A multinational tool manufacturing company in Texas recently sat down with Firetrace to discuss their experience with different types of EDM and CNC fire suppression systems they have had experience with, and why it is so crucial to assess options before installing.
The company we spoke with manufactures carbide cutting inserts for various applications at multiple sites around the world. They have multiple grinders equipped with diamond plated aluminum and steel grinding wheels that are using oil-based coolants in the process.
After a major fire seven years ago that burned down an entire building and cost the company over $2.4M in machine loss alone, the company decided to mandate fire suppression on all of their machines running with cutting oil. The company initially chose to go with a UVIR fire detection system to keep the method of detection uniform as they had installed this type of detection in other locations around the globe. They then had two fire incidents less than two months apart.
The first machine fire happened when the setup dimensions were put into the machine incorrectly which led to the work holding clamp failing to keep the part secure, and as a result, the carbide part dug into the grinding wheel, shearing through the diamond coating and hitting the steel, causing sparks to ignite the oil mist inside the machine. Once the fire occurred, the UVIR detector failed to detect the fire, forcing the operator to activate the system by hitting the manual release, but it took them 21 seconds to get there.
The second incident occurred in the middle of a run cycle and was operator error. They were able to see the axis jump on the machine and, after looking at the program, realized there was an error that made the tool jump one hundred thousandths more than it was supposed to, which again resulted in sparks to ignite the oil mist. The company typically has one operator running three to four machines, so even though there is someone onsite, they are not always right next to a machine to react to an incident like this one. In this case, the UVIR detector did not go off again, and it took 17 seconds before the operator was able to hit the manual release to actuate the suppression system.
Because they had two fires in such a short period of time, and the second fire incident happened just three weeks after the UVIR detector had been replaced after annual inspection, they decided to do some testing to see the root of the problem.
Using the FS7 detector that was in the machines, and a sample of the cutting oil they were using, they tested whether the device would detect a fire with the cutting oil itself smeared on the lens, and a light oil mist on the lens. In both cases, the UVIR detection was obscured due to the oil residue on the lens, which caused the failures.
Upon talking to other sites within the company, they realized that they had also encountered issues with their UVIR detection in the same manner. The cutting oils used at the different sites were slightly different, but the issue of the lens being coated and becoming non-functional remained the same. The temporary fix was to have operators continually wiping down the detector's face, but this has resulted in an operator wiping cleaning the lens between every cycle, which still isn’t enough to ensure it is always clean.
Luckily, the machines sustained relatively little damage from these fire events, but the downtime did cost the company upwards of $20K. The second incident was more costly due to the investigation and testing that needed to occur before they were comfortable getting the machine back up and running.
Both incidents have spurred additional training within the company. One of the operators almost opened the compartment as the fire was going, which would have resulted in a flash as the system became exposed to more oxygen. The company has also re-evaluated their detection methods and have determined that a pneumatic system would be an ideal way to ensure there is no electronic or visual failure due to the oil mist build up in the machine. They are planning to install this as a backup detection method along with the UVIR detection to cover all the bases.
