Engineering Controls Database
Jar Filling Machines – Noise Case Study
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Overview: The case history presented here is one of sixty-one case histories that were published by the National Institute for Occupational Safety and Health (NIOSH) in 1978 as part of an industrial noise control manual [NIOSH 1979]. The case histories are examples of engineering tasks that have been completed not only by professional noise control engineers but also by non-acoustical specialists who used common sense to solve their noise problems. The case histories were chosen primarily because the amount of noise reduction actually achieved was measured. Such engineering results, even if not directly applicable to a specific situation, illustrate general principles that may point the way to a successful result. They are intended to be useful to production and safety engineers, health personnel, and other factory personnel who are not specialists in noise control. Case study: Two Nalbach filling machines used to fill freeze-dried coffee in glass jars were located in a 65 ft x 23 ft x 10 ft room at an Ohio plant. There are two fixed worker stations for each machine. An operator station is directly in front of the filling machine, and an inspection station is located downstream of the machine discharge conveyor. A roving worker also works in this area. The filler operator maintains a steady flow of bottles into the filling machine and checks and adjusts the filled weight of product as required. The inspector's function is to ensure that each jar is properly filled and that lids are securely fastened to the jars. The roving worker fills the lid bins with lids and maintains cleanliness in the area. |
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The company retained consultants to evaluate the noise environment and recommend controls to ensure that all noise exposures in the area met OSHA limits. The highest worker noise exposure occurred at the filling machine operator location, where the sound level varied between 94 and 96 dBA. The sound level was at or above 92 dBA elsewhere throughout the space, because of the highly reverberant nature of the room (typical for food processing facilities where easy-to-clean, hard surfaces are required by FDA regulations). The filling machines were most responsible for the above-90 dBA sound levels, as the sound level dropped to 74 dBA when both filling machines were stopped. Hearing loss is one of the most common occupational diseases in America today and the second most self-reported occupational illness or injury. Approximately 30 million workers are exposed to hazardous noise on the job and there are approximately 16 million Americans with noise-induced hearing loss. |
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Noise engineering controls were implemented because administrative controls, namely job rotation, was deemed to be infeasible. Figure 1 is an example of the conceptual design drawings that were developed in connection with this project. The treatments were fabricated by the E.A. Kaestner Company of Baltimore, Maryland.  |
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| NIOSH [1979]. Industrial noise control manual – revised edition. Cincinnati, OH: U.S. Department of Health Education and Welfare, Public Health Service, Center for Disease Control, National Institute for Occupational Safety and Health, DHEW (NIOSH) Publication No. 79-117. | |
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coffee manufacturing coffee manufacturing filling machines filling machines noise noise noise control noise control |
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Before treatment, the sound level at the filling machines was 94 to 96 dBA, when both fillers were running. Although after-treatment octave-band measurements were not available for the identical running modes, they exist for the condition with one filler running. For the one-filler-running mode, the sound level has decreased to 85 dBA. Figure 2 shows octave-band spectra of the measured before-and-after situations and an estimate of the maximum expected sound pressure levels for the two-filler-running mode. All operators are now exposed to sound levels less than the 8-hr 90-dBA level allowed by OSHA. [img=2] |