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Hand Arm Vibration Syndrome (HAVS) : Prevent & understand the risks

May 28, 2018

Maintenance managers and health and safety executives that learn to protect their workers from Hand Arm Vibration Syndrome (HAVS) will increase the company productivity, profits and reputation.

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.

What is the Hand Arm Vibration Syndrome?

The Hand Arm Vibration Syndrome is recognized as a serious work-related disorder, which is affecting thousands of industrial workers. It is represented by damage to blood vessels, nerves, muscles and joints of the wrist and arm caused by intensive and repeated vibration exposure. This exposure comes from working with vibrating tools or holding shaking materials. The repeated hits on the fingers and hands at certain frequencies constitute a risk for the workers. There is no certainty about how this happens exactly, but numerous studies show damage to the very fine blood vessels in the hands as one probable contributor to the syndrome.

What are the symptoms?

•       Early symptoms: Repeated loss of feeling, numbness, in the fingertips and sensation of needles in the fingers, tingling, are early indicators. These sensations can come and go and are not proof of HAVS, but should be seen as early warnings.

•     Later symptoms: Later, more severe symptoms are often felt like permanent numbness of fingers, causing difficulties in daily life when handling small objects or when buttoning for example.

When getting cold or wet, the fingers will often react by becoming white, then red while being painful. This is called the Raynaud's phenomenon, and is also common in hand arm vibration syndrome cases.

Who could be concerned by HAVS?

All frequent users of power tools that vibrate during usage could be affected. Vibration level and trigger time per work shift are the key factors that together give an indication if the person is at risk. According to a Japanese long-term study on forest workers using chainsaws (Nagoya, 1994), there is a strong relation between the number of years of exposure and the prevalence of HAVS. Among the workers over 50 years of age, 38% showed signs of this syndrome. US National Safety Council estimates that about 2 million U.S. workers are exposed to hand-arm vibration today, and as many as half could develop HAVS (read full article). HAVS is preventable, but once the damage is done, it is often permanent.

Handheld Vibrating Tools: 7 tips to reduce vibration exposure

Many measures can be taken to reduce risk. Limiting time of vibration exposure being clearly the most important one, some other key points can be taken into account to protect yourself, your colleagues or your employees:

  1. Try out different tools. Choose those that do not give numb fingers when using them for a short amount of time.
  2. Always check that tools are serviced and well maintained.
  3. Use the right tool for the right job. Trigger time is essential here, choose a stronger, more efficient tool that can do the job in a shorter amount of time rather than a lighter one.
  4. Limit time per work shift with strong vibrations uptake. With applications giving strong vibrations, the operator can reach a potentially harming vibration dose within minutes. For reference, with an application that gives 20 m/s² of vibration to the operator’s hands, the exposure corresponding to the action value, (the value where the employer needs to take actions to limit vibrations), is reached after only 8 minutes.
  5. Hold the tool loosely, do not squeeze the handle when not necessary.
  6. Keep hands warm and try to avoid direct contact with freezing or very cold handles. Store the tool correctly so that your colleague will also be comfortable. If possible, do not leave tools outside overnight.
  7. Take regular breaks. Avoid long sequences of high vibrations and try to do other jobs in between.

How to identify if the application is a risk

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).
Vibration Magnitude, m/s² Daily exposure action value: 
If reached, technical and organizational actions must be taken to reduce vibration exposure
Daily exposure limit value: 
Should never be exceeded
2.5 8 hours >24 hours 
5 2 hours 8 hours
10 30 minutes 2 hours
15 13 minutes 53 minutes
20 8 minutes 30 minutes

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.

A worked example

Let’s take a look at Joe’s situation:

  • Tool used: CP6135 impact wrench
  • Application: loosen large bolts
  • Tool’s vibration magnitude: 13.6 m/s² (standard testing ISO28927)
  • Vibration exposure: approximately 13 minutes (200 bolts in one work shift, each bolt takes 4 seconds to loosen meaning 200 cycles x 4 seconds)

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.
Célia Esnault- Global Product Marketing Manager at Chicago Pneumatic

In operations with vibration exposure, prioritize best practices by ensuring all employees use safety equipment, maintain tools properly, and keep hands warm to prevent injuries.

Célia Esnault , Global Product Marketing Manager at Chicago Pneumatic

Read more about HAVS:

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.

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