.:: baghouse, cartridge dust collector, pneumatic conveyor, wet scrubber, multi cyclone, blower fan and rotary valve ::.

FILTER BAG FIRE PROTECTION

DAV incorporates fire protection system for bag filter handling dust with low minimum ignition temperature in fire-risk process. In design and selecting appropriate fire protection system, It is important to understand that this ignition temperature differs between its conditions in dust cloud and in silo (called layer). Aluminium flake, for example, has minimum ignition temperature of 610degC in cloud of dust, but drops to 326degC when it is settled in a silo, raising fire risk tremendously. Therefore, it is essential that low temperature flame is detected and extinguished before it glows in storage.

DAV employs leading technology in baghouse fire detection from Firefly, Sweden. Firefly patented infrared (IR) detector reacts to temperature as low as 130degC. Conventional detectors in the market are incapable of detecting ignition source anything below 700degC.

MINIMUM IGNITION TEMPERATURE
	CLOUD	LAYER
Paper	580⁰C	360⁰C
Tobacco	470⁰C	280⁰C
Wood	480⁰C	260⁰C
Cellulose	500⁰C	380⁰C
Grain dust	430⁰C	230⁰C
Polyurethane foam	510⁰C	440⁰C
Aluminium flake	610⁰C	326⁰C
Charcoal	520⁰C	270⁰C
Rice	510⁰C	450⁰C
Stearic acid	420⁰C	440⁰C
Skimmed milk	490⁰C	200⁰C
Nylon polymer	500⁰C	430⁰C

The detector indicates hot particles, sparks and flame in the process duct where the material is moving such as in pneumatic conveyor and dust collector. The detector is infrared-sensitive, measuring radiated energy and having multi-zone detection with high degree of reliability. This unique principle of energy measurement confirms the risk of the ignition source. This means that internal sensitivities, humidity and temperature in the electronic etc. are checked automatically, every minute.

The highly integrated control panel continuously check status of detector, pump power and water pressure. It also allows output signal for alarm activation, system emergency stop on detection of consecutive hot spot signal. The pump generates the required pressure for water spray, and pressurized water tank acts as booster to maintain consistent spraying pressure. Pressure switch is built-in.

Fire extinguishing valves and nozzles are located downstream of the process pipe, 9m away from detection, to provide for response time. Understanding of process characteristic and selection of combination of nozzle and pressure plays an important role in ensuring successful and effective extinguishing of hot spot. Larger water droplet size and high spraying pressure gives the momentum that is required to penetrate into conveying mass, to reach and extinguish hot spot. This is especially the case in pneumatic conveyor application.
Likewise, water mist finds its application in panel press, mill, sensitive machines by suppressing fire without causing residual damage. Microscopic water droplets get evaporated quickly, foaming steam that acts to blanket the surrounding off oxygen.