Case Studies

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Metso Case Study
Metso Minerals, based in Matamata New Zealand, designs and manufactures up to 23 tonne Barmac (Vertical Shaft Impacter) VSI crushers that can pulverise between 10 and 2080 tonnes of rocks per hour into bite-sized smithereens.
With such formidable force the slightest structural imbalance can cause almost as much damage to the machine itself, as it does to the rocks it punishes. While maintenance is critical and repairs are inevitable, Metso design engineers are discovering the advantage of using Commtest VB 2000 to fine-tune prototypes and minimise wear and tear on machinery. In just three years since they incorporated the Commtest vibration analyser system into their test programme, Metso Minerals have more than justified their investment. They have been able to achieve, and pass onto their customers, significant product design enhancements that increase performance and reliability, and reduce costs all round.

Rock On Rock For Crushing Results
Invented in New Zealand the Barmac VSI is globally unique due to its power-saving crushing process. Unlike other types of crusher, which use metallic parts to crush rocks, the Barmac uses rocks fed into the machine to crush others through high velocity impact. Rocks entering the rotating rotor are hurled at high speeds into the chamber and smashed against other rocks falling through the machine. Adjusting the rotor speed controls the size and shape of the reduced product desired for the application.

The Barmac has found a home in many niche applications offering lower power consumption, up to 50% less wear and tear to metal parts, and increased product throughput by up to 30% over other technology.

The machines are used in over 3000 quarrying and mineral processing sites worldwide. Customers include aggregate and sand processing plants, industrial mineral sites from cement clinker to diamond mines, to waste and recycling sites.

In such critical and dangerous environments reliability and productivity is key, and customers can ill afford to have any component of their business out of operation and in need of costly repair. Therefore, a constant challenge for Metso design engineers is building a crusher that can withstand the rock-pounding abuse, is easy to maintain, cost-effective to produce and operate, and requires minimal downtime.

Using Vibration Analysis To Avoid Resonance Damage
The design of Metso machines has advanced considerably over the years and they are now used in more applications and run at a wider range of speeds than ever before.

"We used to employ consultants to perform vibration tests on new prototypes as well as on problematic machines. But this was proving a costly exercise and didn't allow the flexibility or convenience of experimenting with and analysing a variety of tests for detailed design and modification," said David Kenny, R&D Engineer at Metso Minerals.

"We started doing our own tests three years ago after an incident where we were baffled as to what had caused a cracked shaft on one of our machines. We were amazed when a consultant established the fault straightaway using Commtest's vibration analysis equipment in a bump test. He found that, at a certain speed, the resonance - or natural frequency - of the machine was the root cause of the problem. The solution was to adjust the rotor speed above or below its natural frequency, and we had no more problems."

Excited with this fast and accurate analysis Metso decided to invest in an in-house solution. They looked at what their suppliers and consultants were using and chose to purchase the Commtest VB 2000.
"Compared with the cost of employing consultants every time we looked at a design change, and against competing products at almost three times the price, it was easy to justify to management the investment in the VB 2000 vibration analysis system," explained David.

Enhanced Product Design with the vb2000
Since Metso purchased the Commtest vb2000 design engineers have been able to apply regular condition monitoring tests to all new prototypes.

The company has a range of seven Barmac machines on the market, and continually improves them to perform better in existing applications, as well as new applications that are developed. They have also had to deal with more and more customers using variable speed drives that allow them to quickly change the product required that day. Traditionally these machines have belts and pulleys to change increment speeds, which wouldn't change so often. Having more customers using variable speed drives has created a new set of problems and made the design more complex," said David.

"We use the VB 2000 to find the natural frequencies in the speed range that each machine prototype is rated for. This enables us to make the whole frequency range safe to work and eliminates any possibility of excessive vibration that could cause surprise breakdowns."
The ability to do these tests themselves allows Metso instant flexibility, speed and convenience to adapt the structural design of their machines accordingly.

How Commtest's VB 2000 Saves Months on Product Testing and Analysis
Without Commtest's VB 2000 vibration analysis equipment it would have taken Metso up to four months to test and determine at which of the ten speeds the resonance might occur and cause damage to a prototype. Now it only takes one day of tests per prototype to locate where the problems are likely to be.

"The older Barmac machines were over-engineered with higher safety margins, and required more steel and labour than needed to operate without resonance. To save on steel and get the same results we needed to do better testing and design the products more effectively," explained David.

"To meet customer demand for advanced machinery, we've had to learn how to work smarter, not harder. The VB 2000 gives us results we can use to maximise the design of new prototypes for increased reliability and performance, while minimising steel and labour costs."

"Throughout the relationship Commtest have guided us well, and provided excellent customer service and support. The VB 2000 has proved very cost-effective."

pub03.4Metso Minerals (Matamata) Limited, based in Matamata, New Zealand, manufactures the Barmac Vertical Shaft Impact (VSI) rock crusher used in the global quarrying and minerals processing industries. The company was established in 1968 and became part of the Metso Corporation in 2001. They now employ nearly 70 people and exports 90% of its products to the network of Metso Minerals distributors around the world.

The Commtest VB Series are 'intelligent maintenance solutions' designed to provide precision vibration, monitoring and analysis of rotating machinery at a fraction of the cost of comparable packages. Customers can expect up to 35% costs savings when they make a full changeover from preventative maintenance to a predictive maintenance system, and achieve reduction in plant power consumption by 10% or more.


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