جستجوی مقالات مرتبط با کلیدواژه « مداخلات مهندسی » در نشریات گروه « پزشکی »

Noise pollution is the most widespread physical harmful factor in industrial environments. Noise control is intended to control its effects and comfort of work, including general management and engineering control techniques. Harmful noise is considered as an important occupational hazard in the iron and steel, textile and process industries. In addition, noise pollution is a potentially harmful component of the plant industrials. Metal Industry have been identified as one of the environments with higher noise than permissible and for many countries, implemented Hearing protection programs for workers protection in these industrials. Occupational exposure to the noise caused by Devices and Processes productive processes is often described as a form of self-harm. Noise control is intended to control its effects and Convenience of work, including general management control and engineering control. In most industries there is at least one process unit in which the noise pressure level is higher than the permitted level and oil industry is also subject to this. Therefore, the present study aimed to evaluate the noise pressure level in some units of the oil industry and to evaluate the effectiveness of the implementation of engineering control methods including sub-seismic installation, modification of control room doors and windows, floating floor implementation, construction and installation of acoustic chamber.

This descriptive, analytical and interventional study was conducted at an oil factory in Khuzestan province. This study was carried out in four phases, including Phase I; measuring and evaluating noise and identifying important bands and sources of noise production, Phase II designing technical control methods at the resource location, and location of workers, Phase III, Implementation of engineering interventions and Phase IV Reassessment and effectiveness of the interventions were performed. In the first phase, the noise pressure level in the pressing, assembly, installation and bottling sections was measured peripherally and locally. In addition, at some peripheral stations and all local stations, was performed the frequency analysis of one octave of noise by the advanced digital level meter AWA 5688 in accordance with ISO 9612. In addition to for Local Stations the equilibrium, was determined the received dose to determine its reduction after interventions. Then, according to the type and level of noise pressure level as well as the environmental characteristics of the hall, were performed appropriate engineering control measures. Then in the second and third phases in this research in the high noise pressure level units Was performed Interventional actions Includes sub-seismic installation, installation of acoustic panel on the ceiling and absorbent panel on the common wall with assembly hall, installation of absorbent panel on the adjacent walls of press operators, installation of polymer plates on the desks, modification of doors and windows of control room and floating floor installation, installation Metal cab with foam elastomeric inner surface, galvanized steel ceiling and elastomeric adsorbent in cabin cab, acoustic chamber fabrication and installation.  In the fourth phase of this study was performed a reassessment of the noise pressure level in the intervention units and at the workstation to determine the effectiveness of the interventions. For this purpose, was compared the noise pressure level of each indicator station and compared before and after the intervention. also In evaluating the effectiveness of the interventions performed was recorded, the approximate cost per unit separately and was presented their effectiveness in reducing the noise pressure level as a cost-effectiveness index as well as a cost-benefit index to determine each cost reduction How much does it cost to decibel.  

The results of noise pressure level measurement in different units showed that the equivalent noise pressure level was Above than Exposure limit before the intervention in all stations so that The highest level of noise pressure in the vicinity of one of the 63 tone presses was equal to 92/63 dB (A). After the interventions, the noise pressure level was reduced at all stations and was lower than the limit at all points except one press also. The results showed that the largest reduction in noise was in the correction of the tetra pack chambers. Frequency analysis of noise was performed at most of the indicator stations and presented at two sample stations. The results showed that the noise pressure level was effectively reduced. In addition to technical efficiency and scientific justification, noise control techniques must be applied with economic considerations in mind. Due to the cost of technical methods of noise control, it is essential that the designer assess the economic aspects including cost-effectiveness and even cost-benefit before executing the plan until the employer can estimate the cost of the project with economic considerations In addition to the technical results. If so with noise levels are lowered to the permissible level using less expensive methods, there is no need for high costs. In this study, the economic aspects of technical control plans in different units and their total in the company were estimated. In this paper, the cost-benefit index was calculated, which showed that the total direct cost of the project in the press unit was about 502 million Rails and given that the number of people who were disqualified was 13 in three shifts, the average cost-benefit index was 0.70 million Rails per person over a one-year period.

In this study, were used interventional methods of modification and fabrication of chambers for tetra pack and bottle-filling machines in the bottling hall After examining the unit, it was found that environmental control was not a priority in this unit And the problems with this unit were due to technical glitches and the incompleteness of the tetra-pockets cab room and the lack of a queuing bottle chamber. Completing walls reduced the noise pressure level to 9.5 dB and reduced workerschr('39') exposure to below 82 dB by steel sheets and technical modifications to control noise in Tetra pack chambers. Also, the noise of the Bottle Row Unit reduced by Construction and  installation of a simple chamber with steel wall and UPVC door and window  about 10 dB and reduced the exposure to below 79 dB Another intervention in this unit was the use of silicone sealant and Silicone Glue to block all leakage pores. According to the guidelines outlined in the Volume Control Guide, acoustic chamber installation can be a good way of controlling the noise of industrial sources, and the use of steel sheet as the main approved layer of ISO 15667 has been well used in this study. One of the interventions that was effective was the installation of an elastomeric sealant at the base of the presses to reduce vibration, which reduced the noise pressure level in the low frequency range. In addition, the use of rock wool insulation has a significant effect on reducing the noise pressure level. In this study, it was found that enclosure can reduce the noise level in the unit production pump, but should be considered the limitations of the enclosure method. In the industry under review there were two staff control rooms in the liquid production unit and facilities, which had major drawbacks in the number, dimensions, and gender of the windows. In this plan equivalent noise pressure level decreased more than 16 dB in the listenerchr('39')s room with reduced the size and number of windows and replaced them with UPVC double-glazed windows, as well as replacing doors of the same type with a low cost. Eventually the investigations showed that all the control measures performed in different units in this study resulted in a significant reduction in the noise pressure equivalent level. Units taken these indices are within the acceptable range.

Heat stress as a harmful physical agent in workplace, if is not properly controlled, can cause undesirable effects on the performance and health of personnel. This study aimed to evaluate the heat stress and efficacy of engineering interventions on WBGT index in work station of the workers in a forging industry. This experimental study evaluated WBGT index in one of the forging industries of Tehran in summer 2010. In order to control the radiant temperature, as the most effective factor on WBGT, fireproof flexible fabric was used as shield to reflect and insulate radiant heat. Efficacy of the intervention was evaluated by comparison of WBGT index before and after the intervention, using Statistical paired t-test and SPSS software version 14. Average value of WBGT index in all 12 workstations before the intervention was estimated to be 21.31˚C which was higher than the standard limit. This value reached to 45.26˚C after intervention. Radiant temperature was identified as the most important factor which should be controlled. Data analysis indicated that difference in radiant heat at the height of head, and ankles was statistically significant before and after intervention (P≤0.05). However it was not statistically significant at the height of waistline (P≥0.05). Results of the study showed that using flexible fabric shields is a good way to control the radiant temperature and thermal stress. These shields are inexpensive and easily installed, and don’t block front sight of the operator. These shields are easily shaped to fit the workspace and due to the lack of sharp edges they are safety approved. Hence it seems that these heat shields are able to be widely used in order to control the radiant heat in the forging industry.