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View Full Version : Hazards of vibrating tools combined with high feed forces



dmcfarlane
12-06-2009, 04:28 PM
Dear All,

Back in the eighties Atlas Copco (the Swedish manufacturer) reported
that high vibration amplitudes of Hand Arm Vibration (HAV) combined with
high feed forces (the forces required to press the tool to the work
surface) can cause micro-fractures in bones and have adverse effects on
joints. This concept was mentioned in its book ("Ergonomic tools in our
time") on safe tool design (Atlas Copco, 1986).

In recent years research seems to have concentrated on vibration
exposure assessments. For instance, EU Directive 2002/44/EC states that
"As regards hand-arm vibration (HAV), the action level is likely to be
exceeded by operators of most main percussive and roto-percussive tools
(such as chipping hammer, demolition hammer, rock drill, breaker, impact
drill, scabbler, rammer, vibratory rammer), of main rotative tools (e.g.
grinder, impact wrench, sander) and main alternative tools (e.g.
jig-saw, file). The limit value for exposure to vibration may be
exceeded if percussive and roto-percussive tools are used for more than
one to two hours a day, or in the case of some rotative tools if used
for more than four hours." (page 6)

Until recently most risk management guides on the topic HAV concentrate
almost entirely on the high vibration amplitudes and barely mention feed
forces or the factors that might affect them (posture, work practices,
tool design, tool size, task nature, handle design, coupling effects due
to gloves et cetera).

However, European Agency for Safety and Health at Work has published
"Workplace exposure to vibration in Europe: an expert review" (2008)
which notes that with respect to HAV, the authors note that awkward
postures, static muscle forces, grip and feed forces should also be
taken into account and mention tht there has been progress in
force-measurement equipment (as shown by the Vibtool report). The
authors also mentioned the use of servo valve controls the air pressure
according to the feed force for vibration reduction for rivet hammer
users.

The authors noted that advice on risk control has tended to concentrate
mainly on engineering strategies and this has its limitations. Reduction
of vibration from low-frequency percussive tools requires suspension
with several centimetres of travel. Therefore, it is not technically
possible to develop efficient anti-vibration gloves adapted to this
family of tools. Tests carried out according to ISO standard 10819:1996
(5) show that no vibration reduction is achieved below 150-200Hz. This
means that most anti-vibration gloves are both expensive and inefficient
as PPE; their main benefit is that they keep the operator's hands warm.

Our lack of data on grip forces and feed forces for using various
vibrating hand tools is worrying. Could it possibly be that large gloves
magnify the grip force needed and amplify injury rates?

Seidel et al (2007) developed a biomechanics model to predict spinal
stress in drivers at work, which incorporates data on body posture,
vibration input and driver characteristics but I have had little luck in
tracking down research that has used it. Does anyone know of any
research papers on the topic of the feed forces that are needed to
control vibrating hand tools for typical tasks?

Regards,

David McFarlane MAppSc (Ergonomics)
Ergonomist, WorkCover NSW

References

1. Atlas Copco, (Stockholm, 1986), "Ergonomic tools in our time", ISBN
9178105358.
See Vibration syndrome building a case on shaking grounds at:
http://www.thefreelibrary.com/Vibration+syndrome:+building+a+case+on+sha
king+grounds-a020018003

2. EU Directive 2002/44/EC (the EU Directive on the measurement of
exposure to vibration). The full text of the EU Directive is available
at this website:
http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2002:177:0013
:0019:EN:PDF
An abstract is available at this website:
http://www.mmf.de/PDF/AN21e-Human%20Vibration,%20EC%20Directive.pdf

3. European Agency for Safety and Health at Work, (2008), "Workplace
exposure to vibration in Europe: an expert review", ISSN 1830-5946, ISBN
978-92-9191-221-6.
http://osha.europa.eu/en/publications/reports/8108322_vibration_exposure

4. Seidel, H, Hinz, B, Bluthner, R, Menzel, G, Hofmann, J, Gericke, L,
Schust, M, Kaiser, H and Mischke, C. (BAuA). "Prediction of spinal
stress in drivers from field measurements",
http:// www.vibrisks.soton.ac.uk/reports/Annex19

See also Vibrisks, (2007), "Risks of occupational vibration exposures,
final technical report', February 2007. Hyperlink VIBRISKS Final
Technical Report


Disclaimer

The views expressed above are those of the author and they do not
necessarily reflect the views or policies of WorkCover NSW. Any
recommendation concerning the use or representation of a particular
brand of product in this document or any mention of them whatsoever
(whether this appears in the text, illustrations, photographs or in any
other form) is not to be taken to imply that WorkCover NSW approves or
endorses the product or the brand.


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