KANBrief 4/13

Only strong men need apply: operating forces on agricultural machinery are often too high

Agricultural machinery possesses a range of heavy parts, hatches and ladders which must regularly be moved by the user. To prevent this from being too onerous, the standards state maximum values for the operating forces. In the view of the OSH lobby, however, these values are too high. In addition, no simple method exists for the performance of measurements on machines. In order to close these gaps in knowledge, KAN has commissioned a study.

To operate levers, to swing hatches, covers and ladders into position or latch them there or to move other parts, the users of agricultural machinery must exert certain forces. During the revision of standards governing agricultural machinery, the experts on the standards committee considered whether the existing requirements concerning operating forces were in need of revision. Some standards state that the force to be exerted must not exceed 400 N. However, women for example are on average unable to exert this force (cf. Klußmann, A. et al.: ASER Handmaß und Kraftdatenbank. Publications of Institut ASER e.V., research report, in preparation.). In addition, the values stated in the standards have no (known) scientific basis. Nor has, as yet, a measurement method been described by means of which manufacturers or personnel of the German Social Accident Insurance institutions could measure operating forces simply, cheaply, but nevertheless reproducibly.

Spotlight on a practicable measuring method and ergonomic operation

In 2012, KAN commissioned a study by the Institute of Occupational Health, Safety and Ergonomics (ASER) in Wuppertal. The study was to determine a suitable measurement method and to draw up recommendations for force values for certain operating scenarios KAN Study "Safety of agricultural machinery".

The project team examined a number of operating scenarios on agricultural machinery, and performed corresponding measurements in different ways. One form of measurement involved a number of test persons, equipped with hand-held instruments, operating controls/moving parts in various different postures and with different directions of force exertion. To estimate the validity of the measurements performed in this way on test subjects, comparative measurements were performed with the aid of a winch connected through a force transducer to the handle or hatch.

Results for standardization

The study confirmed the impression of the OSH experts, namely that the values stated in the standards are substantially too high, unless only particularly strong persons are to be able to operate agricultural machinery. This means that the values should also consider female trainees or older workers on farms.

The scope of the study did not enable definitive values for specific application scenarios to be determined that could be included in the standards. Owing to the limited body of data, the values determined can serve only as recommendations. For robust values to be obtained, the body of data would have to be considerably expanded.

The study nevertheless yields constructive recommendations for instruments and measurement techniques. Hand-held instruments that can be connected to a computer produce robust values. Owing in addition to their low cost, they could conceivably be used by mobile employees for the purpose of market surveillance and by the accident insurance institutions and manufacturers. The results of the study can also be applied to mobile machinery in other sectors, such as that of construction machinery.

Conclusion for standardization: solutions must be sought

The force values currently stated in agricultural machinery standards are too high. The priority is for the approach described in the study now to be developed further. Standardization activity either requires robust values based upon an extended body of data, or must seek other solutions by which requirements can be formulated even in the absence of specific values, in order to enable all users of agricultural machinery to work with it safety and ergonomically.

In conjunction with OSH experts, KAN will check the need for further investigations and incorporate the measurement method described in the study into a proposal for a standard to be submitted to DIN.

Katharina von Rymon Lipinski
vonrymonlipinski@kan.de