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KidPLC

American Wiring & Safety Standards

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Hi Guys, I am the electrical/programming component of a team who will be designing and building an assembly machine to be shipped to our parent company in the USA. It will be a reasonably common style of automation consisting of a rotary table, bowl feeders, some vision and pneumatic pick and place stations......it is early days yet, design wise, however there could be some SCARA Robots or ABB 6 Axis Robots, no hydraulics. We have built this style of machine in house in Australia before following our AS (Australian Standards) electrical wiring standards and machine safety standards (which are heavily based on European Standards) however I have not designed anything for shipment to the USA before so there will be a host of design aspects to consider. I was wondering if you could help me to identify the relevant American Standards I should be focusing on. We have received a specification that has highlighted NFPA 79 and UL508 as the standards the automation should conform to. My questions are as follows: 1. Our Australian Standard AS3000 and AS3008 are specifically targeted at electrical installation covering everything from cable sizing and fault current limiting to clearance requirements infront of switchboards. Do these standards cover the same subject matter?? or is there a more relevant ANSI or NEC standard that is normally followed in America. 2. Our Australian Standard AS4024 specifically targets machine safety, methods to identify and grade hazards, document and validate solutions, guidence and location of emergency stops, reach distances to hazards etc etc. Do these standards cover the equivalent subject matter??? I have no doubt I will have to acquire these standards regardless and become familiar with them however my main concern at this point is that I am not overlooking other relevant important standards that apply in the USA. Any assistance would be greatly appreciated. Thanks

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Here is what little help I can give as Plant Maintenance Foreman. 1. NFPA 79 - Otherwise known as the National Electric Code . Comes out Every 3 years. Current Revision is the 2011 Edition which became effective 8/25/2011. Those words "became effective" are a misnomer because we have a concept here called AHJ or Authority Having Jourisdiction. That could be the City, County, State, Federal {OSHA} Building or Safety Inspector or more likely a combination thereof. It is not uncommon for some cities to exercise their AHJ and declare that the previous version NFPA 79 - 2008 or even NFPA 79 -2005 is the current enforced standard in their Jurisdiction. As a foreign builder I'd suggest you consult your customer and plan for meeting 2011. The NEC covers all those issues AS3000 and AS3008 would appear to cover. 2. NFPA 70E - Standard for Electrical Safety in the Workplace. Comes out every 4 years. Current Revision is 2009 Edition. This covers the Safe Work practices your customer must adhere to. It behooves you to know these at least in passing. The key details for a builder will be the Arc Flash Label which is required on each cabinet and the Shock Hazard Boundary Label. 3. ANSI B11 Standards - Probably the closest thing you'll find in American System to your AS4024. This is the Machine Safety Standards which OSHA {Occupational Health and Safety Administration} enforces {fines} to. You'll find a good writeup on these on the Omron STI website. http://www.machinesafety.net/na_machine_safety_standards.html. If you're familiar with current European union Stndards you'll find these a few generations behind {MPO}. 4. ANSI RIA 15.06 - You mentioned robots so I include this standard from the Robotics Industry Association. It was the Bleeding Edge of machine Safety in the US last Time I looked {aka 2002}. My personal experience is that whatever RIA is doing to guard robots the general US Industry lags by 5 to 10 years for regualr machinery. 5. UL 508 - I've only seen this standard as a sticker on machines. It is an insurance/underwriter deriven standard and meant to work hand in hand with NFPA 79. I'd suggest visiting the UL website for the best information on UL-508. One final freebie - {disclaimer - the author has no ties to service he recommends and presents it as is for the readers benefit and discretionary use} - Check out NECPLUS.ORG. They have a one day free trial and a $9 per month subscription service to all the major US Electrical Codes. You also get free access to the committee notes and discussions that surround each item for a deeper understanding if you ahve time to read them. Worth you using the free day at least.

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What a coincidence..... I work for an OEM and we export to the USA (Citrus industry). I am currently reviewing our standards to ensure that we are meeting all the requirements for the USA market. Wizard made a slight mistake: NFPA 70 (National Electrical Code) is a Federal code and different versions apply to different states. This covers building and infrastructure electrical requirements. Only of limited use for an Industrial machine application. NFPA 79 Electrical Standards for Industrial Machines. This is the manual which gives the information that you will require. UL508A Standard for Electrical Control Panel. If you go to the Rockwell Automation (USA) site and search for "American Standards" it will show a PDF file "Introduction to North America Standards." (ul-wp001_-en-p.pdf). This will give a good starting point for further information. Feel free to PM me for further information/help.

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Easy mistake when you've been awake 18 hours Monkey. I would disagree on one area though NFPA 70 calls out wire sizing, motor overloads and breakers and fuse sizing for motors. Unless these are dupluicated in NFPA 79 he'll need NFPA 70 for them.

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Thank you both for your replies and the links I will do some reading and see how I go. Thanks Bob for pointing out the Arc Flash label and shock hazard boundary label I will need to make sure I understand these requirements. Thanks Monkey for the PM offer I will do some reading and get a bit more up to speed before I ask questions that I could answer myself.

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Arc flash has to be determined on site. You can't do it without local calculation information. That's why no panels come with them. You can read the NFPA 79 standard online (www.nfpa.org). It's just basic information about how to set up controls. Things like IEC 61508 are tighter than it. UL 508/508A is fairly complex. The basic problem is that everything in the U.S. has to be Listed (as per NFPA 70, National Electrical Code). Until recently, at least in theory any assemblies that you built had to be sent to UL for testing to get them approved. The whole idea of UL508A is that you can now follow a very long set of rules to create a listed assembly without necessarily having to go to UL to get it tested. There are of course other listing agencies than UL...they are just the most popular. There's also TuV and CE. I've had clueless inspectors complain about lack of UL sticker (when it has a CE one).
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While, I agree this doesn't stop customers from demanding the stickers. It almost seems like you have to add a caveat to your labels that says: Arc Flash data is XXX For a load supply of XXX.

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Nope. You have to calculate available fault current AND trip time, and it gets much more complicated if you have any current limiting devices (fuses) upstream. Trip time can't be calculated without knowing the impedance of devices in your panel, so this is the catch-22 that makes it impossible to do it all the way around. I can easily contrive real world examples that destroy your load supply assumptions, hence the reason for local studies. The only exception that I can think of is that some manufacturers (Square D) of dead front 120 VAC panel boards are labelling them as effectively "no arc flash" with the cover on because if you use it under listed conditions (don't exceed the AIC/SCCR), arc flash can't happen anyways. You can put on a "danger, arc flash potential" sticker with NO information as well. It is nowhere near the arc flash requirements in NFPA 70E but you do have a warning sticker (albeit a generic one). Arc flash determinations have to be done locally at the site. You can either use an engineering calculation (better, lower results), in some cases an assumption (AF = "0" [almost none] if fed from single transformer <125 kVA with <=240 VAC secondary), or the tables (if your situation qualifies). What's much more useful/desirable is to put SCCR ratings on the panels. I believe this is quickly becoming a requirement, if it isn't already. And that you definitely can determine by what's inside the panel.

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CE is meaningless in the USA and is not "listed". Perhaps you meant ETL or CSA? Both are, supposedly, equivalent to UL. I find that unless you wanna spend the rest of your life educating / fighting inspectors, it's best to just go with UL.

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CE is just as valid as UL. NEC does not specifically prescribe a listing agency. Any recognize agency works. It's just that the vast majority actually only recognize UL. But yes, inspectors flip out whenever they don't see a UL sticker. To the original poster's issues/questions: 1. Australian electrical standards are more stringent than their US equivalents, at least as far as mining equipment goes (the only area that I have cursory knowledge of). 2. The National Electrical Code (NEC, aka NFPA 70) is required in ALL 50 states in some form. Usually each state adopts NEC with a long or short list of exemptions where they get rid of parts they don't like. In practice if you follow NEC in a strict manner in terms of machinery design, it will be accepted. There are rare instances such as banning certain wiring methods in certain jurisdictions but as a rule those are rare. 3. ALL equipment used in the U.S. must be "Listed" by a recognized listing agency, which means almost exclusively UL (Underwriters Laboratories). Installations must be done in the manner in which they are listed within UL (you must use manufacturers instructions). You can deviate from this requirement ONLY if the Authority Having Jurisdiction allows it as it wouldn't be "Listed" otherwise (tested/verified by UL and used in the manner in which the manufacturer got their UL listing). 4. The latest UL requirement is UL 508/508A. Previously at least theoretically as a machine builder you had to hire UL inspectors to come in and validate your construction and get a UL listing as well for your assembly because obviously you couldn't sell/install it without meeting these requirements. This is the law but few machine builders actually complied and it was rare that they got "called" on it. UL developed 508/508A specifically to address this. This made UL listing practically possible and opened the door so that now most machine builders actually comply under the listed assembly rules. 5. The above is what is LAW in all 50 states, though of course there are local variations. In practice like I said, the variations are usually very minor. For example, New Jersey specifically exempts schools from NEC entirely and has a long list of sections of NEC that they exempt. Another example is Code adoptions. Most states lag the current Code by a few years, so implementing things according to the most recent revision is usually the safest approach. 6. OSHA has a few areas where they have very specific machinery requirements and it is best to look at these. For instance the regulations for presses are quite specific. However, in recent years they've gotten away from doing this because the update cycle for government regulations is so long that the regulations are usuallly outdated before they get approved. In more recent years OSHA (and MSHA) have taken the approach of simply fining companies for not doing things right and using a consensus safety standard of THEIR choosing. They will use pretty much any consensus safety standard however if the company names one (because there's enough overlap between standards). 7. As a result, appropriate consensus safety standards for both the industry, and type of equipment are appropriate to use. In general there are a few that are specific to the U.S. but there's a lot of overlap. For instance, IEC 61508 for equipment design for safety is probably the best out there and is outright used in general in the U.S., rather than being reworded. The various safety standards that have already been mentioned (such as the RIA standard) codify the equipment requirements but don't specify how the components are designed, and this is where UL 61508 fills the gap. ISA's safety instrumented systems standard (a safety standard for process industries) specifies process design but defers to UL 61508 for the equipment portion of things. The RIA and ISA codes by the way are very different...if you are dealing with mechanical and/or assembly line type systems, RIA is probably the best out there. For process design, ISA is probably the best out there. They cannot in general be used interchangeably because their respective processes are so different...RIA is focussed on moving equipment while ISA is focussed more on chemical systems. Neither does well in covering the other.

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