Engineering Controls Database

800-Ton Blanking Press – 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: The 800-ton Verson press is a massive unit weighing about 275,000 pounds (lb), and mounted on four footings set on heavy concrete piers. Production on this press was automobile chassis steel sections of 1/4-in. steel about 10 in. wide and 8 to 10 ft long. Normal operating speed was 30 strokes/min. Steel stock was fed to the press from a reel. Noise levels were about 120 dBA on impact, 105 dBA at quasi-peak, and 94.5 dB at operator location, which was about 4 ft in front of the press.
What this means to you:	The 94.5 dBA sound level measured at operator location only allows for 47 minutes of exposure according to NIOSH guidelines. Unprotected exposure to levels greater than the recommended exposure time begins to cause permanent damage to nerves within the ear. 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:	From the data supplied on strokes per minute and press weight, the isolators were specified to be Vibration Dynamics Corporation (of La Grange, Illinois) series BFM micro/level isolators, under the press feet. The isolators reduce vibration in the press itself, as well as the foundation the press is sitting on. See Figure 1. Figure 1. Isolator used under press feet Figure2. Vertical acceleration at the pier before and after isolation. Figure 3. Horizontal acceleration at the pier before and after isolation. Figure 4. Quasi-peak levels 4 ft from press foot, before and after isolation.
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:	333513
Keywords:	automobile manufacturing automobile manufacturing blanking blanking noise noise noise control noise control press press
How well does this control work?	Data shows that there was a 105-dBA quasi-peak sound level before isolation and a 98.5-dBA level after isolation. With a relationship of about 10 dB quasi-peak to rms, a reduction in level from 94.5 dBA to 88 dBA at operator location has been made. Additional presses will add their own noise and will increase levels to above 90 dBA. Other operational noise sources in the press must be controlled separately. The major pitfall of this approach is that airborne sound level reduction from vibration isolation is almost impossible to predict. However, a serious noise control program in such operations should include isolation devices for all presses. A reward is that the die life and maintenance of such machines is significantly increased for presses that are vibration-isolated. Isolators improve operation and maintenance by reducing fatigue of anchor bolts, foundation failure, or breaking press feet.