Repeated and excessive contact with vibrating tools, equipment and materials will over time cause various patterns of diseases casually known as HAVS or VWF (vibration white finger). These can affect nerves, joints, muscles, blood vessels or connective tissues of the hand and forearm. The symptoms may include tingling or numbness in finger tips, fingers turning white or blue when exposed to the cold or vibration and in severe cases loss manual dexterity with attacks occuring not only at work but also during leisure activities, such as gardening, car washing or even watching outdoor sports.
The effect of vibration is cumulative. When symptoms first appear, they may disappear after a short time. HAV symptoms are preventable, but once damage is done further exposure to vibration can worsen the symptoms and make them permanent.
A European Directive requiring member states to legislate against the risks of exposure to excessive vibration whilst at work has been implemented in The Control of Vibration at Work Regulations 2005. The regulations set Action and Exposure Limit Values, averaged over an 8 hour working day, for hand-arm vibration and require employers to manage workplace and prevent damaging exposure through:
• Risk Assessment
• Health surveillance
• Control and mitigation
Risk assessment and health surveillance in respect of HAV were explained in a previous article. Here we explain how to control and mitigate exposure.
When considering control measures health and safety legislation requires employers to consider whether exposure can reasonably be eliminated; if workers are not exposed they can not be harmed. Elimination of exposure to HAV is possible in a number of cases by mechanising or making changes to the work process. For example using a jack-hammer mounted on a mini-excavator rather than a handheld tool or pre-drilling components using fixed machinery rather than drilling on site, or improving the quality of welding so that welds do not require ‘tidying up’ with a hand grinder.
Old and poorly maintained portable tools and hand guided machines are likely to generate higher levels of vibration than machines that are well maintained. Similarly damaged and worn cutting tools or the wrong choice of attachment will increase the vibration generated. Proper maintenance and the correct choice of attachment will help to control HAV exposure.
New machines are also likely to generate lower levels of vibration because manufacturers are legally obliged to build in vibration control measures and to publish standard test measurements for each of their products. When purchasing new equipment employers should make it their policy to carefully consider and compare the declared vibration levels and choose the machine most suited to the job with the lowest vibration level. More powerful machines don’t always produce more vibration for example on manufacturer sells a 1.6 Kw chainsaw that produces a vibration level of 6.3 m/s2 (above the Exposure Limit Value and which should normally only be used for a maximum 1.3 hours per day) and a more powerful 2.3 Kw machine that produces 2.6 m/s2 which is only just above the Exposure Action Value and could be used for 7.4 hours a day without any further action.
Close examination of the databases on vibration exposures will show that since the publication of the Exposure and Action Levels the number of tools available with vibrations at or below the Action Level has substantially increased. As time passes it is increasingly likely that you will be able to find a tool for the job that will normally be safe for use buy one person for a full working day.
If you use equipment that produces vibrations in excess of the Action Level and know the vibration it is possible to control exposure by rotating jobs between employees. For example an angle grinder producing vibration at 3.6 m/s2 can be used without further precautions for 3.9 hours a day. So it might be possible for a worker to use the angle grinder for the first part of the day and swap to a job involving no exposure for the rest of their day. The machine would be in use for a full day and neither worker would be exposed above the Action Value.
Do not be misled by advertisements which claim that gloves can be used to reduce the risks from exposure to HAV. While they may produce some attenuation of the vibrations there are no independent validated tests to show that they make a significant contribution to controlling exposure. A more significant reason for encouraging operators to wear gloves is that the majority of the tools which produce HAV are used outdoors or in exposed areas. There is evidence to show that people may be more susceptible to the symptoms of exposure to HAV when their hands are wet and cold and blood circulation is reduced.
For this reason is also recommended that employers pay particular attention to their workers’ welfare during winter and whilst working outdoors. Where they are likely to be cold or wet it is important to ensure that throughout the working day they have regular breaks and opportunities to get dry and warm.
Engineering controls should also be introduced where possible. Altering machine controls to remove the need to keep fingers constantly on the ‘trigger’ will reduce vibration exposure. Where the source of HAV is through the application of a work piece to a fixed tool, such as a pedestal grinder, vibration exposure can be reduced by providing a work rest which is fixed to the floor with anti-vibration mountings.
Whatever method you choose to control exposure to HAV, don’t forget to explain to your workforce why the control measures are required and train them to follow the correct safe system of work.
If you use portable power tools hand arm vibration may be a health and safety issue that you need to actively manage within your business. Consider the advice in The Bottom Line Express and decide whether you need to take any further action. You will find further information in our Guidance Note 27a which can be found in your Guidance Note pack or online in BusinessWise.
The 24 Hour Health & Safety Advice Service is on hand to answer any queries that you may have. Just call them now on 0844 892 2785.
Preventing Hand Arm Vibration Syndrome (HAVS) - Part 2
January 29 2010