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| Dangerous Equipment Condition https://brainfiller.com/arcflashforum/viewtopic.php?f=33&t=3415 |
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| Author: | Jim Phillips (brainfiller) [ Sun Aug 10, 2014 3:45 pm ] |
| Post subject: | Dangerous Equipment Condition |
Part of the 2015 edition of NFPA 70E addresses "normal operation" One of the criteria to be considered normal operation includes equipment that has been properly maintained. There are many reasons that can lead a person to to conclude equipment has not been properly maintained but let's go to the extreme with this week's question. Have you ever seen electrical equipment that you consider dangerous just by the appearance? i.e. missing covers, exposed conductors, "duct tape repairs" etc. Stories are always welcome!
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| Author: | tish53 [ Mon Aug 11, 2014 5:01 am ] |
| Post subject: | Re: Dangerous Equipment Condition |
The worst was a small cement block room in a factory, that had accumulated so much stuff in it we had a terrible time just getting the door open. When we got inside, there was broken pieces of factory equipment piled as high as the switchgear giving no access to the gear. When we asked how long it looked like that the response was, "well I have worked here for 15 years and I never even knew we had this switchgear, and I have never been in this room". It was a 2500 amp rated switchgear with a main and 5 draw out feeder breakers that had not been maintained for over 20 years. After killing power, we found all 5 feeder breakers had defective trips, but I knew just by looking. a miracle the place didn't burn down. |
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| Author: | mollysydney [ Mon Aug 11, 2014 6:42 am ] |
| Post subject: | Re: Dangerous Equipment Condition |
4000A 480 drawout main breaker, directly below the coal hopper for the paper plants 200,000 lb/hr main boiler. Door of breaker was propped open with a 2x4 with a pedestal fan two feet away blowing air, and lots of dust, into cubicle to "cool" the breaker to keep it from tripping. Pointed out the danger to the maintenance manager and he said "I don't know what your concerned about, we only do it in the summer and its been that way for 10 or 15 years. Since we put the fan on it we haven't had it trip once in ten years!" Fortunately the plant was shutdown three years later and yes the door was still propped open with the 2x4 and fan was still blowing coal dust on the breaker when it shutdown. |
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| Author: | PaulEngr [ Mon Aug 11, 2014 1:25 pm ] |
| Post subject: | Re: Dangerous Equipment Condition |
Personally, I think the 70E definition is useless. It just says that it is properly installed and maintained. It doesn't really say anything about a visual inspection of any sort. It begs many issues: 1. To what standard should it be maintained? There are maintenance standards (70B, NETA MTS) but they have a lot of things in them that nobody would do such as unwiring every single low voltage control wire to megger it every few years. And just try to figure out how often you should PM a breaker, I dare you. It's all over the map on recommendations and some of the ones that appear to be data oriented have blatant data mining issues such as saying every 3 years because IEEE 493 gives data for "1, 2, and 3+" years. 2. How does one check if it is properly installed or for that matter, properly maintained? Especially before opening the doors and doing a lot of looking at engineering and installation reports? 3. Even if all this is satisfied, I'd personally say that 95%+ of the issues are environmental or field issues when conditions change. For instance if you come up on an MCC which had just recently tripped off and there are black soot marks around the edges of the door before you open it, is it safe to do so without PPE? 4. More broadly, does it make a difference if the reaosn for operating or doing maintenance on a piece of equipment is because it just tripped on a fault or if this is just normal, routine stuff such as unwiring a motor in order to send out a piece of equipment for repairs? I would think that knowing that it just tripped makes a huge difference. Although we all probably have battle scars or at the very least, war stories, these are just anecdotal evidence. I can easily collect data on any given scenario such as specific equipment, conditions, tasks, etc., and find lots of anecdotal evidence. Some might be fish stories (contrived). Some is just plain paranoia and idle conjecture about things which have not actually ever happened "but could". What we are unlikely to find though is any kind of likelihood data...something that says that even if XYZ is the case (such as the simple case of a tripped breaker or fuse), what is the likelihood of an arcing fault occurring while doing some specific task. Or even the likelihood while performing a certain task. Even something as basic as racking a breaker in and out of a cell in draw out gear. Personally, I'm pushing locally to scrap the definition in 70E for what is acceptable because it is completely unworkable. It is confusing as hell and way too hung up on the type of equipment. Instead, I'm using the table recommended in OSHA final rule 1910, Subpart V, Subchapter R, "Assessment for Various Tasks", Appendix E, Table I, draft published 4/1/2014. This table has a much simpler set of requirements that can be visually determined. For operation of equipment (energizing/de-energizing) where equipment is not being inserting or removed (no draw-out cases), I have broken it down as follows: 1. Remote operation where tools and hands do not cross either the limited approach or the arc flash hazard boundary: anything goes. 2. "Has not tripped on an electrical fault, no visible evidence of arcing, overheating, parts of equipment are not loose or sticking, no visible signs of a lack of maintenance, no exposed conductors": no arc flash PPE or shock protection needed. 3. "Evidence of arcing or overheating, tripped on an electrical fault, parts of equipment are loose or sticking, or the equipment otherwise shows a lack of maintenance": Arc flash PPE required. This is also subdivided into exposed conductors (shock PPE required) and no exposed conductors (no shock PPE required). Looking at OSHA investigation records from 2007 to 2011 (5 years), I found 4 cases of as far as I can tell what would be considered "normal operation" cases which caused hospitalization. None were fatal: In #202539953, a breaker exploded. In #202597183, the cover (which had previously been improperly repaired and was put together loosely) fell in such a way that it initiated an arc flash The two other cases involved medium voltage equipment owned and operated by a utility in which a "switch" faulted. The failure mechanism is not reported so we have nothing to go on. These are all strictly arc flash cases as the task tables are specifically speaking to arc flash. There are far more shock injuries than arc flash injuries (roughly a 2:1 ratio), and there are far more serious injuries than fatalities due to arc flash (at least 10:1 or higher ratio). So...if we properly maintain, that is don't just keep resetting a breaker and do periodic testing and maintenance and don't do shoddy workmanship and/or do inspections to catch this kind of thing, then of the two out of millions of man-hours of work over a 5 year time period would not have happened. I would comment similarly on the utility switches but I have very little data on precisely what happened. I'm thinking non-LBS switches that were opened or closed under load and showerred someone with molten metal as that is a pretty common thing. |
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| Author: | K. Engholm [ Thu Aug 14, 2014 6:51 am ] |
| Post subject: | Re: Dangerous Equipment Condition |
I don't think anyone would even need to be in the electrical business to answer yes to this question. How many times do you walk through a parking lot to find the base of the parking lot lighting open and wires sticking out. I can think of a lot of similar "public" unsafe installations/situations Great question - how many of you have seen similar types of problems? |
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