The SCR ELEKTRONIKS Heated Wire Tester is used for testing Ignition of Materials by Hot Wire Sources as per ASTM D 3874. As suggested by the standard, Heated Wire Tester is designed to evaluate a material's ability to resist ignition when exposed to abnormally high temperatures.
As per the standard, the center position of the specimen is wrapped with a Nichrome wire in a specific way as per clause 10.1 of ASTM D 3874. The free ends of the wire is connected to a circuit which supplies current as per clause 6.3 “Supply Circuit” of ASTM D 3874. Next the circuit is energized such that it dissipates 0.26 W/mm. When the ignition occurs or after 120 seconds (whichever is earlier), the circuit is switched off and the time to ignition is noted. If the material under test melts, then the circuit is switched off when the material is no longer in touch with the 5 turns of the heated wire. In such case the time to melt is noted.
UL 746A refers to ASTM 3874 - 88 for this hot wire ignition test. As per UL 746 A, for a given material, the Hot Wire Ignition Performance Level Category (PLC) is to be assigned based on the determined mean time for ignition (IT). Please refer to table 31.1 of UL 746A.
Like-wise for all other standards such as IEC 60947 - 1 and IEC 60695 - 2 - 20 (Fire hazard testing - Part 2: Glowing / Hot wire based test methods - Section 20: Hot-wire coil ignitability test on materials) the testing method is same.
The SCR ELEKTRONIKS Heated wire test apparatus has a micro-controller based dedicated logic unit to conduct this test. It’s built in extruded aluminium chassis with all material carefully chosen for durability & dependability. It’s used by leading test labs world-wide.