The potentially explosive dust resulting from metal finishing operations is a major concern among fabricators today, not only because it is a safety hazard, but also because recent changes in NFPA regulations have toughened compliance.
The grinding and sanding of metal work pieces produces fine metallic dust that – even after filtration – can be exposed to sparks, resulting in the dust smoldering, catching fire or causing a dust explosion. Combustible metals that are common in manufacturing and machining operations include aluminum, lithium, magnesium, niobium, tantalum, titanium, zirconium and even cold-rolled steel.
There are different applications for industrial dust collection, including dry or wet collection systems. In some circumstances, the dust from different metals might mix during certain types of dry dust collection and create a hazardous environment.
Safety professionals can help prevent dust fires and improve air quality by choosing the best dust collection system for their specific worksites.
Addressing Dust Hazards
Midwest Products and Engineering (MPE), a Milwaukee-based designer and fabricator of enclosures, carts and consoles used by the medical and electronics industries, decided to take a new look at its dust collection system requirements to ensure compliance and reduce costs.
MPE’s primary dust concern focused on handling that generated fine dust during the metal finishing (grinding and sanding) of regular cold rolled steel. Due to the more hazardous situation of combining dust from aluminum grinding with that from steel, the aluminum metal finishing area is located in a completely separate part of the shop.
“The steel that we’re grinding turns into a form much like steel wool lint,” explained Teresa Stortz, MPE process improvement engineer. “The hazard occurs when that lint is hit by grinder sparks; it could smolder and ignite. Of course, that is a situation that we absolutely must prevent. In addition, we want remove as much of the very small dust particulate from the air as is possible.”
For its purposes, MPE decided to use wet downdraft tables, which purify the air through a combination of centrifugal force and violent mixing of water and contaminated air. As the air stream passes the fixed baffles, particulate is separated by a heavy, turbulent curtain of water that is created by high-velocity air. The centrifugal force caused by the rapid changes in airflow direction forces the dust particles to penetrate the water droplets and become entrapped. Contaminated water is then removed from the airstream by special mist filters. Dust, as sludge, settles to the collector bottom, and the water is reused.
Dust collection systems may present ergonomic challenges. MPE therefore made important ergonomic considerations while choosing and designing its dust collection systems.
“The parts can get fairly large, weighing in excess of 100 pounds,” Stortz explained. “We’ve designed the equipment and area so that each operator would have lift-assist equipment available at his or her workstation. This will improve worker safety as well as increase productivity.”
Terry Graham, an equipment engineering specialist at Bell Helicopter, agreed that companies considering dust collection systems keep ergonomic concerns in mind. According to Graham, Bell Helicopter’s dust collection units “are configured so that the work surfaces are more in the worker’s power zone.”
“Where there are stations that work on heavy parts, the filters have slots so that the crane can move a part inside the booth and load the part on the table,” Graham explained. “The improved ergonomics benefit seems to speed up production and also help employee morale as well as making it less likely that workers will be off due to an injury.”
Choosing the best dust collection system for your worksite therefore may result in more than simple compliance – it can create a happier, healthier and more productive work force.
Ed Sullivan is a Hermosa Beach, Calif.-based writer. He has researched and written about high technologies, healthcare, finance and real estate for over 25 years.