Michael Van Niekerk from ASP Fire offers an in-depth expose on the importance of choosing the right conveyor belt fire detection for mining applications.
Belt conveyor systems are used extensively in the mining industry – they provide an ideal solution to transport manageable sized material from one processing point to another. Using such a system reduces the reliance on manpower and reliability is maximised. However, a key protection area that has to be considered is how to best handle the issue of conveyor belt system fires.
So says Michael Van Niekerk from ASP Fire, who goes on to add: “Conveyor belt systems and supporting structures are normally of non-combustable construction, however, any large fire may damage or cause the collapse of the structural elements. The principal fire load includes the material being conveyed, the mechanical components of the system, and the belt itself.”
He says that there is a misconception that conveyors are not easily ignitable, which can often prevent mines from taking the necessary precautions to ensure that there is sufficient fire protection in place: “Once a conveyor fire starts, it will grow rapidly, and become very difficult to control in a very short period of time. Belts contain polymeric materials, which present a serious risk in terms of rapid fire spread and the generation of toxic, corrosive smoke – making these fires lethal and the control of which, incredibly difficult.”
In June this year for example, a fire that burned a multi-story conveyor belt at a Lake Elsinore aggregate mining and crushing business in the USA, caused an estimated $13-million in damage and took firefighters more than two hours to contain. “When you consider the overall loss caused by a conveyor belt fire – you can’t just think about the possible loss of lives, injured staff and the loss of expensive equipment, but you also have to consider the excessive loss of revenue that will be incurred by the downtime required to fix or rebuild the conveyor belt.
“As such, the essential ethos behind any quality conveyor belt fire protection needs to revolve around the preservation of the conveyor belt system itself. Hence, the need for early detection and the quick and successful extinguishing of any fire, while simultaneously cooling the effected structure, remains key.”
Possible sources of fire on a conveyor
“It is important to note that every conveyor belt system is unique, and as such, an individual assessment has to be made for each system in order to adequately and accurately determine where the fire risks lie for that particular system design,” explains Van Niekerk. Having said that however, he notes that in his experience, the most common causes of conveyor belt fires result from either static heat build-up from friction caused by belt movement, moving fire on the belt itself, electrical failure or overheating of the conveyor belt motors.
He offers the following outline of common causes of fire on conveyor belt systems:
• Friction due to a belt losing traction and slipping on the drive roller, or due to a misaligned belt slipping off the jam rollers and jamming. This can generate sufficient heat to ignite the belt itself or the product it is transporting.
• Cutting or welding activities generate hot molten metal particles that can ignite the belt.
• Accumulated waste below the belt due to lack of regular housekeeping.
• Overheated materials from ovens, kilns or dryers that have not been sufficiently cooled before being placed on the conveyor belt.
• Undetected electrical malfunctioning of conveyor belt motors.
Early detection, fast-acting fire prevention solutions are key
To ensure early fire detection in conveyor belt environments, ASP Fire recommends the installation of a variety of Technoswitch Fire Detection technologies, which are specially suited to long-distance and moving environments – these include:
• The 246-1 Ember Detector, which recognises a smoldering ember on a moving conveyor belt before it bursts into flames.
• Linear heat detection cable is used for very long distances, which are prevalent on conveyor belts, and responds to a rise in heat that is above the alarm threshold.
• The 40-40 IR3 uses three different Infrared light wavelengths to detect an open flame.
• The TEC247 is a fire control panel that manages all of the detection devices, the alarms and the suppression equipment valves.
• The TEC057-1 is an interface unit that allows for multiple suppression systems or cylinders to be connected to a single fire control panel.
Over and above this, van Niekerk recommends other industry-leading technologies to provide a cost-effective and efficient solution for conveyor belt fire-suppression solutions: “The I-Cat Firetrace self-activating fire-detection and suppression system is a prime example. This technology can automatically detect fire and effectively suppress it in a matter of seconds before it becomes a problem.”
The Firetrace system boasts polymer tubing that will rupture when exposed to a flame. This specialised Firetrace Detection Tubing combines leak resistance, flexibility, durability and precise temperature sensitivity, allowing it to react quickly when the heat from a fire is present. It connects to a custom-engineered valve and a Firetrace cylinder that contains the best fire suppression agent for a particular hazard.
“These low-pressure systems cause no thermal shock, have long operational life, allow for on-site refilling of the systems, are electrically nonconductive and use sustainable, clean technology, and can even be used with other external fire-detection systems,” explains Van Niekerk.
The I-Cat T-Rotor Technology systems are another prime example of innovative New Age technology – providing localised protection, hand-held extinguishers, fast response back-packs and vehicle protection systems. They comprise extinguishers that use a combination of water and/or foam in a mist form, as opposed to traditional fire extinguishers that use either dry foam or chemical powders.
“The misting technology of the T-Rotor Technology uses a small rotor unit that atomises water and charges it with kinetic energy, creating a fine atomised mist, with a size of between 50μ and 60μ at water pressure of 3 bar, in a mobile unit. Using water as the main agent, and nitrogen as a propellant – it can extinguish all types of fire, including rubber and plastic fires, kitchen cooking oil fires, diesel and petrol fires and electrical fires rated up to 245kV,” explains Van Niekerk.
The system can also be designed to create cooling zones on conveyor belts to detect and cool hot material without adding to the moisture content of the product, to reduce any potential fire risks.
Van Niekerk concludes by noting that the Water Mist extinguisher range is SABS-approved: “Using water and nitrogen is safe, effective and saves on maintenance and service costs. Each litre of water amounts to 120 square metres of coverage capability, and the small quantity of water that is used has the added benefit of ensuring little to no redundancy, damage or environmental contamination.”
Operational features of Water Mist technology from ASP Fire:
• The I-Cat Water Mist range boasts an operational time span four to five times longer than standard dry chemical powder extinguishers to ensure greater cost-savings.
• The EXTINGUISHmist fire extinguisher emits a superfine atomised mist that quickly expands and forms an inert atmosphere in the fire zone.
• The extinguisher has a high degree of dispersion and forms a large screening surface, or halo, shielding the operator from the heat radiation caused by a fire.
• The small amount of water sprayed from the EXTINGUISHmist – only 6ℓ per minute – guarantees longer-lasting fire-fighting capacity of up to four times, compared with traditional dry chemical powder extinguishers.
• A hand-held Water Mist fire extinguisher can suppress all types of fires without causing additional collateral damage to property, people, animals and the environment.
• The EXTINGUISHmist can be sprayed directly onto victims threatened by fire, enabling responders to swiftly and effectively execute rescues.
• The extinguisher’s universal application across all common fire classes accelerates response times and reduces the need to carry multiple types of equipment.
• The EXTINGUISHmist portable fire extinguisher consists of a proprietary nozzle and T-Rotor unit, unique to I-Cat’s water mist and foam mist range.
• The EXTINGUISHmist technology is also available in a hose reel device that can be mounted onto fire trucks, vehicles and trailers.