Volume 19, Issue 1 (2022)
ioh 2022, 19(1): 270-284 |
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Research code: A-11-61-6
Ethics code: IR.zums.REC.1398.453
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zabehi M, Azimi Pirsaraei S R, hajizadeh R, fallah R. Assessment of workers' exposure to hand-arm vibration of impact wrench in heavy vehicles punctured shops and provide vibration control methods. ioh 2022; 19 (1) : 18
URL: http://ioh.iums.ac.ir/article-1-3304-en.html
URL: http://ioh.iums.ac.ir/article-1-3304-en.html
, roohalahhajizade@gmail.com
Abstract: (1310 Views)
Introduction
In today's world, with the advancement of technology, hand tools that required the physical strength of the body have given way to electric and pneumatic tools. Despite all the advantages that these tools have, there are many limitations and problems due to their use for people, including sound and vibration. Most different machines and tools produce vibrations in varying proportions, the forces and effects of which are transmitted to the body through the hands called hand-arm vibration (HAV) 1. These vibrations can cause cardiovascular, neurological, or skeletal disorders in the upper extremities. Hand-transmitted vibration (HTV) 2 can also lead to peripheral neuropathy syndrome, whose symptoms include numbness, impaired sensory perception (tremor, cold, heat, pain), and loss of hand skills. Another complication of hand-arm vibration is blood vessel spasm, which is a clinical manifestation of the white finger phenomenon and varies depending on the intensity and duration of hand contact and the amount of hand-arm vibration. This study was performed in heavy machine puncture workshops. In punctures, workers use an Impact wrench to unscrew and tighten the machine wheel bolts. Using this wrench exposes operators to sound and vibration. The aim of this study was to Evaluation of workers' exposure to hand-arm vibration of impact wrench in heavy vehicles puncture shops and providing control methods
Method
This study was conducted with the participation of 20 employees of heavy vehicles puncture workshops who worked in different workshops with different Impact wrenches and were randomly selected. At first, the personal Demographic of the employees such as age, work experience, height, weight and level of education and the characteristics of the Impact wrench including weight, power, function life and manufacturer were recorded.
Hand-arm vibration measurement
GA2003 HARM VIBRATION METER made by CASTEL with a piezo electric T-shaped sensor was used to measure hand-arm vibration. Measurements were performed on the X, Y and Z axes according to ISO 5349-1. The effective vibration acceleration was measured in RMS mode and using a HARM filter. Then the effective total value vibration acceleration was calculated using Equation 1.
ahv: total value effective vibration acceleration ( 
( ahwx: X-axis effective vibration acceleration ( ( ahwy: Y-axis effective vibration acceleration ( ( ahwz: Z -axis effective vibration acceleration ( (
1. Hand Arm Vibration
2. Hand Transmission Vibration
Image (1). Pneumatic wrench on the left, a worker using it on the right
There are about 10 screws in each wheel of heavy machinery, considering that the time required to open and close the screws of a wheel is 3 minutes, and considering the average number of wheels that can be opened and closed by one person during a day ( 20 wheels per day) The average exposure time was calculated as 1 hour, then using Equation No. 2, the effective acceleration equivalent to 8 hours of exposure per person was calculated and the results were compared with the allowable occupational exposure threshold of the country.
A (8): the amount of effective vibration acceleration is equivalent to daily exposure
ahv: the total value effective vibration acceleration
T: the vibration exposure time
T0: the base time which is 8 hours per day.
Result:
Mean personal Demographic including age, work experience, weight and height were 36
8.97 years, 10.55 7.52 years, 
10.86 kg and 175 4.9 cm, respectively.
The mean characteristics of pneumatic wrenches including torque (power), weight and function life were 2750
N/M, 13.7 2.04 Kg and 1.45 1.05 years, respectively. 50% of the wrenches belonged to Genius Company, 25% to TAITIAN Company and 25% to other companies.
The maximum effective acceleration measured in the front handle of the Impact wrench was 20.35 on the Z axis. The mean effective acceleration of vibration in the front handle on the X, Y and Z axes was 16.95 
8.98 , 18.35 6.93 and 20.35 10.39 , respectively. Also, the total value of the effective vibration acceleration for the front handle was 32.34 
14.88 . Measurements performed on the rear handle of the Impact wrench showed that the total value of effective vibration acceleration for the rear handle was 45.22 21.99 and the maximum effective acceleration measured was 28 on the Z axis. The mean effective acceleration of hand-arm vibration in the rear handle of the Impact wrench in the X, Y and Z axes was 22.85 12.79 , 25.2 8.78 and 28 15.9 , respectively.
The mean effective vibration acceleration obtained after using felt in the tool handle on X, Y and Z axes was 7.1 1.33 , 8.25 1.69 and 7.2 ± 2.1 , respectively. The Vibration total value of effective acceleration of three-way vibration after using felt was 13.27 
2.57 . The maximum vibration reduction was related to the Z axis. The mean effective vibration acceleration obtained after using elastomer in the Impact wrench category in X, Y and Z axes was 14.45 6.06 , 17.15 6.68 , 14.45 6.06 , respectively. The mean Vibration total value of effective three- axes vibration acceleration after elastomer use was 29.21 10.76 .
The mean vibration acceleration of the 8-hour exposure of the Impact wrench with the exposure time of 1 hour per day is 16.38 7.58 and is higher than the allowable occupational exposure limit (5 ). The mean effective vibration acceleration of the 8-hour exposure after using felt whit Exposure time of 1 hour per day was 4.67 0.887 which is less than the allowable daily exposure limit and more than the action limit (2.5 ). The mean effective vibration acceleration of exposure 8 hours after elastomer use was 10.18 3.78, which is higher than the occupational exposure limit.
Comparison of the means of the three modes of the total value of effective vibration acceleration of Impact wrench vibration, the total value of effective vibration acceleration after felt application and the total value effective vibration acceleration after elastomer application in Impact wrench handle, showed that the reduction of effective hand-arm vibration acceleration by using felt and elastomer in Impact wrench is significant (P <0.05). Also, according to the obtained results, felt is more efficient than elastomer and reduces the effective acceleration of hand-arm vibration to a greater extent, which is also a significant reduction of vibration (P <0.05).
Graph of changes in mean effective vibration acceleration
Evaluation of the relationship between Impact wrench vibration total value with power (torque), weight and function life variables showed that there is a significant relationship between power (torque), Impact wrench and hand-arm vibration total value (p <0.05) and As the power increases, the vibration rate increases. But there was no significant relationship between the variables of Impact wrench weight and function life with the total value of effective acceleration of hand-arm vibration caused by Impact wrench.
Discussion
The aim of this study was to evaluate the exposure of heavy machinery puncture workshop workers to hand-arm vibration caused by Impact wrenches and to provide control strategies. According to the results, the amount of hand-arm vibration caused by the Impact wrench is more than the allowable occupational exposure limit of the country and the highest vibration is in the rear handle of the Impact wrench and in the z axis (28). It is effective and increases the amount of hand-arm vibration by increasing it. The use of felt and elastomer in the Impact wrench category significantly reduced hand-arm vibration.
The most effective acceleration of the hand-arm vibration was in the rear and front handles of the Impact wrench in the Z axis. The Z direction is along the length of the hand (from the fingertips to the arm) and when working with an Impact wrench is the maximum force and pressure applied to the back, i.e. in the direction of the hand. Therefore, most of the vibration is in the Z direction and in the same direction as the force generated by the Impact wrench.
The maximum reduction in hand-arm vibration was by using felt on the Z axis and the maximum reduction was by using elastomer on the Y axis. Felt reduced by 70% and elastomer reduced by 43% the effective acceleration of hand-arm vibration caused by the Impact wrench. Although the results of repeated measures statistical tests showed that both coatings used in the Impact wrench handle significantly reduce hand-arm vibration caused by the Impact wrench, but the use of felt due to higher efficiency and the greatest reduction in hand - arm vibration in the Z axis (the maximum amount of vibration is caused by the Impact wrench in this axis) Can have a greater effect in reducing hand-arm vibration.
According to the obtained results, the power or torque of the Impact wrench affects the vibration of the Impact wrench and with increasing torque, the amount of hand-arm vibration also increases. Statistical analysis by linear regression method also showed a significant relationship between Impact wrench strength and effective vibration acceleration (P <0.05), but there was no significant relationship between vibration and two variables of weight and function life. The amount of use of the Impact wrench during its function life is important and with the increase of the operating time of the Impact wrench, its power decreases so that in some cases it does not have the necessary efficiency to open and close the screws and employees are forced to change their Impact wrench. On the other hand, it is possible to increase the vibration rate by increasing the function life of the Impact wrench and the Depreciation of its parts. It seems that these two issues, i.e. increasing the Depreciation of parts and decreasing the power of the Impact wrench, neutralize the effect of each other on the resulting vibration. As a result, increasing the function life of the Impact wrench does not have a significant effect on hand-arm vibration.
Conclusion
In heavy machine puncture workshops, the level of daily occupational exposure of employees with hand-arm vibration caused by Impact wrenches is higher than the allowable occupational exposure of the country. The use of felt in the handle of the Impact wrench reduced by 70% and the elastomer reduced the vibration of the hand-arm by 43%, so the use of elastomer coatings and especially felt in the tool handle can be a good way to control the effective acceleration of hand-arm vibration.
In today's world, with the advancement of technology, hand tools that required the physical strength of the body have given way to electric and pneumatic tools. Despite all the advantages that these tools have, there are many limitations and problems due to their use for people, including sound and vibration. Most different machines and tools produce vibrations in varying proportions, the forces and effects of which are transmitted to the body through the hands called hand-arm vibration (HAV) 1. These vibrations can cause cardiovascular, neurological, or skeletal disorders in the upper extremities. Hand-transmitted vibration (HTV) 2 can also lead to peripheral neuropathy syndrome, whose symptoms include numbness, impaired sensory perception (tremor, cold, heat, pain), and loss of hand skills. Another complication of hand-arm vibration is blood vessel spasm, which is a clinical manifestation of the white finger phenomenon and varies depending on the intensity and duration of hand contact and the amount of hand-arm vibration. This study was performed in heavy machine puncture workshops. In punctures, workers use an Impact wrench to unscrew and tighten the machine wheel bolts. Using this wrench exposes operators to sound and vibration. The aim of this study was to Evaluation of workers' exposure to hand-arm vibration of impact wrench in heavy vehicles puncture shops and providing control methods
Method
This study was conducted with the participation of 20 employees of heavy vehicles puncture workshops who worked in different workshops with different Impact wrenches and were randomly selected. At first, the personal Demographic of the employees such as age, work experience, height, weight and level of education and the characteristics of the Impact wrench including weight, power, function life and manufacturer were recorded.
Hand-arm vibration measurement
GA2003 HARM VIBRATION METER made by CASTEL with a piezo electric T-shaped sensor was used to measure hand-arm vibration. Measurements were performed on the X, Y and Z axes according to ISO 5349-1. The effective vibration acceleration was measured in RMS mode and using a HARM filter. Then the effective total value vibration acceleration was calculated using Equation 1.
| Equation(1) |
1. Hand Arm Vibration
2. Hand Transmission Vibration
Image (1). Pneumatic wrench on the left, a worker using it on the right
There are about 10 screws in each wheel of heavy machinery, considering that the time required to open and close the screws of a wheel is 3 minutes, and considering the average number of wheels that can be opened and closed by one person during a day ( 20 wheels per day) The average exposure time was calculated as 1 hour, then using Equation No. 2, the effective acceleration equivalent to 8 hours of exposure per person was calculated and the results were compared with the allowable occupational exposure threshold of the country.
| Equation (2) |
A (8): the amount of effective vibration acceleration is equivalent to daily exposure
ahv: the total value effective vibration acceleration
T: the vibration exposure time
T0: the base time which is 8 hours per day.
Result:
Mean personal Demographic including age, work experience, weight and height were 36
8.97 years, 10.55 7.52 years, 10.86 kg and 175 4.9 cm, respectively.The mean characteristics of pneumatic wrenches including torque (power), weight and function life were 2750
N/M, 13.7 2.04 Kg and 1.45 1.05 years, respectively. 50% of the wrenches belonged to Genius Company, 25% to TAITIAN Company and 25% to other companies.The maximum effective acceleration measured in the front handle of the Impact wrench was 20.35
8.98 6.93 10.39 14.88 21.99 12.79 8.78 15.9 The mean effective vibration acceleration obtained after using felt in the tool handle on X, Y and Z axes was 7.1
1.33 1.69 2.57 6.06 6.68 6.06 10.76 The mean vibration acceleration of the 8-hour exposure of the Impact wrench with the exposure time of 1 hour per day is 16.38
7.58 and is higher than the allowable occupational exposure limit (5 0.887 which is less than the allowable daily exposure limit and more than the action limit (2.5 3.78, which is higher than the occupational exposure limit.
| effective vibration acceleration is equivalent to 8 hours of exposure | |||||
| Row | Variable | Mean ( |
SD | Min | Max |
| 1 | Equivalent acceleration related to 8 work hours exposure | 16.38 | 7.58 | 7.46 | 29.37 |
| 2 | Equivalent acceleration related to 8 work hours exposure using felt | 4.67 | 0.887 | 2.57 | 5.99 |
| 3 | Equivalent acceleration related to 8 work hours exposure using elastomer | 10.18 | 3.78 | 6.41 | 16.08 |
Comparison of the means of the three modes of the total value of effective vibration acceleration of Impact wrench vibration, the total value of effective vibration acceleration after felt application and the total value effective vibration acceleration after elastomer application in Impact wrench handle, showed that the reduction of effective hand-arm vibration acceleration by using felt and elastomer in Impact wrench is significant (P <0.05). Also, according to the obtained results, felt is more efficient than elastomer and reduces the effective acceleration of hand-arm vibration to a greater extent, which is also a significant reduction of vibration (P <0.05).
Graph of changes in mean effective vibration acceleration
Evaluation of the relationship between Impact wrench vibration total value with power (torque), weight and function life variables showed that there is a significant relationship between power (torque), Impact wrench and hand-arm vibration total value (p <0.05) and As the power increases, the vibration rate increases. But there was no significant relationship between the variables of Impact wrench weight and function life with the total value of effective acceleration of hand-arm vibration caused by Impact wrench.
Discussion
The aim of this study was to evaluate the exposure of heavy machinery puncture workshop workers to hand-arm vibration caused by Impact wrenches and to provide control strategies. According to the results, the amount of hand-arm vibration caused by the Impact wrench is more than the allowable occupational exposure limit of the country and the highest vibration is in the rear handle of the Impact wrench and in the z axis (28). It is effective and increases the amount of hand-arm vibration by increasing it. The use of felt and elastomer in the Impact wrench category significantly reduced hand-arm vibration.
The most effective acceleration of the hand-arm vibration was in the rear and front handles of the Impact wrench in the Z axis. The Z direction is along the length of the hand (from the fingertips to the arm) and when working with an Impact wrench is the maximum force and pressure applied to the back, i.e. in the direction of the hand. Therefore, most of the vibration is in the Z direction and in the same direction as the force generated by the Impact wrench.
The maximum reduction in hand-arm vibration was by using felt on the Z axis and the maximum reduction was by using elastomer on the Y axis. Felt reduced by 70% and elastomer reduced by 43% the effective acceleration of hand-arm vibration caused by the Impact wrench. Although the results of repeated measures statistical tests showed that both coatings used in the Impact wrench handle significantly reduce hand-arm vibration caused by the Impact wrench, but the use of felt due to higher efficiency and the greatest reduction in hand - arm vibration in the Z axis (the maximum amount of vibration is caused by the Impact wrench in this axis) Can have a greater effect in reducing hand-arm vibration.
According to the obtained results, the power or torque of the Impact wrench affects the vibration of the Impact wrench and with increasing torque, the amount of hand-arm vibration also increases. Statistical analysis by linear regression method also showed a significant relationship between Impact wrench strength and effective vibration acceleration (P <0.05), but there was no significant relationship between vibration and two variables of weight and function life. The amount of use of the Impact wrench during its function life is important and with the increase of the operating time of the Impact wrench, its power decreases so that in some cases it does not have the necessary efficiency to open and close the screws and employees are forced to change their Impact wrench. On the other hand, it is possible to increase the vibration rate by increasing the function life of the Impact wrench and the Depreciation of its parts. It seems that these two issues, i.e. increasing the Depreciation of parts and decreasing the power of the Impact wrench, neutralize the effect of each other on the resulting vibration. As a result, increasing the function life of the Impact wrench does not have a significant effect on hand-arm vibration.
Conclusion
In heavy machine puncture workshops, the level of daily occupational exposure of employees with hand-arm vibration caused by Impact wrenches is higher than the allowable occupational exposure of the country. The use of felt in the handle of the Impact wrench reduced by 70% and the elastomer reduced the vibration of the hand-arm by 43%, so the use of elastomer coatings and especially felt in the tool handle can be a good way to control the effective acceleration of hand-arm vibration.
Article number: 18
Type of Study: Research |
Subject:
Vibration
Received: 2021/09/19 | Accepted: 2022/05/8 | Published: 2022/11/12
Received: 2021/09/19 | Accepted: 2022/05/8 | Published: 2022/11/12
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