Bucket Wheel Excavators: 3D Machine Control on a Large Scale

During a recent business trip to Australia, I had the pleasure of visiting several open pit, coal mines. These operations are colossal in scale.

Because of their enormity, constant analysis of productivity is extremely important.  Even small improvements in their processes yield big dollars. The purpose of this article is to focus on how 3D Machine Control can improve the Bucket Wheel Excavator’s productivity.

Bucket Wheel Excavators (BWE) are continuous cutting machines for soft to semi hard materials like clay, sand, gravel, marl and their blendings as well as lignite and hard coal. Tenova TAKRAF BWE excavate a wide range of capacities between 200 and 16000 m³/h and at working bench heights from less than 5 m to maximal 51 m.

The BWE is connected to a conveyor belt system.  These systems can literally traverse hundreds of meters until they reach their destination; usually a bunker at the power station or spread onto a stockpile awaiting transport.

According to local mine conditions Compact and Large BWE’s are offered – whereas the selection mostly is determined by required cutting height and width (working block).


The characteristic parts of a BWE are the cutting wheel with buckets, the wheel boom, the superstructure with counterweight boom, the substructure, the undercarriage with crawler tracks and a transfer boom to the bench conveyor (or a connecting bridge to the loading unit). All main parts are designed to meet the demands of the project regarding optimization, standardization and maintenance.


BWE’s are among the largest terrestrial vehicles ever constructed - the biggest machine built, the Tenova TAKRAF SRs 8000, has a weight of 14.200 t and moves 240,000 m³ of overburden per day. <http://www.takraf.com/en/products/miningequipment/bucketwheelexcavator.htm>

Specifically, the RB293 is a giant bucket-wheel excavator made by the German industrial company TAKRAF. It was recorded as the largest and heaviest terrestrial vehicle in the Guinness Book of Records (2001–2009). <http://en.wikipedia.org/wiki/MAN_Takraf_RB293>

History

While researching the history of Bucket Wheels Excavators, I found the picture below. This is one of two bucketwheel excavators fabricated in the Lauchhammer works, in 1926.

In 1990, TAKRAF Schwermaschinenbau AG manufactured their 500th bucketwheel excavator and in 2005, production reached completion for the 1000th.
<http://www.takraf.com/en/aboutus/history/main.htm>

I was in awe at the sheer size of these machines but had no idea of their long history until preparing for this article.

New Technology Meets Traditional Brawn
New life has been given to this massive historical workhorse. The Bucketwheel Excavator is an excellent candidate for 3D Machine Control.  One of the sites I visited had 5 Bucketwheels retrofitted with 3D Machine Control. It was amazing to see 5 of these 5+ story tall machines munching away, almost silently, at the coal.  

Let's discuss briefly the general anatomy of a 3D Machine Control Bucketwheel.  First, there is a dual GNSS receiver installed. One GNSS antennae is installed at the center or pivot point. This offers a base position for the machine and proximity to the site and surface. The second GNSS antennae is positioned so as to monitor the arm swing. There are also a series of axial sensors installed at strategic locations to monitor all articulation. (See picture below)

The Operators Cab

The operator’s cab is as big as small apartment I once rented in the San Francisco Bay area.  The cockpit rivals a commercial jet.  All of the sensors feed into a computer system loaded 3D Machine Control Software.  The software  calculates (in real time) all positioning information presenting the operator with simple to follow instructions for cut/fill, productivity and machine proximity on the site.  A radio system wirelessly transmits this data in real time back to the mining office for each of the 5 machines.  A command and control center receives this data in real-time while logging to a database for further analysis. Reports and playback are also possible. The office software can also send data to all BWE’s over the same wireless network.

 

Software Screen above and yours truly at the controls.

Benefits
Several benefits are realized by retrofitting the BWE with 3D Machine Control. First and foremost is safety.  No longer does a person need to be at the cutting wheel measuring surface progress no does the machine have to stop to accommodate this task.  The accuracy is greatly improved at +/- 50 mm.  And productivity gains increased due longer time periods of uninterrupted operation while calculating the volume of coal, real-time.  This is key for producing the right amount of coal based on the power plants fluctuating demands

 

Summary
There is a responsibility for providing the best energy at the best price.  The mining industry is ever challenged in this quest.  By implementing new and emerging technologies, the industry has proved that advances can be realized without losing the investments of past implementations. RN July 2009

 

 

I have posted a video presentation of footage I gathered while on site.  Please check the front page of MachineControlOnline.com and our Exclusive Video section.  Or link direct to the video here

Click Here for complete article PDF with high res pics.

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