Qualitative versus Quantitative evaluation of Whole body Vibration Qualitative versus Quantitative evaluation of Whole body Vibration. Are employees a reliable source in determining vehicle vibration risk? Dale Kennedy (MSc. Ergonomics) Certified Professional Ergonomist This presentation is the intellectual property of Ergomax Holdings Pty (Ltd.) ©

Sample population n=607 – ongoing projects. Sample from range of underground and open pit mine through out Southern Africa

Often one relies on the operators self report of vibration to assess the likelihood of vibration risk of the vehicle. This presentation investigates the relationship between operator perception and vibration magnitude. During the numerous surveys there appeared to be little reliability in operator perception and the corresponding vibration magnitude dose and reported symptoms of pain and discomfort.

Whole-body vibration can cause fatigue, stomach problems, headache, loss of balance and "shakiness" shortly after or during exposure. occupational exposure to whole-body vibration could have contributed to a number of circulatory, bowel, respiratory, muscular and back disorders. The combined effects of body posture, postural fatigue, dietary habits and whole-body vibration are the possible causes for these disorders.

A review of clinical studies, medical evidence, differential diagnostic evaluation protocols, surveillance programs, national and international standards established that with an increasing duration and intensity of occupational WBV exposure, primarily musculoskeletal or neurological disorders of the spine occur. Other organ damage has also been reported. (Johanning: 2015) Workers with whole-body vibration exposure report a variety of physical disorders. Health and safety providers may not recognize such injuries, or may be unfamiliar with exposure assessment and prevention. 

Falls from nonmoving vehicles (53 fatalities) were the fourth most frequent type of fatal fall to a lower level (Bureau Labor Statistics) Whole-body vibration (WBV) has been thought to be a contributing factor to loss of balance, more specifically, falls while descending from a vehicle.

Limits for occupational exposure Directive 2002/44/EC (ISO 5349), prepared under contract for the European Commission Directorate General Employment, Social Affairs and Equal Opportunities, has set a daily exposure action value of 0.5 m/s2 and daily exposure limit value of 1.15 m/s2 for whole- body vibration. ISO 2631 Part 1: Evaluation of human exposure to whole-body vibration -- Part 1: General requirements and Total exposure limits

Methodology In field testing made use of the SVANTEK 106. Human vibration meter and analyser, SV38V – seat accelerometer. Risk calculator used to assess vibration risk is aligned directly to those published by the Health and Safety Executive and quantifies the risk accordingly. Testing was conducted for a minimum of 1 hour whilst drivers were requested to drive their normal route within the mines.

Discussion The tentative results appear that operators only correctly perceive vibration risk 76% of the time when the vibration magnitude is above the daily exposure limit value of 1.15 m/s2. However when vibration is between the daily exposure action value and daily exposure limit value (0.5 m/s2 - 1.15 m/s2) operators reported excessive vibration levels 56% of the time. A concern is when the quantified vibration magnitude was below the daily exposure action values in other words, scored as minimal risk, operators still perceive excessive vibration 52% of the time.

Statistical analysis Null Hypothesis: No difference in employee perception between vibration exposure levels. Chi-Squared test with 5% confidence level P Values scored at: 0.100 Have to accept that the perception of vibration is random. Employees are not able to correctly identify the vibration magnitude. Similar results with perceptions of discomforts, they too were randomly distributed.

These tentative finding suggest that the operators perception of vibration is not only based on the vibration magnitude of the vehicle. There clearly are other factors (duration, posture…) at play causing discomfort- not necessarily the vibration. Operator perception of vibration may be a poor indicator of vehicle vibration risk. Reports of Lower back pain appears to be completely independent of vibration magnitude. These results indicate that one should not rely on employee self- report of vibration magnitude before the vehicle is addressed.