Testing satisfies vibration legislation

AV Technology is experienced in assessing vibration levels for a diverse range of equipment, ranging from pneumatic drills and cutters to drivers' cabs on tractors.

The Control of Vibration at Work Regulations 2005 are a complex, yet important, set of regulations based on the European Physical Agents (Vibration) Directive (2002/44/EC) and brought into UK law via Statutory Instrument (SI) 2005 No 1093.

The directive deals with risks from vibration at work and is one of several covering physical agents such as noise and vibration.

The regulations divide vibration in the workplace into two distinct categories namely, hand-arm vibration (HAV) and whole body vibration (WBV).

Action and limit values based on daily eight hour exposure limits are defined in terms of single figure accelerations.

The regulations also allow a transitional period for hand-arm vibration until 2010 to allow work activities to continue in certain circumstances, where the use of older tools and machinery cannot keep exposures below the limit value.

It is estimated that around five million workers in the UK are exposed to hand-arm vibration in the workplace and 40% of these are exposed to levels where there are clear risks of developing health related problems.

Hand-arm vibration comes from the use of vibratory, rotating or percussive hand guided power tools and is the cause of significant ill health, including painful and disabling disorders of the blood vessels, nerves, joints and muscles of the hands and arms.

High risk industry sectors include heavy engineering and ship building, foundries and construction.

Whole body vibration relates to mechanical vibration which is transmitted into the body via the supporting surface when the operator is seated or standing, more commonly defined as "seat or feet" vibration.

Drivers of some mobile machines, including tractors, ride-on mowers, road rollers, fork lift trucks and quarrying or earth-moving machinery, can be exposed to WBV and shocks, which are usually associated with back pain.

The effects of WBV are more difficult to quantify and other work factors, such as posture and heavy lifting, are also known to contribute to back problems for drivers.

As a result continuing research is being carried out to understand and assess the relative importance of WBV.

The responsibility of protecting employees from the effects of vibration falls on two distinct groups.

Manufacturers have a legal obligation to design their equipment to minimise vibration when in use, whilst employers must ensure their employees are not exposed to dangerous levels of vibration during normal working practices.

AV Technology (AVT) has broad experience in assessing vibration levels for a diverse range of equipment, ranging from pneumatic drills and cutters to drivers' cabs on tractors.

The company carries out assessments for HAV and WBV on behalf of both manufacturers and user groups in the UK and abroad.

The company has recently carried out work in the USA for several manufacturers of power tools and machinery who export their equipment into the EU.

Manufacturers of hand-guided power tools, machinery and vehicles are required to mark their equipment with vibration levels in line with the legislation.

(With certain types of machinery such as ride-on mowers, both HAV and WBV regulations apply).

However, although the tests carried out on behalf of the manufacturer may cover a wide range of operational conditions, these may still differ from the actual working practices when the equipment is used in the field.

Complicating matters further is the fact that different operators may use the equipment in different ways.

AVT's Paul Francis understands the complexity of covering every eventuality and as he explains: "The test procedures can be complex and need to be carried out under what are deemed to be 'realistic working conditions'".

"However, it is virtually impossible for manufacturers to envisage every single possibility for how their products will be used in practice".

"For instance the way equipment is held and the pressures applied can be contributory factors which increase exposure to vibration levels".

"In addition some operators may be more prone to vibration than others".

"Consequently, manufacturers cannot guarantee the exposures which will result from the use of their equipment and machines".

"As a result we have found that a growing number of employers, whose operators use hand-guided power tools or mobile machinery, are having equipment tested independently under conditions stipulated by them rather than the manufacturer".

"This ensures that their employees are not subjected to vibration levels outside the legal limits within their actual working environment".

Tests on the equipment are carried out using accelerometers either placed on the seat or fixed as close as possible to where the operator holds the equipment.

Vibration levels are then recorded over a range of frequencies with the equipment running in its various operating modes.

The data from the test results are analysed and frequency weighting curves are applied in the calculations to arrive at a single acceleration figure.

For HAV the regulations introduce an "exposure action value" of 2.5m/s2 at which level employers should introduce technical and organisational measures to reduce exposure, and an "exposure limit value" of 5.0m/s2, which should not be exceeded.

For WBV the figures are 0.5 and 1.15m/s2, respectively.

The vibration levels are based on exposure during an eight hour period.

This exposure may be continuous, periodic or spasmodic and the HSE publishes guidance levels for exposures below eight hours.

Back to top