Hand-arm-vibration measurement inaccurancy at workplaces

Status:

completed 03/2014

Aims:

In order for the reliability of measurement results to be assessed, the measurement uncertainty must be determined. Determining the quality of measurement results obtained by different test bodies requires the associated measurement uncertainty to be recorded, particularly when these results are input into databases. The measurement uncertainty is also needed for the validation of risk analyses, for prognoses of vibration reduction, and for programmes conducted for this purpose. Since direct application of ENV 13005 (GUM) is not possible at reasonable expense, the advisory council of the DIN Acoustics, Noise Control and Vibration Engineering Standards Committee (NALS) has begun developing a guidance document for the areas of noise and vibration. The knowledge available in the area of vibration quantities is still minor. Factors influencing the sources of uncertainty that can be determined only experimentally by comparative measurements remain unknown. The objective of the project is to determine values for the uncertainty associated with test bodies that are suitable for use in practice to determine the correctness and precision of workplace measurements.

Activities/Methods:

The project was conducted jointly by the IFA and the IAG. Support for the aspect of the independent observer and neutral interpretation was provided by the IfEP (Institute for Proficiency Tests) in Marl. In order to determine the influencing parameters, measurements were conducted by different test bodies, at the same workplace, with use of the same equipment and on the same test subjects (i.e. round-robin testing at the workplace). Since this would have placed an unacceptable burden upon an actual company, a model workplace was set up at the IAG's practical facility. Two experienced test subjects and three different operating principles and drive types were selected. The measurements were conducted by the test bodies on different days, completely separately from each other, but with a neutral observer. Test bodies from the accident insurance institutions, inspection bodies, institutes, engineering offices and the German Länder authorities were involved.

Results:

The results were evaluated based upon statistical methods by means of which the inclusion of outliers obtained by individual test bodies was reduced to a minimum. The correctness and pre-cision of the results obtained by the test bodies and the comparison, repetition and laboratory-specific uncertainties were calculated. The results were presented and discussed in the "Uncertainty of vibration quantities" sub-committee of the DIN/VDI Standards Committee A-coustics, Noise Control and Vibration Engineering (NALS). The guideline values obtained from the round-robin test were incorporated into Annex A of DIN SPEC 45660-2, Guide for dealing with uncertainty in acoustics and vibration – Part 2: Uncertainty of vibration quantities. Publicati-on of the draft of the prestandard is planned for the end of 2014. This provides guideline values for calculation of the measurement uncertainty to GUM for workplace measurements, on the basis of which the confidence interval for the risk assessment can also be determined.

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