Recording and analysis of the musculo-skeletal load upon employees in container ports

Status:

completed 06/2001

Aims:

Working days lost due to illness among employees in container ports, in particular among gantry crane and van carrier drivers, are due to a large part to disorders of the musculo skeletal system. Knowledge of the load factors arising during particular activities is required before prevention measures can be drawn up. Among gantry crane and van carrier drivers, the loads in question comprise on the one hand the whole-body vibrations acting upon the employee, and on the other the body posture. The objective of the project was to record the load profiles associated with specific activities. These in turn were to be employed in the organization of a targeted health promotion programme.

Activities/Methods:

A measurement system developed by the BG Institute for Occupational Safety (BIA) was employed for the measurement of body posture and movements. The following body movements were measured continuously on the employees themselves by means of sensors located on the work clothing: inclination of the head (sagittal), inclination of the cervical spine, forward and lateral inclination of the trunk, pelvic inclination (sagittal), movement of the hip and knee joints (sagittal). The data, recorded over a number of hours on several subjects, were then analysed with respect to musculo-skeletal risk factors (static load, repetitive load, unfavourable joint positions, handling of high load weights). The vibration measurements were performed by the institution for statutory accident insurance and prevention in the wholesale trade and warehousing industry, in accordance with DIN 45671 "Measurement of exposure to occupational vibration; vibrometers; requirements and testing" and VDI 2057 "Effect of mechanical vibrations on human beings; fundamentals, classification, terms" and based upon the assessment curves to ISO 2631:1997 "Mechanical vibration and shock - Evaluation of human exposure to whole-body vibration - Part 1: General requirements". A four-channel human vibration analyser (AST) was employed to record acceleration of the seat on the x, y and z axes, and on the chassis in the z axis. The vibration and body movement data were recorded synchronously, and evaluated both individually and in combination.

Results:

Vibration measurements show that the daily vibration exposure associated with the displacing of van carrier drivers lies in the region of 2.8 to 6.6 and during the displacing of portainers in the region of 1.7 to 6.9. The values therefore lie below the recommended maximum daily vibration exposure value of 12.5. The body posture measurements revealed a particular impact upon the portainer operators owing to static and unfavourable body postures. Head inclination angles of 30° and above typically arise for over 50% of the displacement time. The van carrier drivers operators work primarily in an upright seated position. They assume unfavourable postures when picking up and depositing the containers, however. Sideward torso inclination angles of 20° and over are assumed for approximately 10 to 15% of the working time. The current level of scientific knowledge does not permit a reliable assessment of exposure to vibration and unfavourable body posture in combination. It may be assumed however that vibrations and unfavourable body posture arise during both activities, and that a combined effect is possible. The conclusions drawn from the measurements are to be exploited in a health promotion programme planned for the plant, in which they will serve as a basis for a targeted prevention approach.

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