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Can operator do his job ?
https://brainfiller.com/arcflashforum/viewtopic.php?f=10&t=1759		 Page 1 of 1
Author:  toolbbin [ Tue Jun 21, 2011 11:48 pm ]
Post subject:  Can operator do his job ?
An operator for electrical equipment operates start / stop button and the like all control switches that are installed in electrical panels labeled 2- 4 hrc. Does the operators need ppe to turn on/off the equipment using control switches in this type of situation ?
Author:  glen1971 [ Wed Jun 22, 2011 5:05 am ]
Post subject: 
Is he doing it with the panel doors open or closed? Assuming closed, then no..
Author:  Zog [ Wed Jun 22, 2011 6:45 am ]
Post subject: 
I disagree, the panels are labeled HRC 2 and 4, that is the PPE required regardless of the status of the doors.

The operators need to be trained and qualified per 70E, even if it is only for that specific task.
Author:  cbauer [ Wed Jun 22, 2011 10:53 am ]
Post subject: 
I agree with Zog. You are interacting with the electrical system.
Author:  SCGEng1 [ Wed Jun 22, 2011 11:40 am ]
Post subject: 
Here we go again, another “doors open / doors closed” discussion along with the typical disagreement among the members.
Author:  ZeroSeq [ Wed Jun 22, 2011 1:08 pm ]
Post subject: 
Exploding Door

SCGEng1 wrote:
Here we go again, another “doors open / doors closed” discussion along with the typical disagreement among the members.


Door closed then door opens....
http://www.youtube.com/watch?v=2LZ0q78OWZE&feature=related
Author:  SCGEng1 [ Wed Jun 22, 2011 1:56 pm ]
Post subject: 
I’m not saying every case is the same. I’ve personally seen many events over the years; one recently on 600V switchgear where the breaker was not ejected into the operators chest and the doors stayed closed. We calculated over 35 calories for the LV breaker cubical, based on the PPE condition after the event, the operator was exposed to maybe 6 calories of heat at the most…the breaker body and door shielded most of the energy for this event.

Would this be the case every time, I don’t know, know body knows, that’s my point. There has not been enough testing on real world equipment to know what the real dangers are. Everyone assumes all conditions are the same, I don’t think so….even 70E gives credit for doors in the look up table. If it was cut and dry then people would stop asking the same questions over and over.
Author:  Zog [ Wed Jun 22, 2011 3:39 pm ]
Post subject: 
SCGEng1 wrote:
I’m not saying every case is the same. I’ve personally seen many events over the years; one recently on 600V switchgear where the breaker was not ejected into the operators chest and the doors stayed closed. We calculated over 35 calories for the LV breaker cubical, based on the PPE condition after the event, the operator was exposed to maybe 6 calories of heat at the most…the breaker body and door shielded most of the energy for this event.
"Only 5 times the heat it takes for a 2nd degree brun, Oh gee, that is nothing :rolleyes:

So your door held, and only put a guy in the burn unit or worse, and that was best case. Did you have vents on your doors as some gear does? Were all of your panel screws secured, as they seldom are? Was you gear in good physical condition? You get the point.

[QUOTE=SCGEng1;8548Would this be the case every time, I don’t know, know body knows, that’s my point. There has not been enough testing on real world equipment to know what the real dangers are. Everyone assumes all conditions are the same, I don’t think so….[/quote] Exactly, no one knows, there are too many variables.

[QUOTE=SCGEng1;8548even 70E gives credit for doors in the look up table. If it was cut and dry then people would stop asking the same questions over and over.[/QUOTE] Tables are risk based, analysis results are hazard based, apples and oranges. Think of it like this, because OSHA and the lawyers will. You have identified, through a detailed analysis by an engineer, that the hazard level for a point is "over 35 calories", and then you say that iit is safe to operate the breaker with the doors closed based on an assumption that the doors will hold (With no real data to support that claim). A guy wearing no PPE gets hurt, who are they coming after????

It IS cut and dry to most people in this industry, there are only a few that seem to question it, and I bet those few have never been in a burn unit.
Author:  SCGEng1 [ Thu Jun 23, 2011 6:57 am ]
Post subject: 
[quote="Zog"]"Only 5 times the heat it takes for a 2nd degree brun, Oh gee, that is nothing :rolleyes:
[QUOTE]

No, you missed my point. My point (from an engineering view) is the accuracy of the model (1584) for this situation. By the way, the operator was wearing a 40cal suite and was uninjured, that’s the good news and nothing else really matters.

Had the 1584 guys simulated “a breaker in the cubical and doors closed” we may have a different model for these situations and a better overall understand of the different hazards. Maybe in some situations tight doors are worse; vents may help dissipate the blast allowing the doors to remain shut providing protection. The video above appears to be an MCC bucket failure. While the heat is very bad (you need your PPE) that door blowing off could be the unprotected hazard in this situation…so should everyone be wearing crash helmets and chest protectors?

The point is unless the science evolves then we maybe over protecting for some situations (and hurting the credibility for the program) but under protecting for others. It could be that heavy built metal clad switchgear is not as bad but light weight panels and box are more hazardous; maybe they will fly apart much easier. Maybe, in reality, that Level 2 sticker on the panel is actually worst than that Level 4 sticker on the switchgear…only testing will tell.

Again in my opinion, the science is not keeping up with the need or the number of questions that are out there. Again just look at how many of the same type of questions show up on this forum every month. Someone is always asking “can I do this” or “can I do that”, and IMO, no it’s not cut and dry because not everyone on here agrees, simply refer to replies #2 and #3 (yours) above.
Author:  jghrist [ Thu Jun 23, 2011 7:11 am ]
Post subject: 
It would be reasonable for a hazard/risk analysis to reduce PPE requirements for something like motor starter operations on 600 V MCCs with doors closed. For instance, Table 130.7(C)(9) assessed this as "5 to 10 cal. risk extremely low" and reduced the HRC to 0 from HRC 3. This is from the NFPA 70E May 2003 ROP Preprint.

You would have to do some formal analysis to justify a reduction in your particular circumstances. Annex F of NFPA 70E has an example evaluation. NFPA 70E ROP A2011 has a better example.
Author:  Zog [ Thu Jun 23, 2011 8:29 am ]
Post subject: 
SCGEng1 wrote:
The point is unless the science evolves then we maybe over protecting for some situations (and hurting the credibility for the program) but under protecting for others. It could be that heavy built metal clad switchgear is not as bad but light weight panels and box are more hazardous; maybe they will fly apart much easier. Maybe, in reality, that Level 2 sticker on the panel is actually worst than that Level 4 sticker on the switchgear…only testing will tell.


Agree 100% :)
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