Re: [PSES] A question about FDA language and interlocking devices
Thanks all for your responses. You’ve given me a few clues that I can use to start a deeper dive. 邏 Doug Nix d...@ieee.org +1 (519) 729-5704 > On 5-Feb-19, at 15:59, MIKE SHERMAN wrote: > > I see another probably more likely interpretation of "knife edge and finger > stock" in this context. Look up a knife edge fuse on the internet. Presumably > the socket the fuse seats in would be the finger stock. > > > > Mike Sherman > > Graco Inc. > >> On February 5, 2019 at 2:34 PM "Schmidt, Mark" >> wrote: >> >> Please see test below: >> >> >> “Safety Interlocks [21 CFR 1020.40(c)(4)(i)]:Each door of a cabinet x-ray >> system shall have a minimum of two safety interlocks. One, but not both of >> the required interlocks shall be such that door opening results in physical >> disconnection of the energy supply circuit to the high-voltage generator, >> and such disconnection shall not be dependent upon any moving part other >> than the door. [Note: Safety interlock is defined in 21 CFR 1020.40(b)(11).] >> >> >> The primary door interlock should be of conventional design. The second door >> interlock must physically disconnect the energy supply circuit to the high >> voltage generator. Physical disconnection means opening the energy supply >> circuit by removing a piece of the circuit. This is usually accomplished >> with a ‘knife-edge and finger stock’ or ‘plug and socket’ type connection. >> It is good practice to assure the primary interlock will remove power from >> the energy supply circuit before the physical disconnection occurs. Relays, >> micro switches, and ‘safety switches’ all contain moving parts and, >> therefore, cannot be used to satisfy the requirement that the physical >> disconnect interlock is "not dependent on any moving part other than the >> door."” >> >> >> Compliance Guide for Cabinet X-Ray Systems >> https://www.fda.gov/MedicalDevices/ucm094358.htm >> <https://www.fda.gov/MedicalDevices/ucm094358.htm> >> >> >> Mark >> >> >> >> From: Nyffenegger, Dave [mailto:dave.nyffeneg...@bhemail.com] >> Sent: Tuesday, February 5, 2019 12:31 PM >> To: EMC-PSTC@LISTSERV.IEEE.ORG >> Subject: Re: [PSES] A question about FDA language and interlocking devices >> >> >> That seems to make more sense. I don’t know anything about X-ray >> requirements but the FDA requirements laser interlocks are not specific, >> only referring to “interlocks”. >> >> -Dave >> >> >> From: MIKE SHERMAN [mailto:msherma...@comcast.net >> <mailto:msherma...@comcast.net>] >> Sent: Tuesday, February 05, 2019 12:27 PM >> To: EMC-PSTC@LISTSERV.IEEE.ORG <mailto:EMC-PSTC@LISTSERV.IEEE.ORG> >> Subject: Re: [PSES] A question about FDA language and interlocking devices >> >> >> Doug -- >> >> >> "knife-edge and finger stock" sounds more like the gasketing around the door >> to keep the radiation inside. I think you'll find similar gasketing on doors >> to EMC chambers. I've not heard of this term applied to interlock switches. >> >> >> Mike Sherman >> >> Graco Inc. >> >> >> On February 5, 2019 at 10:35 AM Doug Nix > <mailto:d...@ieee.org>> wrote: >> >> Colleagues, >> >> >> I had a question come my way yesterday that I need a little help with. >> Here’s the question: >> >> >> I have a customer that produces X-ray equipment. The FDA requires that the >> door that gives access to the X-ray source must have an interlock with a >> ‘knife-edge and finger stock’ type connection. Also the FDA mentions that >> interlocks should be of conventional design. What is understood by >> “conventional design”? >> >> >> My reading on this requirement is that any conventional electromechanical >> interlocking device like this: >> >> >> >> will meet the basic requirements as described by the FDA as “knife-edge and >> fingerstock” connection, but I am concerned that this may not be at all what >> is meant. >> >> >> As always, any guidance you can offer will be welcomed and appreciated! >> >> >> Best, >> >> >> Doug Nix >> d...@ieee.org <mailto:d...@ieee.org> >> +1 (519) 729-5704 - 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 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 Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald:
Re: [PSES] A question about FDA language and interlocking devices
I see another probably more likely interpretation of "knife edge and finger stock" in this context. Look up a knife edge fuse on the internet. Presumably the socket the fuse seats in would be the finger stock. Mike Sherman Graco Inc. > On February 5, 2019 at 2:34 PM "Schmidt, Mark" wrote: > > > Please see test below: > > > > “Safety Interlocks [21 CFR 1020.40(c)(4)(i)]:Each door of a cabinet x-ray > system shall have a minimum of two safety interlocks. One, but not both of > the required interlocks shall be such that door opening results in physical > disconnection of the energy supply circuit to the high-voltage generator, and > such disconnection shall not be dependent upon any moving part other than the > door. [Note: Safety interlock is defined in 21 CFR 1020.40(b)(11).] > > > > The primary door interlock should be of conventional design. The second > door interlock must physically disconnect the energy supply circuit to the > high voltage generator. Physical disconnection means opening the energy > supply circuit by removing a piece of the circuit. This is usually > accomplished with a ‘knife-edge and finger stock’ or ‘plug and socket’ type > connection. It is good practice to assure the primary interlock will remove > power from the energy supply circuit before the physical disconnection > occurs. Relays, micro switches, and ‘safety switches’ all contain moving > parts and, therefore, cannot be used to satisfy the requirement that the > physical disconnect interlock is "not dependent on any moving part other than > the door."” > > > > Compliance Guide for Cabinet X-Ray Systems > https://www.fda.gov/MedicalDevices/ucm094358.htm > > > > > > Mark > > > > > > From: Nyffenegger, Dave [mailto:dave.nyffeneg...@bhemail.com] > Sent: Tuesday, February 5, 2019 12:31 PM > To: EMC-PSTC@LISTSERV.IEEE.ORG > Subject: Re: [PSES] A question about FDA language and interlocking devices > > > > That seems to make more sense. I don’t know anything about X-ray > requirements but the FDA requirements laser interlocks are not specific, only > referring to “interlocks”. > > -Dave > > > > From: MIKE SHERMAN [mailto:msherma...@comcast.net] > Sent: Tuesday, February 05, 2019 12:27 PM > To: EMC-PSTC@LISTSERV.IEEE.ORG mailto:EMC-PSTC@LISTSERV.IEEE.ORG > Subject: Re: [PSES] A question about FDA language and interlocking devices > > > > Doug -- > > > > "knife-edge and finger stock" sounds more like the gasketing around the > door to keep the radiation inside. I think you'll find similar gasketing on > doors to EMC chambers. I've not heard of this term applied to interlock > switches. > > > > Mike Sherman > > Graco Inc. > > > > > > > > On February 5, 2019 at 10:35 AM Doug Nix > mailto:d...@ieee.org > wrote: > > > > Colleagues, > > > > > > > > I had a question come my way yesterday that I need a little help > > with. Here’s the question: > > > > > > > > > > > > > > I have a customer that produces X-ray equipment. The FDA > > > requires that the door that gives access to the X-ray source must have an > > > interlock with a ‘knife-edge and finger stock’ type connection. Also the > > > FDA mentions that interlocks should be of conventional design. What is > > > understood by “conventional design”? > > > > > > > > > > > > > > My reading on this requirement is that any conventional > > electromechanical interlocking device like this: > > > > [Image result for keyed interlock switch images] > > > > will meet the basic requirements as described by the FDA as > > “knife-edge and fingerstock” connection, but I am concerned that this may > > not be at all what is meant. > > > > > > > > As always, any guidance you can offer will be welcomed and > > appreciated! > > > > > > > > Best, > > > > > > > > Doug Nix > > d...@ieee.org mailto:d...@ieee.org > > +1 (519) 729-5704 > > > > > > > > > > > > > > > > > - > >
Re: [PSES] A question about FDA language and interlocking devices
Please see test below: “Safety Interlocks [21 CFR 1020.40(c)(4)(i)]:Each door of a cabinet x-ray system shall have a minimum of two safety interlocks. One, but not both of the required interlocks shall be such that door opening results in physical disconnection of the energy supply circuit to the high-voltage generator, and such disconnection shall not be dependent upon any moving part other than the door. [Note: Safety interlock is defined in 21 CFR 1020.40(b)(11).] The primary door interlock should be of conventional design. The second door interlock must physically disconnect the energy supply circuit to the high voltage generator. Physical disconnection means opening the energy supply circuit by removing a piece of the circuit. This is usually accomplished with a ‘knife-edge and finger stock’ or ‘plug and socket’ type connection. It is good practice to assure the primary interlock will remove power from the energy supply circuit before the physical disconnection occurs. Relays, micro switches, and ‘safety switches’ all contain moving parts and, therefore, cannot be used to satisfy the requirement that the physical disconnect interlock is "not dependent on any moving part other than the door."” Compliance Guide for Cabinet X-Ray Systems https://www.fda.gov/MedicalDevices/ucm094358.htm Mark From: Nyffenegger, Dave [mailto:dave.nyffeneg...@bhemail.com] Sent: Tuesday, February 5, 2019 12:31 PM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] A question about FDA language and interlocking devices That seems to make more sense. I don’t know anything about X-ray requirements but the FDA requirements laser interlocks are not specific, only referring to “interlocks”. -Dave From: MIKE SHERMAN [mailto:msherma...@comcast.net] Sent: Tuesday, February 05, 2019 12:27 PM To: EMC-PSTC@LISTSERV.IEEE.ORG<mailto:EMC-PSTC@LISTSERV.IEEE.ORG> Subject: Re: [PSES] A question about FDA language and interlocking devices Doug -- "knife-edge and finger stock" sounds more like the gasketing around the door to keep the radiation inside. I think you'll find similar gasketing on doors to EMC chambers. I've not heard of this term applied to interlock switches. Mike Sherman Graco Inc. On February 5, 2019 at 10:35 AM Doug Nix mailto:d...@ieee.org>> wrote: Colleagues, I had a question come my way yesterday that I need a little help with. Here’s the question: I have a customer that produces X-ray equipment. The FDA requires that the door that gives access to the X-ray source must have an interlock with a ‘knife-edge and finger stock’ type connection. Also the FDA mentions that interlocks should be of conventional design. What is understood by “conventional design”? My reading on this requirement is that any conventional electromechanical interlocking device like this: [Image result for keyed interlock switch images] will meet the basic requirements as described by the FDA as “knife-edge and fingerstock” connection, but I am concerned that this may not be at all what is meant. As always, any guidance you can offer will be welcomed and appreciated! Best, Doug Nix d...@ieee.org<mailto:d...@ieee.org> +1 (519) 729-5704 - 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 mailto:emc-p...@ieee.org>> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html<https://urldefense.proofpoint.com/v2/url?u=http-3A__www.ieee-2Dpses.org_emc-2Dpstc.html=DwMGaQ=9mghv0deYPYDGP-W745IEdQLV1kHpn4XJRvR6xMRXtA=RsvNGGiEXp8Wa3AN0R9oJL3JV5vFvlTsmxQpMmBLBIw=vyaFOhjo-plOUNaXICPTF5v8c1AZLKllr7lyVp2wGwk=WXEKr-BkVSmhSljRxt3Sf9e6PaKu6vocdIDAQUX0lbE=> Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/<https://urldefense.proofpoint.com/v2/url?u=http-3A__product-2Dcompliance.oc.ieee.org_=DwMGaQ=9mghv0deYPYDGP-W745IEdQLV1kHpn4XJRvR6xMRXtA=RsvNGGiEXp8Wa3AN0R9oJL3JV5vFvlTsmxQpMmBLBIw=vyaFOhjo-plOUNaXICPTF5v8c1AZLKllr7lyVp2wGwk=9w0Eac3b2fyPyltp4geID5oNKrateHEb3c9-cs4rpO8=> can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/<https://urldefense.proofpoint.com/v2/url?u=http-3A__www.ieee-2Dpses.org_=DwMGaQ=9mghv0deYPYDGP-W745IEdQLV1kHpn4XJRvR6xMRXtA=RsvNGGiEXp8Wa3AN0R9oJL3JV5vFvlTsmxQpMmBLBIw=vyaFOhjo-plOUNaXICPTF5v8c1AZLKllr7lyVp2wGwk=0OqoBTaattMTUzyJFyc_G4v_t_a2wBBR6lpaMP7KRi4=> Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe)<https://urldefense.proofpoint.com/v2/url?u=http-3A__www.ieee-2Dpses.org_list.html=DwMGaQ=9mghv0deYPYDGP-W745IEdQLV1kHpn4XJRvR6xMRXtA=RsvNGGiEXp8Wa3AN0R9oJL3JV5vFvlTsmxQpMmBLBIw=vyaFOhjo-plOUNaXICPTF5v8c1AZLKllr7lyVp2wGwk=EtdCPAbnmQ0LVqUapPCFdsB6d-CW40mAcgRjJXo
Re: [PSES] A question about FDA language and interlocking devices
That seems to make more sense. I don’t know anything about X-ray requirements but the FDA requirements laser interlocks are not specific, only referring to “interlocks”. -Dave From: MIKE SHERMAN [mailto:msherma...@comcast.net] Sent: Tuesday, February 05, 2019 12:27 PM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] A question about FDA language and interlocking devices Doug -- "knife-edge and finger stock" sounds more like the gasketing around the door to keep the radiation inside. I think you'll find similar gasketing on doors to EMC chambers. I've not heard of this term applied to interlock switches. Mike Sherman Graco Inc. On February 5, 2019 at 10:35 AM Doug Nix mailto:d...@ieee.org>> wrote: Colleagues, I had a question come my way yesterday that I need a little help with. Here’s the question: I have a customer that produces X-ray equipment. The FDA requires that the door that gives access to the X-ray source must have an interlock with a ‘knife-edge and finger stock’ type connection. Also the FDA mentions that interlocks should be of conventional design. What is understood by “conventional design”? My reading on this requirement is that any conventional electromechanical interlocking device like this: [Image result for keyed interlock switch images] will meet the basic requirements as described by the FDA as “knife-edge and fingerstock” connection, but I am concerned that this may not be at all what is meant. As always, any guidance you can offer will be welcomed and appreciated! Best, Doug Nix d...@ieee.org<mailto:d...@ieee.org> +1 (519) 729-5704 - 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 mailto: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://www.ieee-pses.org/list.html (including how to unsubscribe)<http://www.ieee-pses.org/list.html> List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas mailto:sdoug...@ieee.org>> Mike Cantwell mailto:mcantw...@ieee.org>> For policy questions, send mail to: Jim Bacher mailto:j.bac...@ieee.org>> David Heald mailto:dhe...@gmail.com>> - 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 mailto: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://www.ieee-pses.org/list.html (including how to unsubscribe)<http://www.ieee-pses.org/list.html> List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas mailto:sdoug...@ieee.org>> Mike Cantwell mailto:mcantw...@ieee.org>> For policy questions, send mail to: Jim Bacher mailto:j.bac...@ieee.org>> David Heald mailto:dhe...@gmail.com>> - 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 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 Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald:
Re: [PSES] A question about FDA language and interlocking devices
EN ISO 14119 Safety of machinery - Interlocking devices associated with guards - Principles for design and selection has good information to refer to for safety interlocks. Compliance with this standard is required for machinery under the Machinery Directive for CE marking. While there may not be any formal requirement to follow this standard for X-ray machines it may still be a useful reference and wouldn’t hurt to follow it. This standard would apply to CE marked X-ray machines if they fall under the Machinery Directive. -Dave From: Kunde, Brian [mailto:brian_ku...@lecotc.com] Sent: Tuesday, February 05, 2019 2:07 PM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] A question about FDA language and interlocking devices Doug, These type of interlock switches are new to me. They are used in industrial applications where they protect the user from a very hazardous condition. These switches usually have what is called a Positive Mechanical Action or Certified Direct Opening mechanism which forces a Normally Closed contact OPEN when in the SAFE State. In these cases, when the key is removed from the switch there is an internal mechanism which forces a NC contact OPEN (removing the hazard). If the contact is stuck closed, then the key cannot be removed from the switch. There are usually other contacts within the switch that can be used to monitor the switch to verify its proper function. If the switch is certified to EN60947-5-1 for the direct opening mechanism, the switch will have a symbol that looks like an arrow pointing to the right inside a circle. That is about all I know about these. The Other Brian From: Doug Nix [mailto:d...@ieee.org] Sent: Tuesday, February 05, 2019 11:36 AM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: [PSES] A question about FDA language and interlocking devices Colleagues, I had a question come my way yesterday that I need a little help with. Here’s the question: I have a customer that produces X-ray equipment. The FDA requires that the door that gives access to the X-ray source must have an interlock with a ‘knife-edge and finger stock’ type connection. Also the FDA mentions that interlocks should be of conventional design. What is understood by “conventional design”? My reading on this requirement is that any conventional electromechanical interlocking device like this: [Image result for keyed interlock switch images] will meet the basic requirements as described by the FDA as “knife-edge and fingerstock” connection, but I am concerned that this may not be at all what is meant. As always, any guidance you can offer will be welcomed and appreciated! Best, Doug Nix d...@ieee.org<mailto:d...@ieee.org> +1 (519) 729-5704 - 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 mailto: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://www.ieee-pses.org/list.html (including how to unsubscribe)<http://www.ieee-pses.org/list.html> List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas mailto:sdoug...@ieee.org>> Mike Cantwell mailto:mcantw...@ieee.org>> For policy questions, send mail to: Jim Bacher mailto:j.bac...@ieee.org>> David Heald mailto:dhe...@gmail.com>> 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 mailto: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://www.ieee-pses.org/list.html (including how to unsubscribe)<http://www.ieee-pses.org/list.html> List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas mailto:sdoug...@ieee.org>> Mike Cantwell mailto:mcantw...@ieee.org>> For policy questions, send mail to: Jim Bac
Re: [PSES] A question about FDA language and interlocking devices
Doug, These type of interlock switches are new to me. They are used in industrial applications where they protect the user from a very hazardous condition. These switches usually have what is called a Positive Mechanical Action or Certified Direct Opening mechanism which forces a Normally Closed contact OPEN when in the SAFE State. In these cases, when the key is removed from the switch there is an internal mechanism which forces a NC contact OPEN (removing the hazard). If the contact is stuck closed, then the key cannot be removed from the switch. There are usually other contacts within the switch that can be used to monitor the switch to verify its proper function. If the switch is certified to EN60947-5-1 for the direct opening mechanism, the switch will have a symbol that looks like an arrow pointing to the right inside a circle. That is about all I know about these. The Other Brian From: Doug Nix [mailto:d...@ieee.org] Sent: Tuesday, February 05, 2019 11:36 AM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: [PSES] A question about FDA language and interlocking devices Colleagues, I had a question come my way yesterday that I need a little help with. Here’s the question: I have a customer that produces X-ray equipment. The FDA requires that the door that gives access to the X-ray source must have an interlock with a ‘knife-edge and finger stock’ type connection. Also the FDA mentions that interlocks should be of conventional design. What is understood by “conventional design”? My reading on this requirement is that any conventional electromechanical interlocking device like this: [Image result for keyed interlock switch images] will meet the basic requirements as described by the FDA as “knife-edge and fingerstock” connection, but I am concerned that this may not be at all what is meant. As always, any guidance you can offer will be welcomed and appreciated! Best, Doug Nix d...@ieee.org<mailto:d...@ieee.org> +1 (519) 729-5704 - 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 mailto: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://www.ieee-pses.org/list.html (including how to unsubscribe)<http://www.ieee-pses.org/list.html> List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas mailto:sdoug...@ieee.org>> Mike Cantwell mailto:mcantw...@ieee.org>> For policy questions, send mail to: Jim Bacher mailto:j.bac...@ieee.org>> David Heald mailto:dhe...@gmail.com>> 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 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 Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald:
Re: [PSES] A question about FDA language and interlocking devices
Hello Doug, I have only a limited amount of knowledge in this area, and I hope another listserv member can either correct me or provide more detail. I also believe Mike Sherman may be correct on the knife edge/finger stock description. The CDRH at the FDA is generally very conservative and they don't update requirements often as technology changes. (Their inspection guide<https://www.fda.gov/downloads/MedicalDevices/DeviceRegulationandGuidance/GuidanceDocuments/UCM135868.pdf> still dates from 1985.) I believe that the restrictions on interlock type is based on making it difficult to override the interlock. I do believe that your interpretation is correct. The interlocks you show should meet the CDRH requirements. Ted Eckert Microsoft Corporation The opinions expressed are my own and do not necessarily reflect those of my employer or the FDA. From: Doug Nix Sent: Tuesday, February 5, 2019 8:36 AM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: [PSES] A question about FDA language and interlocking devices Colleagues, I had a question come my way yesterday that I need a little help with. Here's the question: I have a customer that produces X-ray equipment. The FDA requires that the door that gives access to the X-ray source must have an interlock with a 'knife-edge and finger stock' type connection. Also the FDA mentions that interlocks should be of conventional design. What is understood by "conventional design"? My reading on this requirement is that any conventional electromechanical interlocking device like this: [Image result for keyed interlock switch images] will meet the basic requirements as described by the FDA as "knife-edge and finger stock" connection, but I am concerned that this may not be at all what is meant. As always, any guidance you can offer will be welcomed and appreciated! Best, Doug Nix d...@ieee.org<mailto:d...@ieee.org> +1 (519) 729-5704 - 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 mailto:emc-p...@ieee.org>> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html<https://nam06.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.ieee-pses.org%2Femc-pstc.html=02%7C01%7Cted.eckert%40microsoft.com%7C33c8c3b6623942c20d5a08d68b880468%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636849813639518671=FhbSMY%2Bqr4sAYXq%2FXH920slb5Hcjb62ZgUXu%2FPAKY48%3D=0> Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/<https://nam06.safelinks.protection.outlook.com/?url=http%3A%2F%2Fproduct-compliance.oc.ieee.org%2F=02%7C01%7Cted.eckert%40microsoft.com%7C33c8c3b6623942c20d5a08d68b880468%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636849813639518671=Uswp8CEWq65ViemNYJoawksry%2Fx%2F2C9lbGzKsy8qgFk%3D=0> can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/<https://nam06.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.ieee-pses.org%2F=02%7C01%7Cted.eckert%40microsoft.com%7C33c8c3b6623942c20d5a08d68b880468%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636849813639528671=rMd2vT6b8l5Ym9CU5iRRms2WR4dWyWprObZ%2F7HmSc30%3D=0> Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe)<https://nam06.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.ieee-pses.org%2Flist.html=02%7C01%7Cted.eckert%40microsoft.com%7C33c8c3b6623942c20d5a08d68b880468%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636849813639538675=9ydgYf7XRuNuO1KUSrG6CFY0npfCaIMDryzNfx%2FN%2FCY%3D=0> List rules: http://www.ieee-pses.org/listrules.html<https://nam06.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.ieee-pses.org%2Flistrules.html=02%7C01%7Cted.eckert%40microsoft.com%7C33c8c3b6623942c20d5a08d68b880468%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636849813639538675=3M9cjNRyHnS%2BWNKTve0xT1daWdN%2BKkX%2F8KKciHU8Ef8%3D=0> For help, send mail to the list administrators: Scott Douglas mailto:sdoug...@ieee.org>> Mike Cantwell mailto:mcantw...@ieee.org>> For policy questions, send mail to: Jim Bacher mailto:j.bac...@ieee.org>> David Heald mailto:dhe...@gmail.com>> - 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 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 unsub
Re: [PSES] A question about FDA language and interlocking devices
Doug -- "knife-edge and finger stock" sounds more like the gasketing around the door to keep the radiation inside. I think you'll find similar gasketing on doors to EMC chambers. I've not heard of this term applied to interlock switches. Mike Sherman Graco Inc. > On February 5, 2019 at 10:35 AM Doug Nix wrote: > > Colleagues, > > I had a question come my way yesterday that I need a little help with. > Here’s the question: > > > > > I have a customer that produces X-ray equipment. The FDA requires > that the door that gives access to the X-ray source must have an interlock > with a ‘knife-edge and finger stock’ type connection. Also the FDA mentions > that interlocks should be of conventional design. What is understood by > “conventional design”? > > > > > > My reading on this requirement is that any conventional electromechanical > interlocking device like this: > [Image result for keyed interlock switch images] > will meet the basic requirements as described by the FDA as “knife-edge > and fingerstock” connection, but I am concerned that this may not be at all > what is meant. > > As always, any guidance you can offer will be welcomed and appreciated! > > Best, > > Doug Nix > d...@ieee.org mailto:d...@ieee.org > +1 (519) 729-5704 > > > - > > > 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 > mailto: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://www.ieee-pses.org/list.html (including how to > unsubscribe) http://www.ieee-pses.org/list.html > List rules: http://www.ieee-pses.org/listrules.html > > For help, send mail to the list administrators: > Scott Douglas mailto:sdoug...@ieee.org > > Mike Cantwell mailto:mcantw...@ieee.org > > > For policy questions, send mail to: > Jim Bacher mailto:j.bac...@ieee.org > > David Heald mailto:dhe...@gmail.com > > - 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 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 Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald:
[PSES] A question about FDA language and interlocking devices
Colleagues, I had a question come my way yesterday that I need a little help with. Here’s the question: > I have a customer that produces X-ray equipment. The FDA requires that the > door that gives access to the X-ray source must have an interlock with a > ‘knife-edge and finger stock’ type connection. Also the FDA mentions that > interlocks should be of conventional design. What is understood by > “conventional design”? My reading on this requirement is that any conventional electromechanical interlocking device like this: will meet the basic requirements as described by the FDA as “knife-edge and fingerstock” connection, but I am concerned that this may not be at all what is meant. As always, any guidance you can offer will be welcomed and appreciated! Best, Doug Nix d...@ieee.org +1 (519) 729-5704 - 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 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 Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald:
