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.

Acceleration - the rate of change of velocity in speed or direction per unit time (e.g., per second)

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.

…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

– Reduced sensitivity to pain, touch and temperature

– In later stages, hands become numb and fingers appear blue/black. Gangrene is possible.

– Blanching (whitening due to lack of circulation) of fingers. Recovery from blanching attacks is accompanied by acute pain and flushing.

– Tingling or numbness in the fingers or toes

Disorders Associated with HAV

Damage to blood vessels from vibration causes vessels to collapse, preventing oxygen to reach tissues. It is often made worse by cold.

Vibration White Finger (VWF)

Raynaud’s DiseaseA 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

Controls

Buy lower vibration tools

A link to the European Hand Arm Vibration Database is in the

Links and References at the end of this presentation

Tape existing handles with vibration dampening tape

Regularly maintain and balance hand tools

Use full fingered anti-vibration gloves

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.

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.

Powered Hand Tools

Point of operation

grip

motorIsolation point

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

Hand-Arm Vibration DatabaseHand-Arm Vibration Calculator

Links

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

Health Risks from Hand-Arm Vibration

Advice for EmployersVibration isolation example