We recently visited an Aran modular mixing plant which has proven its weight in gold, producing cemented backfill for the Gossowong underground mine on remote Halmahera island in Indonesia. Aran visited this remote mine site to perform a condition review of the plant and make recommendations for to ensure its continued successful operation for another decade.
It was impressive to see how well this machine has been maintained after 10 years of highly ulitized operation. Producing up to 150m3/hr of backfill for schedule critical mining, this plant is an excellent example of high availability as a result robust equipment design and good attention to cleaning and maintenance.
The Gossowong gold mine extracts ore from very narrow seems in areas of fractured and highly stressed rock. Located in a highly seismic region, this underground mine is presented with many risks to the safety of underground workers. In order to safely and efficiently extract ore, narrow stopes are created, then quickly filled with cemented paste. This cemented paste must be strong enough in allow continued mining operations. Target strengths in some areas can be as high at 2mpa in 7days. This strength requirement can demand a mix recipe with up to 24% cement for a 230-260mm slump paste.
The Gossowong mine utilises volcanic dust, Tuff, as the primary product in the fill material. This fine dust like material is incredibly porous, capable of holding up to 35% moisture. When wet, it can be somewhat challenging to handle. Additionally the water retained within the Tuff can make the goal of optimising the cement to water ratio, difficult. Accurate cement addition to the paste backfill mix is critical, not only to ensure fill underground is structurally competent, but cost of the fill is tightly contained.
The Aran backfill plant receives screened Tuff material into a metering hopper which accurately meters the material into the mixer. Cement, delivered to the mine site in bulk bags, is unloaded and transferred into the mixing plant silo. Accurately metered cement is then added to the mixer with water for mixing. The Aran twin shaft, high intensity mixer combines these ingredients, before delivery into the underground reticulation pipeline system.
Whilst the machine’s external appearance represents a plant exposed to the tropics for ten years, mechanically and electrically it is still in excellent condition. Of course, over ten years of product development, there are many possible upgrades which can be installed on this older machine however, what currently exists on this site is a credit to the owners and operators passion for care and maintenance. Very few system and hardware upgrades are needed.
If you would like to learn more about what makes Aran mixing systems so accurate and reliable, please ask us. If you have a project challenge you are confronted with, we would like to listen to your story.