Tronox used to have three employees manually bulk bag rutile and zircon for exports, sweating 10-hour days and cumbersomely using two forklifts to hold a bag and a hopper while a wheel loader poured in the material.

While the work was getting done, Tronox felt a smarter solution would not hurt and went to Flexicon for help. The latter’s response to the issue was “Rhonda”.

Rhonda is a heavy-duty skid-mounted bulk bag filling station that integrates a 2.5 cubic metre capacity hopper, a 4.5m long steel tube screw conveyor and a Twin-Centrepost bulk bag filler.

Since its deployment onsite, the unit has enabled Tronox to double its shipping output, with just two employees filling about 90 bags in an 8-hour day.

“Formerly, three employees filled about 80 bags in a 10-hour day,” Flexicon said.

“The unit doubles output per operator over the former method, while improving health and safety since filling is enclosed and essentially dust-free.” 

Rhonda has a throughput capacity of about 20cu.m/h, which means it can fill a 1.8t bag with zircon in about one to one and a half minutes.

The unit’s two steel posts can handle varying bag weights and support a fill head and pneumatically retractable hooks on which the bag must be placed manually to hang.

The bag’s inlet spout must then be placed over an inflatable collar that holds it in place and provides a dust-tight seal during the filling process. Above the bag comes the hopper, which can hold up to 7.3t of zircon or up to 5.4t of rutile in granular form.

Surrounding all this is the station’s outer frame, which also supports the 4.5m long tubular screw conveyor.

To use Rhonda, two Tronox employees split the work, with one using a front end loader to empty material into the hopper, while the second controls the filling operation with a programmable logic controller (PLC).

The PLC is used to preset the bag weight and switch on the conveyor, which draws the material from the inlet at the bottom of the hopper out to a transition adapter and telescoping steel downspout into the bulk bag.

“The bulk bag filling station moves between the zircon- and rutile-filling operations, which are located approximately 800m apart,” Flexicon explained.

“Due to its relatively small footprint, the skid-mounted system can be moved using a 3t forklift.”  

The screw is said to automatically self-centre within the tube, allowing a 100% fill rate.

Once the bag is almost full, the conveyor speed slows and stops when the bag reaches the desired weight. This is achieved thanks to four load cells located under the steel deck supporting the filler. 

A small piston valve at the transition adapter draws samples to check quality of the material being bagged.

After filling, the process turns back manual, with a forklift truck needed to take each filled bag to a storage area prior to shipment.