Whole Body Vibration (WBV) Evaluation of Solid Rubber and Filled Pneumatic Tires on a Test Course. Rome, GA July 19-20, 2016

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1 Whole Body Vibration (WBV) Evaluation of Solid Rubber and Filled Pneumatic Tires on a Test Course Rome, GA July 19-20, 2016 Helmut W. Paschold, Ph.D., CSP, CIH Safety Consultant 191 Siebert Lane Apollo, PA Purpose of the Study This study measured and recorded total vibration and whole body vibration (WBV) levels on a Telehandler at a constructed test track facility at 349 Burlington Road, Rome, GA. The study examined differences in vibration levels between the use of solid and polyurethane-fill tires on a single piece of equipment on the track designed to approximate conditions that might be found at an industrial or construction site. Background Vibration transmitted to a vehicle is of great concern. Exposure to constant and severe vibrations will ultimately cause premature fatigue and damage the vehicle components. As vehicles are operated by a riding driver, the effects of vibration on the human component cannot be ignored. The road surface, vehicle components/configuration, and operating speed/style contribute to vibrations within the system.

2 These vibrations are transmitted to the driver from a chassis mounted seat. Reduction of vibration in the vehicle will ultimately reduce the vibration exposure transmitted to the operator. Environmental WBV is transmitted from the contact surface to the whole human body while standing, sitting or reclining. Occupational seated exposure is found with operators of a variety of vehicle categories such as cars, buses, fork-lifts, tractors, trucks and heavy machinery either on or off paved roads (Padden & Griffin, 2002). Locomotive engineers are also exposed to significant levels of WBV (Johanning, et al., 2006). While WBV is not a part of current OSHA standards, the National Institute of Occupational Safety and Health (NIOSH) has conducted research in the area of WBV. In its conclusions about WBV, NIOSH (1997) states: Laboratory studies have demonstrated WBV effects on the vertebra, intervertebral discs, and supporting musculature. Both experimental and epidemiologic evidence suggests that WBV may act in combination with other work-related factors such as prolonged sitting, lifting, and awkward postures to cause increased risk of back disorder. (p. 6-33) WBV exposure and resultant LBP has been recognized as an occupational disease qualifying for compensation in four European countries as of 2002; however, each country s regulations differ significantly with regard to compensation and WBV exposure relative to standards (Hulshof et al., 2002). WBV is measured by the root-mean-square (r.m.s.) using units of m-s -2 in three measurement axes identified as X, Y and Z with a triaxial accelerometer. The European Union (EU) Directives, Physical Agents (Vibration) Directive of June 25, 2002 establishes 0.5 m-s -2 as the action value and 1.15 m-s -2 as the limit value for an eight-hour time weighted average. A vibration dose value (or VDV) is a measure with a more sensitive evaluation of vibrations that include shocks. The units for VDV are m-s and are cumulative values requiring normalization to actual hours operated. When a crest factor, CF, (ratio of the maximum peak to the average) exceeds 7 or 8, the VDV is generally consider a more reliable measurement of human exposure. Johanning, E., Landsbergis, P., Fischer, S., Christ, E., Göres, B., & Luhrman, R. (2006). Whole-body vibration and ergonomic study of US railroad locomotives. Journal of Sound and Vibration, 298(31), National Institute of Occupational Safety and Health (NIOSH). (1997). Musculoskeletal Disorders and Workplace Factors. DHHS (NIOSH) Publication No Paddan, G. S. & Griffin, M. J. (2002). Evaluation of whole-body vibration in vehicles. Journal of Sound and Vibration, 253(1), Hulshof, C., Van der Laan, G., Braam, I., & Verbeek, J. (2002). The fate of Mrs. Robinson: Criteria for recognition of whole-body vibration injury as an occupational disease. Journal of Sound and Vibration, 253(1),

3 Testing: Location/Date Final onsite testing was conducted at the Rome, GA site on Wednesday, July 20, Trial test runs to assure optimal data collection methods were made on the previous day. Test Vehicle The vehicle was a JLG Industries, Inc. Telehandler Model# 6036 T4F manufactured in 2016 supplied by Sunbelt Rentals. The Milsco seat was set in the mid-adjustment position by the operator. Tires Tires were installed by a crew retained by Accella. 1. Solid aperture tires 2. Armstrong tires filled with Accella polyurethane product 3

4 Vibration Monitoring A Larson Davis HVM100 human vibration meter was connected to a triaxial accelerometer seat pad placed on the vehicle seat. The HVM100 is configured to produce data compliant with the International Standards Organization (ISO) requirements for WBV monitoring. The unit was factory calibrated in May An Apple iphone 6 using a newly released smartphone application, WBV by Byte Works, Inc. 2014, measured WBV using methods prescribed in ISO2631.1, and reports accuracy close to gold standard instruments. The iphone was secured with duct tape below the operator (and seat pad) on the vehicle cab floor. It was oriented such that the X and Y axes were switched to allow easier operation and alignment. The cab floor measurement is valuable because it depicts the WBV potential delivered to the seat and the seating structure. A vehicle seat should reduce WBV; however, it is possible for a seat to amplify WBV, especially in the lower frequency range. 4

5 Test Course and Vehicle Operation The Telehandler was operated on a test course laid out and constructed by Accella personnel. The course attempted to simulate conditions, which may be found at a construction site or other rough terrain. The course was approximately 800 feet in length configured in a long axis figure eight. Three 2x4s and three 4x4s with 50 foot spacing in between were secured to the second quarter of the track. Other preexisting irregularities were kept in place. Loose debris that could easily shift was removed to help assure the vehicle encountered the same obstructions consistently in all trial runs. A prior attempt in May 2016 to test tire types at an established test track presented too many unrealistic conditions to offer highly reliable, repeatable data. Test trials were run on Tuesday, July 19, 2016 to identify operational conditions and establish uniform monitoring protocol. The test results were obtained the following day, July 20, 2016, with the two tire types and loaded/unloaded conditions. One person drove all test runs at an approximate speed of 5 mph. The use of a single driver removed a number of confounding variables by assuring an identical weight load on the seat pad accelerometer and near-identical driving patterns on the course during all runs. Each tire set was subject to six runs, without a load (unloaded) and with a plastic container filled with colored water estimated to weigh 2,000 pounds (loaded). 5

6 Results: WBV is evaluated according to the dominant axis, which is the Z-axis for all data recorded. The lowest observed Z-axis r.m.s value on the cab floor was running the Armstrong tires unloaded as shown in Table 1. With r.m.s., no significant difference (using SPSS software) was found between loaded/unloaded within each tire type; however, the mean WBV values of each tire type were significantly different than the other tires, reference Table 4. The combined Z-axis WBV values were 48% and 91% higher for the AP and Lightning tires respectively when compared to the Armstrong. Table 1. iphone r.m.s. data obtained on cab floor below seat WBV, r.m.s., cab floor below seat 2 Tires, Telehandler loaded and unloaded separate Axis x y z Tire/Run SD/AVG SD/AVG SD/AVG N AP loaded AP unloaded % > min value Armstrong loaded Armstrong unloaded Tires, Telehandler loaded and unloaded combined AP Armstrong The HVM 100 WBV data on the seat surface was also Z-axis dominant. The HVM 100 WBV data is reported in Table 2, combining and averaging all trial runs for each tire. Comparing these values to those in Table 1, it appears the seat amplified WBV with the use of the AP and Armstrong tires. 6

7 Table 2. All trials combined HVM 100 r.m.s. data collected between seat and driver WBV, r.m.s., between driver and seat, set values combined Axis x y z Tire type AVG AVG AVG % > min value AP Armstrong Table 3. iphone VDV data obtained on cab floor below seat. WBV, VDV(8), cab floor below seat 2 Tires, Telehandler loaded and unloaded separate Axis z N % > min value Tire/Run SD/AVG AP loaded AP unloaded Armstrong loaded Armstrong 2.75 unloaded Tires, Telehandler loaded and unloaded combined AP Armstrong A review of the HVM 100 data for the various trial runs showed CFs over 20, indicating a large presence of shock in the vibration data. For this reason, a CF > 7, the VDV values presented in Table 3 present a better assessment of human exposure to the WBV. Statistical analysis of the data in Table 3 (VDV) found a significant difference between the tire types and also loaded/unloaded conditions at the.05 significance level Table 4. If the unloaded values only are used, the AP tires are 54% and higher than the Armstrong unloaded. 54 7

8 Similarly for loaded, they are 43% higher. The differences in the VDV values are very similar to those of the r.m.s. Table 4. Statistical analysis of differences between loaded/unloaded VDV values. Conclusions: The Armstrong tires clearly presented the lowest WBV values, both r.m.s. and VDV, loaded and unloaded, among the tires both on the cabin floor and seat/operator interface. In summary: WBV r.m.s. loaded/unloaded cabin floor trials combined, comparing AP to the Armstrong: Armstrong 0.87 AP % Similarly, the WBV VDV loaded/unloaded cabin floor trials combined, comparing AP to the Armstrong: Armstrong AP % The WBV differences are not random, but are significant. The data obtained on the cabin floor should be of greatest interest as it discounts the effects of the vehicle seat. Careful selection of an effective properly adjusted vibration-attenuating seat coupled with the use of Accella polyurethane fill in select tires can greatly reduce WBV exposure levels and associated human health risk. Helmut W. Paschold, Ph.D., CSP, CIH August 8,