Reducing Hand-Arm Vibration

You Will Learn: What Hand-Arm Vibration (HAV) is and how it can hurt you Sources of Hand-Arm Vibration Current methods for controlling and reducing exposure to hand-arm vibration

Where is it? Found in electric, pneumatic or gas driven tools Industries: Construction Logging Equipment and machinery repair Ship Yards Automobile manufacturing and repair Building and maintenance of roads and railways Foundries Mines and quarries Plate and sheet metal manufacturing Public Services and public utilities

What is Hand-Arm Vibration? Hand-Arm Vibration is the transfer of vibration from a tool to a worker’s hand and arm. The amount of HAV is related to the acceleration level of the tool when grasped by the worker and in use. The vibration is typically measured at the handle of the tool while in use to determine the acceleration levels transferred to the worker. Acceleration - the rate of change of velocity in speed or direction per unit time (e.g., per second) …another way of putting it is the speed at which the vibrating surface goes back and forth…

Measuring Vibration Acceleration is measured in hertz (hz) or meters per second. A vibration level below 3.5 m2 is a safe vibration level for an 8 hour exposure to hand arm vibration. As vibration numbers go up, the duration of safe exposure decreases.

Tools Moderate vibration High vibration impact wrenches carpet strippers chain saws percussive tools jack hammers scalers riveting or chipping hammers grinders sanders jig saws

Tools Power tools can transmit vibration to the hands and arms, and this has a number of effects on the body. If you’re exposed to enough vibration, it can cause damage to the nerves and blood vessels in your hands and arms. Vibration also tends to make the muscles tighten up. The tighter you grip the tool, the more vibration gets transmitted to your hands and arms, and this makes injury more likely.

Tools Some tools put out a high level of vibration, and this can start to have these effects on your body in as little as half an hour of use per day. Among them are: Concrete breakers and road drills Hammer drills Nut Runners Pedestal Grinders Power hammers and chisels Riveting hammers and bolsters Brush cutters

Symptoms Associated with HAV Tingling or numbness in the fingers or toes Blanching (whitening due to lack of circulation) of fingers. Recovery from blanching attacks is accompanied by acute pain and flushing. Reduced sensitivity to pain, touch and temperature In later stages, hands become numb and fingers appear blue/black. Gangrene is possible.

Disorders Associated with HAV Vibration White Finger (VWF) Damage to blood vessels from vibration causes vessels to collapse, preventing oxygen to reach tissues. It is often made worse by cold. Raynaud’s Disease A disease in which people who may be pre-disposed develop symptoms similar to those of VWF, only vibration and cold may or may not play a part.

Prevention Development of HAV is dose related, meaning that effective control procedures should be: reducing the intensity of the vibration reducing the duration of the exposure to vibration early recognition of signs and symptoms identifying vibration sensitive individuals Dose means the amount of exposure to vibration measured either in units of time, or intensity of vibration Reducing the time would be to reduce the actual time per work day the person was exposed to the vibration. The effects of vibration are cumulative, so frequent breaks would not be a way to reduce time exposure. Reducing the intensity of the vibration would be done by dampening the vibration by using anti-vibration gloves, taping the grip with a foam tape, or purchasing tools with lower vibration levels. Encouraging employees to report the symptoms associated with vibration exposure early can both serve to limit the severity of a vibration induced injury and to help identify vibration sensitive individuals

Buy lower vibration tools Controls Buy lower vibration tools Tape existing handles with vibration dampening tape A link to the European Hand Arm Vibration Database is in the Links and References at the end of this presentation Use full fingered anti-vibration gloves Regularly maintain and balance hand tools Suspend tools from tool balancers to reduce hand grip force

Monitor Exposure Monitoring exposure can be as simple as applying a simple questionnaire on a regular basis (weekly or monthly) which addresses signs and symptoms to those who regularly use vibrating hand tools. Another method would be to monitor the exposure of the worker directly. However this is much more time consuming. It is important to understand that people often over estimate the length of their exposure to vibration. They may report the total time they were doing the job which may differ significantly from the time they were actually applying the tool to the task(s) involved. Some experts suggest that the monitoring of exposure is better assessed by someone other than the worker doing the job.

Actions That Can Help Wrapping handles with visco-elastic tape Using full fingered anti-vibration gloves Replacing tool gaskets with nitrile vibration reducing gaskets Suspend tools from tool balancers to reduce grip force

Work Practice Guide: Use only ergonomically designed anti-vibration tools Be trained on the proper method for using the tools Use only anti-vibration full-finger protected gloves Use tool wraps, but for only short periods of time Grasp the tool as lightly as possible, consistent with safe work practices Rest the tool on a support as much as possible or use with overhead balancers

Work Practice Guide: Operate tools only when necessary and at reduced speeds if possible Avoid continuous exposure by using rest breaks Avoid using worn out, unbalanced tools which probably have higher vibration levels Keep the hands and entire body warm and dry Avoid smoking because nicotine enhances the ability of blood vessels to go into spasm Seek medical attention immediately if finger tingling or numbness or finger blanching is experienced

Isolation and Damping Isolation alters the pathways between the machine and the person, by reducing the vibration arriving at the person. Example: shock absorber on a car. Damping is a method of converting vibration into a small amount of heat. The vibration is absorbed by the gloves or tape and heat is generated from the dampened motion. Example: anti-vibration gloves, or taping the handles of vibrating tools. Many new tools are being designed to separate the motor from the grip, and some separate the grip from the point of operation

Powered Hand Tools Isolation point motor Point of operation grip

Purchasing Hand Tools Purchase hand tools which are ergonomically designed: Lower weight Lighter weight battery Tool grip: keps the wrist straight correct size for the user (1 ¼” to 2”) dampened with rubber, foam, or tape isolated from the motor better

Links & References Links References Hand-Arm Vibration Calculator Hand-Arm Vibration Database Health Risks from Hand-Arm Vibration Advice for Employers Vibration isolation example References Hand-Arm Vibration – A Comprehensive Guide for Occupational Health Professionals P.L. Palmear, MD, FFOM, and D.E. Wasserman, MSEE,MBA OEM Press Second Edition, 1998 ISBN:1-883595-22-3