Tag Archives: dragline

FLANDERS AC system retrofit boosts dragline productivity at BHP South Walker Creek

After retrofitting an aged DC 8050 dragline with a safer AC power system, a multi-dragline coal mine operating in Queensland experienced a major boost in productivity and power efficiency, substantially diminished operating costs and a positive return on the investment within 18 months, FLANDERS says.

In 2018, senior management of BHP’s South Walker Creek coal mine was developing a plan for the DRE28 DC 8050, a nearly 40-year-old dragline on which the DC rotating equipment and DC control system had reached the end of their operating service life. The dragline was still operating with the original Westinghouse DC motors and generators, which had also reached their end of service lifespan.

At a minimum, the DRE28 motors and generators needed to be replaced. They could upgrade to new DC equipment that would maintain productivity for another 25-plus years with similar operating costs. However, the DC system required regular maintenance and was at a high risk of extended periods of machine downtime due to waiting for parts and maintenance techs, both of which were harder and harder to find, FLANDERS says.

Another option was to retrofit the DRE28 with an AC system. AC dragline systems were already known to have safety advantages and reduced maintenance costs compared with DC systems, according to FLANDERS. They also had the same service life expectancy of 25-plus years.

The team decided to move forward with an AC retrofit from FLANDERS. In July 2019, the boom was lowered on DRE28 DC 8050 and the on-site retrofit began. After 90 days, the DRE28 AC 8050 was back online.

“AC systems are designed with safety built in,” FLANDERS said. “Hardware compatibility, simpler and safer operating mechanisms and scalability are benchmarks of FLANDERS’ AC system design.”

One of the key features of the AC system is the unique, easy-to-access drive cabinet designed to replace DC motor-generator sets, FLANDERS says. Water-cooled semiconductors remove heat, so the cabinets keep parts protected from debris. This results in a substantial reduction in noise, dust, heat, and rotating parts, and reduced exposure of employees and maintenance technicians to these safety hazards associated with DC systems.

The drive cabinet also eliminates the need for on-site machining to blow out dust, balance parts, clean brushes and other regular maintenance DC systems require.

AC hoist/drag motors

The 690 V AC hoist/drag motors are designed to fit in the same size box as the DC motor, with the same footprint, allowing for easy drop-in installation. No modification to brakes, gearing, or coupling is necessary. Class H insulation and high-output blowers help the motors safely produce a 25% higher kilowattage than the DC motor can achieve.

Arc flash safety system

The FLANDERS AC system design mimicked the DC design in generating low- and medium-voltage interactions. The motors and drive cabinet have a category zero arc flash rating, requiring little intervention with specialists or the need to manually isolate systems within the machine.

There are several systems in place to ensure safety from arc flashes:

  • Metal doors safely hide high-power components, and all doors use Fortress Interlocks to ensure appropriate isolation of high-voltage before access is gained;
  • Electronic control boards can be separated into low voltage panels, nullifying the need to access high-powered areas;
  • Arc flash optical relays installed in each drive cabinet monitor for arcs and trip high-voltage VCBs to reduce potential energy below arc venting requirements; and
  • Fast-acting fuses are located on a) the secondary drive transformer and, b) bridge cabinets feeding to drive line-ups, and the DC bus in drive line-ups.

Ground fault detection

The built-in Bender IRDH265 Ground Fault Monitor eliminates the risk of electric shock, providing a system shut down override at the sign of a catastrophic event. Each drive line-up has a manual ground fault test function to supplement the auto test function of the Bender. This allows electricians to manually verify functionality of the ground fault monitoring system, FLANDERS explained.

The system is programmable logic controlled, which prevents the circuit from operating while the drive is in operation.

Opportunities for optimisation

Where the DC commutator is limited in output, AC capability is expanding and growing for draglines. There is still potential to be unlocked by analysing machine data and implementing optimising upgrades, according to FLANDERS.

AC conversion delivers results

From September 2019 through June 2021, the DRE28 AC 8050 operated at the previous DC 8050 electrical, mechanical and structural settings. In July 2021, after system optimisation, the AC 8050 surpassed the limits of DC 8050 machines, reaching output levels closer to the 8200 DC draglines models, and continued to bank gains in reduced maintenance costs, increased productivity and improved energy efficiency.

A side-by-side comparison of DC and AC dragline operations over 12 months and including three months of data reported after the July 2021 upgrades, shows the results.

The DRE28 AC 8050 is – operationally and electrically – the safest dragline in its fleet, according to FLANDERS, with the drive cabinets and motors maintaining a category zero arc flash rating since installation.

“The overwhelming response from our client was related to the safe and easy operation of the AC system,” Owen Uebel, Strategic Business Development Manager for FLANDERS, said. “Operators were vocal with management about the improved work conditions.”

In terms of productivity, the low-maintenance design of DRE28 AC system has resulted in reduced machine downtime and proportional gains in machine availability. A twelve-month comparison study confirmed that, compared with the DC 8050, the AC 8050 moved an additional 2 million bank cu.m (BCM).

With the July 2021 optimisation, the AC dragline is expected to reach a minimum of 15 million BCM annually in 2022, setting a record for this mine.

An independent study confirmed an 11% boost in power efficiency over the DC 8050 dragline over an operating period of January 1 to December 31, 2020, meanwhile.

“As previously mentioned, one of the major benefits of the AC system is its scalability,” FLANDERS said. “The 2021 optimisation increased the system’s peak power, resulting in a 4.5 second reduction in cycle time with no additional structural or mechanical stress on the machine. This finding was verified independently by MineWare reports and outside consultants.”

The AC system’s solid-state components have substantially reduced the amount of mechanical wear on dragline parts, extending savings across the lifecycle of the machine, according to FLANDERS. Maintenance costs are down over 55% on average (and potentially upwards of 65% based on available data since July 2021 upgrades).

Additionally, the AC dragline’s efficiency translates to 4.5 kilotons of CO2 offset, with major implications. To put that into perspective, at a global price of $200 per ton, that’s $450,000 annually and $900,000 over the two years of this study.

The AC retrofit achieved a return on investment within 18 months of being online, making it the lowest-cost pre-strip solution on the market, according to FLANDERS.

As of October 2021, the mine’s overall electrical and mechanical maintenance expenditures bottom line decreased by 60%.

Monadelphous expands BHP relationship with iron ore, coal, Olympic Dam work

A month after securing several major contracts with BHP, Monadelphous Group has announced another series of works packages with the major miner that come with a combined value of around A$120 million ($87 million).

Two of the construction and maintenance contracts were awarded under its WAIO Asset Panel Framework Agreement with BHP.

This includes a contract to provide structural, mechanical and electrical upgrades at the Newman Hub site in the Pilbara of Western Australia, where work will commence immediately and is expected to be completed before the end of 2021.

The second agreement is at BHP’s Jimblebar iron ore mine site, in Newman, where the company will be dewatering surplus water from the operation.

In addition, Monadelphous has entered into the Olympic Dam Asset Projects Framework Agreement with BHP to provide multi-disciplinary construction services at the Olympic Dam copper mine, in South Australia (pictured). The first contract secured under this agreement is for the supply and construction of acid storage tanks and connection to the existing operating acid plant.

Finally, the company’s Maintenance and Industrial Services division has been awarded a contract to undertake a major dragline shutdown for BHP Mitsubishi Alliance at its Saraji coal mine, located near Dysart, Queensland. The work will be completed by the end of December 2020.

Last month, Monadelphous’ latest construction and maintenance contract awards from BHP included a contract for the supply and installation of the Jimblebar Transfer Station project, and a contract for the refurbishment of Car Dumper 3 at Nelson Point, Port Hedland.

Condra to show off crane building abilities on South Africa coal mine dragline contract

Condra is to manufacture a “technically complex crane” to service a dragline at a coal mine in Mpumalanga, South Africa, following a contract win by its authorised agent for the Witbank region, GTB Industrial Services.

The order, won against strong competition, calls for a maintenance crane capable of working within the very constricted area of the dragline house. This contains motors and gearboxes controlling the excavating boom and dragline, and large hydraulic cylinders to control the pontoons, meaning space is at a premium.

Condra said: “Condra proved better able than its rivals to meet the complex criteria of the specification, chief of which was the requirement that the hoist be capable of separating completely from the maintenance crane, and moving away along individual roof beams as an independently operated underslung hoist to recover machine components to the central working space.”

The hoist must also be able to independently deliver loads to transport waiting outside the dragline house, should component repair within the house not be possible, the company added.

The requirement was met by designing the crane’s 12.5 t hoist as a beam changing machine, and fitting the crane with an interlock to prevent the hoist from leaving it unless the crane is securely connected to the selected beam, according to Condra. Power to the hoist is supplied via a cable drum instead of by the crane’s cable loop system.

Managing Director, Marc Kleiner, said Condra was able to draw upon previous experience of dragline maintenance cranes, overcoming engineering complexities to deliver a machine that allows a single hoist to carry out work that would more usually be undertaken by multiple units.

“Our design office tabled an innovative proposal that was also able to deliver more working room than our competitors,” he said. “We can quite often pull a rabbit out of the hat when nobody else can, but we think that this time it was also our ability to manufacture within a short lead time that helped win the order (lead time for the contract is just 14 weeks).”

A key component of Condra’s overall design for the crane is its manual beam interlock, which incorporates an anti-derailment limit switch to prevent hoist movement until beams are locked together, the company said.

Besides rendering impossible any movement of the hoist close to the end of the beam, this design also delivers the large tolerances needed to cope with beam movement when the dragline moves position, according to the company. Dragline movement takes place by ‘walking’ on pontoons repositioned for each step, tilting the machine house forward and placing stress on the structure as well as on the crane itself.

A hoist from Condra’s K-Series was chosen for the design because of its adaptability and particularly robust construction, well suited to these stresses, the company said.

K-Series hoists are produced in three main configurations: foot-mounted, underslung monorail and double-rail crab. Fully covered hoists in the series provide lifting capacities to 32 t, while open-drum units have capacities in excess of 250 t (open-drum and closed-drum Condra K-Series hoists are featured in the photo, painted green).

Features on all models include electromagnetic DC disc brakes, standard frame-size motors with parallel rotors, double-acting limit switches, solid bronze rope guides and totally enclosed splash-lubricated gearboxes. Lifting and reeving arrangements include centre lift.

Condra says it will deliver the dragline maintenance crane during the month following the easing of COVID-19 quarantine restrictions.

Genrec Engineering keeps downtime to a minimum at South Africa coal mine

Genrec Engineering has demonstrated its skills and capabilities in steel fabrication and engineering, successfully repairing a damaged dragline excavator boom in record time for one of South Africa’s leading coal mines.

This project also marks another important milestone in the company’s drive to diversify into specialist and niche markets since it was acquired by the Southern Palace Group (SPG) in 2016, the company said.

Genrec Engineering completed the project in around 10 weeks, helping reduce downtime at the mine in the Mpumalanga coalfields.

Producing coal for domestic thermal energy production and for export to global markets, the dragline excavator is an essential component of the mine’s open-pit mining. It is used in combination with drilling and blasting and dozers to expose the seam before wheel loaders and dump trucks are deployed in extensive load and haul operations.

Genrec Engineering’s involvement in this project commenced with a full-scale investigation into the damaged boom structure at the site in August 2017.

Managing Director of CMTI Consulting, Dr Danie Burger, was part of the team that participated in the investigation with various insurance companies.

Burger said a decision to award the boom repair contract to Genrec Engineering was based on the company’s long legacy in the South African and international steel engineering and fabrication industry.

“There is no other steel fabricator and engineering company in South Africa with the necessary infrastructure, as well as capacities and technical competence to take on such a complex project. Had the boom been sent to the original equipment manufacturer’s premises in Australia for repairs, it would have taken up to four times longer to return the dragline excavator back to service with obvious negative ramifications on the mine’s production,” Burger said.

Representatives of the mine’s management team visited Genrec Engineering’s factory in Wadeville, Gauteng, a week ahead of the commencement of the repairs.

Mark Prince, Divisional Director of Genrec Engineering, said: “The depth of experience and expertise of our team have allowed us to constantly innovate, which is a strategic differentiator in this industry and a trait that we proudly demonstrated on this complex design and build project.

“My team of professionals had to be able to think out of the box and on its feet to overcome a myriad of challenges to ensure the timely and quality completion of the project in an extremely short timeframe. The fact that we were able to complete this project in such a short timeframe speaks volumes of the capabilities housed here in Wadeville that have placed us firmly on our next growth path.”

The boom comprises a 37-ton (34-t) mid-section, which is 30 m long and 13 m wide, and the 43-ton (39-t), 32 m long and 13 m wide front portion. Both have a transportation height of 3.5 m.

It was completely remodelled by Genrec Engineering’s design team with assistance from CMTI Shared Services, in a process that took about a week-and-a-half to complete.

The original drawings of the Bucyrus dragline excavator were more than 30 years old and updated versions were later received from Caterpillar.

They were used to generate models to develop the manufacturing drawings and upgrades to the boom, in addition to the manufacturing sequence, work procedures and transport sections, according to Genrec.

The project also involved careful and complex logistical planning, considering that Genrec Engineering had to locate and source up to 34 tons (31 t) of chord material from various Australian mines to supplement insufficient supplies of the required specification.

“A comprehensive analysis was undertaken of all available material sources to ensure quality and, importantly, traceability in line with the stringent requirements of the OEM,” Genrec said.

The chords were buttered up and machined to specification and all lacing laser cut to fit assembly.

It took about three weeks of round-the-clock operations to complete the complex laser cutting by approved specialists located in Vanderbijlpark, with Genrec Engineering team members located permanently on site to advise, as well as monitor progress and quality.

They were delivered to the plant in the correct assembly sequence and welding was then undertaken in a 2,200 m² bay converted for specialised manufacturing projects.

Burger says: “The process commenced with pre-heating and the roots undertaken with tungsten-inert gas welding and CO2 used as a filler. Non-destructive testing was done using magnetic-particle, phased array ultrasonic, radiographic and ultrasonic testing. Personnel from NJM Heat Treatment & NDE Services, as well as NDT specialists, were stationed permanently on site to ensure that we were able to maintain sound productivity rates and adhere to exacting quality standards.”

A total of 2.3 tons (2.1 t) of weld material and eight weld feeders were also sourced from Australia to supplement available resources for this project.

One of the complexities of the welding operations was the varying diameters and positioning of the larger chords and smaller lacing, Genrec said.

A total of 129 welders were tested by Genrec Engineering and 52 metal inert gas, or gas metal arc, and tungsten inert gas welders employed to work on this project, together with 18 boiler makers and assistants. Ranks were bolstered with five specialist boom welders, as well as an expert boom weld engineer and project coordinator from Australia.

They also assisted in undertaking the four successful Procedure Qualification Records ahead of welding activities.

Genrec also highlighted the rotators designed and developed especially for this project. These complement the large investment already made by the company and SPG in acquiring the capital equipment needed to diversify into niche and specialist markets.

Among these are the computer-numerically controlled machines housed on the factory floor that have been fully integrated into the SolidWorks engineering programme to ensure high levels of precision and productivity, Genrec said.

These, alone, represent about a R50 million ($3.6 million) investment that is also being supported by continued skills development and training as Genrec Engineering builds up its skills base to cater to the high demand for its specialist services.

As part of the project, Genrec Engineering was also tasked with upgrading the dragline excavator’s boom-point box.

A special furnace was designed and developed around this box and soaked at 600°C for six hours and then cooled down to 37°C for five days. The furnace was heated with gas at a rate of 37°C/h to 600°C.

A canopy was also designed to allow sand blasting to continue apace in the workshop while welding progressed according to plan to maintain high productivity rates.

The components were transported to the mine site by Mammoet using a 13-wheel Nicolas trailer and resting on 11-ton (10-t) cradles specially designed and manufactured by Genrec.

It took three days to transport the two loads to site as part of the last phase of the project.

“This is the largest abnormal load to have ever travelled on the Gauteng road network, and Genrec Engineering was also involved in the extensive road survey, in addition to obtaining all necessary road permits from the Gauteng Department: Roads & Transport,” Genrec said.

The mid-section of the dragline excavator boom was dispatched to site at the end of November and the front end in early-December. It was successfully assembled by Caterpillar’s southern African dealer, Barloworld Equipment, on site in December over a period of four weeks.