Protecting workers from HAVS – understanding the risks

Does your organization perform intensive jobs such as shut downs in oil and petrochemical refineries, assembling large pipe elements into a liquid or gas pipeline, or tightening metallic structures in buildings and infrastructure?

Do operators use vibrating hand tools such as grinders or impact wrenches for long periods in a day, day-in, day-out, all year as shown in the table below? Do operators sometimes complain about numbness or white fingers after using hand tools, or pains in their hand after temperature change?

If so, then workers are at risk of HAVS and it’s time to take action before it’s too late.

There are two things to consider to identify if workers are at risk: the tool’s level of vibration and the time of exposure.

• The vibration level, which is typically listed in the tool’s manual, is the vibration magnitude as calculated in m/s² according to the standard ISO28927 (the standard for test methods for evaluating vibration emission of hand-held portable power tools). The time of exposure is calculated by the time of vibration for each cycle or hour multiplied by the number of cycles/hours the tool is used per day.
• The main standard which dictates how long a worker can safely operate a tool for is the European Directive 2002/44/EC, and it has been accepted globally as the main reference on HAVS – it’s even referred to in the US Army Vibration pocket guide. The guide stipulates the time limit after which some actions need to be taken (daily exposure action value) and the maximum amount of time per day someone can be exposed to each vibration level (daily exposure limit value).

It’s worth noting that manufacturer values of vibration magnitude are indicative only and they should always be measured in the application’s real conditions. This may not always be possible, and if this is the case then a safety coefficient multiplier should be applied to the manufacturer’s value and Standard ISO5349 referred to for further information on measuring the vibration level.

Let’s take a look at Joe’s situation:

According to the Directive, for a vibration of 15 m/s², the action value is at 13 minutes. Since Joe’s tool has a slightly lower vibration than that, there is no risk. There is a larger margin to the limit value, which he would reach after about one hour.

However, if the situation was to change and he was required to loosen many more bolts per shift, he would be at risk of exceeding the action value and the employer would need to take steps to reduce this. Some examples might be:

• Rotate the workforce so each worker loosens fewer bolts.
• Review the tool being used to ensure it’s the most ergonomic tool in its class.
• Change the tool to a more powerful one which gives a shorter trigger time.
• Change the design of the assembled objects so that they require fewer assembly points.

Disclaimer: This article is neither a magnum opus control exposure to hand-arm vibration nor legal advice for your company to use in complying with your local regulations. Instead, it provides background information to help you better understand how to address some important points. This information is not the same as legal advice, where an attorney applies the law to your specific circumstances, so we insist that you consult an attorney if you’d like advice on your interpretation of this information or its accuracy. In a nutshell, you may not rely on this paper as legal advice, nor as a recommendation of any particular legal understanding.