Maybe I should have saved this for a Friday question, but here goes. This is a general question regarding ignition sources and exposure time.
In reviewing the flammability (UL 94) tests and the hot wire ignition (UL 746) tests, it seems 30 seconds is the magic number for igniting the sample being evaluated. I want to turn this premise around the other way to look at the source itself. Can it be said that if ignition is exposed to an arbitrary material for less than 30 seconds, it is no longer a source of ignition? In general I think not, as many materials are capable of ignition with less than 30 seconds exposure. So how about an ignition source of say 1 second? Still possible, if there is enough energy available to transfer to the ignitable material. How about 100 microseconds? Like an electric spark or possibly a sudden explosion? I realize ATEX understands the concept of flameproof enclosures for explosive atmospheres, but what if I have an explosion occur in a non-explosive atmosphere? Is the enclosure material required to be flame proof or is it only evaluated for mechanical strength? It also seems this line of questioning could lead down a path of time vs. energy. For example the UL 94 test is a 30 second exposure to a 50W flame. Would a 15 second 100W flame be equivalent? This might even be converted into watt-seconds and Joules. Any advice or even opinions are welcomed. -Doug -- Thanks, -doug Douglas E Powell doug...@gmail.com http://www.linkedin.com/in/dougp01 - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <emc-p...@ieee.org> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <emcp...@radiusnorth.net> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher: <j.bac...@ieee.org> David Heald: <dhe...@gmail.com>
