A major concern when automating a valve bagging system is the false start. A false start is when the bagger is started and the bag is not properly positioned on the filling spout; product can be dumped to the floor and dust can quickly fill the building.
Production increases, downtime decreases
Increasing global demand for its high quality industrial garnet meant GMA Garnet Group (GMA) needed an updated bag filling system. Consequently, the garnet mining and processing company headquartered in Perth, Western Australia, installed Premier Tech equipment to increase production rate, reduce downtime and minimize maintenance.
Industrial garnet is a hard mineral used in waterjet cutting and as a cost-effective and higher-performance replacement for silica sand and metal slag in abrasive blasting, also called sandblasting. Garnet’s used to clean oil-drilling pipes, as well, an application whose use is increasing in tandem with oil and gas industry activity.
The toughness and low friability that make industrial garnet effective at abrasion blasting and cutting—its Moh’s hardness rank is 6.5 to 7.5 and on the Koop hardness scale, it’s two to four times harder than slag and silica sand—mean it doesn’t generate an appreciable amount of dust during processing and handling, an additional advantage over sand and slag. All these attributes are attractive to GMA’s customers. So attractive, that satisfying customer demand required a higher production rate. And that’s what GMA expected the new equipment to deliver.
A DS-LCB326 Level Control Bin was installed to feed material to new DS-725NXT Force Flow (Air) Packers. The bin’s level switches maintain material within a specified range, producing constant head pressure above the air packers for consistent material density and cleaner, more accurate filling. The control bin also provides residence time for material before it is fed into the packer. This residence time allows many types of materials, including GMA’s garnet, to de-aerate inside the bin. As a result, material has a more consistent bulk density when it is fed into the packer. Consistent head pressure and consistent material bulk density are key factors that enable the air packer to fill bags quickly and accurately, explains Mr. Gary Ritter, Sales Manager at Premier Tech.
The air packers themselves are well-suited to the need for dependable, accurate bag weight because they are fitted with a pinch-tube-type cut-off assembly that provides bulk-and-dribble material feed rate control during filling of the fine powders, flakes, pellets and granules with a particle size of 3/8” or smaller that these packers bag at a rate of up to 10 bpm per spout. The packer’s small footprint allowed multiple packing units to be installed under a single hopper for higher production rates.
Because garnet is abrasive, minimizing the number of moving machine elements within this material’s flow path was essential to minimize maintenance of the equipment and associated downtime, and to maximize the equipment’s life span. This requirement was met by the packers’ plug/stack configuration, which has no moving parts in the flow path. Filling was additionally enhanced by installing DS-45URAI Roots Blowers, which supply the packers with a consistent flow of low-pressure air that fluidizes material for smooth conveying through the packers and into bags.
Before bagging was updated, empty bags were applied to filling tubes by an automatic applicator whose speed couldn’t match demand—or the speed of the DS-RA Robotic Empty Bag Applicator. With the new robot in place, the operator only needs to replenish the bag magazine’s supply of empty bags on a part-time basis. This frees the employee for other, value-added activity. The robot is well-suited to this application because its sealed joints are unaffected by abrasive material.
After a bag is filled, it’s discharged from the air packer onto the model DS-860C Packer Conveyor, which is designed to cushion the bag as it lands on the conveyor. This conveyor transfers bags to the model DS-850C Slider Bed Conveyor, which aligns each bag and transfers it to downstream conveyors for subsequent operations such as bag flattening and checkweighing. Both conveyors were customized with rubber belts to withstand the abrasive nature of the material being bagged, given the possibility that a small amount of material may leak from the valve of filled bags as they are discharged from the packer. For customers for whom even minor leakage is not acceptable, an ultrasonic bag sealing system is available.
The main challenge that needed to be surmounted during this project was the integration of new equipment with existing upstream and downstream equipment, and ensuring that the new equipment’s safety devices met the requirements of the Australian Safety Standards organization. Premier Tech provided detailed documentation necessary for installation by local contractors, maintaining an exchange of information throughout all phases of the project. “The commissioning of the unit was conducted by a Premier Tech field service technician who was very knowledgeable, and was well-executed,” recalls Ms. Amanda Gundry, GMA’s General Manager, Midwest Operations.
Equipped to compete
In June 2015, the U.S. Geological Survey called the market for industrial garnet “very competitive,” with global demand expected to continue increasing as it has done since the last global recession. This bodes well for GMA, now that new equipment has improved the company’s operation and its ability to meet customer expectations. The new bag filling line has “Increased production rate and reduced downtime [that was] due to maintenance issues with the old … bagging unit,” Ms. Gundry reports. “Consistency in the material feed rate has also improved, which has improved efficiency” because fewer bags are rejected by the palletizing unit, she adds. Most importantly, has GMA seen its own customers’ satisfaction increase? “Yes.”
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