Ergonomic Exposure And Controls: Truck Unloading And Sorting

Description Of Work Tasks

Employees walk into a tractor-trailer to manually unload a variety of boxes that are stacked from floor to ceiling. The boxes vary in size, shape and weight. The boxes are lifted and placed on a floor level conveyor where they are mechanically moved for distribution into the warehouse. Within the warehouse, the boxes are manually sorted by employees for distribution onto racks in the warehouse.

Exposures

• Flexing the torso to place packages on the central roller conveyor within the truck.
• Lifting parcels from the floor and from under the central conveyor. Accomplishing these tasks forces the employees to flex at their waist up to or in excess of 90 degrees. Repeatedly flexing the torso, even if there is no load in hands, is a recognized risk factor for back injuries since the entire upper body must be supported in this posture.
• Twisting when moving large parcels.
• Performing repeated lifting operations.
• Lifting heavy loads.
• Highly repetitive lifting tasks.

Controls

• Tag or mark all packages that are heavier than about 40 pounds so employees have an idea of the package’s weight prior to attempting to lift it.
• Use a telescoping conveyor with vertical adjustment to unload the trailers, instead of a roller conveyor mounted on the floor of the trailer. Many unnecessary torso flexions are used to lower parcels to the floor from locations well above waist height. Use of a telescoping conveyor would permit moving of these parcels without bending at the waist.
• Instruct trailer un-loaders to modify their unloading technique to minimize the amount of lowering to floor level. A technique which uses a controlled stack toppling is preferable to lifting and lowering each individual package (assuming the contents are not fragile); this technique would permit pulling over an entire stack and allowing all the packages to fall to the floor. When on the floor they could be pushed or slid without lifting onto the roller conveyor.
• Provide a bridge conveyor for sorting tasks such as those where items are moved from one conveyor to another. The bridge will allow employees to move items from the origination conveyor to the destination conveyor without lifting. Transport of items could be accomplished by simply pushing them across the bridge. Further improvements in hazard reduction could be accomplished by administratively designating the highest volume destinations to the conveyor serviced by the bridge. Hinging the bridge conveyor would allow the unit to be moved out of the way for egress purposes.
• Completely modify the sorting areas so packages can be moved with the assistance of gravity rather than fighting gravity, which is the case when packages must be lifted prior to movement to another area. Packages would come to the station on a central supply conveyor, where the first employee would presort parcels in one of two directions. After a package has been sorted to one side or the other, a subsequent sort would be performed and the package could be pushed down the appropriate chute. In all cases, packages would be mechanically lifted to elevated locations by conveyors, a sort would be performed, and then the sorted packages would slide down a chute to a new conveyor. Since employees in this type of station would not need to lift, turn, throw or bend, the overall page at which they could work could be faster, enabling fewer employees to perform at a higher output. Since no lifting would be performed, the risk to the back and shoulders should be significantly reduced.
• Since different positions have varying volumes of work and use different sets of muscles, regular rotation of employees will provide on-the-job rest and recuperation for affected muscle groups.
• Redesign the sorting process such that all packages are not removed from the supply belt during the sort process. Under this scenario, the packages from all trucks would be placed on a single belt. Sorting could then be performed along the belt.

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