As featured in Mining Magazine.
When determining how best to protect a piece of heavy off-road equipment from the threat of fire, a Fire Risk Assessment is the most indispensable procedure one can use. This process entails an evaluation of the main hazards of a specific machine and its operating environment. The assessment provides a decision-making framework to help one evaluate a vehicle's risk potential, implement changes to mitigate those risks, and, when deemed necessary, to design and install a fire suppression system that appropriately addresses those risks. It is so helpful, the US National Fire Protection Association (NFPA) has a guide to explain and encourage its use.
A thoroughly executed analysis is required for proper fire suppression system design, installation and performance. A common Fire Risk Assessment "checklist" includes, but is not necessarily limited to:
- The engine size
- Normal operating temperatures
- The amount of hydraulics on-board
- The type and size of after treatment components
- The hazards related to the operating environment
- Any potential impact fire would have on personnel’s safety
Determining how the aspects listed above affect fire suppression system recommendations include a combination of industry experience, the system manufacturer’s recommendations (which ought to be based on third-party testing results), and industry standards such as those of the NFPA and the US Mine Safety and Health Administration (MSHA).
Identifying Fire Ignition and Fuel Sources on Heavy Equipment
To begin with, the high temperature areas of a machine need to be accounted for, such as the exhaust manifold, turbocharger, hydraulic pumps, torque converters, brakes, and gears. Other ignition sources are electrical components such as batteries, fuse panels, generators, alternators, electrical wiring and starters. These areas are potential ignition sources for a fire because any flammable liquids which come into contact with them are likely to flash, or because they can catch fire themselves due to malfunction.
Once the ignition sources have been accounted for, one should evaluate the potential fuel sources, which are divided into three separate classes of combustible materials:
- Class A materials are referred to as debris, which would include coal dust, electrical insulation, upholstery, tires, etc.
- Class B materials are fuels such as gasoline, diesel fuel, hydraulic fluid, grease, oil, or battery acid.
- Class C hazards are electrical in nature and result from electrical shorts, defective wires, defective wire insulation, and the like.
After the fuel sources have been evaluated, one must then determine the probability of their co-existence with the ignition sources. Part of making a thorough job of this step is to have some base familiarity with the fire and maintenance history of the vehicle model in general.
An assessment should be made of existing areas where lubrication, hydraulic oil, fuel lines, rubber and plastic, and other combustibles are in proximity to an ignition source. An evaluator will also look for areas where fuel sources might leak, drip or spray fuel onto hot surfaces or potential spark generators. The presence of accumulations of combustible materials, such as oil-soaked waste and fuel spillage, represent potential fire hazards as well. One should also account for cooling fans and/or air flow to determine how it might impact flame propagation. With these factors in mind, a picture of a properly sized and configured system will emerge.
Accounting for the Machine's Operating Environment
Another significant consideration when determining a fire suppression system’s design is the machine’s operating environment. When the product itself is flammable and/or there is debris created, the Fire Risk Assessment, and therefore the fire suppression system design, will be impacted. How any by-product materials influence a system design will depend on their relative flammability, which of course impacts the chances of a fire starting.
This is where the ‘housekeeping’ of a machine comes into play. A machine that is kept clean and relatively debris free is at less risk than one which has build-up on it. End users must be reminded that machine cleanliness is always the first line of defense against a fire in any industry.
By the same token, regular mechanical upkeep can prevent fires caused by part failures. Keeping an eye out for damaged hoses is especially important in mining as the majority of vehicle fires in that industry are caused by high pressure flammable liquids spraying upon a hot machine surface.
Fires Present High Risk Situations for Personnel
The exposure of personnel to fire is obviously a significant concern, and one which cannot be over emphasized. To properly account for this critical issue, one must determine the number of persons involved with the machine under the Fire Risk Assessment and their location during operation and maintenance.
Beyond that, the exposure to potential fire risks for each person and whether fire and smoke could impair safe egress needs to be determined. There is a broad range across which operators’ risk goes from practically non-existent to high. Determining where along the continuum a particular job falls is also part of a Fire Risk Assessment.
An example of a high risk situation would be the driver of a large haul truck whose cab is 20ft (6.1m) above the ground, essentially sitting atop the engine, with a ladder required for egress.
Once personnel concerns have been assessed, one should fully evaluate the cost of repair or replacement of a vehicle, the cost of damage to a site, and the potential issue of site clean-up. These economic risks, along with the cost of vehicle down time and lost production, can significantly impact the amount of suppression deemed appropriate for a given machine. So too can the cost of any potential loss of natural resource.
Considering Fire Suppression System Options
Once these steps have been taken to determine the need for fire protection, one can begin to select fire suppression system hardware and agent types. This process includes determining the number of nozzles required to cover the high-risk areas, and, accordingly, the number of agent tanks required in the system.
There are two options for fire-fighting agents to choose from: dry A:B:C powder and A:B liquid. A third option, combining the two and taking a dual agent approach, is often the most efficient and appropriate because it utilizes the benefits of each type and doesn’t take up as much space physically, or cost as much, as a liquid-only system. It should be noted that choosing the appropriate agent for the hazard is a process which should involve the suppression system supplier as there is no one-size-fits-all solution.
Other configuration particulars that need to be determined at this point are whether an automatic or manual system is most appropriate; the type, number and placement of fire detecting sensors; and the number and location of manual actuation points. System options like engine shutdown, remote alarms, and telematics integration can also be chosen at this point to complete a system configuration.
It is important that a right-sized system is settled upon once this stage is reached. It is easy to subscribe to a ‘more is better’ mentality at this point, but sufficiently sized systems are the most desired outcome for the end user. On the other hand, undersized systems that are insufficiently sized might seem attractive due to their lower price points, but their effectiveness when discharging is suspect at best.
To find the appropriate solution, one which is aptly sized yet economical, one should request that a copy of the system manufacturer’s recommendation be provided. If a specification sheet is not available, one should ask the service provider if the basis of its recommendation is founded on a solid Fire Risk Assessment, thereby ensuring it is not arbitrary in nature or that non-certified components are not being offered.
Whether the result of a legal requirement, an industry standard or a proactive machine owner, every fire suppression system needs to be at least sufficient for the task at hand. AFEX Fire Suppression Systems believes in an open and honest assessment of the particular situation to establish its recommendations, the basis of which is a Fire Risk Assessment. End users should be aware of this tool and be sure that their best interests are being taken into account through its use.