Fire protection UHF furnaces/hot air tunnels

Vulcanisation of rubber profiles takes place in a continuous process in UHF installations and hot air tunnels, which are powered by electricity or gas. The profile travels at a constant speed on the continuous processing lines. Optimum vulcanisation is achieved at temperatures between 200 and 500 °C.

Increased fire risk in UHF furnaces and hot air tunnels

The above mentioned processes are often disrupted by fires. The most frequent causes are:

• An accumulation of residue inside the furnaces.
• An excessively high temperature absorbed by the profile.
• Arcs caused by UHF on reinforced type profiles.

A fire occurring in this type of installation can have serious consequences:

• The process speed (15 to 25 m/s) can result in the propagation of the fire throughout the installation.
• The presence of inflammable residues in aspiration ducts encourages the fire propagation.
• Certain processes involve using highly flammable lubricants (flocking).
• The fire only becomes visible after the extraction systems can no longer suffice to evacuate all the smoke.

We have developed a range of safety equipment that immediately detects and extinguishes the fire and keeps it from spreading. The system guarantees limited fire damage and less down-time.

Different detection systems for different UHF furnaces

The type of detection system you need, depends on the type of furnace.

• If the speed of the extracted air is not less than 20 m/s, a spark detection system (item 2) can be fitted on the extraction duct or ducts.
• If this is not the case, a flame detection system (item 3) has to be fitted directly on the profile, through the furnace walls.
• A manual triggering device (item 4) is also available.

CO2 to extinguish a fire in a UHF furnace

The supply tank with the extinguishing medium must be situated close to the risk. Except in certain specific situations, CO2 can be used in virtually all cases. However, the quantity to be used depends on the parameters below:

• The volume of the furnace
• The suction speed of extraction
• The diameter of the extraction ducts
• The ambient temperature of the process

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

CAUTION: the extinguishing installation must be designed in such a way that no pollution can obstruct the extinction ducts.

Control and indication in a hot air tunnel

A control and indication panel is positioned in the vicinity of the risk. 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 hot air tunnel

When sparks are detected in the extraction duct, or directly on the profile surface, 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 UHF.
• Extinction. The extinguishing substance reservoir opens and empties itself inside the furnace. As soon as the fire has been put out, the extinction process is automatically stopped. It is therefore possible to use one and same reservoir for several extinction cycles.

CAUTION: the profile must not stop moving as this would create a risk of it catching fire over the whole heating area.