Conveyors

Volume 1, Number 31

There are many industries where in-process and finished goods are transported by conveyor. While widely seen in manufacturing facilities, conveyors are prevalent in other industries such as agriculture, manual material handling, and retail grocery stores. Conveyors reduce manual material handling requirements by eliminating carrying tasks. However, conveyors can introduce new risk factors to the workplace since employees must retrieve goods from them.

Concerns with Conveyors

• Reach Distance. The posture that an employee must use to access goods on a conveyor is highly influenced by the conveyor’s geometry. Bending forward at the waist (trunk flexion) and working with the arm above the shoulder (shoulder flexion) are found where conveyors are too low or too wide.
• Contact Stress. Conveyors often have a lip—a raised edge—that can be a source of pressure on soft tissue if the employee frequently leans on or over the conveyor.
• Standing Work. Conveyor workstations are almost exclusively standing and result in the same issues as other standing workstations. Given the range of motion and level of physical exertion involved with work on a conveyor, a standing posture is preferable.
• Pace of Work. The demands of the job and pace of work are often driven by the speed at which the conveyor is set. Employees often have no control over this rate and can be outpaced by the machinery, resulting in strenuous work-rest cycles and increased error and defect rates.

Addressing Concerns

• Conveyor Width. Conveyors should only be as wide as the goods being transported on them.
• Use Both Sides. A simple way to reduce reach distances is to place workers on both sides of the conveyor.
• Diverter Bars. When conveyor width is an issue, and product size allows, diverter bars should be used to guide goods to the employee.
• Adjustability. Workstations should be designed for the tallest employees to minimize trunk flexion. Shorter employees should be provided with height-adjustable platforms to stand on.
• Standing Work. Standing at conveyors should be addressed with the interventions outlined in ErgoMatters® Standing Workstation Guidelines. When broad ranges of motion or high levels of physical exertion are necessary, seating should be provided for resting, not working.
• Staging Goods. Unloading conveyors is three times more likely to cause overexertion injuries (Cohen 1979). A staging area where parts accumulate may remove some of the pace pressure associated with conveyor work.

Pictures from Fed/OSHA Web site: www.osha.gov/SLTC/etools/poultry/additional_material.html

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