Manual handling, repetition and job design options

Why it matters

Manual handling cannot be explained by the kilogram value of the load alone. The same mass creates different conditions when it is picked up from the floor and set down after turning to the side, and when it is transferred up close at a suitable height. The way of gripping, the size of the load, the blocking of vision, the carrying path and the control of setting down are examined together. A job being repetitive does not mean only the number of products; the same movement may be made several times for each product. Measuring the carrying element in a time study does not automatically mean these conditions have been evaluated. The time record shows where the job is concentrated; the design decision looks at how the load will be eliminated or reduced.

The total mass carried per hour is a useful indicator describing the volume of material movement. The mass of a single carry is multiplied by the hourly repetitions. However, this total is not a validated health risk score. The same total mass can be carried as a few large loads or as many small loads. In the first, the strain of a single carry may differ; in the second, the repetition and recovery conditions may differ. Lifting from the floor can be eliminated without reducing the total; an unsuitable reach can be added while reducing the total. For this reason the indicator is given its proper name in the report. The phrase "manually handled mass per hour" is more honest and useful than an "safety score" that cannot be explained.

Job design is not limited to making the worker carry the same load faster. Material presentation that leaves no need for carrying, an arrangement that supports the load safely or a solution that separates the carrying path can be investigated. When a smaller container option is evaluated, the increased replenishment and empty-container jobs also enter the calculation. When an aid is chosen, the loading, unloading, pushing, pulling and stopping conditions are examined too. The use of support does not mean all human work has disappeared. If the aid creates a new pinch point or an obstruction to vision, the design is not complete. The improvement must be achieved without transferring the strain to the neighboring station or to the person who replenishes.

A task change requires more careful planning than giving the same job to another person. Two tasks with different names may keep the same grip and the strain on the same body part going. In that case, swapping places on the schedule may not provide variety of exposure. The competence of the workers, the safe working conditions and the preparation needed for moving to the task are also examined. When it is possible to improve the design at its source, relying only on task change can leave the problem permanent. In this lesson the options are compared on a common amount of material and a common time boundary. Suitability from a health point of view requires a competent assessment beyond these simple calculations; the training numbers are not used as a universal limit.

Formula