Fire detection systems for high-risk facilities
In many countries, solid household waste is now being collected and carried to waste incineration plants, rather than being dumped directly in a landfill site. The waste is stored in so-called waste bunkers or transfer stations until it can be destroyed. These waste bunkers can contain thousands of metric tons of solid waste which is potentially self-combustible and subject to fire. Self-combustion, (heat development due to pressure) and spontaneous chemical reactions between the disposals and methane gas-building are all potential fire creators and concerns at these plants.
In May 2015 a major fire started at the Wingfield Recycling Depot in South Australia, the fifth fire at this facility in 18 months. John Fetter, SA Waste Industry Network secretary told the ABC: “This has happened one too many times and we’re concerned about the health and wellbeing of our employees who work around the site and the local residents as well, and it’s just got to stop.”
Waste station fires can be incredibly hazardous for both the on site operators and the environment. Fires are invariably resource intensive, long duration jobs with the potential to create significant interference and detriment to normal community activity, including public health issues.
Disposing of the heavily contaminated firefighting water, which hampers the further processing of the waste by making it harder to burn, has to be disposed of somehow, and water does not always reach the potential fire hot spots that can still smolder anywhere within the waste. Think of it like a campfire; the hotter and longer it burns during the night, the more lasting the coals will burn. You only have to peel off a few layers in the morning for that fire to come right back to life. A waste facilities fire could easily burn for 2-3 weeks if not fully extinguished. This is why the stored waste has to be permanently moved, mixed and turned by plant operators. It keeps any one spot from becoming too dangerous.
A review commissioned in 2012 by the Fire Services Commissioner of Victoria into improved fire management in landfill sites. The report stated that “Early intervention is essential to prevent any fire from developing into a large and difficult to extinguish event. Once a fire is well established there seems no substitute for copious quantities of water to contain the spread and enable access by machines to physically disturb and remove the burning material. The application of more water is often needed until it is certain that all burning material has been extinguished.”
Fire is also seen as one threat that is becoming increasingly important to the regulatory controlling bodies as well as many environmental groups. Early response to a fire that could damage or impact on equipment operating or controlling treatment plants will assist in reducing waste, environmental damage and pollution.
Having regard for the issues a reliable early warning smoke detection system coupled with a pre-planned response strategy is one way to enable early intervention.
Very early warning detection can assist in mitigating the fire risks in waste treatment or recycling facilities by detecting smoke from a fire or any potential smouldering smoke event such as:
- Overheating and faults in electrical switch equipment and cabling
- Spontaneous combustion events
- Potential fires from high frictional heat sources in large collection and sorting equipment.
- The ignition of onsite fuel and toxic chemicals which can lead to a potential fire
- Human error
- Faults and the overheating of pumps and machinery
- Gas leakage
Aspirating smoke detection has long been seen as one of the most reliable and effective means of detecting fires in industrial facilities. With manageable controls and sensitivity capability of detecting the smallest amount of smoke, an appropriate purpose-built ASD will have a high resistance to background pollution or contamination providing early warning and time to intervene and respond before a fire gets out of control.
A reliable and early warning fire detection system with a pre-planned response strategy are essential to protecting the facility, community and the surrounding environment.
Paul Leslie is the Special Practices Manager for Xtralis Pty Ltd – Asia Pacific. His current position within Xtralis is with Product Line Management which includes the promotion and development of Aspirating Smoke Detection technology. His role also includes involvement in ASD Codes and Standards.