KEYWORDS: workshop, sound level meter, time weight average, dose, noise exposure.

Transcription

1 ASSESSMENT OF NOISE LEVEL FOR LATHE MACHINE AND FITTING WORKSHOP Asmira Ashari Department of Mechanical Engineering, Politeknik Sultan Salahuddin Abdul Aziz Shah, Norasiah Muhammad Department of Mechanical Engineering, Politeknik Sultan Salahuddin Abdul Aziz Shah Mohd Shahrom Ismail Department of Mechanical Engineering, Politeknik Sultan Salahuddin Abdul Aziz Shah ABSTRACT In engineering a hearing level cannot be generalized to be similar for workshop activities, as noise exposure varies depending on application work activities, types of materials and machine, the layout of the workshop and threated guidelines, duration of exposure to noise. Therefore the objective of this study was to assess the level of noise generated in teaching workshops and compare the findings with the guidelines 29 CFR table G-16 (NIOSH 1998).This study only focused on the maximum level of sound production in the workshop base on total number of students involved at a certain period of time. The noise level generated in this workshop had never been assessed before. The management believes, potential risk to the students is still in the safe limit. Time weight average (TWA) and dose percentage method was used to produce the profile of the noise reading measured by the sound level meter in 8 hours every day. Exposure maximum noise level is a determining factor that has been identified by performing output data analysis from time measurements exposure of noise level meters in three days observation. Data in three days were finding total TWA amount and dose each noise level depending with time exposure. In summary, this finding can be used appropriately for the same activity for this shop only. Evaluation measurements should be taken if it involves different activities in the workshop. During the observation, possibility of measuring income difference is not that significant unless there is unexpected activity when measurements are taken. This study also developed for noise risk matrix and noise mapping after identify the measurement location and know dose percentage and TWA amount for each station and rating noise produce. KEYWORDS: workshop, sound level meter, time weight average, dose, noise exposure. 1. INTRODUCTION It cannot be denied that the percentage probability lecturers, technicians and students are exposed to harm in the higher workshop as a threat which is one of the acoustic field. Lecturers and technicians who have spent more time teaching and working in workshops involved with the operation of the machine is at a higher risk for exposure to threats noise. 1

2 Institute for Occupational Safety and Health (NIOSH) had proposed some rules, provide talk sessions and workshops to address noise issues among workers in Malaysia (Occupational Noise Exposure, 1998). Legal Environment in Malaysia had recommended the guideline noise exposure generated from a machine Factories and Machinery which is must not exceed 85 decibel (db) without Personal Protection Equipment (Noise Exposure, 1989). If the level of noise generated in excess of 85 db, the management needs to take some action to handle this problem Legal Research Board. They aim to guarantee the safety and comfort of employees in the workplace and indirectly provide an atmosphere of harmony in the workplace. Noise is one of the most important environment factors, which affects the workers' health and efficiency. Noise can increase the overall workload of operators during a specific task and can affect the performance. As a result, noise affects workers' health directly and indirectly (Malchaire, 2001). Exposure to intense noise has been shown to damage the human hearing process and noise has been labeled as the most pervasive hazardous agent in the workplace (Muzet Alan, 2007). Maximum sound pressure level for 8 hours per day exposure is accepted to be 85 db at frequencies higher than 1000 Hz. At levels lower than this value, the risk of noise becomes the least (Job, 1988). With help of a person who is trained in wear hearing protection, employees can choose the most suitable size and type of hearing protection for their work environment. It is the employer s responsibility to ensure that employees wear hearing protection properly. Employers are responsible for conducting annual training for their employees who are exposed to a TWA of 85 db. The training should cover effects of noise, the pros and cons of different types of protective equipment, aspects of audiometric testing, personal hearing protective devices, and characteristics of noise attenuation of hearing protection (Hawkins et.al,1991). 2. METHODOLOGY The proposed strategy to measure noise exposure, refer to the ISO 9612: This strategy is based on full-day measurements (FDM). The work has been selected by the environmental features that affect sound output to enable a thorough comparison between the size of the output sound different, daily personal exposure level (LEX, 8h), uncertainties related to the time spent in the work area (Hawkins et.al, 1991). Strategy is based Full Day Measurement (FDM) this should be done considering the requirements of each workplace in terms of its exposure characteristics. As stated in ISO 9612: 2009, the selection of the most appropriate strategy (called recommended strategy in the standard) to measure noise exposure will depend on the job characteristics, namely the work type and pattern, including the mobility of the student and the complexity (number and predictability) of the task carried out. 2

3 2.1 Sampling Lathe Workshop Sampling of this study includes 20 unit machines in lathe workshop, which involved 2 lecturers and 20 students from Mechanical Engineering Department. Noise measurements were conducted over three consecutive days for 8 hours but readings for two hours noise exposure are not taken into consideration in data analysis. Placement of three measurement locations where the station 1 (STN 1), station 2 (STN 2) and station 3 (STN 3) was generated simultaneously. 2.2 Sampling Fitting Workshop Sampling of this assessment includes 20 working area in fitting workshop, which involved 2 lecturers and 20 students from Mechanical Engineering Department. Noise measurements were conducted over three consecutive days for 8 hours but reading for 2 hours noise exposure was not taken into consideration in data analysis. Placement of two measurement locations where the station 4 (STN 4) and station 5 (STN5) were generated simultaneously. 3. RESULT AND DISCUSSION Figure 1 shows a graph of data collected in the lathe workshop for Day 1 between STN 1, STN 2 and STN 3. Meanwhile Figure 2 shows a noise level graph in the fitting workshop for Day 1 between STN 4 and STN 5. Measurement time period was taken is 8 hours but in the graph and the data collected is only called up to 6 hours. Included a 6 hours time period to avoid a significant drop when plotting graphs and show total of time exposure to students and other person around in workshop during measurement. To facilitate detection, the method of finding the graph is described by the table and any existing lines in the graph. For ease of data taken up to the first day of the third calculation noise level has been set at a workshop lathe machine. For the fourth day until the sixth day of Sound Level Meter (SLM) has been placed in the workshop fitting. 3

4 Figure 1: Noise Level in Day 1 between STN 1, STN2 and STN3 3.1 Review result of noise level at STN 1, STN 2 and STN 3 in Day STN 1 At maximum line: the value of sound level is increased until at 60 minute. After point 60 minute the value mostly uniform until point 225 minute with 87.3 db. Noise level decrease to 78.3 db at 240 minute and increased to 89.5 db at point 375 minute. The maximum value 90.2 db at point 390 minute., the noise on the line that exceeds 85 db is 3 hours minutes. The frequency of the high readings occur between 9.00am-9.15am,11.00 am to pm and 2.00 pm pm. At minimum line : the value of sound level increased until at point 75 minute. After point 75 minute the value not uniform and sharp increased at point 225 minute with 64.9 db. Noise level decrease at 240 minute are show 49.1 db and cover the minimum value. The simplified data can be referred in Table STN 2 At maximum line: the value of sound level is increased until at point 75 minute with 86.7dB. After point 135 minute the value are not uniform. Noise level decrease to 78.7 db at 240 minute and increased to 86.6 db at point 420 minute. The max value 88.9 db at point 450 minute., the noise on the line that exceeds 85 db is 1 hours 45 minutes. The frequency of the high readings occur between am to pm. At minimum line : the value of sound level increased until at point 75 minute. After point 75 minute the value not uniform until point 480 minute. Minimum noise level at 15 minute are 35.2 db. 4

5 3.1.1 STN 3 At maximum line: the value of sound level is increased until at point 75 minute with 83.7 db. After point 90 minute the value are not uniform. Noise level decrease to 72 db at 240 minute and increased to 83.6 db at point 390 minute. The max value 86.3d B at point 165 minute. the noise on the line that exceeds 85 db is 1 hours. The frequency of the high readings occur between am am. At minimum line the value of sound level start to increase at point 30 minute. After point 90 minute the value not uniform until at point 480 minute with 51.3 db. Noise level decrease at point 30 minute is shown 35.1 db and cover the minimum value. Table 1: Day 1 - STN 1, STN 2 and STN 3 Description at Lathe Machine Workshop STN Max noise level db Min noise level db Exposure Duration exceed PEL hrs hrs 45 min Time of high level 9.00am to 9.15am 11.00am to 12.00pm 2.00pm to 3.45pm 10.00am 12.00pm Remarks Student make initial lathe process hrs 10.45am-11.4am 5

6 Figure 2: Noise level in Day 1 between STN 4 and STN Review result of noise level at STN 4 and STN 5 in Day STN 4 At maximum line: the value of sound level increased until at 30 minute. After point 90 minute the graph not uniform until point 480 minute with 86.2 db. The maximum value of 92.6 db at point 90 minute, the noise on the line that exceeds 85 db is 3 hours minutes. The frequency of the high readings occurs between 9.00 am to am and 3.00 pm to 4.00 pm. At minimum line: the value of sound level increased until at point 30 minute. After point 30 minute the value are not uniform and decreased at point 105 minute with 38.9 db and assume the minimum value. The simplified data is tabulated in Table STN 5 At maximum line: the value of sound level is increased until at point 45 minute with 86.7 db. After point 45 minute the value are not uniform. Minimum noise level decrease to 68.9 db at 375 minute and maximum increased to 98.8 db at point 135 minute. The noise on the line that exceeds 85 db is 1 hours 45 minutes. The frequency of the high readings occur between am to am, 2.00 pm to 2.30 pm and 3.00 to 3.15 pm. At minimum line: the value of sound level decreased until at point 15 minute. After point 15 minute the value not uniform until point 480 minute. Minimum noise reach at point 105 minute are shown 40.1 db. 6

7 Table 2: Day 1 - STN 4 and STN 5 Description at Fitting Workshop STN Max noise level db Min noise level db Exposure Duration exceed PEL hrs hrs 45 min Time of high level 9.00am to 11.00am 3.00pm to 4.00pm 10.00am to 11.00am 2.00am to 2.30pm 3.00pm to 3.15pm Remarks Equation (1) and (2) are used (Petrick et al, 1996) for data collection at STN 1, STN 2, STN 3, STN 4 and STN 5 during six day of measurement. Eq 1: Dose = 100 x (C1/T1 + C2/T2 + C3/T3 +...Cn/Tn) Eq 2: TWA = Log10 (D/100) + 90, From calculation data in Table 3, during noise measurements conducted obtained STN 1 shows the total percentage of the highest dose in the second and third days which and respectively. STN 4 recorded the highest reading on the first day which 54.76%.STN 3 shows a balanced reading all the measurements and the total percentage of 92.34%. STN 5 is the lowest station noise exposure which by 80.75% and STN 2 is the second high level %. If the sum total percentage dose STN 1 is the highest station between each station. However, when referring to OSHA 29 CFR (Petrick et al, 1996), it is still within safe levels for all three days of exposure. Table 3: Dose Percentage and TWA during Measurement 1 st Day 2 nd Day 3 rd day TWA (db) Dose (%) TWA (db) Dose (%) TWA (db) Dose (%) STN STN STN STN STN During noise measurements conducted obtained STN 1 as shown in Figure 3, the total percentage of the highest dose in the second and third days which and respectively. STN 4 recorded the highest reading on the first day which 54.76%. STN 3 shows a balanced reading for all the measurements and the total percentage of 92.34%. STN 7

8 5 is the lowest station noise exposure which total percentage are 80.75% and STN 2 is the second high level %. If the sum total percentage dose STN 1 is the highest station between each station. However, when referring to OSHA 29 CFR (Petrick, 1996), it is still within safe levels for all three days of exposure. STN 5 Dose exposure during 6 hours perday STN 4 STN 3 STN 2 STN STN 1 STN 2 STN 3 STN 4 STN 5 DAY DAY DAY Figure 3: Percentage of Dose Figure 4 is a graph of the TWA value for each STN per day. It shows that TWA of the highest in the second and third days which are and respectively. STN 4 recorded the highest reading on the first day which TWA is STN 3 shows a balanced reading all the measurements and the total TWA STN 5 is the lowest station total TWA which by and STN 2 is the second high level TWA , and the sum of TWA STN 1 is the highest between each station. However, when referring to OSHA 29 CFR (Petrick et al, 1996), it is still within safe levels for all three days of time weight average exposure. TWA exposure during 6 hour per day 8

9 3.3 Risk Matrix Noise Level Assessment Figure 4: TWA Value for Each STN Per Day Risk matrix in this assessment use to analyze potential harm be exposure for student do learning process at lathe and fitting workshop depend time be exposure (Markowski et. Al, 2008). Statistically, the level of risk can be calculated as the total noise level probability that harm occurs to student based on the OSHA regulations. Risk matrix analysis have low possibility for noise affect to student because during assessment as shown in Table 5, the noise level still in safe limit. This analysis maybe have major difference and need to reanalysis if capacity of student, total of machine, type of working process and layout of workshop will change. Noise level are the major fact to develop this matrix. Table 5: Risk Matrix Lathe and Fitting Workshop Likelihood Severity/Consequence high significant moderate low minimal Noise Mapping A Noise mapping is a map of an area which is coloured according to the noise levels in the area (King and Rice, 2009). The noise levels are shown by contour lines which show the boundaries between different noise levels in an area. green colour indicated to noise level > 85dB and yellow as indicated noise exposure range around 85 db to 89 db. Action required for this case already previous part. Based on the risk matrix, noise mapping was determine to detect areas at higher risk of noise as shown in Figure 6. 9

10 Figure 6: Noise Mapping STN 1,STN 2, STN 3, STN 4 and STN5 4. CONCLUSION It was indicated that the lathe workshop more potential produce high noise exposure compared to fitting workshop. It was found that STN 1 has greatest exposure to noise during three day observation. However the results show that the percentage of dose and time weight average (TWA) the sound level in the area measurement was within the range of OSHA standards for noise exposure. The factor of sound also be found from station located and environment situation. Noise matrix and noise mapping were develop base on the noise level produced high risk at STN 1 and STN 4 as a guide for user in a both workshop. The data indicates that Mech Eng. Dept needs to planning a hearing conservation program to meet both Factories and Machinery (Noise Exposure Regulations, 1989) and DOSH recommendations for noise exposure. AKNOWLEDGEMENT The authors are grateful to the Mechanical Engineering Department for the technical support. The authors also gratefully appreciate to Politeknik Sultan Salahuddin Abdul Aziz Shah for approving facilities and sampling during the experiment assessment. 10

11 REFERENCES Hawkins, N.C., Norwood, S.K., and Rock, J.C. (1991). A strategy for occupational exposure assessment. American Industrial Hygiene Association (Akron, Ohio), 179. Job, R. F. S. (1988). Community response to noise: A review of factors influencing the relationship between noise exposure and reaction. The Journal of the Acoustical Society of America, 83 (3), King, E. A., & Rice, H. J. (2009). The development of a practical framework for strategic noise mapping. Applied Acoustics, 70(8), Malaysia Factories and Machinery Act 1967 (1967) Noise Regulation Malchaire, J. (2001). Sound measuring instruments. In B. Goelzer, C. Hansen, & G. Sehrdt (Eds.) Occupational exposure to noise: Evaluation, prevention and control (pp ).Geneva, Switzerland: World Health Organization. Markowski, A. S., & Mannan, M. S. (2008). Fuzzy risk matrix. Journal of Hazardous Materials, 159(1), Muzet, Alain.(2007) "Environmental noise, sleep and health." Sleep medicine reviews 11.2 pp National Institute of Occupational Safety and Health (NIOSH). (1998). Occupational Noise Exposure. (Publication No ). Cincinnati, OH: U.S. Government Printing Office. Petrick, M., Reist, P., Royster, J., & Royster, L. (1996). Comparison of daily noise exposures inone workplace based on noise criteria recommended by ACGIH and OSHA. 11