Hi, I am working on a research project about ignition of plastics used in electrical equipment. As you all know, UL 746C has a test called hot wire ignition. The test is specified by ASTM D 3874 - Standard Test Method for Ignition of Materials by Hot Wire Sources. I would be grateful if someone provided me the following information:
1. This standard (ASTM) was first published in 1988, under jurisdiction of ASTM Committee D-9 on Electrical and Electronic Insulating Materials. I have not found any research work that provided basis for this test. Does anybody know of any? 2. The standard requires a power density of 0.26 W/mm to be dissipated in 250 mm of Nichrome wire (24 AWG, 0.05 mm in diameter). How these values were established? (By the way, the standard suggests that a current of 60 A and 1.5 V should result in a power density of 0.3 W/mm. I figured out that they meant 6.0 A and 15 V, since the calibration of the wire must be made from 1 to 8 A. Furthermore, a current of 60 A through a 24 AWG nichrome wire is just unfeasible). 3. For those who have ever performed this test, what was the variability of the mean time to ignition between samples? Any additional information regarding this test would be very appreciated. Thanks! -------------------------------------------- Luiz Claudio Bonilla de Araujo Graduate Student - Safety Engineering Texas A&M University - College Station - TX http://www.tamu.edu --------------------------------------------
