Ergonomic risk screening in a time study

Why it matters

A job taking less time does not by itself show that it has become more suitable for the worker. A new layout that brings the part closer may reduce reaching; the same layout may also require the neck to stay bent for a long time to see the part. If a time study looks only at the cycle total, this trade-off disappears. Ergonomic risk screening links which sign of strain was observed in which job to its duration. The aim is not to rank workers by their speed. It is to identify the situations in the job design that need a detailed review and to develop a safe option. The observation is used as a record for understanding the work the worker does; it is not presented as a judgment about personal health.

Exposure is the description of the time spent in a given condition or of the repetitions of that condition. The time the trunk is bent forward, shoulder elevation, forceful gripping and twisting while carrying a load can each be a separate recording heading. They are not all the same kind of quantity. Adding kilograms, seconds and repetition counts without justification does not produce a meaningful risk score. The time calculation in this lesson shows how long a selected posture lasts during the working hour. It does not by itself determine the size of a health effect, suitability for a given person or the safe limit of a job. The boundary between a time record and a health assessment should also be kept in the heading of the result.

A photograph may show a straining posture; it does not show how many times and for how long that posture occurs during a shift. Conversely, a single frame that looks acceptable is not enough to declare the rest of the cycle safe. Product variety, how full the box is, and the start and end of the job can change the observation. For this reason the chosen time interval and the situations it does not cover are stated. A difficulty reported by the worker improves where the measurement should look; the absence of a report does not prove that there is no problem. When a clear hazard is seen, the safe way is to stop and review, not to continue the hazardous work to collect more data.

The screening result is the basis for the next decision. For frequently repeated reaching, the material presentation can be changed; for long-duration holding, suitable support can be investigated. However, a solution that reduces one condition may increase another. For this reason the same product, output and measurement boundary are kept in the before and after methods. The time reduction is written separately from the change in observed strain. With Yamazo Studio, a time study can be done by marking elements on video. The interpretation of the posture and any required expert review are carried out separately. The measurement tool helps organize the observation; it does not put certainty in the place of a missing observation.

Formula