Firetrace fire suppression systems are installed in thousands of machine shops, manufacturing facilities and other locations around the world, but no two shops are exactly the same and not all fires are created equal.
Different raw materials, machinery, lubricants, coolants and components all present their own unique properties and fire risks, sometimes combining on the same shop floor or even in the same machine.
In this post, we identify six key differences between Class B and Class D fires (numbered below) and make recommendations on the safest, simplest and most cost-effective ways to suppress them.
Class B fires involve flammable liquids and gases, which in the CNC and machining world are most often linked to oil-based coolant.
Class D fires involve the burning of combustible metals like titanium, magnesium and zirconium. They are by nature much less common than Class B fires, but are significantly riskier due to their chemical properties and extremely high temperatures.
In the real-world reality of an oil vapor-laden environment of the cutting area of a CNC machine, the risks of Class B and Class D fires co-exist in close proximity, and the more common Class B fire could potentially lead to a Class D fire outbreak.
The ignition point for oil-based coolant is around 300 degrees F.
But according to NFPA 484, the National Fire Protection Association’s standard for combustible metals, the ignition point of Class D metals is much, much higher: Magnesium burns at 623 F; Zirconium at 1400 F; Titanium at 1593 F.
These ignition points are graded based on solid metals – metal dust or powder can ignite at significantly lower temperatures.
If you have dust or powder as a byproduct, you should strongly consider conducting a dust-hazard analysis to identify your risk profile and the best fire suppression/explosion suppression plan for you.
Class B fires can reach temperatures up to 1,000 degrees F and present danger to both people and property.
By comparison, Class D metals burn at between 1800 and 7000 degrees F.
These extremely high temperatures present unique challenges and risks, as fires this hot produce harmful, potential hydrogen gas when exposed to water and can split off oxygen atoms, creating self-fueling fires.
Class B fires present danger to both equipment and people.
While most common fire regulations require a Class D-specific fire extinguisher to be stored in close proximity heavy metal cutting areas, in practice it is highly dangerous for any human to approach a Class D fire due to incredibly high temperatures, dangerous off-gassing and risk of explosion.
Avoiding human intervention with Class D fires is a prudent move.
Class B fires in CNC machines call for a total flooding application, wherein Clean Agents or CO2 are deployed and meant to fully fill a confined area and snuff out a fire.
But Class D fires are best suppressed using a hyper-local application aimed at covering the surface area of the fire. Nozzles on Firetrace’s Class D fire suppression solution are specially-engineered to aim directly at the source of fire, encrusting it to reduce further spread and allowing for safe human intervention even as the fire continues to smolder or burn in a controlled manner.
The average ignition point of cutting oil is substantially lower than that of Class D metals, so the oil vapor-laden cutting area of a CNC machine will always catch fire first. The first line of defense against these fires is a fire suppression system that deploys either an FK-5-1-12 Clean Agent or CO2.
To combat Class D fires, Firetrace recommends the use of Amerex Super D Dry Powder, a Class D fire suppression agent specifically designed to suppress combustible metal fires such as magnesium, titanium and zirconium.
Unlike conventional Clean Agents, Super D is engineered to isolate and cool burning metals without causing dangerous reactions.
At Firetrace, we offer a range of versatile fire suppression solutions, ready to be tailored to your unique environment. Our experienced team of experts is ready to help you better understand the risk Class D and Class B fires pose and explore your options for fire suppression. To learn more, get in touch with us today.