While fire itself has been around for hundreds of thousands of years, our ability to harness it still remains juvenile at best. It is for this reason that learning and developing ways to combat fire on heavy-duty off-highway equipment remains an important critical issue to solve.
Distinguishing fire from fire
Fires are typically classified based on the fuel of the fire. Class A fires involve ordinary combustibles including plastics, rubber, wood and paper, typically found in wiring insulation material and hydraulic hoses.
Flammable liquids consisting of fuel, hydraulic fluids and brake fluids constitute a Class B fire hazard.
Any fire involving electrical energy is given a Class C rating which indicates that the suppression agent to be utilized is approved for use on energized electrical equipment such as battery terminals and electric control areas of the machine, states Ted Ritter, sales manager - vehicle systems, Kidde Fire Systems, Ashland, MA.
Each industry is susceptible to different types of fires depending on its environment and the machines themselves. "Mining equipment has predominately class B hazards, but several class A hazards are also on board. In some mining applications, class A materials can also collect on various portions of the machinery.
orestry equipment has both B and A (wood fibers)," says Joe Beranek, marketing manager — Tyco Fire Suppression and Building Products, Tyco Safety Products, Marinette, WI.
"Class A hazards bring another element to the fire scenario. Fuel and oil can soak into wood fibers, chips, bark and sawdust (and coal dust on mining vehicles) found in various places below the engine. This is an area of the vehicle not normally protected by the fixed fire suppression system, but must be protected on forestry equipment."
Every system is special
Each fire suppression system is custom designed in relation to the piece of equipment, its application, and the environmental concerns of the owner/operator.
Tyco has a library of basic designs used by its installation partners, says Beranek. "The systems will differ depending upon changes to the equipment and the different installers or designers." Tyco makes sure all of its Ansul (a brand of Tyco Fire Suppression and Building Products) distributors are fully trained and factory certified to design, install and maintain the equipment.
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For Kidde, work starts with a meeting of design engineers to gain a comprehensive understanding of the machine to be protected: identifying potential ignition points that will guide the location of detection devices and nozzle placements. "This is done originally on site then progresses via computer graphics transmitted electronically," says Ritter.
Once a design and mounting locations are developed, Kidde works with quality control to ensure the suppression and detection lines are mounted securely and without interference with the OEM's required maintenance procedures.
Finally, production engineers are consulted to ensure the system is installed at the proper time in the machine's assembly process. "For example," says Ritter, "nozzle brackets can be installed early on. Agent lines can be pre-cut and installed at the proper time. However, we must assure that certain components are not installed until after machine painting is done, for to paint over an installed detector could cancel out the approval of the detector and more importantly, negate its proper function."
This process is, of course, for only one model of machine. If an OEM has multiple lines with multiple models, a considerable amount of time is spent to ensure each variant has the optimum design.
There are various ways to detect fire. Infra-red (IR) technology allows a flame to be detected in milli-seconds. "This improves the potential of controlling fires on board heavy vehicles as the fire is detected and agent applied before the fire can spread to a size previously unmanageable," says Ritter.
Beranek explains that Tyco typically uses IR detectors on the largest of surface mining equipment in conjunction with linear or spot detectors. "[They] are ideal to spot fires in the very early stages of ignition." Its SharpEye IR detector features sensitivity selection, compact size and 100-degree field of vision.
IR detectors work by sensing three separate spectral bands of IR energy and triggering a signal. Kidde's IR-1 infrared detector features 90-degree field of vision, 0.5 second response time and is immune to nuisance alarms from sunlight, lighting, artificial forms of light and welding arcs.
Detection options are utilized with the Ansul Checkfire SC-N, a self-contained, electric detection and actuation system which activates a pneumatically-actuated suppression system, either manually or automatically. Its rugged control modules feature internal diagnostics and internal/external power sources to ensure 24-hour protection.
Though many fires occur during operation due to the machine running at full capacity for extended periods of time, fires can easily happen after the engine has been shut off and the operator has left the vehicle. "Hydraulic or fuel lines come loose and fuel comes in contact with superheated surfaces like manifolds and turbochargers," says Beranek. If the fire suppression system was tied into other systems, there wouldn't be fire protection during machine downtime.
The Linear Heat Sensing (LHS) cable from Kidde and the Ansul linear wire thermal detection option from Tyco are among the most commonly used fire detectors. A short occurs in the system when the ambient temperature reaches a pre-specified limit causing the suppression system's actuation.
Linear heat detection systems are ideal for applications where ambient conditions prohibit the use of spot-type smoke, flame or some types of heat detectors. Environmental conditions may also warrant a particular type of detection. If an environment is too hot or cold (below 32 F or above 130 F, for example) or too dirty, detectors can fail or cause accidental actuation.
There are three basic options of fire suppression: dry chemical, liquid chemical, or a combination of dry and liquid.
"We use dry chemicals on all vehicles," explains Tyco's Beranek. "We use wet chemical in conjunction with dry chemical in a twin agent type system. The wet chemical is used to cool superheated surfaces and soak into class A debris, like wood chips on logging equipment where there may be a chance for a deep seated fire scenario. The dry chemical is superior to the current wet chemicals in fighting the pressure fires, three-dimensional fires, and free-flowing fires often found on off-road vehicles."
Cold Fire Super Systems, New Windsor, NY, employs ColdFire, a product of FireFreeze Worldwide Inc. ColdFire is an environmentally friendly, liquid fire extinguishing agent that earned its name by its ability to remove extreme heat from whatever it comes in contact with.
When Cold Fire suppressant is applied to a fire, it extracts the heat from the fire without steam conversion, as well as breaks down the molecular structure of the hydrocarbon fuel source to extinguish the fire and prevent re-ignition.
Ron Biberstine, president, Cold Fire Super Systems, explains, "ColdFire is a liquid based fire suppressant that is non-toxic and biodegradable which makes it the perfect choice for equipment used in any off-road work."
Cold Fire systems were created to work specifically with the ColdFire suppressant, explains Biberstine. The company's CT and CTX automatic systems use proprietary modified nylon detection tubing which is permanently attached to standard cylinders. "The detection tube is used to activate our automatic systems at either 176 F (red tube) or 230 F (blue tube)."
Extreme heat at any point on the tubing causes it to rupture, releasing the ColdFire in the cylinder and tube directly toward the heat source. This creates a system with seemingly infinite detection points and nozzles.
The CTX version allows for a multiple nozzle system for locations where several fires can occur simultaneously, or in conditions of high turbulence, such as by the engine cooling fan where the direction of the fire on the detection tube can be distorted. Once the detection tube senses the fire, the tube ruptures and the resulting drop in pressure causes the CTX valve to activate. This diverts most of the flow from the detection tube to the larger discharge ports.
Tyco offers systems like its A-101 dry chemical system, the LVS Liquid Agent system, and the LT-A-101/LVS Twin Agent system for a combined wet and dry chemical suppression. While the FORAY dry chemical cuts off the fire's oxygen supply to kill the flames, the LVS wet chemical cools the area to help minimize the chance of reflash.
Kidde's KVS vehicle system gives three heat detection options for sensing a fire: IR sensor, spot heat detector, or linear heat sensing cable. A dash-mounted control unit alerts the operator to the fire situation. The system discharges multi-purpose dry chemical agent throughout the protected areas of the vehicle.
Fire suppression systems make work safer, protecting both the operator and the equipment investment. Companies like Tyco, Kidde and Cold Fire develop and design specialized systems to keep operator and equipment safety priority number one.
Lean, green, fire fighting machine
Eco-friendly chemicals protect the operator and environment.
ColdFire is a non-toxic, non-corrosive, biodegradable substance, and has been listed by the Environmental Protection Agency (EPA) under its SNAP Program Vendor list as an acceptable alternative to Halon 1211 and 1301.
The SNAP (Significant New Alternatives Policy) Program was established by Congress to make sure that alternatives to ozone depleting substances did not incur more environment, health or exposure issues than the compounds they were replacing.
Kidde Fire Systems recently released its Aqueous Fire Suppression System for mobile machinery at 2008's MinExpo in Las Vegas, NV. The Kidde Sentinel is a fully integrated control, detection and suppression system which can be designed to use the environmentally non-reportable wet agent, AquaGreenXT.
Its engineered fire suppression system is designed for use with 3M Novec 1230 fire protection fluid, engineered to provide clean protection for applications requiring a "green" solution to fire suppression. Novec 1230 fluid presents environmental benefits including a zero ozone depletion factor (ODP) and the lowest global warming potential (GWP) of an chemical based clean agent.