The Fire Protection Blog.

Fire Suppression Focus – Waste Shredders

20th June 2019

Posted by: Ardent

Ardent

Waste shredders face some of the most challenging working environments in industry. Run to provide the lowest possible cost per tonne, they usually work long hours with little human interaction. In addition, the materials they process are often very flammable.

The result is a very high fire risk that needs to be managed correctly; otherwise the consequences can be catastrophic and go far beyond damage to the machine.

Whether it is a mobile or stationary shredder, an automatic fire suppression system is a must to protect the machine, site and staff against the high risk of machine fires. However, not all systems available in the market are designed to provide effective and reliable fire protection to these assets. Here are some considerations when choosing fire suppression to protect waste shredders.

What are the challenges?

For a fire to occur, three things are necessary: heat, a fuel source, and oxygen. The environments in which shredders operate are abundant in highly combustible fuel sources – wood chippings, biomass, paper and cardboard, to name a few. These materials can quickly build up in the engine compartment and belly pan of the machine, and, when combine with heat generated by engine components, turbocharges and exhaust manifolds, can quickly ignite. With plenty of fuel to feed it, the fire can rapidly spread.

Waste shredders routinely operate unmanned for prolonged periods of time, which can worsen the situation and allow a fire to develop significantly before it is discovered.

In addition, shredders often work inside sheds or other facilities, which widens the risks to the business as the potential losses of machine fire increase beyond machine damage.

What are the main fire hazard areas?

The following areas pose a fire hazard as they are either a source of fuel or heat. However, fire hazards will differ from model to model, working environment and work schedule, so we always recommend a fire hazard analysis on each machine.

Fire hazard areas in waste shredder

Common fuel sources in waste shredders include build-up of debris which accumulate in areas such as the engine compartment and belly pan, as well as flammable fluids, fuels, oils and greases. On the other hand, the engine, exhaust manifold and turbocharger often reach very high temperatures which, when in contact with any fuel source, can cause a fire to start.

What extinguishing agents are required?

Due to the high amounts of combustible material in shredders, the risk fire re-ignition after the system has discharge is significantly high.

Re-ignition can happen when the flammable materials come into contact with extremely hot surfaces such as turbochargers or exhaust manifolds after the fire suppression system has discharged.

The best way to achieve rapid fire suppression and significantly reduce the risk of fire re-ignition is to install a Twin Agent fire suppression system. Twin Agent systems combine dry and wet chemical extinguishing agents. The dry chemical agent provides rapid fire knock-down and excellent coverage of the hazard areas, but its cooling capabilities are limited. The wet chemical agent is able to cool down super-heated components such as the turbocharger and exhaust manifold to help protect against fire re-ignition.

The quantity of each extinguishing agent must be adequate to cover all identified fire hazard areas through strategically located discharge nozzles.

What other system features are recommended?

As shredders often operate unattended and in remote locations, automatic engine shutdown and battery isolation are also important to help minimise the potential of fire re-flash.

When a fuel or hydraulic line or connection fails, it can spray fluid on to a super-heated component such as a turbocharger or exhaust manifold, starting a fire. As long as the engine continues to operate, this fluid will continue to fuel the fire. Additionally, damaged wiring can be a source of electrical fire. By including an option to cut power to the battery and fuel to the engine, we can significantly reduce the risk of fire re-ignition.

A sounder beacon can also be helpful to alert the staff in the event of the fire suppression system detecting a fire.

Conclusion

When it comes to fire suppression, waste shredders pose specific challenges that need to be considered in order to provide the right level of fire protection.

Some fire suppression suppliers offer single agent systems to protect shredders; however, we strongly recommend fitting a Twin Agent system as a single agent system might not be sufficient to protect these machines. Quantity of extinguishing agent and number of discharge nozzles are also important aspects of effective fire suppression.

For more information on how to protect your shredders and other machines against the risk of fire, you can contact one of our experts on 01423 326740 or using our contact form.

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