How to control hand arm vibration in construction
Types of Vibration
Most people are exposed to minor vibration during everyday activities, from common devices such as an electric toothbrush or a PlayStation controller. Generally, these vibrations are not significant enough to cause health concerns. But vibration is a common hazard within construction health and safety. With the tools used and the types of activities carried out on a construction site, vibration can lead to permanent health conditions if it is not controlled. The HSE estimates over two million workers in the UK are at risk from hand-arm vibration alone.
There are two types of vibration we need to be aware of. These are hand-arm vibration (HAV) caused by hand-held tools such as concrete breaking drills and reciprocating tools, and whole-body vibration (WBV) caused by machinery such as construction site dumpers. This factsheet looks specifically at HAV.
Health Impact of Vibration
HAV can lead to hand-arm vibration syndrome (HAVS), which includes multiple disorders of the blood vessels, nerves and joints. The most common disease is vibration white finger where vibration impacts the blood circulation. The more exposure to vibration, the more risk of developing vibration white finger. This condition can lead to permanent loss of feeling, pain and numbness, loss of grip and – in severe cases – amputation of the affected area.
Understanding Trigger Times
The Control of Vibration at Work Regulations 2005 place a duty on employers to assess risks from exposure to HAV and identify measures to eliminate or reduce these risks. To measure vibration exposure, you need to know tool trigger times as the exposure limits are based on the length of time you are exposed to vibration.
There are two values to be aware of, an exposure action value (EAV) and an exposure limit value (ELV). Both are measured in m/s2 A(8). This is the technical measurement for vibration, time-weighted over an average eight-hour day.
- The EAV – set at 2.5 m/s2 A(8) – is the limit where control measures should be implemented.
- The ELV – set at 5 m/s2 A(8) – is the limit that must not be exceeded.
The longer you use a vibrating tool, the bigger the risk. Wristbands and tool tags are available to automatically measure vibration levels and alert workers when they reach the EAV and exceed the ELV. If this isn’t an option, the HSE’s vibration calculator helps calculate and simplify vibration exposure.
Using the HSE’s Vibration Calculator
The HSE’s vibration calculator simplifies a complex concept by turning vibration into points. The number to keep an eye on is the total exposure points. 100 points is equal to the EAV, where control measures should be implemented, while 400 points is equal to the ELV where use of vibrating equipment should cease. The HAV calculator also allows you to put in intended trigger times and warns you if you are going to exceed the EAV and ELV.
Let’s take a reciprocating saw as an example. The vibration magnitude is 18m/s2. Using the HAV calculator this gives 648 exposure points per hour. The 100-point mark (EAV), where controls need to be implemented, is only 9 minutes. The ELV – equivalent to 400 points – is reached after 37 minutes. That means with control measures implemented, a worker cannot use a reciprocating saw for more than 37 minutes in a standard working day. And as they have reached the ELV, they are also unable to use any other vibrating tool that day. If not monitored vibration exposure can quickly add up to unsafe levels.
Implementing Control Measures
The good news is vibration can be controlled. These control measure should be followed in hierarchy and are as follows:
Eliminate. Where possible it is always best to try and eliminate the need to use vibrating equipment altogether. You can do this by ordering materials such as concrete slab pre-cut to the right size.
Substitute. Look for alternative work methods which can reduce exposure to vibration. For example, you could use a breaker attachment on an excavating machine to break concrete rather than using a hand-held breaker.
Engineering controls. Select the right equipment for the task by considering the vibration emissions of different tools. Newer tools and machines are likely to emit lower levels of vibration than older equipment. It is important to keep tools well maintained as these will emit less vibration than older tools that are not looked after.
Administrative controls. Tasks should be planned taking EAV and ELV limits into consideration. This could mean rotating operatives to limit their exposure to vibration. Using the reciprocating saw as an example once again, we know it has a trigger time of 37 minutes. If the cutting time is 60 minutes, then the task will need two operatives to complete the work. Worker exposure to vibration should be monitored and recorded in writing by supervisors to ensure compliance with EAV and ELV.
It is vital for employers and employees to understand vibration levels so that work activities can be properly planned, and effective control measures put in place. Nobody should develop the very serious and uncomfortable health conditions caused by vibration because of a lack of understanding, or poor choices in job design, tools and equipment.