Noise and Vibration
Published: 01st Jul 2003
New Regulations for the Workplace
After many delays and false starts, a pair of directives arrive within a few months of each other. Regulations based on the directives must be implemented by member states before July 2005 for Hand - Arm Vibration and February 2006 for Noise. As the new requirements come into force so close together, there is a considerable incentive to spread the workload involved in updating risk management procedures and assessments by taking proactive action now.
The changes in these procedures required by the new directives also represent a good opportunity to incorporate recent developments in "best practice" that can substantially reduce the costs, resources and time required to manage the risks of noise and vibration at work under both current and planned regulations. There is also an additional incentive generated by the upward trend in insurance liability premiums.
This article by Peter Wilson of the Industrial Noise and Vibration Centre not only provides a summary of the new requirements for occupational noise and hand-arm vibration in the directives, but also a guide to what constitutes current "best practice" in risk management based on new techniques and practices.
Introduction to the Directives
The contents of the Noise Directive hold few surprises (despite a few alarming suggestions during the negotiations) and have been expected for the last 10 years. However, the vibration directive is something of a curate's egg. Whilst the Hand-Arm Vibration (HAV) section represents a development of the current requirements, the whole body vibration (WBV) section shows signs that a political agenda has displaced the scientific process. There is actually little evidence that the vibration action levels in the WBV part of the Directive cause any harm or damage over and above those caused by ergonomic factors.
The new vibration directive has been welcomed in the UK by the HSE as it provides a strong boost to action on Hand-Arm Vibration - and they are recommending early action. Much of industry has yet to come to terms with HAV, in part due to the particular difficulties associated with risk management in this field. In the meantime, in the UK the requirements of the HSE guidance note HS(G)88 issued in 1994 will still apply.
Physical Agents (Noise) Directive
What's New in the Directive?
The following chart (page 44) shows a comparison between the main requirements under the existing Noise at Work Regulations and the revised requirements under the new Directive: The following is an assessment of some of the practical implications inherent in the new requirements:
1. Action Levels and Units
(i) "New" Units: LEP,d changed to LEX, 8h. No implications whatsoever! The existing LEP,d is exactly the same as the new LEX, 8h. New directives, new names...
(ii) 1st Action Level: 85 dB(A) v 80 dB(A) + 140 dB peak v 135 dB peak. It has always been good practice to measure the noise in quieter areas as well as noisy areas so that you can prove that the storeman making a claim was only ever likely to have been exposed to a maximum of 77 dB(A). However, it will now be necessary to put the same detail into your assessments of areas that are above 80 dB(A) as you previously did above 85 dB(A) You will also need to carry out more peak noise readings to check single (very loud) events against the new 135 dB 1st Action Level
(iii) 2nd Action Level: 90 dB(A) v 85 dB(A) and 140 dB peak v 137 dB peak. Simply apply the same practices and procedures at 85 dB(A) that you currently employ at 90 dB(A)
Note: In practice, there is actually no way you could differentiate between 135dB and 137dB peaks due to the limitations of measurement accuracy and repeatability. Consequently, this is a meaningless differentiation that can safely be ignored by assuming a 2nd Action Level of 135dB peak i.e. bring the 2nd Action Level down to the same value as the 1st Action Level.
2. Exposure Limit Value
The new 87 dB(A) LEX, 8h exposure limit value represents the maximum permissible estimated operator noise dose including the use of hearing protection i.e. it represents the noise that actually enters the ear under all circumstances. The old 140dB peak 2nd Action Level becomes an exposure limit value with the same requirements as above. Thus it will be necessary to ensure that dose calculations are extended to take account of the noise exposure that includes the use of any PPE.
3. Weekly Noise Exposure Level
Where shift patterns vary substantially, in principle it will be possible to sum the noise doses for each day of the week and subtract 7 dB to calculate the weekly exposure level for comparison with the action levels.
The new requirements imply that the noise level inside PPE should be 87 dB(A)LEX, 8h as a maximum - assuming that there is no other noise exposure during the day.
As the typical field performance of PPE is only a fraction of the theoretical assumed performance and as a 100% wear rate for any operator cannot be guaranteed, then it becomes very difficult indeed to ensure that workers are adequately protected for noise levels much above 95 dB(A). This is illustrated by the plot above. Assuming that a 99% wear rate is the maximum you can achieve in practice and using field performance data (rather than the theoretical data from the manufacturers), the plot shows that, in practice, muffs can provide a typical reliable protection of only c 15 dB protection and plugs only c 10 dB.
5. Health Surveillance
The requirement for hearing checks at 85 dB(A) in the current regulations is unchanged. There is also a requirement for "appropriate health surveillance of workers where the results of the assessment and measurement indicate a risk to health". The practical implications of this will depend on the precise wording of the new regulations, particularly with respect to audiometry which must be "available" for workers exposed above the 2nd Action Level.
Cutting the Costs of Noise Management
Industry in general could not only more than halve the typical costs of managing noise but could also increase effectiveness by implementing the latest developments in "best practice". The following are some of the main areas where significant improvements can most often be made:
1. Dosemeter assessments
Dosemeters are not only a time consuming and costly approach to assessment, but the results are inherently inaccurate giving figures that can easily be up to 6 dB(A) too high when compared with a hand-held meter. When there is a difference between the readings from a dosemeter and a hand-held meter (as is often the case) the dosemeter is always wrong as the risk statistics were compiled using the latter. This inaccuracy can be very costly e.g. when wrongly or unnecessarily designating Noise Hazard Areas. Consequently, dosemeters should only be used on the very rare occasions when there is no alternative.
2. Assessment Quality
Risk Assessments - As with other risks, the training and experience of the "competent person" carrying out the work will determine the quality of the assessment. However, due to the technical nature of noise, the variation in quality between assessments can be very wide. A three day risk assessment in a factory generating a 10cm thick report could be completed by someone else in only one day producing a slim report of far higher quality and usefulness. When sub-contracting assessments, take a critical look at examples of past reports. Alternatively, there are benefits in getting someone trained to carry out the assessment inhouse - an intimate knowledge of the site and ready availability can be valuable assets.
Reporting - An assessment is an archive of noise data and company practices. As this data will need to be accessed and used in the future (e.g. for dealing with potential hearing damage claims), great care should be taken with the layout of the reports and format of the data to make this process as simple as possible. There is a very good reason for the results of the HSE research in the UK showing that each £1000 paid out in compensation settlements actually costs the company between £7000 and £36000 in indirect expenditure. Many assessments are written without considering how to present the data so that it is easily accessible for future use. Moreover, the general quality of assessments is poor as the HSE considered (2002 UK figures) that only 37% were of an "adequate" standard.
A quick and effective solution is to acquire template documentation in digital form. The Digital Noise Assessment (DNA) developed by the INVC, for example, provides a benchmark "best practice" quality standard for all future assessments. The digital format also provides instant access to past data which minimises the indirect costs mentioned above.
3. Action plan
A noise assessment is not an end in itself. The only reason to carry out an assessment is to generate an action plan for the next 1-2 years. This should include a list of detailed recommendations and a schedule for implementation. Too many assessments are long on results, but short on clearly defined recommended actions.
4. Noise control options
There is a specific requirement in both the current and planned regulations for a noise control programme. However, most assessments either lack this important element entirely or present information that is too vague or general to be useful. Ideally, an assessment should include an audit of the noise control options (with costs and likely noise reductions) that can be used as the basis for implementing an effective programme of noise reduction. Noise control technology has also moved on a long way from the traditional palliative measures such as enclosures, screens and silencers - there are now many more cost effective options available.
Physical Agents (Vibration) Directive
What's New in the Directive?
The current HSE Action Level is set at either a highest axis daily (8 hour) dose of 2.8 m/s2 A(8) or a vector sum daily dose of 4 m/s2 A(8) (the vector sum is the total vibration from all 3 measurement axes). Where workers' exposure regularly exceeds the action level, the HSE recommends "programmes of preventive measures and health surveillance". The new Directive reduces the Action Level and introduces a new Limit Value exposure values as summarised in the following figure:
The important changes with respect to the vibration action values and risk management programme implementation are summarised below:
1. As both the Exposure Action Value (EAV) and Exposure Limit Value (ELV) are vector sums, it will no longer be possible to use single axis vibration levels in risk assessments. In addition, existing risk assessment data and conclusions will need to be reviewed and updated - which could take some time if it is done manually.
2. The ELV dose must not be exceeded. However, where the likely operator exposure is usually below 2.5m/s2 A(8) but varies substantially from day to day including periods above the ELV, then a "weekly average" derogation may be granted provided the 40 hour average does not exceed the ELV. There is also likely to be a 5 year transitional period across industry where equipment is provided before 06/07/07 with a further 4 year transition in agriculture and forestry.
There will be some cases where it will still not be possible to comply with the new exposure limit value with currently available equipment. It is not yet clear what employers should do in these circumstances, and further guidance is anticipated. The best way to manage the risks successfully is by implementing an effective hand-arm vibration risk management programme as outlined below.
Hand-Arm Vibration Management Programme
The following is a summary of the principle features of any effective programme. The objective for a company should be to implement "best practice" for each element:
1. Identify and Assess Hazardous Operations
The accurate measurement and assessment of hand-arm vibration exposure is a much more complex, difficult and time consuming process than for noise whilst vibration terminology is also less familiar. Consequently, the quality of HAV measurements (and associated risk assessments) is generally poor and full assessments including both measurements and dose calculations should only be carried out by a "competent person". In addition, as there is often a high degree of variability in the results, it can be misleading to generalise from a single measurement. Consequently, it is best practice to use a reliable database of field measurements as the basis for risk assessments, supported by live measurements as required. This provides a higher quality and more accurate assessment than measurements alone and at a fraction of the cost and time. The first step is to identify and list activities and tools that may be hazardous and then check the tools against the database. It is usually possible to carry out risk assessments on most tools and activities directly from the database. Then, if required, carry out the minimum number of additional "live" measurements needed to complete the assessment of a representative sample from the tools in use on typical "jobs".
Train and educate operators, supervisors and managers to the appropriate level. As personal behaviour can have a substantial effect on the risks associated with exposure to a given level of vibration, effective training is an important element in the management programme. The three main areas that need to be covered are:
(i) Management Briefings and Competency Training - Establish/ update company policy and ensure that managers understand their responsibilities under the programme. Train some personnel up to competency standard so that they can manage the programme effectively.
(ii) Supervisor Briefings - A cut down version of the above, slanted towards practical implementation and procedures.
(iii) Operator Toolbox Talks - Short, memorable, educational and motivational for users of vibrating equipment.
3. Implement a Risk Reduction Programme
The risk reduction programme should cover the areas outlined below:
(i) PPE - If you are considering the use of "Anti-Vibration" gloves as possible PPE, it is necessary to carry out a detailed frequency analysis of the vibration of each type of tool and then calculate the likely protection afforded. Currently, despite the claims of suppliers, there is no generally effective PPE for hand-arm vibration. In practice, for virtually all applications, any vibration reduction is negligible - and the gloves tend to be both expensive and un-ergonomic.
ii) Operation - In addition to the vibration amplitude itself, there are a number of operational factors that affect the degree of risk:
- the grip, push and other forces used to guide and apply vibrating tools or workpieces
- the exposure pattern, length and frequency of work and rest periods
- how much of the hand is exposed to vibration
- factors affecting blood circulation such as temperature and smoking
- drugs and toxins
- individual susceptibility
(iii) Personal behaviour - Train operators at risk to modify their behaviour:
- maintain blood flow - keep hands warm, exercise hands regularly during work, stop smoking before and during work
- minimise grip strength (ergonomics)
- break up work periods - shorter periods are better than longer continuous use
- maintain tools and use the right tool for the job
(iv) Symptom reporting - Set up a reporting system that actively encourages personnel to report symptoms.
(v) Ergonomics - Select tools for ergonomic reasons as well as for levels of vibration. Create guidelines for correct tool selection/use and ensure operators are properly trained.
(vi) Maintenance - Ensure tools are well maintained and that there is a procedure for reporting problems.
(vii) Reduce vibration - The options are either to modify the process / substitute different equipment (e.g. use hydraulic shears in place of a ripping chisel) or to introduce engineering modifications such as:
- source control - reduce vibration at source through design changes or modifications
- vibration isolation - reduce the transmission of vibration to the hands in the critical frequency range
- vibration damping - convert vibration energy to heat to reduce the amplitude at structural resonance frequenies
4. "Buy Smooth" Purchasing and Hiring Policy
One of the most cost effective long term measures to reduce vibration exposure is the purchase or hire of low vibration tools as new (or replacement) equipment. Suppliers are gradually bringing out new designs that generate lower vibration levels and are ergonomic in use. Buyers and project and specifying engineers of potentially hazardous plant should implement a vibration purchasing and hiring policy.
Hire companies usually provide only manufacturers' data which is completely inadequate as an aid in the selection of low vibration tools. As manufacturers are very often reluctant to stray beyond "declared values", it is still almost invariably necessary to use your own field data as the basis for low vibration tool/plant selection. Using a centrally maintained database of vibration values is a particularly effective approach for projects where tool hire is a regular issue.
5. Health Surveillance
A health surveillance programme is likely to be appropriate for all workers in jobs giving rise to significant risk of HAVS, i.e. workers likely to be exposed above the current HSE action level. This programme should include the following elements:
(ii) reporting system - a formal and effective system (e.g. questionnaires) for reporting any symptoms
(iii) health checks - carried out by a qualified medical practitioner, including:
- pre-employment assessments - baseline data, Raynaud's syndrome, drug use, smoking
- routine assessments - initially after about 6 months, annually
thereafter. If there are no reported symptoms after a reasonable length of time, discontinue the assessments but maintain the reporting procedure
(iv) record keeping
(v) communication - inform workers of the results and implications
6. Audit the Programme
Operate an effective, verifiable auditing procedure for all the above elements. Record keeping is important as it provides evidence that "best practice" is being followed for each part of the management programme. Few companies consistently audit the costs and benefits associated with the measures they are taking to minimise the risks of HAVS. There is thus little feedback as to the cost effectiveness of each of the elements of the Vibration Management Programme as implemented in practice. There should be a clear policy on responsibilities, supervision and performance monitoring to provide the information required to ensure that the management programme is as cost effective as possible.
Effective auditing can also be extended to include changes in accounting procedures to match costs with responsibility. A common example of a poor match is where employers' liability insurance premiums are paid from a central pool with no feedback to a particular site or department. Thus, if there are a number of damage claims in one area, the increase in premiums is not directly reflected in the overheads of the manager responsible.
More detailed information on managing both noise and vibration is available free from the INVC. This includes the Digital Noise Assessment (DNA) templates, the Hand-Arm Vibration database and detailed HAV Management Manual plus competency training in both subjects.
The INVC is an engineering consultancy that has established a reputation for successful innovation in the fields of noise and vibration management and control. On the management side, for example, the company has built-up the largest database of field HAV data available in Europe and has become the major supplier of competency training in both noise and vibration in the UK and Ireland. The engineering heritage is reflected in the case studies illustrating the wide range of source control techniques developed as low cost alternatives to conventional noise and vibration control measures.
Industrial Noise and Vibration Centre 889 Plymouth Road, Slough, Berkshire, England SL1 4LP. Tel: +44 (0)1753 698800 Fax: +44 (0)1753 567988 Email: email@example.com . Web: www.invc.co.uk
Published: 01st Jul 2003 in Health and Safety International