By Jack Rubinger
It stands to reason that a 4-mile-long, ½-mile deep pit mine would require enormously powerful and gigantic trucks to haul iron ore from bottom to top. Along with the sheer enormity is the overpowering noise these trucks create. And that’s a major problem because noisy trucks are not in compliance with the Mine Safety and Health Administration (MSHA).
Larry Hansen, Aeroacoustic Engineering Consulting, likened the sound of a mining truck’s brakes to a locomotive’s steam whistle. So Hansen’s team designed a high mass flow silencer — much like those used in the aerospace industry — to quiet brake blower noise.
As a result, the actual noise reduction was 13 dB and all noise exposures for operators and mine pit personnel dropped below the action levels mandated by MSHA regulations — good news for driver/operators and Minnesota and Michigan residents living near the mines who were being kept up at night.
Mines are not alone in the noise-producing arena. Bottling plants, metal fab plant and others are also extremely noisy.
Indoor Industrial Noise
There are several steps industrial noise consultants deploy to reduce, redirect or redistribute industrial noise, starting with an initial site visit to quantify how loud the noise is. In some cases it may be possible to reduce noise from machines and sometimes it is possible to block sound with barriers, silencers, curtains or enclosures.
Because there may be widespread noise throughout a facility, one useful technique to visualize the noise is by creating a site-specific noise map of a facility with an industrial labeling system. Overlay red areas as loudest, so it’s easy to see where problems are and how to address them.
Unfortunately, some never notice noise warning signs. That’s why experts recommend creating 9-foot tall, high-visibility signs and labels that are highly reflective and designed to withstand chemical spills and UV exposure.
Site-specific signs and labels give you the option of including emergency contact information so workers know whom to contact in the event of an emergency and specifics about noise levels, as well as warnings to wear hearing protection if you’re working in a particularly noisy area of your facility.
“My clients tend to put signs up throughout a workplace rather than for specific locations because it is easier to enforce,” said Tim Kelsall, an acoustician with the consulting engineering firm Hatch Associates, board certified by the Institute of Noise Control Engineering.
Depending on noise levels, Elki Lahav, A Acoustics, recommends three types of noise-reducing products:
- Noise-cancellation plugs, ear plugs or ear muffs
- Using both plugs and muffs together
- Ear plugs and a special helmet. For very loud noise (120 dB) the sound enters through the mouth and the skull. Then, only helmets can help
Back to the Bottle
At one of North America’s top bottling companies, improperly lubricated chains used to drive plant operations were using more power than necessary — threatening the life of motors, sprockets, gears and the chains themselves and creating an unbearably loud and high-pitched screech — a constant deafening metal-to-metal noise like a train. The chains in question were in the heat shrink tunnel. There are probably about 300 of them — each segment about 12 inches long. They run at different speeds to turn and redirect boxes of soda pop. It’s worth noting as well that the product was used in conjunction with automatic lubrication systems.
A major factor here is heat, which tends to burn out lower quality lubricants. In the food industry, it’s tough to find good lubricants that are food grade approved for both U.S. and Canadian requirements. Consultants from Krown Industrial came to the rescue with a lubricant that has been approved for use in food plants, is approved by the Canadian Food Inspection Agency (CFIA) and approved by the NSF for use in food plants in the U.S. Plus, the lubricant is 100% non-flammable, not toxic, poisonous or corrosive.
Another up side? Only small quantities of the lubricant are needed, it’s less messy and it doesn’t leave a build-up of residue. Within ten minutes of application, the noisy chain was all but silenced. Now the line is running more smoothly and drawing less amperage to run the electric motors that drive the chains.
Kelsall and his team are also designing plants that are quiet from the beginning. Fan silencers, pneumatic silencers, blow off silencers and noise enclosures are commonly used measures. Clients benefit because it is cheaper and better to design facilities right in the first place than to retrofit after the fact.
“The other important point is to only put one piece of noisy equipment in a room. Too often people put more than one generator in a room, leading to high noise exposures when one of the units requires maintenance. Putting each in a separate room is more difficult, but gives a much better result,” added Kelsall.
Whether the industrial noise is coming from the depths of a pit mine or inside an urban bottling plant, there are many tools and technologies that are cost-effective, will perform in harsh industrial conditions, and will have a dramatic impact on the safety and comfort level of workers and managers. Identifying the problem areas is a great first step toward making improvements.
Jack Rubinger, has authored a wide range of articles on industrial topics, including lean manufacturing, improving facility safety, and streamlining operations for Graphic Products. He can be reached at [email protected]. Further information on labeling and signage can be found at www.GraphicProducts.com.