MRF improvements

Internal Fire Suppression System installed at A303 Materials Recovery Facility continuously look to improve and develop their facilities further to ensure that they can continue to offer sustainable solutions within a safe environment.

Their proactive approach to fire prevention saw them seeking advice with the local fire authority and Environment Agency, and this resulted in investigations for fire prevention. asked Wright Rain Environmental Ltd to come up with a solution for their A303 Materials Recovery Facility by considering fire suppression within the building using the existing water sources and potential links with the fire alarm automation.

Where it would be normal to provide tanks to hold enough water for the purpose of fire suppression, the site has ample clean water stored in a lagoon close to the building and, with an automated floating arrangement to keep the pump primed at all times, it was decided to install underground piping across the roadway to the back of the building and keep the system constantly pressurised with a speed variator and pressure transducer.

Utilising specialist fire nozzles the system was designed to operate using six nozzles providing a wetted diameter of 10 – 12 metres of full cone, relatively heavy droplets to cover the areas of waste stock, machinery and combustible product bays. These nozzles were mounted on three steel pipelines high in the roof of the building, just below the lights, to prevent damage from the mechanical grab. The steel pipes exit the building and pass down to ground level where a valve manifold is mounted, with a low voltage solenoid valve, the three individual spray line isolating valves and a valved side tee for regular testing purposes.

The solenoid valve operates, via specialist fire cable, on a low voltage supply from the main building entrance next to the fire alarm system. This is activated by breaking the glass on the modified red fire alarm glass call point which links in with the fire alarm system, manual activation using the red box override key or by using the manual opening at the valve point.

Due to potential problems with false activation from both dust and exhaust fumes; the normal laser alarm sensor can be replaced with a flame/heat sensing system.

On opening, the pressure in the pipe system drops and the main pump is automatically activated to discharge the water through the spray system for a programmed time of around 10 minutes, to allow enough time for the fire to be doused whilst preventing the site from being flooded. This time span is fully adjustable.

The system is designed with non-combustible materials within the building and the pumping system and power supply are separate to the building to prevent disruption and help comply with fire regulations for insurance purposes.

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