Hand-arm vibration exposure: On-tool measurements vs. vibration emissions data
In this blog, Mary Cameron, team leader within SOCOTEC’s Occupational Hygiene team, discusses the role that measured vibration levels and manufacturer’s data plays when assessing HAV exposure and implementing subsequent control measures.
As per the Control of Vibration at Work Regulations 2005, employers are required to protect their employees against the health and safety risks associated with hand-arm vibration (HAV) exposure in the workplace, reducing exposure to as low a level as is reasonably practicable (ALARP). With symptoms such as pain, tingling, numbness, muscle weakness and white finger caused by overexposure to vibration, it is important to ensure that the level of risk is adequately managed.
Understanding the level of exposure to HAV may require employers to take a range of different actions. This includes the observation of specific working practices, the on-tool measurement of the magnitude of the vibration to which employees may be exposed, or the application of the manufacturer’s vibration emissions data provided in the tool’s user manual.
What is the latest HSE guidance surrounding HAVS assessment and control measures?
In August 2020, new guidance was published by the HSE entitled HAVS Inspection and Enforcement Guidance Document for all inspectors, specialists and visiting officers, replacing the Topic Inspection Pack on Hand-arm Vibration. The document states that hand-arm vibration should be considered as a matter of evident concern where:
- Exposure is likely to be at or above the Exposure Action Value (EAV);
- There is evidence of vibration-related ill health (e.g HAVS, CTS) not being properly managed;
- Employees report tingling when using vibrating tools, which persists for 20 minutes or more afterwards.
Aimed at those responsible for the inspection of occupational activities involving exposure to vibration levels, as well as those investigating cases of HAVS and carpal tunnel syndrome through RIDDOR, the document provides a consistent framework for assessing compliance and making enforcement decisions. It advises on the impacting exposure levels of varying factors, as well as the actions required in the event of high exposure levels and inadequate control measures. Vibration magnitude is one of the key factors which impacts the assessment of HAV exposure, with two methods for the determination of vibration magnitude examined below:
On-tool vibration measurement data
Measured vibration levels play a major role within a HAV risk assessment, allowing the employer to understand the magnitude and extent to which their employees are exposed to vibration under the actual conditions of equipment use. On-tool measurements often provide more accurate data based on actual tool usage within a particular process, as the measurement relies on the operator to demonstrate typical tool usage under those process-specific conditions. This is opposed to the equipment’s vibration magnitude data issued by the manufacturer, which is based on specific circumstances of application under laboratory conditions.
While arguably more accurate, the data produced from an on-tool vibration assessment should still be treated with caution, should this data have been gathered in a situation not reasonably representative of typical exposure. On-tool measurements can be impacted by variable factors such as hand placement, tool age, maintenance date, the materials being worked on, application style, the type of tool head, accessories and power settings. It is therefore important to ensure that a competent person, such as a qualified occupational hygienist, is employed to conduct a vibration monitoring risk assessment, as they will be able to accurately gauge typical conditions and consider any variable factors.
Manufacturer’s vibration emissions data
When carrying out a HAV risk assessment, employers should still consider any relevant data provided by the equipment manufacturer, who is required to provide details on the residual risk. This is a statutory requirement and can serve a purpose in providing a ballpark figure of the tool’s vibration emission level. This data is instrumental during the tool purchasing stage, as by applying a ‘buy smooth’ policy, the employer can focus on buying low-vibration tools.
It is worth noting that the vibration emission level stated by the manufacturer usually represents the average amount of vibration generated from the main applications of the tool. Therefore, any usage outside of its usual applications may significantly increase the exposure level over the total working period. The HSE’s standpoint is that it may be reasonable to expect that the manufacturer’s data is representative of the range of exposure which may be experienced on site, and that this data may therefore be applied for the purposes of a preliminary assessment of exposure. This can be carried out instead of on-tool measurements in the event of a specialist not being readily available to attend site.
However, caution should be taken to assess how closely the conditions of on-site tool usage match the conditions of laboratory-based testing. HSE guidance also cautions that vibration test codes tend to underestimate the vibration of tools when used in the workplace (by a factor of 1.5 to 2 for pneumatic and electric tools).
Which set of data is more effective when assessing and reducing HAVS exposure?
Although on-tool measurements can be argued to provide more accurate readings of vibration exposure levels, the subsequent control measures applied would be the same if both these measurements and the manufacturer’s data were to produce the same general range of vibration magnitudes. As long as the employer has sourced the general range of the tool’s expected vibration magnitude in that process, both the manufacturer’s data and on-tool measurements can provide the information needed to sufficiently assess the level of risk and control measures required.
Both data sources have their limitations, and employers should therefore choose the most appropriate method for their situation and focus on understanding the level of risk through a soundly-based risk assessment. And thereafter monitoring the effectiveness of the implemented control measures by ensuring they are regularly reviewed.
It is in my experience, however, that the manufacturer’s data can often underestimate the level of HAV exposure compared to the on-tool measurements obtained for that tool under actual/typical conditions of use. In some cases, the manufacturer’s data has been misunderstood and used as a means to ‘work up to the limit’, unwittingly causing exposure over the limit should the manufacturer’s data be under-representative. Therefore, although the manufacturer’s data serves a purpose (such as at tool purchasing stage or a preliminary risk assessment), an occupational hygienist may often be required to attend site to carry out on-tool measurements. In either case, the principle of ‘ALARP’ should be maintained.
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