Features, Safety systems and solutions, Work health and safety

Fire suppression for mega-class mining vehicles

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Single-agent fire safety solutions can simplify installation, activation and clean-up when protecting heavy-duty industrial mobile equipment, according to Johnson Controls.

Fire suppression solutions have become more sophisticated to match the growing complexity of ultra- and mega-class mining vehicles. Capable of moving hundreds of tonnes of material, these industrial vehicles have bigger parts, contain larger engines, carry more fuel and, consequently, present a greater fire risk than standard industrial vehicles. 

Dry chemical systems have been the go-to for fire protection on large industrial vehicles since the 1950s, but dual-agent systems emerged in the 1990s to better protect ultra- and mega-class giants. 

Despite the availability of an FM-approved single-agent system, National Fire Protection Association (NFPA) standards require the use of a twin-agent suppression system in ultra- and mega-class equipment with “hydraulic systems containing more than 150 gallons [568L] in the lines”. 

Dual-agent – or twin-agent – systems use dry chemical and liquid agents in a single design. 

The dry chemical agent rapidly knocks down flames, and the liquid agent cools hot surfaces and minimises reflash potential. 

However, the suppression benefits of these dual-agent configurations come with additional complexity – including costly clean-up and repairs after a dry chemical discharge, careful planning for side-by-side installations, and the need to activate two separate systems simultaneously. 

These challenges, in addition to shifting regulations regarding the use of per and polyfluoroalkyl substances (PFAS), emphasise the need for a new, non-fluorinated suppression solution that simplifies fire protection while meeting the needs of today’s heavy-duty industrial vehicle operations.

Testing an innovative new solution 

The latest evolution of firefighting technology has the potential to provide extraordinary performance for ultra- and mega-class earthmovers, exceed the capabilities of previous systems, and simplify fire suppression system design. 

The ANSUL Vehicle Systems fire team recently conducted extensive testing to evaluate the effectiveness of a new, non-fluorinated single-agent liquid system versus other single-agent and twin-agent set-ups currently used in the industry.

According to the Queensland Mines Inspectorate, 60 per cent of fires on turbocharged diesel engines resulted from hydraulic or engine oil spraying on the turbocharger, 11 per cent were caused by engine fuel contacting the turbocharger, and 13 per cent from turbocharger failure. 

With these statistics in mind, the chosen fire test protocol required agents to achieve the following:

Suppress fire through a pressurised fuel spray

Cool a superheated surface (simulating a turbocharger, manifold, etc)

Extinguish a fuel pool fire that could potentially be caused by fire or fuel propagation in real-world scenarios

Prevent flame reflash

Tackling any one of these four objectives is difficult, but the protocol used incorporates all of them into a single test. 

What makes this test especially challenging is the fact the suppression agent is sprayed horizontally at the vertical reignition plate and must therefore suppress and secure the pool fire by indirect coverage. 

Achieving meaningful results 

The testing demonstrates the speed at which the new ANSUL LVS (liquid vehicle system) NF-40 liquid agent can extinguish high-pressure fuel sprays and fuel in-depth pool fires, while also cooling the entire mass of the plate and the fuel in-depth pan below. 

What’s more, the lower discharge time illustrates that less ANSUL LVS NF-40 agent is required compared to the legacy LVS agent for effective fire suppression.

Given the dry chemical used in test one could not knock down the flames alone, tests three and four suggest that the addition of a liquid agent – either legacy or NF-40 – suppressed and secured the pool fire.  

Tests three and four demonstrate another shortcoming of the dry chemical. Although the twin-agent systems achieved complete suppression, the thermocouple data showed that the plate remained superheated. It is thought the dry chemical created a barrier that isolated the heat of the plate from the fuel spray and prevented the LVS liquid agent from efficiently removing the heat from the plate surface. 

Consequently, these tests demonstrate that the dry chemical component of a twin-agent system is not only ineffective in suppressing the fire, but may even hinder the suppression effect of the liquid agent. 

In other words, under these testing conditions it was more effective to use ANSUL LVS NF-40 as a standalone system. This finding should influence the future design of heavy-vehicle fire suppression systems. 

The physiochemical properties of ANSUL LVS NF-40 also impact fire suppression system design for haul trucks and other mining vehicles. The enhanced properties of this new agent allow for installation of more nozzles per tank and make it possible for each nozzle to cover more area compared to previous liquid agents. This design flexibility is critical as the size and complexity of these vehicles continues to grow. 

With NF-40 liquid agent, the number of nozzles per tank may range from one to 24, depending on the size of the tank. The nozzle design and an extended maximum spray distance of 54 inches (137.1cm) helps the agent flow into hard-to-reach areas along the same path where flammable liquids may have migrated.

An operating temperature range of -40–60°C helps ANSUL LVS NF-40 agent protect mining operations in the most extreme conditions. 

While heavy industrial vehicles have depended on twin-agent fire protection systems for decades, and some applications still require them to meet the NFPA 120 and 122 standards, these systems are complex to install, activate and clean-up. 

Using ANSUL LVS NF-40 suppression agent alone not only streamlines complexities but can provide a better and more cost-effective solution for ultra- and mega-class mobile equipment. 

This advancement in fire protection technology offers the mining industry a new standalone single-agent option while meeting the growing need for a high-performing non-fluorinated solution. 

Utilising new insights gained from the in-depth testing conducted at the Johnson Controls fire technology centre of excellence, mining operations can select the most effective vehicle systems solution for protecting personnel, property and operational continuity. 

This feature also appears in the May-June issue of Safe to Work.

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