In the U.S. there are two voluntary consensus standards, the American National Standards Institute (ANSI), which has established a voluntary consensus standard (ANSI S2.70-2006), and the American Conference of Governmental Hygienists (ACGIH). They established Hand Arm Vibration and Whole Body Vibration Threshold Limit Values. These guidelines recommend methods for the measurement, data analysis, vibration and health risk assessments, and reporting of human exposures to hand-transmitted vibration. The guidelines echo the action and exposure limit values prescribed in the European Union (EU) directive established by the CEN. But with no enforceable standard in the U.S. to regulate tool makers, every manufacturer is free to define their tools’ vibration levels as they wish. Burdick thinks the industry would benefit if all manufacturers could agree on the same measurement protocols, such as those established by the ISO.
When you shop for a power tool, it’s difficult to know which manufacturer makes the tool with the least amount of vibration acceleration. You won’t find these numbers printed on the box as they are in Europe. Burdick says instead buyers must look at marketing claims about how they reduce vibration and impact.
How manufacturers reduce vibration
Workers shouldn’t use jackhammers to break concrete or rock for extended periods of time without taking breaks. But Richard Elliott, product development specialist for Atlas Copco, says they are doing their best to minimize the risk. They developed air cushions for the top and bottom of hammer piston strokes to reduce vibration, and they sell optional handles which are linked to the tool by means of springs that are adjusted to decrease the vibration impact to the operator’s hands and arms by as much as 75 percent when used properly. Elliott adds that his company sells their products in Europe so they follow ISO standards and EU directives in the U.S. too.
Mark Michaels, director of product management for Husqvarna Construction Products, says they make both concrete saw and demolition robots for the concrete industry. “We are moving toward remote controls as a way to completely separate workers from vibration and impact,” he says. They sell breakers and crushers mounted on small track vehicles, allowing workers to stand away from the machine while operating a joystick controller. Their wall saws have remote controls too. Their walk-behind concrete saws and hand-held power cutter saws have less vibration because handles are isolated from the crankcases.
The manufacturers of small hand tools such as angle grinders, reciprocating saws, hammer drills and chipping hammers also work to reduce vibration. Burdick says they do this by machining moving parts more precisely, introducing counter-weights to minimize impact on hands, improving overall performance and efficiency, and developing handles that are “de-coupled” from the tool. Reducing tool size and weight also helps. Rempel’s laboratory is developing a bench top method for measuring handle vibration for hammer drills.
Nobody wants to experience physical disability that exposure to vibration acceleration and constant impact can cause. Manufacturers don’t want to cause harm either. But in a very competitive industry, there’s a strong motivation to sell products at the right price and the voluntary guidelines offered by ANSI and ACGIH aren’t likely to be adopted by U.S. regulatory agencies anytime soon. Unfortunately, for now workers are put in the position of “let the user beware.”
In the meantime, research continues to understand how vibration and impact affect our physiology and what we can do to minimize the risk.
Joe Nasvik is a writer and editor serving the concrete industry. He has 18 years experience as a concrete contractor. Contact him at email@example.com.