The aerospace, automotive, and medical industries increasingly rely on exotic metals including aluminum, titanium and magnesium.
Many companies are at risk of generating fires or explosions from metal working. Here are risk factors, new official guidelines, and solutions you need to know to help your company avoid tragic consequences.
WHAT CAUSES FIRES AND EXPLOSIONS?
Let’s look at types of dust that can provoke such unfortunate events. Combustible metals that are common in manufacturing, fabricating and machining operations include aluminum, magnesium, niobium, tantalum, titanium, zirconium and even cold-rolled steel.
In order for an explosion to occur, there must be a source of oxygen – an explosion or a fire cannot occur in a vacuum. Then, there must be an ignition source. The most common sources are sparks, flame, or heat (perhaps, from a machine used in processing) – and even static electricity.
Next, dust must be dispersed (for example, an airborne dust cloud suspended in the air) in order to provide fuel for the event to spread. One word of caution: we must not leap to the conclusion that if we eliminate dispersion, we have eliminated danger.
An equally dangerous but opposite process to dispersion is confinement: if dust is confined – even within a dry dust collector, the concentration can expand and explosive pressure can build up. Fires can occur when dust settles on a filter or when an ignition source lands on combustible dust (or vice versa), and the fire will propagate.
In terms of ability to cause a fire or explosion, not all dust is created equal. One such “danger quotient” is the KST value, which rates airborne dust. The higher the value, the more reactive or explosive the dust is. People in all levels at facilities that work with metal must be aware metal dust has higher KST values (and is therefore more hazardous than many other by-products of manufacturing).
Typical industrial applications that generate such dust are grinding, deburring, finishing, sanding, buffing, and polishing. Even the post-processing of 3D printed parts can generate dangerous combustible dust.
WHAT ARE SOME CONSEQUENCES OF ALLOWING FIRES OR EXPLOSIONS TO OCCUR?
When such tragic events occur, they leave the employer vulnerable to serious property damage, lawsuits as well as fines and penalties from regulatory institutions.
If the company is at fault for using the wrong type of dust collection equipment, insurance carriers may either refuse to indemnify the business for the event and/or drastically increase their premiums. Even from the standpoint of production, company owner’s do not want their facilities and operations to burn down. And ultimately – no sane and rational person views the risk of human injury or death as trivial or inconsequential.
Since fires and explosions are a serious risk for anyone working in industrial environment, government and regulatory institutions scrutinize many companies and are very concerned about combustible metal dust (OSHA and NFPA are the primary regulators).
WHAT DO YOU NEED TO KNOW ABOUT STANDARDS AND GUIDELINES?
The NFPA (National Fire-Prevention Association) reveals the disturbing fact that industrial dust is the leading cause of fires and explosions.
In 2015, the NFPA came out with a revised code (NFPA484), with new guidelines and standards for combustible dust. Every industry that produces combustible dust in any of its operations will need to select equipment that not only conforms to the new standards, but ensures maximum safety for workers.
Regardless of the question of personal liability, conformance with these standards can make the difference between whether or not companies are indemnified by insurance carriers – and such conformance can carry heavy weight in case of a lawsuit.
WHAT SOLUTIONS PROTECT YOU AND YOUR WORKERS?
One apparent solution is the use of specialized equipment to eliminate dust from the source. Large Centralized dust collectors are often used for this purpose. Even better, dust can be eliminated at the source by means of downdraft tables. Not only do these tables provide ventilated surfaces upon which workers can perform their metal finishing work, but collect and filter dust to keep it out of the shop air.
Once again, just as all dust is not equal in its capacity to lead to fires and explosions, all downdraft tables are not equal in their ability to prevent combustible dust fires. Some downdraft tables (called “dry draft tables”) use a dry pleated filter media. One danger with these tables is that even though the dust has been collected, it still remains combustible or flammable (remember the principle of confinement mentioned above).
The revised NFPA code prescribes a new type of table – a wet downdraft table. This type of downdraft table works by using the suction of the blower to cause water to cascade around inside the unit. Dust is sucked through the cascading water, which acts as a filter. This, in turn, neutralizes the dust particles, making them incapable of causing a fire or explosion as they are submerged in water.
STILL NOT SURE WHAT TO LOOK FOR?
Here are some characteristics to look for in selecting a wet downdraft table: First, look at the material the table is made of. To avoid the frustrations – and costs – of premature corrosion, the material of choice is stainless steel. You want to look at your operations, since you need to know how far off the surface dust is being generated. Some tables can only collect dust 12-16 inches off the table. But if your application generates dust higher off the table surface, you want to be assured the velocity is high enough to collect dust from that distance. The addition of a back draft hood allows for dust capture further above the table surface.
Instead of two separate units (a table plus an external dust collector), you can save floor space if both units are consolidated. Some wet downdraft tables are integrated into a self-contained portable unit – solutions like this have the additional advantage of being more cost effective.
You also want to know about the company that manufactures the table. Some companies have a series of standard models allowing you certain limited choices. However, if you have special requirements (for example, in terms of worksurface dimension), it would be useful if the company providing the dust-collecting equipment is willing to work with you to meet your specific needs. A good company to do business with will also have contact people trained to help you find the solutions you need in your facilities.