Experts, I have seen Interlock circuits using "interlock switches" (as specified by their manufacture), on doors, panels, and guards with hazards behind them that were NOT "Positive Mechanical Action" (PMA) switches. (Also known as Direct Contact, Forced Break, Direct opening action, Positive open action, Positive-mode operation, etc.).
So I'm confused. When do you have to use a PMA switch (sensor) and when it is ok not to? Then there are Non-Contact switches such as Magnetic Interlock Switches. Are these PMA? I do not see how. But I see magnetic switches used as Safety Interlock Switches also. What if you use two switches (double fault required)? Can you get away from PMA switches? Also, I cannot see how a PMA switch (sensor) can be used on a removable guard or panel. I see examples of a cam with a notch used on hinges of doors, but how are they used on a panel or guard? It seems to me as if it is impossible. Also, as many of you know, our company makes Laboratory Equipment (Test & Measurement) which has a Family Standard of EN 61010-1. It says nothing about PMA switches. Only that a Single Fault is Unlikely to occur. Products with moving parts fall under the Machinery Directive in Europe but the EN 61010-1 Safety Standard is not Harmonized (It is harmonized to the LVD). A major problem I often have is with inspectors who try to apply Industrial Machinery standards to our products as if it is a factory machine run by uneducated employees. They expect us to use expensive Sensors, Switches, PLCs, Control logic, etc. like what you would use in an industrial machine. It is difficult to explain to inspectors that operators of our equipment are trained and expected to have access to hazards that would not be allowed in a factory environment. Now I'm rambling. Sorry. Thanks to all for any explanation or guidance you can provide. The Other Brian ________________________________ LECO Corporation Notice: This communication may contain confidential information intended for the named recipient(s) only. If you received this by mistake, please destroy it and notify us of the error. Thank you. - ---------------------------------------------------------------- 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: 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://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
