BHP dragline retrofit goes off without a hitch

Flanders has helped to perform an Australian-first at BHP’s South Walker Creek coal mine in Qld's Bowen Basin.

Flanders has helped to perform an Australian-first at BHP’s South Walker Creek coal mine in Queensland’s Bowen Basin, completing an AC dragline retrofit right on time.

In 2018, the DC rotating equipment and DC control system on BHP’s South Walker Creek dragline had reached the end of their operating service life.

Ongoing maintenance and an increased risk of machine downtime prompted project managers to solicit solutions from their partners.

FLANDERS proposed an AC retrofit solution which offered improved safety advantages, more than a 25-year service life expectancy, increased efficiency, and reduced maintenance costs and greenhouse gas emissions compared to the outdated DC systems.

In July 2019, the retrofit commenced with the dragline boom being lowered on DC motors.

FLANDERS Asia Pacific strategic business development manager, Owen Uebel, said the choice was made simple for BHP once it visited FLANDERS’ factory in the United States.

“My colleague and I went to site and presented what FLANDERS could offer and how we would deliver the project and provide the onsite support post-retrofit. We then invited them to go to the U.S where they could see several draglines that FLANDERS had already retrofitted to AC,” Uebel told Australian Mining.

As the only manufacturer to have performed an AC dragline retrofit in the world, FLANDERS held a key advantage to win the tender.

Flanders Australia engineering manager Gary Free was also able to show BHP how each piece of equipment was designed for dragline duty and manufactured in-house, giving the major miner a high degree of comfort and reduced the overall risk of the project.

“The fact that they could see the machines working was a real benefit. But what’s more, the visits with the end users confirmed how the FLANDERS AC system was increasing productivity and reducing their operating costs,” Free said.

The benefits of transitioning from DC motors and generators to AC motors and static drives are numerous.

The cost of maintaining and replacing DC motors and generators and keeping the skills required to keep this outdated equipment running is increasing, according to Uebel, making the decision to transition a near no-brainer.

“DC motors and generators on draglines are limited with safety and productivity improvements due to their commutator construction and capability. AC motors do not have these limiting factors and therefore you can explore and realise improvements in safety, productivity, and efficiency,” he said.

In more than two years of operation since the retrofit was complete, the mine has reported significant gains from the AC dragline retrofit.

A 12-month comparison study showed the AC dragline was on track to achieve an additional two million bank cubic metres compared to the DC model.

A return on investment was achieved within 18 months of the AC going into production, showing that AC draglines can significantly lower the cost of overburden removal and potentially reduce the amount of diesel-powered equipment used in pre-strip operations.

In July 2021, an AC system optimisation increased the draglines’ peak power at South Walker Creek, resulting in a substantial reduction in cycle time with no additional structural or mechanical stress on the machine.

But instead of taking all the credit for these achievements, Uebel took the time to acknowledge the team effort that went into installing the AC retrofit on time.

“M2E Electrical completed the electrical installation work and Richglen Maintenance Services performed the mechanical work,” he said.

“They were all outstanding people and we worked well together with the project team from South Walker Creek.”

The AC retrofit project was delivered on time and within budget, a notable achievement as the first one in Australia.

But the most pleasing thing for Uebel and his team was not completing it on time, or the performance it’s given BHP, but the response from people at the coal face.

“There is always several operator and maintenance crews working with these machines. We expected and were prepared to receive a varied and substantial range of feedback,” Uebel said.

“But the response from all the operators, all the maintenance people and all the mine management to date has been extremely positive and unified in that the AC retrofit has surpassed their expectations.

“To us, that’s the thing we’re most proud of.”

This feature appeared in the May issue of Australian Mining.

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