Considerations on Whole-body Vibration Exposure Evaluation Procedures

Standards on whole-body vibration provide procedures to measure, evaluate and assess exposures and are assuming increasingly influence on important decisions. Nevertheless, the International Standard ISO 2631-1 (1997) is not entirely clear on several aspects, which can cause unnecessary confusion and lead to uncertain results. Vibration measurements were performed on a representative sample of 48 urban buses operated at different driving speeds and different ground roughness roads. Root-mean-square acceleration values were obtained on the seat pan for three axes from one-third octave band spectra: fore-and-aft (x), lateral (y) and vertical (z). The ISO 2631-1 (1997) standard evaluation procedures were applied and discussed. It seems that this standard tends to underestimate risks from exposure to whole-body vibration, and therefore tolerates longer daily exposures to this particular type of motion.
Keywords: 
whole-body vibration, evaluation procedures, standards, bus
Main Author: 
Rui Bettencourt
Melo
Co-authors: 
A. Sérgio
Miguel


Melo, Rui Bettencourt

Departamento de Ergonomia / Faculdade de Motricidade Humana / Universidade Técnica de Lisboa / Estrada da Costa / 1495-688 Cruz Quebrada, Portugal 351 214 149 128 / rmelo@fmh.utl.pt

Miguel, A. Sérgio

Departamento de Produção e Sistemas / Escola de Engenharia / Universidade do Minho / Campus de Azurém / 4800-058 Guimarães, Portugal 351 253 510 369 / asmiguel@dps.uminho.pt

ABSTRACT

Standards on whole-body vibration provide procedures to measure, evaluate and assess exposures and are assuming increasingly influence on important decisions. Nevertheless, the International Standard ISO 2631-1 (1997) is not entirely clear on several aspects, which can cause unnecessary confusion and lead to uncertain results.

Vibration measurements were performed on a representative sample of 48 urban buses operated at different driving speeds and different ground roughness roads.

Root-mean-square acceleration values were obtained on the seat pan for three axes from one-third octave band spectra: fore-and-aft (x), lateral (y) and vertical (z). The ISO 2631-1 (1997) standard evaluation procedures were applied and discussed.

It seems that this standard tends to underestimate risks from exposure to whole-body vibration, and therefore tolerates longer daily exposures to this particular type of motion.

Keywords

Whole-body vibration, evaluation procedures, standards, bus.

INTRODUCTION

Occupational exposure to whole-body vibration occurs in a wide range of working environments. Industrial, construction, mining and forestry equipment operators as well as most forms of transportation drivers (buses, trucks, rail vehicles, airplanes, helicopters, and boats) are among the professionals submitted to this stress factor almost daily. It is recognized worldwide that this exposure can put the human being at risk and impair comfort, the human work capacity and health. Therefore, it is desirable to have methods capable of predicting the conditions responsible for it. This implies means of measuring vibration (e.g. to obtain a numerical indication of the vibration),

means of evaluating vibration (e.g. to obtain a measure of the vibration severity), and means of assessing its severity (e.g. to predict the likely consequences of exposure) [1]. Standards on the human vibration domain provide those means and are assuming increasingly influence on important decisions, such as equipment orders, employees’ legal claims against their employers, and litigation against machines’ manufacturers.

The European Parliament and the Council of the European Union have recently adopted a new Directive [2] on the minimum health and safety requirements regarding the exposure of workers to the risks arising, or likely to arise, from vibration. It was considered necessary to introduce measures protecting workers from vibrations due to their effects on the health and safety of workers, in particular muscular/bone structure, neurological and vascular disorders. This new European Directive recommends the International Standard ISO 2631-1 (1997) [3] guidelines to be followed when measuring, evaluating and assessing whole-body vibration exposures. Thus, ISO standard’s methods for vibration measurement, evaluation and assessment are expected to be unambiguous and accurate. However, this seems not to be the case. Some of the procedures recommended by the standard are not entirely clear causing unnecessary confusion and leading to uncertain results.

These documents should be clear, precise and based on scientific evidence but unfortunately standards do not conform to the principles of published scientific work often [1].

Griffin [1] already compared three existing standards in detail: ISO 2631/1 (1985) [4], BS 6841 (1987) [5] and ISO 2631-1 (1997) [3]. He also applied the corresponding procedures with Lewis [6] and Paddan [7] to different transport environments. McPhee et al. [8] have done a similar work. All of them revealed differences between the frequency weightings, averaging procedures and assessment methods.

The present study discusses some of the procedures established by ISO 2631-1 (1997) standard [3].

MATERIALS AND METHODS

Vibration Measurement

Acceleration was measured at the driver’s seat with piezoelectric accelerometers. A triaxial Brüel