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No Easy Answers on Vibration Gloves
Anti-vibration gloves are a hot topic in industrial safety, but the development of the industry surrounding it has been around since the symptoms of Hand Arm Vibration Syndrome (HAVS) were first diagnosed in 1911.
There are roughly 1.5 million to 2 million U.S. workers who are regularly exposed to hand-arm vibration (HAV) through regular use of pneumatic, hydraulic, electrical, or gasoline-powered hand tools as a part of their jobs. This regular exposure often leads to the incurable, irreversible HAVS, originally called Raynaud's Phenomenon or Vibration White Finger. It happens so often, in fact, that the Journal of Occupational and Environmental Medicine has predicted 50 percent of exposed workers will develop symptoms.
Common symptoms of HAVS include blanching of fingers, spasms, numbness, and loss of coordination and dexterity. These symptoms are exacerbated by cold temperatures and can culminate in attacks that can last between five and 15 minutes. This progressively debilitating condition can disable workers over time and even lead to amputation.
Anti-vibration gloves aim to absorb and dampen the vibrations emitted by these tools that can affect the central nervous system long term. There are several variations of these gloves in the marketplace today that use different methods of reducing sonic repetitive injury, ranging from simple foam padding to air pockets and gels. The effectiveness of these materials varies by glove manufacturer as much as it does by material.
Vibration Glove Testing
In an effort to protect workers on job sites around the world and create a uniform playing field, the PPE industry has made inroads in developing a suitable vibration-reducing glove testing standard that measures a glove's ability to help dampen a portion of the vibrations unavoidably transmitted by impact and power tools. The ANSI S2.73/ISO 10819 tests have been both a blessing and a curse to both the manufacturing and end user sides.
Changes in the Anti-Vibration Glove Testing Standard: ISO 10819 in 2013 were not highly publicized and made adjustments to the way the handle and adapter readings were calibrated and measured from the original 1996 standard. ISO 10819 aims to gauge the vibration transmissibility of a glove with a vibration-reducing material that covers the palm, fingers, and thumb of the hand.
The basic setup of this test involves a person wearing a glove gripping a vibrating handle with load cells to gauge the transmissibility of the vibrations through the glove. An "anti-vibration glove" must not amplify the vibration in the medium frequency range (1.5Hz to 200Hz); in the high frequency range (200Hz to 1250 Hz), the glove must reduce the frequency weighted vibration by at least 40 percent.
The most accurate method to determine the actual vibration magnitude exposure of workers is to perform on-site vibration analysis, which can vary significantly from the values declared by the tool manufacturers. In-use vibration, where the operator is using a tool in a real work situation in a specific workplace, depends not only on the vibration produced by the tool, but also on many other variables, such as the condition and quality of the inserted tool, type of product, the state of maintenance of the power tool, the design of the process, the worker’s posture and technique, etc. Multiple tests should be performed accounting for all variables, and an average of these tests should be used as the vibration value.
In independent study funded by the U.S. Navy, researchers found while many gloves that were submitted for testing passed vibration transmissibility criteria specified by the standard, none of them could be classified as an AV glove because none of the gloves could meet the standard's criterion for the thickness of the glove fingers.
Applications where workers must maintain a steady grip on a potentially dangerous power tool are relatively ignored by the standard that requires gloves to maintain a uniform thickness of vibration-dampening material between the thumb and finger as in the palm. The resultant lack of dexterity has many glove makers scratching their heads. "We were floored by the requirements of the vibration standard," said Elli Choi, president of Cestus Gloves. "Our company motto, 'Work in Comfort' was really stretched to the limit by the standard’s requirement of anti-vibration material in the saddle of the glove. Luckily, we were able to overcome the design obstacle, but it was no easy feat."
Dexterity and flexibility are top-rated concerns of any end user or safety manager. They know flexible, ergonomic gloves reduce hand strain, and industrial accidents directly related to hand strain and hand fatigue can often have serious consequences. Lamar Hutchinson, a seasoned safety consultant for the oil industry in Louisiana, reported, "Many injuries occur towards the end of the shifts, when workers let their guard down. Add fatigue and muscle strain, and you see the severity of incidents spike." He added, "Fatigue is a difficult thing to measure, but the consequences of repetitive injuries make a noticeable impact on our experience ratio."
To control the risk of HAVS, you have only two possibilities: Lower the vibration value or decrease the exposure time. Time can be reduced by changing to a more efficient process or by introducing job rotation. Modern tools with vibration control are in many cases more efficient and often show considerably lower vibration values. Paired with vibration-reducing gloves, the exposure to HAV transmission is lowered even further.
Anti-vibration gloves will continue to evolve as the industry develops new, engineered component materials. The use of AV gloves as part of a comprehensive ergonomic safety program, including job duty rotation, will hopefully start a downward trend of HAVS injuries on the work site. Trialing the gloves on the work site will give your team the best estimation of their ability to balance vibration reduction with dexterity and grip control.
This article originally appeared in the November 2014 issue of Occupational Health & Safety.
Jennifer Choi is Vice President of Business Development at Cestus Armored Gloves of Vancouver, Wash. Her role in strategic account management includes hazard assessment, root cause and incident trend analysis, product evolution projects, and change management.