Dust Control Handbook for Industrial Minerals Mining and Processing

CHAPTER 6: BAGGINGThis chapter discusses techniques used by mineral producers for controlling worker dustexposures while bagging and stacking product in various types of bags for shipment tocustomers. The loading of product into some type of container is normally called "bagging."The stacking of these bags of product onto pallets for shipment to customers is typically called"palletizing." There is a wide spectrum of different types of bags that are used to ship product tocustomers, ranging from 50-pound to over one-ton bulk bags. Only the smaller type bags(100 pounds or less) are typically palletized because the larger bulk bags are in most cases,individually shipped. Both the bagging and palletizing process can be performed manually orthrough some type of semi-automated or totally automated process. Dust generated by themanual bagging and palletizing of 50- to 100-pound bags directly affects a number of worker'sdust exposure.Workers performing bagging and stacking tasks, or working in and around these areas, typicallyhave some of the highest dust exposures of all workers at mineral processing operations. A fewof the difficulties with controlling dust in work processes associated with bagging and palletizingare the wide range of different equipment being used, as well as the variety of bag types. Thebagging process can range from single-station manual bagging units to fully automated multistationmachines.In addition to the potential for high respirable dust exposures from the bagging and palletizingprocess, there is also a significant risk for musculoskeletal disorder (MSD) from all the repetitivemotion and the significant weight lifted by workers while performing tasks associated with theseprocesses. The dust exposure and MSD concerns have motivated many operations to pursue theimplementation of equipment that either semi-automates or totally automates these work tasks.BAGS AS DUST SOURCESTo address problems associated with the bagging process, a number of different dust sourcesneed to be addressed and controlled, specifically product blowback, product "rooster tail," andcontaminated bags. When manually bagging and stacking 50- to 100-pound bags, these dustsources directly affect the worker's exposure. Two different types of bags that are used totransport product within this weight range are open-top bags and closed bags with an internalvalve.Open-top bags are slid up over the loading chute and filled with product in a mass loadingtechnique. Open-top bags are typically used for larger particle sizes called whole-grain, whichare normally greater than 120 mesh (0.125 mm) in size. The dust sources when loading open-topbags are leakage from the loading chute once the bag is removed and liberation from the openbag before it is sealed. Sometimes these open-top bags are moved into a cage device to properlyposition the bag before sealing; this task of moving the bag into the cage can also be a dustsource. Since these bags are typically used with large particle sizes, dust generated or liberatedis not normally as significant as with the valve-typed bags (closed-top).Bagging 157