U.S. workers benefit from EU vibration-control standards
While not mandated in this country (yet), European vibration-control standards for power tools benefit U.S. workers. Impact and vibration won’t kill you, but they can kill productivity. Sustained vibration can cause damage to nerves and blood vessels in workers’ hands and arms. Vibration also tends to make muscles tighten up. The tighter you grip the tool, the more vibration gets transmitted to your hands and arms, making injury more likely. In the most extreme cases, hand-arm vibration syndrome (HAVS)—the term used in the industry for a range of cumulative trauma disorders caused by vibration—causes blood vessels to collapse and prevents oxygen from reaching tissues.
One of the most common HAVS caused by impact tools like breakers and rotary hammers is often called “white finger disease” (photo, left). In this case, sustained vibration causes the capillaries in the hand and fingers to constrict, which blanches and numbs the fingers. When the blood finally returns, the tingling and pain can be uncomfortable—even more so in cold weather.
HAVS can manifest also as arthritis, tendonitis, and changes to muscle tissue that result in a person’s loss of grip, reduced mobility, and pain in the hand and arm.
Jack hammers and breakers, scalers, rotary hammers, hammer drills, jumping jacks, and other compactors, are among the most notorious for causing problems, some that manifest within just a half-hour of work. But extended use of many other tools, including grinders, impact drivers, vibratory screeds and concrete vibrators, takes? a toll on workers. Even if a worker doesn’t suffer from HAVS, fatigue from sustained vibration can sap productivity, so there’s ?no reason not to opt for anti-vibration technology.
In the European Union, tools must be tested and rated for “vibration magnitude,” which is measured in m/s2. It’s an inverse relationship: the lower the vibration, the longer the tool can be used, and as long as it’s not too wimpy to get the job done, the more attractive it may be for an employer to buy.
EU standards set two limits: Exposure Action Value—the total vibration allowed from the tool—and Exposure Limit Value— the total vibration a worker is legally allowed to see in a day. It’s this latter value that toolmakers selling in EU markets typically focus on. The ELV for better-quality impact tools on today’s market typically ranges from 4 to 6 hours, but as technology advances, some are achieving an 8-hour rating. Vibration limits are plotted on a chart, which is used to determine how long a worker can legally be allowed to use a tool.
Not surprisingly, the EU market has spawned a surge in industrial design aimed at reducing power-tool vibration. In our global economy, we benefit from the innovations toolmakers have employed in order to sell in the EU. Here are some examples of a “total package” for anti-vibration on a tool like a rotary hammer:
Counterbalance mechanism. Rotary hammers get their name from a rotary mechanism that drives a piston up and down in a cylinder. This piston, which has 0-rings (shown in blue in photo here) to create a tight seal in the cylinder.
As the piston moves, it pushes (or pulls) a slug of air, which in turn pushes and pulls the “striker”—a free-floating, “flying” piston that when pushed slams into the impact bolt behind the bit to create the hammer effect on the rotating bit. It needs the air to cushion this blow. You can imagine the effect if the piston beat directly on the impact bolt; the intense shock would destroy the rotary mechanism. (Hammer drills essentially have this direct mechanism, just with much less force.) Despite?the air cushion that softens each blow on the rotary drive-train, the tool as a whole still vibrates with the high-speed blows to the impact bolt. The tool user absorbs these impacts through the handles. In an effort to further reduce this overall force, some manufacturers add a counterbalance that is driven by air from the cylinder, which is redirected to move weights in side chambers in the opposite direction from the striker. This effectively cancels some of the impact force and reduces the overall vibration.
Vibration-absorbing housings. Even? less vibration gets transferred to a user through the main handle, which is designed to move independently of the motor and drive mechanism . The same isolation can be applied to the side handle.
A damper spring is sometimes installed at the base of the impact bolt to absorb impact vibrations from the drill bit.
Lock-on or trigger. If a user doesn’t have to constantly grip the handle, but can relax the hand, the blood vessels in the hand will not be strained as quickly. Along with a lock-on trigger, tools often feature electronic speed control that automatically applies additional power to the motor to maintain speed under load, allowing the tool to complete the job more efficiently.
Soft start suppresses start-up reaction for more control and better accuracy.
Assuming a tool is designed not to exceed the Exposure Action Value, don’t underestimate raw power and better bits (such as a four-way cutter instead of an ordinary two-way) to complete the job faster. Working the tool for less time means a worker is exposed to less vibration.
Finally, during the time the worker is exposed, the following will help:
- Keep the hands and entire body warm and dry.
- Wear gloves made with a vibration-absorbing foam.
- Avoid smoking; nicotine enhances the ability of blood vessels to go into spasm.
- Seek medical attention immediately if finger tingling, numbness, or blanching is experienced. The sooner you address a developing HAVS problem, the easier it is to avoid long-term tissue and nerve damage.