Ounce of Prevention

Oily metal turnings are a fire hazard no matter which elements are found in the metallic scrap. Machinists handling titanium and some other metals, however, carry an extra risk of working with volatile elements.

Business owners, shop supervisors and managers at all levels are aware that fire prevention is their responsibility. Unfortunately, it is one of many responsibilities that they juggle and it can get lost in the shuffle of day-to-day deadlines and production goals.

As difficult as it may be to do, though, managers owe it to themselves and their employees to understand the risks and then work to minimize the possibility of a fire igniting in their scrap and waste storage areas.

Distant observers do not necessarily think of metal objects as especially flammable. After all, iron and steel do not begin to melt until 2,500 degrees Fahrenheit or higher.

However, as all too many scrap recyclers can testify, when petroleum is added to the mix, any collection of metal can become a potential flash point for a fire that can burn stubbornly and hot.

Additionally, machinists and fabricators working with certain types of metal have the added risk of dealing with a metallic element that may be much more volatile or flammable than steel, copper or other common metals.

A handbook published by the U.S. Department of Energy (DOE) notes, "A variety of metals burn, particularly those in finely divided form. Some metals burn when heated to high temperatures by friction or exposure to external heat; others burn from contact with moisture or in reaction with other materials."

Metals "in finely divided form" can be found at machine shops, as can sources of friction, external heat, moisture and other materials—all of the triggers cited by the DOE.

Among the metals later cited in the DOE handbook as being especially volatile are titanium, magnesium, lithium and zirconium, as well as aluminum or zinc in certain circumstances.

In 2001, a recycler of specialty metals in the eastern United States suffered a devastating fire when a few sparks created by the forks of a forklift truck scraping concrete ignited a bin of nearby titanium turnings.

The resulting three-alarm fire destroyed one production building and caused evacuations in the surrounding neighborhood. The fire and resulting fire-fighting effort damaged the company’s offices as well, but fortunately no one was injured.

A December 2003 fire at a magnesium recycling company located near Cleveland destroyed that business and produced pyrotechnics witnessed by neighbors for miles around.

And while rainy weather is often an ally in fire-fighting efforts, in this case Cleveland’s rainy weather only served to make the five-alarm fire worse, as burning magnesium reacts explosively to water.

Fully preventing fires in metalworking areas can be difficult, as employers are helpless to change the volatile chemistry of the materials with which they work.

An added difficulty is that oily metal turnings can combust without the need for an ignition source such as a spark or open flame. Oily, volatile metals can combust spontaneously if left for too long in the wrong conditions.

The Marine Accident Investigators’ International Forum (MAIIF, at www.maiif.net), in a handbook designed to prevent ship-board fires, cites "finely divided metals" and metal powders as combustible cargo that must be carefully handled. Specific metals mentioned by MAIIF include magnesium, titanium, zirconium and aluminum powder.

The group cites the National Fire Protection Association (NFPA, at www.nfpa.org) when handling metal turnings. "Piles of oily metal borings, shavings, turnings and cuttings have caused fires by igniting spontaneously."

Ultimately one of the few solutions is to remove such turnings from the premises at the earliest opportune time.

Keeping machinery and work areas clear of such accumulations is the first step. "Clean machines and good workshop practice are usually sufficient to avoid any danger of fire when machining titanium," advises Titanium Industries Inc., Rockaway, N.J., in a message on its Web site.

But collecting and storing such turnings and letting them accumulate may simply be creating a new problem. "In a chemical context, all elements that are not in their highest oxidation state can undergo oxidation," writes engineer Charles R. Schmitt in the Pyrophoric Materials Handbook published by Towson State University. "Under appropriate conditions, some metals oxidize rapidly in the presence of air, oxygen and/or moisture and can generate sufficient heat to reach ignition temperatures."

Metals fires, classified by the NFPA as Class D fires, "are dangerous events for the unprepared," fire fighting equipment supplier Diemasters, Skiatook Lake, Okla., writes on its Web site.

Even with a system in place to have scrap removed as quickly as possible, there is still a need to have the right equipment on hand in case a metal fire starts.

Diemasters’ Metal.Fire.Xtingshr (www.diemaster.com) uses a dry powder blend of materials designed "for controlling or extinguishing metal fires," according to the company.

The product is designed to combat the NFPA Class D fires against which water alone can often do more harm than good. The Department of Energy’s Technical Standards Program handbook lists several fire fighting agents and their appropriate uses in combating metals fires (www.hss.energy.gov/nuclearsafety/techstds/).

Steps toward prevention and preparation are both key considerations for machine shop supervisors. Once a volatile metals fire has started, the available time to develop a "plan B" is minimal.

The author is editor of Scrap Management and can be contacted at btaylor@gie.net.