Ignore the Smoke and Detect the People

Fire barriers such as fire doors and flaps are designed to prevent fires from spreading along corridors, passages or chutes. This kind of barrier usually remains permanently closed, but can stay open in exceptional cases if the protected route is used very frequently. However, an automatic closing mechanism with a safety monitor is then required.

A new generation of fire protection sensors manufactured by Pepperl and Fuchs offer greater reliability and a wider range of functions for applications of this nature. Two new products from the sensor specialists are ideal for safety devices on fire doors and similar fire barriers. The type LA28/LK28 thru-beam sensors have a maximum sensing range of 10 meters and RLK28 retro-reflective sensors a maximum range of 3 meters. The Property Insurers Association has certified and approved both versions in accordance with VdS test report FSA. Some defining characteristics of the photoelectric sensors include outstanding performance and functional reserves, the sensors offer more functions and are smaller than previous models.

Time to Switch
The product‘s features include a universal power supply for 12-240 V AC/DC, greater immunity to extraneous light, even from fluorescent lamps, and a high degree of protection to IP67 (dustproof and watertight). Other important features include new timer functions which facilitate the adaptation of devices to the different technical requirements faced in practical applications via programmable ON and OFF delays with adjustment ranges between 0.1 and 10 s.

The fire protection sensors were designed to reliably detect the presence of people in atmospheres where smoke is also present, because open fire doors should only be closed automatically if there are no people in the passageway. In order to maintain insurance claims in the event of damage, only photoelectric sensors certified by the Property Insurers Association (VdS) are permitted for use in such fire barriers. The property insurers have compiled separate test specifications that relate to a "standard fire": the test objects must prove that they provide sufficient functional reserves to generate light that penetrates through the smoke in a defined smoky environment.

Ready State
The fire protection sensor can be switched between light-on/dark-on because they operate with red modulated light and provide a floating changeover relay at the output end. Different green, yellow and red LEDs provide the user with information on operational readiness, switching states and correct alignment. A flashing LED indicates that the excess gain threshold has been exceeded. The areas of application for the new fire protection sensors include installations where safety circuits conforming to VdS regulations are required on devices for fire doors and flaps.