e. mail@unityoccupationalhealth.com
t. 01603 250015
Gloves marketed as ‘anti-vibration’, which aim to isolate the wearer’s hands from the effects of vibration, are available commercially. There are several different types, but many are only suitable for certain tasks, they are not particularly effective at reducing the frequency-weighted vibration associated with risk of HAVS and they can increase the vibration at some frequencies. It is not usually possible to assess the vibration reduction provided in use by anti-vibration gloves, so you should not generally rely on them to provide protection from vibration. However, gloves and other warm clothing can be useful to protect vibration-exposed workers from cold, helping to maintain circulation.
Low hand or body temperature increases the risk of finger blanching because of the reduced blood circulation. You should therefore make sure employees working outdoors in cold weather have adequate protection. The temperature in an indoor workplace should provide reasonable comfort without the need for special clothing and should normally be at least 16 °C. If this is not reasonably practicable, you should provide warm clothing and gloves. (More than one set may be required for each employee if the gloves or clothing are likely to become wet.) Gloves and other clothing should be assessed for good fit and for effectiveness in keeping the hands and body warm and dry in the working environment. You should also ensure that gloves or other clothing you provide do not stop employees working safely and do not present a risk of entanglement with moving parts of machinery.
Information taken from the following HSE report:
Triaxial measurements of the performance of anti-vibration gloves
(Prepared by Health & Safety Laboratory for the Health & Safety Executive 2010)
This report and the work it describes were funded by the Health and Safety Executive (HSE). Its contents, including any opinions and/or conclusions expressed, are those of the author alone and do not necessarily reflect HSE policy.
Objectives
Previous studies of anti-vibration gloves have typically only considered the effect that a glove might have in the direction of compression of the glove material. This project investigates the performance of an anti-vibration glove taking account of the influence that the glove might have in three axes. This requires consideration of the performance of the glove material in both compression and shear. Since the adoption of the revised international standard ISO 5349-1:2001 in the UK as BS EN ISO 5349-1:2001 and the implementation of the Control of Vibration at Work Regulations 2005, the technique for assessment of exposure to vibration requires the measurement of data in three axes to provide a total vibration value. It therefore follows that any estimate of the performance of a glove intended to reduce the vibration exposure of an operator should also consider all three vibration axes.
The aim of this investigation is to either confirm or challenge the assertion made by a particular machine manufacturer, that the glove they supply will provide useful attenuation of the vibration generated by their hand-held power tool products.
Main Findings
The performance of a glove determined by measuring using an adaptor in the palm of the hand is influenced by the test method itself. The adaptor may have significant resonances in the hand-arm vibration frequency range and these resonances affect the results of transmissibility measurements. Wide variations in transmissibility measurements occur due to slight changes in the measurement conditions.
Due to the problems associated with the measurement technique and the wide variability in the results obtained, it is not clear from the results of this study, whether the glove supplied is likely to effectively attenuate the vibration of the manufacturer’s product range.
The measurement technique described here is not suitable for assessing the vibration reduction achievable when using anti-vibration gloves with particular machines, i.e. is not suitable for confirming suitability as required by the Personal Protective Equipment at Work Regulations 1992.
Recommendations
Extensive development of new performance assessment methodologies should be researched if the exposure attenuation provided by anti-vibration gloves is to be quantified satisfactorily in three axes.
Triaxial measurements of the performance of anti-vibration gloves (continued)
BACKGROUND
Some manufacturers of powered hand-tools are recommending the use of anti-vibration gloves for protection against vibration emissions from their machines. One such manufacturer supplies a particular brand of anti-vibration gloves and advocates their use with their products. The model of glove has been shown to achieve the criteria specified in product standard BS EN 10819:1996 such that the glove can be marketed as an anti-vibration glove. This is in accordance with (amongst others) Regulation 8, 11, and Schedule 3 of the Personal Protective Equipment Regulations 2002. However, there is no requirement in BS EN ISO 10819 for the vibration attenuating performance of the glove when used with the manufacturer’s products to be provided for users.
The manufacturer advocating the use of anti-vibration gloves states in their marketing literature that: “gloves are proved for a frequency range f=31,5 Hz to 1000 Hz. The oscillating frequencies of the [machine name] are from 100 Hz up to 350 Hz, depending of the rotational speed of the motor”.
The Personal Protective Equipment at Work Regulations 1992 implementing the Personal Protective Equipment Directive 89/656 in the UK, require an employer to assess and select PPE according to its suitability. For vibration, as with any other risk, the employer must ensure that the PPE is suitable to protect against the vibration risk. They must do this by comparing the character of the risk with the characteristics of the PPE and taking account of any risks the PPE itself may cause. The HSE has recommended against providing anti-vibration gloves for attenuation of hand-arm vibration, unless the gloves have been shown to achieve vibration attenuation in the actual circumstances of use.
No standard exists for estimating the protection afforded by anti-vibration gloves when using vibrating machinery. Most international experts agree that the actual performance is dependent upon contact forces across the hand. The current standard (BS EN ISO 10819) defining the minimum requirements of an anti-vibration glove, including specification of attenuation criteria at one controlled contact force, does not provide any information for predicting in-use attenuation.
Since the adoption of the revised international standard ISO 5349-1:2001 in the UK as BS EN ISO 5349-1:2001 and the implementation of the Control of Vibration at Work Regulations 2005, the technique for assessment of exposure to vibration requires the measurement of three axes of data to provide a total value. It therefore follows that any estimate of the performance of a glove intended to reduce vibration exposure of an operator must also be made in terms of three axes.
To assess the transmissibility of an anti-vibration glove, it is important to measure the vibration simultaneously at the surface of the handle or surface imparting the vibration and between the hand and glove i.e. inside the glove. Without simultaneous measurement, results are subject to potentially wide variations due to the natural changes in vibration magnitudes, contact forces and transducer positioning that can occur. Further uncertainties in measurement results arise when using an adaptor in the palm of the hand due to resonances of the adaptor on the resilient material of the glove. Such resonances can occur within the frequency range of interest for hand-arm vibration and consequently they can have a considerable influence on the results obtained.
Triaxial measurements of the performance of anti-vibration gloves (continued)
BACKGROUND
Although work has been done to investigate the performance of gloves in one axis, there has been little work to investigate the vibration attenuation (or amplification) of a glove, based on triaxial measurements. Where studies have been done they have not involved simultaneous measurements at the surface of the handle and inside the glove.
It is important to realise that there are many limitations to the use of data produced by even the simultaneous measurement technique for estimating the attenuation provided by a glove. As well as the effects of resonance of the adaptor, the data may only be valid in work situations where the contact forces such as grip and feed forces are the same or similar to those used for the test. There are also other variables that can influence the results of transmissibility measurements, such as physical characteristics of the wearer, temperature, humidity etc. Therefore, the approach adopted in this study has been to make a very basic estimation of the potential that the glove has to protect the wearer. It is definitely not advisable to incorporate the type of assessment described here in to a vibration risk assessment with the aim of extending the length of time for which a particular machine can be used.
CONCLUSIONS
The Control of Vibration at Work Regulations (2005) require assessment of vibration exposure in three orthogonal axes. Consequently, any test to assess the performance of an anti-vibration glove, whether for the purposes of declaration, or as part of a risk assessment, should take account of the likely properties of the glove in three axes. To achieve this, it is necessary to consider the properties and performance of a glove in shear as well as in compression modes.
The use of an adaptor in the palm of the hand to measure transmissibility of a glove, is the technique applied in BS EN ISO 10819:1997. It has been shown that the use of an adaptor can heavily influence the results, whether measurements are made under controlled conditions in the laboratory using a shaker, or by measuring directly on a tool handle.
Indications from the evaluation of glove transmissibility made using a shaker in the laboratory show that for the two tools for which the manufacturer is advocating glove use, the glove may provide up to a 30% reduction in the total frequency weighted vibration transmitted to the hand in some instances. In other instances, results show that the glove may cause 3% amplification of the total value. The glove was shown to provide good reduction in vibration transmission in all axes at frequencies above 400Hz.
The attempts reported here to make triaxial measurements of the performance of anti-vibration gloves on the handles of real machines showed that it was not possible to make a satisfactory reference measurement, i.e. to get agreement between simultaneous measurements on the handle and at the palm of the bare-hand. The conclusion is therefore that, any data obtained by using an adaptor for triaxial evaluation of gloves on real machines should be regarded with great caution.
Triaxial measurements of the performance of anti-vibration gloves (continued)
CONCLUSIONS (continued)
The vibration attenuating performance of the glove tested here is shown to be heavily dependent on the main operating frequency of the tool with which the glove will be used as well as the individual operator and the grip and feed force which will be applied by the operator during its use. Therefore it would be necessary to make individual assessments of the properties and performance of a glove for each tool and operator combination to meet the requirements of the PPE at Work Regulations 1992 and even this level of assessment could be subject to considerable uncertainty.
The vibration reducing potential of the gloves tested is small and uncertain and includes the potential for amplification. Gloves cannot be relied upon to reduce an operator’s exposure to vibration, even when the vibration characteristics of the tool are known.
Further work is necessary to develop a satisfactory test method for assessing the performance of anti-vibration gloves in three axes.
Copyright © 2016 Unity Occupational Health & Wellbeing Limited, All rights reserved.
