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The evaluation of human vibration measurements and the effectiveness of different vibration reduction strategies in a sawmill

1150-20 C 1997
(97FS-34)

Issue:	Measurement of structural vibration in a sawmill and in related power hand tools; evaluation of vibration reduction methods for sawmill and power hand tools including chain saws; comparison of subjective and physical measures of vibration.
Agency:	Canadian Forest Products Ltd.
Representative:	Ms. Kimberly D. Zinck
Funding:	$15,800

Long term vibration exposure has been linked to musculoskeletal disorders. The purpose of this project was to:

1. Quantify the levels of hand-arm and whole-body vibration exposure of workers at the Canadian Forest Products Ltd. (Canfor), Fort St. John operation.
2. Identify specific jobs/workers who may be at risk of developing vibration-related disorders.
3. Determine the effectiveness of specific vibration reduction interventions and their practicability.
4. Develop a training program to educate workers on the importance and use of vibration reduction techniques.

Specific vibration interventions such as airbags, seat adjustment and/or cushions, matting, workstation isolation, insoles, vibration dampening gloves and hand tool wraps were used to determine if vibration levels could be significantly reduced. Measurements were made in accordance with ISO, and questionnaires were used to obtain pre/post intervention worker feedback.Vibration exposure was high in planer infeed areas. Workstation isolation provided most effective for reducing whole-body vibration levels. Use of vibration gloves and tool wraps were beneficial in reducing chainsaw but not grinder (ie., 7 and 5 inch Makita grinder) vibration. Gel cushions (ie., sorbothane or t-gel) were not found to significantly reduce vibration. In kiln areas gel cushions were found to amplify vibration to levels linked to health-risk. Potential benefits from matting and tool wraps may not have been realized due to r.m.s. weightings neglect of high frequency ranges. A low relationship between subjective and objective vibration ratings were found.From this study we make the following recommendations for reducing risks associated with mobile equipment use:

1. Eliminate pot holes from work yards.
2. Use air rides where possible.
3. When suspension systems fail, operator seats should be replaced at the same time.
4. Encourage frequent mini breaks where operators stretch and walk around.
5. Rotate machinery operators through sitting and standing jobs throughout their shifts.

Further research is necessary to determine interventions that will be effective at low vibration frequencies.

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