Integrated fire suppression systems for CNC machinery – Part 2

Previously, we explored the common causes of fires in CNC machinery. Now, we’ll examine the machine features reducing fire risk and outline the approach to extinguishing a fire.

The importance of proper mist extraction can’t be understated. Oil mist is the primary ignition source, so reducing airborne mist and fumes directly lowers fire risk. By capturing and removing these particles, a properly designed mist extractor eliminates potential fuel for a fire.

The most common mist extractors are electrostatic. They work by electrically charging oil droplets and drawing them onto oppositely charged plates or grids, efficiently stripping mist from the airflow. Centrifugal mist collectors take a different approach: a high-speed impeller spins the contaminated air, forcing droplets outward into collection surfaces where they can be gathered and removed.

When a mist extractor ties into a central duct system, it’s vital to install a fire damper – also called a fire trap. This flap closes automatically when the fire-suppression system activates, isolating the machine’s ductwork and preventing flames from spreading through the facility’s ventilation network.

Another important safety component is the explosion flap (pressure-relief trap). While a fire ignited by oil mist doesn’t always trigger a full-blown explosion, rapid ignition can create a sudden pressure spike strong enough to blow out the machine’s windows and put the operators at risk.

This explosion flap is a spring-loaded panel mounted on the roof of the machine that opens solely in response to internal overpressure. It pivots on a hinge and remains tethered by a safety chain to prevent it from becoming a dangerous projectile. As it lifts, it trips an integrated switch that immediately triggers the fire suppression system.

Fire detection in CNC machines typically relies on one of these two methods:

Pressurized detection tubing: A network of heat-sensitive polymer tubing is routed across the work envelope and is under constant gas pressure. When a localized fire exposes the tubing to high temperatures, the polymer softens and ruptures, causing a sudden pressure drop that automatically trips the suppression system.

Electronic point detectors: Thermally or optically based sensors (heat detectors or flame detectors) are mounted at strategic high-risk locations inside the machine. When the ambient temperature or light signature exceeds a preset threshold, the detector sends an electronic signal to release the extinguishing agent.

Fire suppression systems protect CNC machining and grinding enclosures by flooding the workspace with an extinguishing medium starving flames of oxygen and interrupting the combustion process. Commonly used agents include carbon dioxide (CO2) and halocarbon clean agents such as FM-200 or similar gases. The National Fire Protection Association (NFPA) defines a clean agent as a “gaseous fire extinguishing agent that’s electrically non-conductive and leaves no residue upon evaporation.”

In modern manufacturing facilities, running CNC machines with coolant oil and without dedicated fire protection measures would be irresponsible. Many corporate insurances mandate the installation and regular maintenance of fire protection systems.

MyGrinding Inc.
https://www.mygrinding.com