Hello Dan: A good start could be to take from the precedence set by BABT 440 (not that they are the first or last to define this...):
Here, safety critical components are defined as: - Any component in a PRIMARY (i.e. mains) CIRCUIT - any component providing BASIC, SUPPLEMENTARY, or REINFORCED INSULATION between different categories of circuits within the equipment (e.g. transformers, optocouplers, relays) - protective devices (e.g. fuses) - insulating materials (e.g. printed wiring boards) where the FLAMMABILITY CLASSIFICATION of the product is specified for safety; - insulating materials (e.g. transformer insulating tapes) where the Comparative Tracking Index (see table 6 of EN 60950) is specified for safety; - devices (e.g. fans, heatsinks) provided to maintain equipment temperatures within safe limits. BABT 440 also makes it very clear that this list is not exhaustive. It also states that "Safety Critical Components are normally identified in a separate table in a third-party safety test report." This is the way, you may have noticed, that the CB scheme reports handle this issue. Rather than having a list of components that your engineers need to run through you before changing, I would recommend that you specify on your engineering prints or component control documents whether or not a particular component is safety critical. i.e., the controlling document for a particular fuse or transformer should specify whether that fuse or transformer is safety critical. If it is, your procedures mandate that you (or the appropriate compliance engineer) must review and OK any substitutions or changes. I think that would leave less question, and would cover you in questionable cases. If you haven't, I would also recommend that you apply similar controls to Network Critical Components also. Hope this helps. Mel Pedersen Midcom, Inc. Homologations Engineer Phone: (605) 882-8535 [email protected] Fax: (605) 882-8633 ---------- From: [email protected][SMTP:[email protected]] Sent: Monday, January 25, 1999 11:02 AM To: [email protected] Subject: Safety Critical Components List I am looking for the above list to give to design engineers. Rather than state to them to come to the compliance department for all changes I would like to narrow it down in layman's terms to a detailed list. Any help would be greatly appreciated. Daniel T. Fitzgerald Regulatory Compliance Engineer American power Conversion
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