If there’s something that is currently controversial in the world of HAV measurements, then it has to be concerned with the placement of the sensor or accelerometer when carrying out measurements. This controversy arises because some measurements are taken with the accelerometer either wrist or glove mounted, instead of being mounted firmly and directly on the vibrating surface of the tool, which is what the relevant international standards specify.
The HSE have included a statement about accelerometer location in a Q and A publication with respect to HAV in the workplace.
Where you place the accelerometer could invalidate your results when carrying out vibration measurements and for determining daily exposures against the exposure limits of the Control of Vibration at Work Regulations (2005). Employers are legally obliged to comply with these regulations.
What DO the HSE publication and Control of Vibration at Work Regulations (2005) say about the sensor placement positions for measurements?
The HSE publication (8 Questions about Vibration Exposure Monitoring) (see http://www.hse.gov.uk/vibration/hav/advicetoemployers/vibration-exposure-monitoring-qa.pdf) (Question 7) states that “Any measurement away from the palm of the hand or where the measurement position is on the back of the hand, fingers or wrist is unlikely to provide reliable measurement. Further advice is given in BS EN ISO 5349-2:2001. There is currently no wrist or glove mounted device which measures vibration suitable for use in a vibration risk assessment...”.
The Control of Vibration at Work (2005) Regulations makes reference to the standards as per the following:
Under the heading “Vibration measurement and instrumentation” (paragraph 281), it states: “Anyone making hand-arm vibration measurements should be familiar with BS EN ISO 5349-1:2001 and BS EN ISO 5349-2:2002 which contain detailed practical guidance on measurement of vibration in the workplace.”
BS EN ISO 5349- 2 contains the clause: “The accelerometers should be rigidly attached to the vibrating surface”. It is important to note that the action and limit values in the regulations are based upon measurements performed in accordance with these BS EN ISO Standards.
Measurements conducted with accelerometers that are mounted elsewhere other than on the tool’s vibrating surface, or tool handle, could produce significantly different results. This may impact the outcome of any court cases with possible expensive consequences.
Risk assessments
When carrying out vibration measurements either in house or by hiring external expertise, you should ensure that this exercise be carried out in accordance with BS-EN-ISO 5349 parts 1 and 2 for compliancy against the regulations. Make this clear to the assessor.
Looking ahead
Further research however, upon alternative methods of hand arm vibration measurement with respect to accelerometer placement should be encouraged as technology advances. If the outcome of such research is accepted by leading experts and recognised organisations that exert influence on the standards and regulatory committees, then the standards and regulations can evolve and therefore be amended accordingly.
Until then you should look to measurements being conducted in accordance with BS EN ISO 5349 parts 1 and 2 standards to comply with the regulatory and HSE requirements.
A free guide to conducting a hand arm vibration (HAV) risk assessment is available for download. It explains, amongst other things, when you should carry one out, and what constitutes a competent risk assessment. Click here to receive it.