“Impact Wrenches Can Be Health Hazard” – Report

Pneumatic impact wrenches such as those typically used for commercial wheel bolting could prove to be a health hazard if used for more than a few minutes a day, says a new assessment.

The study was commissioned by Norbar Torque Tools and carried out by the Industrial Noise & Vibration Centre and compared a typical pneumatic impact wrench and Norbar’s Pneutorque torque wrench. Why bother? New regulations – “Control of Vibration at Work Regulations 2005” – which came into force in July set down limits for workers’ exposure to vibration. In fact there are two exposure values; the Daily Exposure Action Value (EAV) is a level above which an employer must introduce controls to eliminate or reduce exposure and the Daily Exposure Limit Value (ELV), which is the level above which the employer must take immediate action to prevent any further exposure to vibration. These values are expressed in metres per second squared (m/s2) and the limits are 2.5 m/s2 (EAV) and 5.0 m/s2 (ELV). This is a very simplistic summing up of a complicated formula and anyone wishing to know more can have hours of fun by studying the following website: http://www.opsi.gov.uk/si/si2005/20051093.htm

The Norbar-commissioned report found that users of impact wrenches could reach their daily vibration exposure limit in as little as 34 minutes of use. The test involved tightening 10 truck wheel nuts to 600 N/m and the results showed that the impact wrench user reached the EAV in only eight minutes, while the Pneutorque® user could perform the same task continuously for 24 hours without breaching the EAV.

As well as helping to prevent such conditions as vibration white finger and Hand-Arm Vibration Syndrome, which affect hundreds each year, Norbar says that its Pneutorque can be more efficient; as pneumatic impact wrenches are not torque controlled devices, the perceived speed benefits are negated by the fact that a torque wrench is required to check that minimum torque has been achieved. In addition, the use of impact-type tools often results in the over-tightening of bolts, which in turn can cause failure of wheel studs in use.