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October 7, 2009

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Vibration- A hands-on approach

With the decline of heavy industry in the UK, hand-arm vibration is no longer a top-of-the-agenda health and safety issue but some 2 million people are still at risk from the harmful effects of uncontrolled exposure. Brian Mallon provides a reminder of the problems it can cause, and what must be done to avoid them.

Safeguarding the health and safety of those under our care can be a challenging task and, from time to time, certain issues can drop down our priority list — thanks, in part, to other, more high-profile concerns. Vibration in the workplace is, I believe, a case in point: a subject that is not particularly current or ‘sexy’ but whose effects, if not continuously assessed and managed, can cause enormous problems for those exposed to it.

Vibration is, in effect, the oscillatory motion of an object between two points. Hand-transmitted vibration is that which affects the body through operation by the hands of vibrating tools and machinery. If it is not properly monitored and controlled, operators can suffer from hand-arm vibration syndrome (HAVS), which manifests as symptoms in the fingers, hands and arms and is a recognised industrial disease, affecting many thousands of workers across different industries.

The hand or arm can be affected in three ways: neurological, musculoskeletal and vascular. Pain and weak grip are musculoskeletal aspects, while numbness, or lessened sensitivity to touch and temperature are neurological. (Sufferers may complain of “pins and needles”-type sensations.) The vascular, or circulatory element is typified by episodes of finger blanching, which are frequently brought on by cold temperatures, i.e. Vibration White Finger (VWF). The repeated use of hand-held vibrating tools, such as grinders, polishers, riveting guns, etc, may lead to the tips of several fingers suffering blanching initially but will extend to the base of the fingers if not suitably addressed. Sustained usage could lead to permanent damage of the limbs, with gangrene, in particular, a major threat.

Clear and present duties

Vibration and its effects in the working environment are largely governed by The Control of Vibration at Work Regulations (CAWR) 2005, which implement the European Physical Agents Directive. Although they have been in force for four years, the Regulations did allow for a transitional period up to 2010, during which exceptions to the exposure limit value (see below) for hand-arm vibration can be made in certain instances involving old machinery. From 29 December 2009, however, all new machinery built in or imported into Europe will have to comply with the new Machinery Directive 2006/42/EC, which contains more precise requirements concerning noise and vibration than the previous version.

The CAWR aim to provide a clear and concise framework under which employers and operatives can be aware of legal requirements and industry best practice when dealing with vibration in the workplace. The Regulations place certain requirements on employers, regarding how the issue of vibration should be managed. The first and most fundamental of these is assessing the vibration risk to the employees.

The impact of vibration on an operative is influenced by several factors, including vibration amplitude, magnitude, direction, duration and frequency. Occasional exposure to vibration is unlikely to lead to ill health. The frequency range over which injury from vibration can occur is believed to be between 5Hz and 2000Hz. It is, however, at the lower frequencies, i.e. from 5Hz to 150Hz, that the risk is widely believed to be at its highest.

The Regulations discuss the Exposure Action Value (EAV) and Exposure Limit Value (ELV), and how employers must assess and decide if levels in their workplace exceed these stipulated values. The Health and Safety Executive defines the EAV as “a daily amount of vibration exposure above which employers are required to take action to control exposure. The greater the exposure level, the greater the risk and the more action employers will need to take to reduce the risk”. In relation to hand-arm vibration, the EAV is a daily exposure of 2.5 m/s2.

The Exposure Limit Value is defined by the HSE as “the maximum amount of vibration an employee may be exposed to on any single day”. Again, in relation to hand-arm vibration, the ELV is a daily exposure of 5 m/s2. If employees are going to be exposed to levels in excess of the daily EAV, the legal requirements are as follows:

  • The employer must introduce a programme of controls to eliminate risk, or reduce exposure to as low a level as is reasonably practicable;
  • The employer must provide health surveillance for those employees who continue to be regularly exposed above the action value, or continue to be at risk;

Similarly, if employees are likely to be exposed above the daily ELV,

the employer must take immediate action to reduce their exposure below

the limit value.

For good measure

Measuring operative exposure and subsequently making a decision as to whether employees are being exposed to levels above the exposure action value can be difficult. Manufacturers’ vibration data can be used to good effect (checking that the guidelines assume using the equipment in the same way as the employee is using it).

Having ascertained the relevant manufacturer’s data a competent person needs to check for how long the operatives are actually using the vibrating tool (sometimes referred to as the “trigger time”). This is the period of time when the tool is actually in use; thus, it is better to observe the task rather than simply ask the operative, as it can be difficult to get a correct answer from someone so involved in the actual operation itself. Unless the resources exist for continual supervision, it will be necessary to multiply the data by a set variable (e.g. multiplying one hour’s data by eight in order to ascertain the trigger time for an entire shift).

The measurement of vibration can also be divided into five stages. The first would be to identify a series of discrete operations that make up the exposure pattern, and then measure the vibration for each operation. At this point, the typical daily exposure time for each operation can be estimated, as outlined above.

If it is determined that vibration is excessive, various control measures can be implemented, under the following hierarchy:

  • Eliminate exposure by implementing new working practices, such as automated systems. This can be a costly exercise initially but in the long term, the benefits to the workforce and productivity will become apparent;
  • Substitute one working method for another, e.g. welding rather than riveting;
  • Reduce vibration transmission to hands by using tools with low levels of vibration. Older, or less efficient tools can be replaced with more efficient machines and/or those designed with better grip or anti-vibration handles; 
  • Maintain worn parts and/or anti-vibration devices;
  • Reduce the amount of time spent on the task — a logical, practical way of managing the risk;
  • Make sure operatives are properly trained in the use of their machine/equipment, and that they know how to ensure equipment is properly maintained, and how to maintain good blood circulation, so that they can make minor tweaks to their routine or work practices when necessary.     

Further information

Brian Mallon works in local government in Northern Ireland.

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