Hello from Bend, Oregon:
“To determine if the loss of two independent safety functions in your equipment results in a hazard, then you likely need to do an FMEA (Failure Mode & Effects Analysis).” Customarily, the product must be safe under normal conditions and single fault conditions. This is accomplished with two independent safeguards against the same hazard. If one of the safeguards should fail, the second safeguard provides the protection against the hazard. For example, consider a passenger in a car. The first safeguard against an inertia energy hazard is behavior of the driver (or the driver of another car). The second safeguard is a seat belt. Both prevent or reduce the magnitude of body inertia energy expended against a part of the car. The driver controls the car in such a manner as to avoid a crash. In the event of failure of the driver (a crash), then the seat belt prevents or reduces the effect of the body “crashing” into a car part. Consider double insulation, where if one insulation fails, the second insulation is effective. If both insulations fail, then an injury is likely. While some safety standards require two safeguards against a single hazard, some safety standards may not. For example, hanging a product from the ceiling typically doesn’t require a second and independent ceiling attachment except in California (earthquake country). Rich - ---------------------------------------------------------------- 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 [email protected] All emc-pstc postings are archived and searchable on the web at: https://www.mail-archive.com/[email protected]/ Website: https://ewh.ieee.org/soc/pses/ Instructions: https://ewh.ieee.org/soc/pses/list.html (including how to unsubscribe) List rules: https://ewh.ieee.org/soc/pses/listrules.html For help, send mail to the list administrators: Mike Sherman at: [email protected] Rick Linford at: [email protected] For policy questions, send mail to: Jim Bacher: <[email protected]> _________________________________________________ To unsubscribe from the EMC-PSTC list, click the following link: https://listserv.ieee.org/cgi-bin/wa?SUBED1=EMC-PSTC&A=1
