VIBRATION EXPOSURE ASSESSMENT OF SAWMILLING OPERATIONS USING HAND– ARM–VIBRATION EXPOSURE ANALYSIS

Sawmills are workshops where woods are turned into finished products through the use of industrial machines and sophisticated implements. However, sawmills workers become exposed to awkward working postures and vibration from the machines they work with every day, leading to Raynaud's disease and muscle damage. Therefore, this study investigated the effects of the sawmill-machine-generated vibrations on the musculoskeletal disorders of sawmill workers in the Southwestern part of Nigeria using hand-arm–vibration analysis. Sawmills that were fully functional in Osun, Oyo, Ondo, Ekiti, Lagos, and the Ogun States of the Southwestern part of Nigeria were used for this study. After reconnaissance visits, four sawmills operating at full capacities in two cities of each State (i.e. 2 sawmills per city) were eventually chosen and used for data collection, thereby making a total of 24 selected sawmills. Circular Machines (CMs), Planer Machines (PMs), and Band-saw Machines (BMs) which are the commonly used machines by sawmills were considered for analysis, while two machines each of CMs, PMs, and BMs were also selected in each sawmill, making a total of forty-eight (48) machines each of CMs, PMs, and BMs. Vibration level data were collected in m/s2 using Extech VB 450 vibration meter in triplicates, and the corresponding exposure time was obtained. The vibration acceleration magnitude and exposure time data were collected for six days (Monday to Saturday). The daily Exposure Action Value (EAV), Exposure Limit Value (ELV), and exposure points were then determined for each daily operations of the considered sawmilling machines. The average Wood Vibration Acceleration Magnitude (WVAM) ranges in CMs and PMs in each sawmill were 34.2 – 104.1m/s2 and 104.1 –173.7m/s2 , respectively, while the average Machine Vibration Acceleration Magnitude (MVAM) range in BMs in each sawmill was 10.7 – 48.0m/s2 . Also, the minimum and maximum WVAMs in CMs and PMs and MVAMs in BMs in all sawmills were 32.2/106.7, 99.1/187, and 10.2/49.3m/s2 , respectively. The Analysis of Variance (ANOVA) results revealed that there are statistically significant differences in the WVAMs of CMs and PMs and MVAMs of BMs in all the six states. The vibration exposure analysis showed that none of the average values falls within the limit and action values, because the values were well above the exposure limit value of 400 points. The study concluded that the contributing factors responsible for the high values of the exposure analysis experienced by workers were obsolete machines, lack of proper working tools, worker's carelessness, and general negligence by workers