By Richard Tackett
Despite the bus and motorcoach industry’s increased awareness of passenger safety, a significant number of bus fires still occur worldwide. As such, a quality fire suppression system has become a necessity for all thoughtful operators.
BUSRide recently spoke with executives and engineers from a few of the most successful fire suppression system manufacturers in the U.S.
Firetrace International, Scottsdale, AZ, a division of Firetrace USA, has more than 150,000 fire suppression systems worldwide protecting property and life. Firetrace systems are compatible with most commercially available fire-suppressing clean agents, foams and dry chemicals.
Marcus Foster, regional manager, Engineered Systems, says that Firetrace boasts “the world’s smallest fire suppression system.”
Firetrace’s Indirect Fire Protection System uses a plastic tube, known as the Firetrace Tube, as a “Fire Detection” and “System Activation” device.
“That tubing is taken and installed throughout the engine enclosure or other enclosures that we’re protecting,” says Scott M. Starr, director of marketing.
Once the tubing senses the fire, it then ruptures – resulting in a drop of pressure causing the Indirect Valve to activate. This diverts flow from the detection tube to the larger outlet ports.
“That’s how the system actually activates,” Starr says. “The nice thing about it is that it’s very reliable, especially in an environment with a lot of temperature extremes, as well as dirt and grime from the road. It also has to survive periodic steam cleaning, which can be a challenge for some fire suppression systems.”
When the fire suppression system activates, the extinguishing agent is discharged from the cylinder through the diffuser nozzles, flooding the area in a proprietary mix of fire extinguishing chemicals.
“We use ABC dry chemical powder,” Starr explains. “We have access to every kind of chemical agent, but there’s nothing that handles a three-dimensional fire quite like ABC dry chemical powder.”
Starr says that Firetrace’s system will only activate in the presence of an open flame, or if someone were to cut the pneumatic tubing. Because it’s a pneumatic system, it’s operable 24/7. Some bus fires have occurred after-hours in garages with non-automatic systems, and operators have lost multiple buses.
“If there’s a fire event, the system will go off,” Foster says. “It’s a failsafe system, because it doesn’t need somebody to flip the switch or have the key.”
FMNA, a division of USSC Group, Exton, PA, manufactures and installs water mist fire suppression systems for transit buses, motorcoaches, and small and midsize buses. FMNA’s system is geared toward protecting the engine compartment, the battery box and the HVAC area.
The company identifies the “fire triangle” as a crucial part of understanding fire suppression. The fire triangle consists of oxygen, heat and fuel. FMNA says that while other systems suppress a fire by attacking up to two of the three elements of the fire triangle, only the FMNA water mist system attacks all three elements.
FMNA is UL approved as a complete automatic fires suppression system (AFSS). The approval covers the overall suppression and detection elements ensuring overall system performance and component execution. UL testing covers multiple thermal event scenarios as well as over one hundred component level tests.
“Our system is comprised of three key elements,” says Jeff Krueger, FMNA’s director of engineering. “There is the suppression element, which is the most important since it is what knocks out the fire. The main component of suppression is water mist, as opposed to other powder based systems. Unlike powder, water mist may deploy for over 60 seconds and is more efficient in reducing heat and removing oxygen from the environment.”
The mist is driven with FMNA’s piston accumulator, a key piece of the whole system. It holds the water-based mixture and then releases it through the distribution system and nozzles to create the mist which knocks out the fire.
Detection is another key element of any fire suppression system. FMNA’s primary method of detection is loss of pressure (LOP) tubing. The LOP system is completely self-activating, meaning that it is a failsafe system even when the vehicle is not turned on. If there is a thermal event or any issue, the system will activate.
The system’s third element is electrical. FMNA’s system uses electrical output, which includes an output panel for the operator. The panel provides indicators to the operator that the system is active and functioning, or that service is required. In the case of a thermal event, a visual and audible alarm will be activated.
“While all detection systems need to meet the same ATPA standards, our electrical system is unique since it is completely output only,” Krueger says. “That’s a key difference from other systems out there today.”
FMNA says this unique difference in FMNA’s system minimizes the risk of human error.
“Our system will not accidentally activate due to vehicle shorts or issues during maintenance,” Krueger says. “This is because our system doesn’t have electrical input and is completely standalone, which is consistent with FMNA’s FAILSAFE mission.”
In the event of an accidental discharge, FMNA says that clean-up is easy and fast.