Fire protection in a filter

Dust filtration is extensively used in modern production techniques. Dust can be organic, mineral or metallic. In most cases, it is combustible and, when it is in suspension in a confined environment and at a certain concentration, there even is a risk of explosion.

Fire and explosion risk in a filter

Dust ignition in a combustive environment can only happen if sufficient energy is applied. The risk of ignition sources arising inside the filter itself, when closed, is small. In most cases, ignition can occur as a consequence of the presence of sparks or of already ignited dust in the duct, upstream from the filter. The production of sparks is directly a function of the type of process upstream from the filter.

We offer a straightforward system to rapidly control incipient fires in filters.

Detecting a fire in a filter

The type of detection used largely depends on the process configuration.

• Since the risk of ignition from the main duct is inevitable, a spark detection system is imperatively needed.
• In case of a risk of ignition from another source (fall or projection of an extraneous element, works in the vicinity, etc.), detection will have to take place directly inside the filter. It could consist of either flame detection (particularly if the powder is combustible even when it is not in suspension) or temperature threshold detection.
• As a rule, a manual detector is available.

Control and indication in a filter

A control and indication panel is positioned in the vicinity of the filter. It manages the signals generated by the various detectors and controls the automatic extinction. It also controls the information devices (sound alarm, flashing lamp) and generates the interlocking contacts required to stop the process.

Extinguishing a fire in a filter

Except when metallic dust is involved, water and CO2 can be used in virtually all cases.

Water has excellent results, but after the system has been triggered, most filtering devices will need replacing.

CO2 is easy to use, however the quantity to be used is a function of the elements below:

• Volume of the filter.
• Flow rate of the blower.
• Stopping time of the blower.
• Diameter of the ducts.

The extinguishing system consists of steel pipes, hoses and spray nozzles.

CAUTION: The extinction should be designed in such a way that it does not whirl up the dust that is present in the filter. Because if there are already flames inside the filter, there may be a risk of explosion before the flames have been put out.

Immediate activation of the fire protection system

When sparks are detected in the duct supplying the filter, the detectors send a signal to the control cabinet. The elements below are immediately triggered:

• Sound alarm and flashing light.
• The interlocking contacts in order to interrupt the process and particularly the blower.
• Extinction. The extinguishing substance reservoir opens and empties itself inside the filter.