Re: [PSES] Safety Interlock Switches
Many moons ago I went through this exact same cycle. VDE did not like our refrigerator switch so we went hunting. We eventually settled on a Cherry F82A series switch that calmed the VDE engineer down. These may not be available any more. They were rated 50,000 operations. http://tinyurl.com/lrbspbn Then later this was changed out to use a Micro Switch WW1K05D-D9. These were rated 100,000 operations. http://tinyurl.com/nkaaye4 What I liked about this switch is that is has this little plastic I shaped piece that can be inserted to "cheat" the interlock. But if you try to close the cover with that in place, you either can't or more likely the cover will dislodge the "cheat" and cause normal operation to be restored. Just a little something from the way-back machine. On 6/11/2014 8:49 AM, CR wrote: On 6/10/2014 11:39 PM, Nyffenegger, Dave wrote: EN 60950-1 says that interlocks must be designed to prevent inadvertent reactivation and that the ability to operate the interlock with a test finger is considered likely to cause inadvertent reactivation of the hazard. How do they expect the equipment to powered up for troubleshooting? The 300 Kg office copier; it has a combination safe holding the interlock. Cortland Richmond - 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: - 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] Safety Interlock Switches
Hi Dave, I tend to agree with Doug. Applying the Machinery Directive does not necessarily require the use of EN 60204-1. I would however document the Annex I requirements from the MD, and do a risk assessment to ISO 12100, in addition to applying the standards Doug references below. There may be other standards under the MD that apply to your equipment as well. *Paul MiltonG&M Compliance, Inc.714-628-1020 x 104* *Notice *- E-mail Confidentiality Disclaimer: The information in this email along with any attachments may contain privileged or confidential information. It is intended solely for the addressee. If you are not the intended recipient, you may not disclose, use, disseminate, distribute, or copy this message or attachment in any way. Access to this email by anyone else is unauthorized. If you received this e-mail in error, please notify sender and delete message and any attachments. *From:* Nyffenegger, Dave [mailto:dave.nyffeneg...@bhemail.com] *Sent:* Wednesday, June 11, 2014 6:51 AM *To:* EMC-PSTC@LISTSERV.IEEE.ORG *Subject:* Re: [PSES] Safety Interlock Switches Machinery Directive and LVD are most certainly applicable to the products in question, these types of products have been around for quite a while and the NRTLs and independent EU CE inspectors agree. I believe this also means EN 60204-1 and EN 60950-1 are also applicable respectively. I’m not familiar with EN ISO 14119 so I guess I’ll need to get a copy to review. Are there any specific ties between then Machinery Directive and/or EN 60204-1? In other words, to make the argument that compliance to EN ISO 14119 is also applicable to the product assuming the Machinery Directive is or non-compliance to EN ISO 14119 is non-compliance with the Machinery Directive. EN ISO 13849 is applicable, I’ve been reviewing it but I’m not an expert with it yet. (Products do use some pneumatics and vacuum) Certainly the PLr has an impact on the interlock system design but I was hoping to get some general feedback on the specific questions independent of the PLr. Thanks -Dave *From:* Douglas Nix [mailto:d...@ieee.org ] *Sent:* Wednesday, June 11, 2014 9:32 AM *To:* Nyffenegger, Dave *Cc:* EMC-PSTC@LISTSERV.IEEE.ORG; ibm...@gmail.com *Subject:* Re: [PSES] Safety Interlock Switches Dave, After reading your original post, I have to question the use of EN 60204-1 for your application. Can the product reasonably be considered to fit within the scope? Considering the first paragraph of the scope of the 2006 edition: This part of IEC 60204 applies to the application of electrical, electronic and programmable electronic equipment and systems to machines not portable by hand while working, including a group of machines working together in a co-ordinated manner. I especially question the use of EN 60204-1 in conjunction with EN 60950. There seems little value and much confusion to be generated by this decision. Since the product falls under the scope of the Machinery Directive, you should be looking at EN ISO 14119, Safety of machinery — Interlocking devices associated with guards — Principles for design and selection, for information on the interlocking device. This standard will provide you with the requirements for selection and installation of interlocking devices, and I can assure you that, unless the risk related to the hazards inside the machine are extremely low, the device you describe won’t pass muster. This standard also describes the requirements for defeat resistance of the interlocking device. In addition, a functional safety analysis of the safety related control functions is required under the Machinery Directive, and for that you can choose either EN ISO 13849-1 & -2, or IEC 62061 (see EN 60204-1:2006, 9.4). The former is generally easier to use, but the latter may fit the design of the equipment better, since it doesn’t sound like there is any fluidic power systems, and the equipment is predominantly electrical/electronic and programmable. I’d be happy to discuss this with you in more detail off line if you’re interested. Doug Nix +1 (519) 729-5704 d...@ieee.org On 11-Jun-14, at 08:20, Nyffenegger, Dave wrote: Yes, Omron D3D series. And I also have a similar looking switch on my HVAC air handler in the primary circuit made in 1995 for US (probably no CE). I am concerned not only with the issue of inadvertent activation but also the operational acceptability (min operations). Hence the questions about the applicable switch standards. But I don’t know if the argument presented where reactivation buy closing the switch by itself is not normally possible stands up. The challenge with concealing behind a small hole is keeping the equally small switch actuator protrusion from becoming a hazard itself. For example when used with a hinged guard that opens up to avoid a hand getting a good jab when the cover is closed. There are ways to do it with the right mounting arra
Re: [PSES] Safety Interlock Switches
On 6/10/2014 11:39 PM, Nyffenegger, Dave wrote: EN 60950-1 says that interlocks must be designed to prevent inadvertent reactivation and that the ability to operate the interlock with a test finger is considered likely to cause inadvertent reactivation of the hazard. How do they expect the equipment to powered up for troubleshooting? The 300 Kg office copier; it has a combination safe holding the interlock. Cortland Richmond - 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] Safety Interlock Switches
Machinery Directive and LVD are most certainly applicable to the products in question, these types of products have been around for quite a while and the NRTLs and independent EU CE inspectors agree. I believe this also means EN 60204-1 and EN 60950-1 are also applicable respectively. I'm not familiar with EN ISO 14119 so I guess I'll need to get a copy to review. Are there any specific ties between then Machinery Directive and/or EN 60204-1? In other words, to make the argument that compliance to EN ISO 14119 is also applicable to the product assuming the Machinery Directive is or non-compliance to EN ISO 14119 is non-compliance with the Machinery Directive. EN ISO 13849 is applicable, I've been reviewing it but I'm not an expert with it yet. (Products do use some pneumatics and vacuum) Certainly the PLr has an impact on the interlock system design but I was hoping to get some general feedback on the specific questions independent of the PLr. Thanks -Dave From: Douglas Nix [mailto:d...@ieee.org] Sent: Wednesday, June 11, 2014 9:32 AM To: Nyffenegger, Dave Cc: EMC-PSTC@LISTSERV.IEEE.ORG; ibm...@gmail.com Subject: Re: [PSES] Safety Interlock Switches Dave, After reading your original post, I have to question the use of EN 60204-1 for your application. Can the product reasonably be considered to fit within the scope? Considering the first paragraph of the scope of the 2006 edition: This part of IEC 60204 applies to the application of electrical, electronic and programmable electronic equipment and systems to machines not portable by hand while working, including a group of machines working together in a co-ordinated manner. I especially question the use of EN 60204-1 in conjunction with EN 60950. There seems little value and much confusion to be generated by this decision. Since the product falls under the scope of the Machinery Directive, you should be looking at EN ISO 14119, Safety of machinery - Interlocking devices associated with guards - Principles for design and selection, for information on the interlocking device. This standard will provide you with the requirements for selection and installation of interlocking devices, and I can assure you that, unless the risk related to the hazards inside the machine are extremely low, the device you describe won't pass muster. This standard also describes the requirements for defeat resistance of the interlocking device. In addition, a functional safety analysis of the safety related control functions is required under the Machinery Directive, and for that you can choose either EN ISO 13849-1 & -2, or IEC 62061 (see EN 60204-1:2006, 9.4). The former is generally easier to use, but the latter may fit the design of the equipment better, since it doesn't sound like there is any fluidic power systems, and the equipment is predominantly electrical/electronic and programmable. I'd be happy to discuss this with you in more detail off line if you're interested. Doug Nix +1 (519) 729-5704 d...@ieee.org<mailto:d...@ieee.org> On 11-Jun-14, at 08:20, Nyffenegger, Dave mailto:dave.nyffeneg...@bhemail.com>> wrote: Yes, Omron D3D series. And I also have a similar looking switch on my HVAC air handler in the primary circuit made in 1995 for US (probably no CE). I am concerned not only with the issue of inadvertent activation but also the operational acceptability (min operations). Hence the questions about the applicable switch standards. But I don't know if the argument presented where reactivation buy closing the switch by itself is not normally possible stands up. The challenge with concealing behind a small hole is keeping the equally small switch actuator protrusion from becoming a hazard itself. For example when used with a hinged guard that opens up to avoid a hand getting a good jab when the cover is closed. There are ways to do it with the right mounting arrangements and offsets. thanks -Dave From: IBM Ken [mailto:ibm...@gmail.com] Sent: Wednesday, June 11, 2014 1:05 AM To: Nyffenegger, Dave Cc: EMC-PSTC@LISTSERV.IEEE.ORG<mailto:EMC-PSTC@LISTSERV.IEEE.ORG> Subject: Re: [PSES] Safety Interlock Switches I had a very similar situation. Are you using a C&K or Omron switch? I also remember seeing the switch and thinking it looks like the door light switch from an old refrigerator. I have a very similar-looking switch in my home oil furnace (which is from the 1980s) What we did was put the switch inside a little metal enclosure with a small hole on the top. The panel then had a small metal protrusion which reached inside the hole, this way the test finger could never actuate the switch. You could try to take your designer's argument to your NRTL, but I doubt they will accept it; I think the point is not that someone's finger slips onto the switch accidentally and activates it, but rather - a service person
Re: [PSES] Safety Interlock Switches
Yes, Omron D3D series. And I also have a similar looking switch on my HVAC air handler in the primary circuit made in 1995 for US (probably no CE). I am concerned not only with the issue of inadvertent activation but also the operational acceptability (min operations). Hence the questions about the applicable switch standards. But I don’t know if the argument presented where reactivation buy closing the switch by itself is not normally possible stands up. The challenge with concealing behind a small hole is keeping the equally small switch actuator protrusion from becoming a hazard itself. For example when used with a hinged guard that opens up to avoid a hand getting a good jab when the cover is closed. There are ways to do it with the right mounting arrangements and offsets. thanks -Dave From: IBM Ken [mailto:ibm...@gmail.com] Sent: Wednesday, June 11, 2014 1:05 AM To: Nyffenegger, Dave Cc: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] Safety Interlock Switches I had a very similar situation. Are you using a C&K or Omron switch? I also remember seeing the switch and thinking it looks like the door light switch from an old refrigerator. I have a very similar-looking switch in my home oil furnace (which is from the 1980s) What we did was put the switch inside a little metal enclosure with a small hole on the top. The panel then had a small metal protrusion which reached inside the hole, this way the test finger could never actuate the switch. You could try to take your designer's argument to your NRTL, but I doubt they will accept it; I think the point is not that someone's finger slips onto the switch accidentally and activates it, but rather - a service person wants to see if the product he just worked on will start up and so pushes in the interlock to see if what he fixed/replaced worked. -Ken On Tue, Jun 10, 2014 at 11:39 PM, Nyffenegger, Dave mailto:dave.nyffeneg...@bhemail.com>> wrote: Hi folks, I'm reviewing a design for some medium duty office/business equipment which handles mail and is subject to the Machinery and Low Voltage Directives i.e. EN 60950-1 and EN 60204-1. The design is using an interlock switch which I think is more suitable for turning the light on/off in a refrigerator. The switch is in the secondary low voltage circuit to operate the main contactor coils. It's only rated for 50K min operations (electrical) and is approved to UL 1054 and VDE EN 61058-1. The electrical specs are fine for the application. I'm not familiar with these standards so one question is if those standards in anyway qualify or disqualify (by using the switch in a way not intended) the switch for use as a safety interlock. I thought I read in one of the safety standards that interlock switches should be designed/rated to last the lifetime of the equipment (based on some estimate of number of operations in application). But I haven't been able to find that. Does that sound familiar to anyone? My estimate is that 50K operations is much lower than the number of operations over the lifetime of the equipment. A similar older switch is only rated by the manufacturer for 6K operations. EN 60950 2.8.7 basically requires a minimum of 10K operations the way I read it. Am I right in thinking the 6K switch would not be suitable for interlock usage regardless of other aspects? These switches have plungers that can be easily finger operated once the guards are opened. EN 60950-1 says that interlocks must be designed to prevent inadvertent reactivation and that the ability to operate the interlock with a test finger is considered likely to cause inadvertent reactivation of the hazard. The argument from the designer with this switch is that once the guard/interlock is open, reclosing the interlock by itself will not re-energize the protected circuit and therefore there is no inadvertent reactivation. This is because the control circuit requires operation of another start switch in order to energize. This assumes there is no concurrent failure of the control circuit while the interlock is being manually overridden, one person can't operate/reach the start switch and override the interlock at the same time, and no second person operating the start switch while someone is overriding the interlock. My question is if this argument actually holds with! out violating the EN 60950 requirement. thanks David P. Nyffenegger, PMP, SM-IEEE - 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
Re: [PSES] Safety Interlock Switches
I had a very similar situation. Are you using a C&K or Omron switch? I also remember seeing the switch and thinking it looks like the door light switch from an old refrigerator. I have a very similar-looking switch in my home oil furnace (which is from the 1980s) What we did was put the switch inside a little metal enclosure with a small hole on the top. The panel then had a small metal protrusion which reached inside the hole, this way the test finger could never actuate the switch. You could try to take your designer's argument to your NRTL, but I doubt they will accept it; I think the point is not that someone's finger slips onto the switch accidentally and activates it, but rather - a service person wants to see if the product he just worked on will start up and so pushes in the interlock to see if what he fixed/replaced worked. -Ken On Tue, Jun 10, 2014 at 11:39 PM, Nyffenegger, Dave < dave.nyffeneg...@bhemail.com> wrote: > Hi folks, > > I'm reviewing a design for some medium duty office/business equipment > which handles mail and is subject to the Machinery and Low Voltage > Directives i.e. EN 60950-1 and EN 60204-1. The design is using an > interlock switch which I think is more suitable for turning the light > on/off in a refrigerator. The switch is in the secondary low voltage > circuit to operate the main contactor coils. It's only rated for 50K min > operations (electrical) and is approved to UL 1054 and VDE EN 61058-1. > The electrical specs are fine for the application. I'm not familiar with > these standards so one question is if those standards in anyway qualify or > disqualify (by using the switch in a way not intended) the switch for use > as a safety interlock. > > I thought I read in one of the safety standards that interlock switches > should be designed/rated to last the lifetime of the equipment (based on > some estimate of number of operations in application). But I haven't been > able to find that. Does that sound familiar to anyone? My estimate is > that 50K operations is much lower than the number of operations over the > lifetime of the equipment. > > A similar older switch is only rated by the manufacturer for 6K > operations. EN 60950 2.8.7 basically requires a minimum of 10K operations > the way I read it. Am I right in thinking the 6K switch would not be > suitable for interlock usage regardless of other aspects? > > These switches have plungers that can be easily finger operated once the > guards are opened. EN 60950-1 says that interlocks must be designed to > prevent inadvertent reactivation and that the ability to operate the > interlock with a test finger is considered likely to cause inadvertent > reactivation of the hazard. The argument from the designer with this > switch is that once the guard/interlock is open, reclosing the interlock by > itself will not re-energize the protected circuit and therefore there is no > inadvertent reactivation. This is because the control circuit requires > operation of another start switch in order to energize. This assumes there > is no concurrent failure of the control circuit while the interlock is > being manually overridden, one person can't operate/reach the start switch > and override the interlock at the same time, and no second person operating > the start switch while someone is overriding the interlock. My question is > if this argument actually holds with! > out violating the EN 60950 requirement. > > thanks > > David P. Nyffenegger, PMP, SM-IEEE > > - > > 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://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: > - 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 (includi
[PSES] Safety Interlock Switches
Hi folks, I'm reviewing a design for some medium duty office/business equipment which handles mail and is subject to the Machinery and Low Voltage Directives i.e. EN 60950-1 and EN 60204-1. The design is using an interlock switch which I think is more suitable for turning the light on/off in a refrigerator. The switch is in the secondary low voltage circuit to operate the main contactor coils. It's only rated for 50K min operations (electrical) and is approved to UL 1054 and VDE EN 61058-1. The electrical specs are fine for the application. I'm not familiar with these standards so one question is if those standards in anyway qualify or disqualify (by using the switch in a way not intended) the switch for use as a safety interlock. I thought I read in one of the safety standards that interlock switches should be designed/rated to last the lifetime of the equipment (based on some estimate of number of operations in application). But I haven't been able to find that. Does that sound familiar to anyone? My estimate is that 50K operations is much lower than the number of operations over the lifetime of the equipment. A similar older switch is only rated by the manufacturer for 6K operations. EN 60950 2.8.7 basically requires a minimum of 10K operations the way I read it. Am I right in thinking the 6K switch would not be suitable for interlock usage regardless of other aspects? These switches have plungers that can be easily finger operated once the guards are opened. EN 60950-1 says that interlocks must be designed to prevent inadvertent reactivation and that the ability to operate the interlock with a test finger is considered likely to cause inadvertent reactivation of the hazard. The argument from the designer with this switch is that once the guard/interlock is open, reclosing the interlock by itself will not re-energize the protected circuit and therefore there is no inadvertent reactivation. This is because the control circuit requires operation of another start switch in order to energize. This assumes there is no concurrent failure of the control circuit while the interlock is being manually overridden, one person can't operate/reach the start switch and override the interlock at the same time, and no second person operating the start switch while someone is overriding the interlock. My question is if this argument actually holds with! out violating the EN 60950 requirement. thanks David P. Nyffenegger, PMP, SM-IEEE - 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:
