Working with hand tools and machinery can be a major health hazard
Finger pain, numbness and even gangrene are the symptoms of a serious occupational disease that strikes up to 50 per cent of hand tool users.
The cause is vibration. But while the impacts are well-known internationally, WA Safety Show exhibitor Noise and Vibration Measurement Systems describes its effect as a “sleeping giant” in Australian workplaces.
Noise and Vibration Measurement Systems’ Stewart Wood says hand tools such as grinders could damage the health of Australia’s manufacturing workers irreversibly.
“Almost everyone understands the need to protect their hearing in noisy workplaces but
it comes as a shock to most employers that vibration is just as hazardous,” he says.
According to the University of Tennessee Institute for the Study of Human Vibration, 8 to 10 million workers in the US alone are exposed to occupational vibration every day.
The institute explains that vibration falls into two categories. The first, Whole Body Vibration (WBV), or head-to-toe exposure, typically affects truck, bus, heavy equipment, farm vehicle, forklift and overhead crane operators.
The second, Hand-Arm Vibration (HAV), or localized vibration exposure, mainly affects
those who use vibrating pneumatic, electrical, hydraulic, and petrol powered hand-tools.
Symptoms begin with tingling and/or numbness in the fingers, followed by the appearance of a single “white” or blanched fingertip.
“This seemingly innocuous attack of ‘white finger’ marks the beginning of the dreadful
later irreversible finger blanching process,” write the institute’s researchers, Wasserman
and Wasserman, in an overview of the syndrome. “Often these attacks are mistaken by workers who think they have frostbite.”
Early attacks of finger blanching last about five to 15 minutes and are widely spaced apart.
With continuing exposure to vibration, the attacks increase rapidly in number, intensity, duration, and finger pain, especially in cold conditions. ‘Loss of blood supply can lead to gangrene’
In the later stages, attacks occur in all seasons and off-the-job as well as at work.
Tasks like mowing the lawn and touching cold objects such as a vehicle steering wheel early in the morning, or cold water striking the fingers, become painful.
The simultaneous combination of vibration, cold and smoking is “particularly deadly”, says the institute, since all three help to close down blood vessels.
In extreme conditions, the loss of blood supply to the fingers can lead to gangrene, which may require finger amputation.
While the symptoms of HAV Syndrome are clear, measurement is more complex. The
International Standards, ISO 2631 and ISO 5349, that define how vibration exposure is
assessed stipulate that the three axes – x, y, and z – must be taken into account because the human body reacts differently to horizontal and vertical vibration.
Apart from direction, the other three characteristics of vibration must be measured:
magnitude, frequency and duration.
WA’s SafetyLine Institute last year issued a human vibration guide detailing each of the
Magnitude represents the acceleration of the oscillating objects and is expressed as a rootmean- square (rms) value in units of metres per second squared (m/s²).
Unlike other hazards, frequency refers not to the occurrence of vibration but to the motion itself. Because each part of the human body has its own natural frequency, different vibration frequencies have differing impacts across the body.
The SafetyLine guide and ISO standards include complex algorithms for the calculation of exposure and Noise and Vibration Measurement Systems runs one-day courses for workplaces keen to control the risk of vibration-related injuries and recommends participants have basic engineering mathematics.
In good news for workplaces seeking a simpler solution to vibration exposure monitoring, Noise and Vibration Measurement Systems does offer pocket analysers. Stewart Wood says the Human Vibration Analyzer Type 4447 is typically used to sample the vibration workers are exposed to during different tasks.
“Annex B of the EU’s HAV Good Practice Guide shows just how much variation there is in
vibration caused by pieces of equipment,” he says.
“The total vibration figures for grinders, for example, ranges from just over 2 m/s2 to nearly 30 m/s2. It’s important to sample the vibration caused by each piece of equipment performing each task with each type of material so you can assess the risks different tasks present and implement controls.”
Noise and Vibration Measurement Systems will have vibration analysers and noise dosimeters at the WA Safety Show at the Perth Convention Exhibition Centre from August 24-26.
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