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 Post subject: Table H3(b)
PostPosted: Fri Mar 03, 2017 11:01 am 
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In reading the PPE requirements for below 1.2 calories. There is a note on wearing face shields. Can anyone give me a real world example where you feel that you need to wear a face shield? Remember, they specifically say, projectile protection. Better yet, can anyone explain what is meant by "as needed"? They are talking about projectile protection so my question is how do you decide if projectile protection is necessary if the hazard is below 1.2 calories? For example, suppose you're trouble shooting a 480 volt welder and the arc flash energy is less than 1.2 calories. My question is "how do you go about deciding if a face shield is needed based on an arc flash hazard less than 1.2 calories?


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 Post subject: Re: Table H3(b)
PostPosted: Sun Mar 05, 2017 3:02 pm 
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wilhendrix wrote:
In reading the PPE requirements for below 1.2 calories. There is a note on wearing face shields. Can anyone give me a real world example where you feel that you need to wear a face shield? Remember, they specifically say, projectile protection. Better yet, can anyone explain what is meant by "as needed"? They are talking about projectile protection so my question is how do you decide if projectile protection is necessary if the hazard is below 1.2 calories? For example, suppose you're trouble shooting a 480 volt welder and the arc flash energy is less than 1.2 calories. My question is "how do you go about deciding if a face shield is needed based on an arc flash hazard less than 1.2 calories?


In the case of the welder if you are doing overhead welding, you definitely should be wearing a face shield as well as a full welder's jacket because welding always creates small hot balls of slag/iron that have built-in guidance systems that aim for whatever vulnerable part of your body is available.

An example of where a face shield might be appropriate is when closing in cutout fuses. If the fuse triggers and you are positioned below it while operating it, you're going to get a shower of boric acid droplets.

In the case of working on a lead acid battery, we never figured out exactly why it happened but on starting up a bilge pump in an engine compartment, an "8D" (12 V lead acid battery that weighs about 150 lbs.) exploded and threw pieces and acid everywhere. Fortunately for the guy nearby the battery box captured/deflected the shrapnel. This would be another case of where a face shield might be "AN" (as needed).

In the case of doing stupid things in high school, I used to purposely charge up old large electrolytic capacitors to full charge and then short them out with a piece of copper bar with predictable results....mostly that the "tool" was magnetically propelled away at high speed. A face shield might have been a good idea at the time. Any number of other stupid things to do such as shorting phase-to-phase with any kind of loose item intentionally might also count.

Of course these examples all have virtually nothing to do with an "arc flash hazard" (except maybe the last one) and have a lot more to do with hazards other than arc flash. Technically every single piece of PPE in the list should be labelled "as needed" though because there are tons of examples of where the same PPE is required for other hazards. For example gas/oil plants as well as most foundries and steel mills, and some welding tasks, mandate fire retardant PPE. Chemical plants quite often mandate goggles and face shields where splash protection is required. And some plants even have crazy rules about mandating gloves for all tasks unless there is some kind of exception these days.


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 Post subject: Re: Table H3(b)
PostPosted: Mon Mar 06, 2017 9:26 am 
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Thanks Paul,
The welders are machines being serviced because of some break down inside the welder itself. So the mechanic or repair person sometimes needs to leave the welder turned to trouble shoot the problem. The arc flash hazards at the machines are less than 1.2 calories. So the mechanic is exposed to 480 volts shock hazard and possible arc flash. Their mechanic asked about the shield and what does as needed mean in the context of being exposed to less than 1.2 calories. I don't think this has to do with incident energy, but just the idea that the fault could project something into the face of the worker.
That's why I asked for real world examples.


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 Post subject: Re: Table H3(b)
PostPosted: Mon Mar 06, 2017 11:32 am 
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I work on welders. I can't really think of any circumstance for which I would need a face shield other than to drag an arc to test the machine. My point is really that "as needed" is really useless information.

When you are involved in these various committees by the way quite often what happens is that one or two individuals on the committee get very passionate about either an "outlier" case which they had personal involvement in, or they simply have some sort of uangup with one particular issue. So in the interest of finding consensus sometimes some extraneous things such as "as needed" get tacked onto the procedure.

A final example of where I can think that this might apply is with 480 V plugs that are common with welders. With all plugs you're not supposed to insert or remove them under load but people do it all the time. In one case I'm familiar with they had some large industrial fans that had 480 V plugs on them that didn't even have a switch to start/stop them. The welding receptacles all had disconnects. Proper procedure was to operate the disconnect, then insert or remove the plug, and then close the disconnect again. Well, one guy didn't get the message and claimed that he had plugged in and unplugged the fans without using the disconnects "for years" and eventually had a plug explode in his hands. He was convinced that the plug should not have exploded like that. Some plants have even gone as far as using receptacles such as the "Arktites" or Melcor brand plugs that pin the plug into the receptacle when the disconnect is closed so that it is physically impossible to insert or remove it while the disconnect is closed. Obviously this is bad practice but if it's your practice, I would suggest treating it as an arc flash hazard and wear the face shield and probably a pair of arc welding gloves too because it is an arc flash hazard.


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 Post subject: Re: Table H3(b)
PostPosted: Mon Mar 06, 2017 12:18 pm 
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I wondered about what I call "God Help Me" clauses they put in. Seems that "as needed" is a just another catchall phrase the AHJ can use when a person is involved in an accident. The AHJ can then say, "the face shield was needed because of the injury" - a sort of 20-20 hindsight. I did send a question to NFPA asking for examples or at least a better description of what they meant. I'm not holding my breath for a good answer.


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 Post subject: Re: Table H3(b)
PostPosted: Tue Mar 07, 2017 8:53 am 
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Don't forget that these things are consensus safety documents. I've sat through these things before. The format varies from one organization to another but what they will tell you is that you have a panel of experts. People submit ideas for changes and the committee votes up or down on each change. Those are incorporated into the document and that's what you end up with.

However there are two major wrinkles to this. The first one is that quite often change A, B, and C are all addressing different aspects of the exact same section of the standard and the wording conflicts. So the editorial staff takes the approved items A, B, and C, and attempts to synthesize a readable version, not always with the greatest success.

The second issue is that there are always the pragmatists and the academics to deal with. They are both extremists and pretty much won't agree to anything unless you get them to compromise, and compromise is sometimes very hard to achieve. So quite often what you end up with is voting to approve something even though there are elements of it that you really don't agree with or don't think should be in there, or adding some sort of relatively harmless extra clause in there, or watering something down just to get a pragmatist or an academic to agree to it. Often you can put things into fine print notes or annexes because those are not part of the Code and this will satisfy them.

I'm not saying that this is specifically where the "as needed" clauses came from...just that obviously Annex H by itself isn't Code and on top of that when it says that something might be a good idea (as needed), it's pretty obvious that disregarding it is well within the spirit and letter of the overall standard.

Which brings up the last issue. When you approach 70E in general you don't have to follow it word-for-word. It is after all a standard and not a regulation, but there is an affirmative legal defense to claiming that you are following an industry consensus safety standard so I don't suggest ignoring it without a very strong reason. The second point is that fine print notes and annexes are there as information only and not part of the standard per se. The approach to arc flash taken in 70E is that you have two options. In the first option (using the 2015 edition) you first consider the task and whether or not arc flash protection is needed. Then you move on to looking at the type of equipment which gives you a PPE level and then finally you determine the required PPE using the third and final table. The second approach that is acceptable under 70E is that you do the exact same 3 steps (determine whether or not there is an arc flash risk based on the task, determine the incident energy, and determine the required PPE) except that in this case you implement all 3 decisions using your own method. This means that for instance you could use the task table in the annexes in OSHA 1910.269, the equipment tables in IEEE C2 (NESC) for incident energy, and the PPE table in Annex H. You could alternatively use the task table in 70E (or roll your own), calculate incident energy using IEEE 1584, and use the PPE table in OSHA 1910.269. Or you could mix and match, or even use some other risk assessment technique for the task table. Somewhere along the way though you probably should document your decision process and if you are going to achieve the same level of legal defense (following industry consensus safety standards), you probably don't want to be getting too creative. Note that I'm mixing methods here.

Although 70E specifically prohibits you from doing this with the tables in 70E, that does not mean that you can't one or more of the tables as part of your engineered approach. This sounds like splitting hairs but it is a violation of 70E for instance to substitute IEEE 1584 calculations for the PPE levels in the second table. But you could ADOPT the task table, use IEEE 1584 for incident energy analysis, and adopt Annex H (a generalized version of the PPE table) as an engineered approach. You just can't label everything with 70E's "PPE levels". You can rename them as say levels A, B, C, and D, or you could simply use the incident energy value. While you are at it, Annex H gives larger ranges for acceptable incident energies (and OSHA 1910.269 gives even greater ranges) so if you issue 12 cal/cm2 ATPV PPE, you can get a lot more out of it before having to switch over to multilayer arc flash PPE. And if your vendor has a chart for it, you can use layering to achieve something in the neighborhood of 20-35 ATPV with a simple extra set of coveralls, winter wear, or rain suit, and not even bother with maintaining separate 40, 60, or 100 cal/cm2 arc flash PPE.


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