Engineering Controls Database

Steam Generator Feed Pump – Noise Case Study

Problem:	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: Steam generator feed pumps are generally considered to be one of the principal sources of high sound levels inside electric power plants. This case history describes the noise control work associated with the two boiler feeds at a coal-fired electric power plant. The pumps produced a high level of tonal noise. The pump tone was within the 1,000-Hz octave band and, because of its high level (100 to 105 dB near the pump), it impacted the A-weighted sound level throughout the turbine hall. The owner of this plant had decided to study the feasibility of reducing plant sound levels to less than 90 dBA in all frequently occupied areas and to adopt this sound level as a design goal for noise control treatments. The turbine hall is a frequently occupied area of the plant and, because of the boiler feed pump, the sound levels varied from about 92 to 98 dBA.
What this means to you:	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.
Description of control:	A complete enclosure was designed for each pump. The enclosures are about 19 ft x 19 ft x 10 ft high and include several sections easily removed by the existing overhead crane. Three gasketed doors, each with a window, are included to ensure that a worker would not be trapped if a high-pressure steam leak developed while he was inside the enclosure. The walls and roof are constructed of 16-gauge sheet steel outer surface, 4-in.-thick glass fiber insulation, and 22-gauge perforated sheet steel inner surface. Several penetrations of the enclosure were necessary for lines, drive shaft, etc. The penetrations were small, and they were sealed where possible. Interior lighting was provided, as was a temperature monitor. Ventilation of the enclosure was also provided to reduce the build-up of heat. Some difficulties have been experienced in this area. During the summer months, the temperature within the enclosure reached 125°F. While this heat does not affect the pump, it is uncomfortable for a worker inspecting the pump. It is expected that a modification of the ventilation system will correct this heat build-up problem.
References:	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.
NAICS Codes:	221112
Keywords:	electric power plant electric power plant noise control noise control steam generator feed pump steam generator feed pump
How well does this control work?	Sound levels throughout the turbine hall have been reduced from the previous levels of 92 to 98 dBA down to the present levels of 88 to 89 dBA. The sound in the turbine hall is generally broadband and impacted by other sources. Octave-band sound pressure levels measured several feet from the enclosure are shown in Figure 1 and are compared to measurements made before the enclosure was installed. The enclosure insertion loss is at least 19 dB in the 1000-Hz octave band that contained the pump tone. The measured insertion loss shown in this figure is limited by noise from other sources. It is clearly shown that the tonal character of the sound has been reduced, the A-weighted sound level has been reduced to less than 90 dBA, and the speech intelligibility for this area has been improved. [img=1] Comments: Plant workers were somewhat concerned about the effects this enclosure would have on pump accessibility during maintenance work. Since installation, however, the enclosure has been removed twice and reinstalled without difficulty. Removal time in both cases was less than 20 min. It is often important to contact the equipment manufacturer prior to enclosing their equipment. Their advice and experience can lead to improved designs. Discussions with in-house maintenance, safety, and operating personnel are essential.