceramic tile product is a superior coefficient friction. But we wanted to better understand why that was the case,” he said.

So DeVries set about using his own technique, which works by taking a small belt and gluing it to two steel plates. He then sticks it on an apparatus that squeezes two pieces of lagging against it on either side.

The technique can also work in reverse by glueing lagging to the steel plate and pressing the belt up against the lagging.

“Essentially what I can do is measure the force that the belt is squeezing against the lagging, and I pull that steel plate out upward from the two pieces of belt and measure the force it takes to extract that as the plate begins to be drawn out,” DeVries said.

In other words, the technique allows people to measure the force displacement simultaneously and create a plot of what that force and displacement looks like.

When the results first came in, DeVries was surprised and thought he had done something wrong.

“I talked to a lot of different engineers. I said, ‘This isn’t supposed to happen. What’s going on?’,” he said.

DeVries also contacted an expert from a rubber development company who does rubber testing to verify his method. But no one was able to fault his method.

DeVries recently presented his findings to the Conveyor Equipment Manufacturers Association (CEMA) to receive feedback.

“The first reaction I got at the CEMA meeting was that it couldn’t be right. Everyone had used the old methods with the constant coefficient friction for so long that this data was rather shocking to them,” he said.

He has also presented his research at a conference in South Africa.

“There was some serious consideration at that time of [how this has] been practically applied and practically verified in a real world scenario,” DeVries said. “Unfortunately, I haven’t gotten to that stage yet, but we have plans to do that.”

Those plans include a prototype that tries to leverage the fact that lagging has to be flexible both with and against pulley rotation.

“If I can facilitate that with the pattern in the lagging, I should be able to reduce wear,” he said.

He has been working on the prototype for around 12 months and incorporating several features into the product.

“We’re trying to build it on a steel backing plate and we want to make that backing plate flexible enough so that it can be readily installed, but still strong enough to support the load,” DeVries said.

While creating the design for the lagging pattern has not been difficult, DeVries said there are some questions about being able to fill it with rubber and still retain an exceptional appearance.

Final product

DeVries said the final product will be useful for companies who want to carry out in situ repair work for their lagging.

“It’s meant to be welded to the pulley so that pulleys don’t have to be removed from service in order to be re-lagged,” DeVries said.

He expects smaller aggregate producers would benefit, but DeVries is also working on another product that larger customers could use, such as coal mining and iron ore companies that currently use cold bond strip lagging.

However, one barrier to uptake of the product could be due to lagging friction as something that is not typically thought about.

“By knowing the lagging friction more accurately and having this different method for considering the capacity of lagging to drag the belt, it lets you identify a few more decision points,” DeVries said.

“[For example], you can have an increased diameter of a pulley, which would lower the tension in the belt system.”

DeVries plans to start field testing for the prototype in around three months. He will be presenting his white paper to the Australian market at Queensland Mining and Engineering Exhibition, 26-28th July in Mackay, Queensland.

The field test will be carried out at a local sand and gravel operation near the Flexco facility. Following initials tests, it will be expanded to 10 to 12 small sites across the United States.

During the tests, he will monitor aspects such as delivery, installation and how easy it is to use the product, with a product launch in around 12 months.

“Then we’ll install it and monitor it under real life conditions and look at the likely failure modes that we’ve identified and verify that we’re achieving success in those perimeters,” DeVries said.

Don't forget to register for the Australian Engineering Conference 2016 in Brisbane on November 23-25.