Workers who are regularly exposed to high vibration levels may suffer from several kinds of injury to the hands and arms. This can include vascular disorders (generally known as 'vibration-induced white finger'), neurological and muscular damage, and other possible (less understood) kinds of damage leading to pain and stiffness in the hands and joints of the wrists, elbows and shoulders. Collectively, these injuries are known as 'hand-arm vibration syndrome' (HAVS), which is a painful disease widespread in those industries where vibratory tools and machines are used.
The damage caused by hand-transmitted vibration is related to the average vibration magnitude a person is exposed to during the working day. This is referred to as the daily vibration exposure and is expressed as an 8 hour energy equivalent acceleration, or A(8). This accounts for both the vibration magnitude and the time over which the exposure takes place.
HAVS, a history
Many people believe that hand-arm vibration syndrome (or ‘white finger’) is a relatively modern condition, but this is not really the case. The symptoms were first described by Professor Giovanni Loriga in Italy in 1911, although the link was not made between the symptoms and vibrating hand tools until a study undertaken by Alice Hamilton MD in 1918. She formed her theory by following the symptoms reported by quarry cutters and carvers in Bedford, Indiana, while also discovering the link between an increase in HAV symptoms and cold weather, as 1918 was a particularly harsh winter.
The first scale for assessing the condition, the Taylor-Pelmear scale, was published in 1975, but it was not listed as a prescribed disease in the United Kingdom until 1985. The Stockholm scale was introduced in 1987. In 1997, the UK High Court awarded £127,000 in compensation to seven coal miners for vibration white finger. A UK government fund set up to cover subsequent claims by ex-coalminers had exceeded £100 million in payments by 2004. During the period 2008 to 2017, a total of 7115 claims for HAVS were made in the UK with the Health and Safety Executive (HSE) issuing substantial fines for companies not controlling HAV’s in the workplace.
A recent example of a HSE Prosecution is given below:
Manchester and Salford Magistrates recently heard how a local fabrication company failed to ensure its employees were given sufficient information, instruction and training on the effects of working with vibrating hand tools. HSE investigators found that a welder was given a task which involved a significant amount of grinding and polishing. He began to experience numbness and tingling and asked to swap with another worker but was told to carry on. His symptoms continued but he was told by his supervisor to continue using vibrating tools. Some weeks later, a 20-year-old apprentice welder also began to suffer from vibration-related symptoms from using similar tools.
The company pleaded guilty to breaching reg 6(1) and 8(1) of the Control of Vibration at Work Regulations 2005; it was fined £120,000 and ordered to pay £7,241 in costs.
Benefits of vibration monitoring surveying
Accurate measurement of vibration magnitudes for specific tools, tasks and process can form part of a company’s prioritised action plan to control exposure to hand-arm vibration.
SOCOTEC hand-arm vibration surveys and reports can assist clients in assessing and therefore controlling the vibration exposure of employees in a number of ways:
- Provide information regarding what an employer may need to do under the Control of Vibration at Work Regulations
- Indicate if specific tools/processes/tasks are likely to cause excessive vibration exposure and where action to reduce vibration should be focused
- Indicating trigger times to reach HSE exposure action level and the exposure limit values
- Calculate ‘Partial A8’ vibration exposures based on specific tools / activities
‘Partial A8’ vibration is used to describe the vibration exposure received by an employee using a single tool for a period during the shift. It is calculated from the vibration level of the tool and the time the tool is used. During the survey, employees involved in the tool testing are asked typically how long a tool is used during a shift and it is this figure, along with the determined vibration level, that is used to calculate the partial vibration exposure for the tool.
Control of vibration exposure, however, cannot be achieved by simply colour coding tools green, yellow or red according to the partial A8 value.
An example: vibration monitoring in practice
Take, for example, a hypothetical employee called Eric. Eric uses a 9” angle grinder in a fabrication workshop usually for small cutting jobs totalling 10 minutes each day. The employer has had a hand-arm vibration survey carried out which indicates a vibration level of 12.5m/s2 for the angle grinder. This gives a ‘partial A8’ of 1.8 m/s2 for the time Eric is using the tool, so Eric’s exposure is well below the action level.
The company then wins a large production order and Eric’s job changes; he is now using the same angle grinder for 20 minutes per day. While the vibration from the angle grinder hasn’t changed, the partial A8 has now increased to 2.6 m/s2 – so his vibration exposure is above the action level but below the limit value. The company now needs to be taking action to reduce Eric’s vibration exposure.
This example also show the importance of determining accurate trigger times when determining vibration exposure and also the importance of controlling trigger times.
SOCOTEC’s reports contain the vibration levels for each tool tested, the number of exposure points per 10 minutes of use and the trigger time for each tool to reach the action level and limit value.
The report also contains a simple table of tools monitored, the HSE points per 10 minutes of use and a simple calculation table which can be displayed in the workplace. This allows employees to calculate their daily vibration exposure and regulate their own vibration exposure.
Management auditing of these calculation tables can then be part of your prioritised action plan to control exposure to hand-arm vibration.
Vibration levels from SOCOTEC’s HAVS reports can also be used with the HSE exposure calculator to determine multiple tool exposures. Alternatively, vibration measurement from SOCOTEC’s HAVS surveys can also be used with the various wrist worn vibration monitoring systems.
To enable comments sign up for a Disqus account and enter your Disqus shortname in the Articulate node settings.