According to the Health and Safety Executive (HSE), hand-arm vibration is “serious and disabling”, with nearly two million people at risk.
Hand-arm Vibration Syndrome (HAVS), also known as vibration white finger, is represented by damage to blood vessels, nerves, muscles and joints of the wrist and arm, caused by intensive and repeated exposure to vibration from hand-held power tools. It is difficult to determine, on a case-by-case basis, how long it takes to develop HAVS, but according to Harald Odenman, product marketing manager at Chicago Pneumatic Tools, repeated hits on the fingers and hands at certain frequencies constitute a risk for workers, who will experience pain, loss of feeling, numbness and tingling in the fingertips.
“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,” he says. “All occupations where operators frequently use power tools are at risk. These are most commonly maintenance and production applications in construction, foundries, metal-working, shipbuilding and oil & gas industries.”
Talking tools
When workers are exposed to vibration they may experience symptoms such as tingling and numbness in the fingers, loss of strength in the hands, and fingers going white and becoming red and painful on recovery. Anyone that experiences this should stay aware, as HAVS is permanent, with later, more severe symptoms often including permanent numbness of the fingers and difficulties in daily life when handling objects.
“We recommend that workers affected with HAVS discuss the best way to manage the condition with their doctors,” says Odenman.
Dr Karen McDonnell, occupational safety and health policy adviser at the Royal Society for the Prevention of Accidents (RoSPA), warns that breakers, jackhammers, nail guns, and disc saws are just some of the tools that can transfer vibration to the hands. “There are also challenges posed by whole-body vibration,” she says.
Other tools that can transfer vibration include chainsaws, impact wrenches, cut-off saws, grinders, hammer drills and jigsaws. Odenman highlights a long-term Japanese study into forest workers using chainsaws, which showed 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,” he explains. “Any tool that vibrates more than 2.5 m/s² can cause HAVS if not used safely. There are two factors which contribute to HAVS: the level of vibration of the tool and how long the tool is used for.” (The HSE has a ‘ready reckoner’ table for calculating daily vibration exposures. All you need is the vibration magnitude (level) and exposure time: https://is.gd/ufesim).
Atlas Copco, a supplier of handheld power tools, has long been aware of the importance of ergonomics in power tool design and the reduction of vibration to protect operators, whilst improving efficiency and quality. David Embley, general manager of Atlas Copco Tools UK, highlights some tools in the company’s range, although focused more so on manufacturing process.
“Products such as our recently introduced Low Reaction battery and DC-powered tools (see ‘Products and Practices’, Plant Engineer September/October 2018) have been developed specifically to improve operator ergonomics in the assembly process, in terms of reduced vibration and reaction force, whilst supporting factory optimisation and product quality,” Embley explains. “The new Transducer Battery Pulse (TBP) based tools feature a hydraulic pulse unit rather than gears, and an oil-filled chamber, enabling higher torque of up to 55Nm with vibration levels below the minimum standard.”
Embley adds: “For applications involving hard joints, the integration of Atlas Copco’s TurboTight torque management technology means that the tool, rather than the operator, absorbs the reaction force, which has a major benefit to the user’s safety and comfort.” TurboTight sends information about joint stiffness to a power focus unit and, based on this, the unit regulates the speed of the tool. It times the tool’s slowdown phase to the exact millisecond when the target torque is reached, reducing the reaction force in the tool and making it more comfortable to use. This results in less operator fatigue and reduced risk of work-related injuries (video available at https://is.gd/icupun).
Controlling exposure
The HSE says that the most efficient and effective way of controlling exposure to hand-arm vibration is to look for new or alternative work methods to eliminate or reduce exposure to vibration. The Control of Vibration at Work Regulations 2005 aimed to protect workers from risks to health from vibration by introducing action and limit values for hand-arm and whole-body vibration (https://is.gd/zezusi).
Odenman comments: “Many measures can be taken to reduce risk. Limiting time of vibration exposure is clearly the most important one, but some other key points can be taken into account to protect operators.” These include:
● Trying out different tools – choose tools that do not give numb fingers when using them for a short amount of time
● Always checking that tools are serviced and well maintained
● Using the right tool for the right job – choose a stronger, more efficient tool that can do the job in a shorter amount of time rather than a lighter one
● Limiting time per work shift with strong vibrations uptake
● Holding the tool loosely
● Keeping hands warm and trying to avoid contact with freezing or very cold handles
● Taking regular breaks – avoid long sequences of high vibrations and try to do other jobs in between.
McDonnell points to a toolkit, which RoSPA developed as part of a partnership a few years ago (https://is.gd/civuto). It says that workers should avoid using blunt or worn cutting tools, hiring, buying and using high-level vibration tools, using damaged or unmaintained tools, unbalanced rotating discs and wheels, constant and continuous use of vibrating tools and vibrating workbenches.
Embley also gives some pointers, although specifically for reducing HAVS in the manufacturing process. “There are a number of efficient ways to reduce the effects of vibration from hand-held power tools. These include selecting tools with a lower declared vibration emission value (DEV), which will improve the vibration exposure right away, changing a process to one with a lower vibration. For example, instead of using an impact wrench, a nutrunner (used for tightening nuts) can do the job equally well, but with a much lower DEV,” he says. ISO 28927 (the standard for test methods for evaluating vibration emission of hand-held portable power tools), stipulates how to calculate the vibration level, which is typically listed in the tool’s manual.
Embley continues: “In addition, implementing job rotation to reduce power tool ‘trigger time’ cuts exposure, while selecting more powerful tools can also reduce this by 50%, along with a 30% reduction in vibration exposure and a 100% increase in productivity.”
McDonnell concludes: “Have appropriate control measures in place to prevent issues in the first place, as once the condition has developed it is irreversible and, as a result, limits functional capacity.”
BOX OUT: Helpful vibration resources
HSE: Hand-arm vibration guide for employees - https://is.gd/ovemes
HSE: Hand-arm vibration exposure calculator - https://is.gd/erixif
Chicago Pneumatic: Protecting workers from HAVS - https://is.gd/oborus
Atlas Copco: The art of ergonomics - https://is.gd/tarese