We recently had a study of our facility done which is 575 volt and it came back with some class # 3 ,#4 and Extreme danger. I didnt realize that 575 volt could be in these high classes. Since I dont see a class "extreme danger" what does that mean? I have the vendor coming by in two weeks to go over the study but I thought I might ask the question before he get here. We have Square D DSL 2 switchgear put in in 1999 and are 90% fuse protected in most application below the gear. The gear has current limiting fuses also.
Arc Flash clothing class
- Thread starter zmikc115
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bphgravity
Senior Member
- Location
- Florida
That may mean you have some equipment that could produce an arc-blast condition that cannot be currently protected against. 
Thanks for the reply bph. My other question would be is there a way I could check against this report besides having another vendor do it? I am having a hard time understanding how we are this high. We have a sister facility using the same substation 100 yards away and they are only class 2 and below mostly below 2 . So I would like to check against this report if it wouldnt be too hard.
I have several questions for you.
1. Was your sister facility built at the same time?
This can change the equipment used for example the relaying schemes could be diffrent or the service size could be diffrent. If they are diffrent in any way your comparison based upon voltage levels are not valid. While doing an arc flash study for a dam circa 1950 I found a class 4 panel the feeder for this panel was coming from a class 0 panel. The point of this example is that voltage or even fault current do not have nearly the effect that the protection has on the Arc flash hazard.
2. Is your sister facility closer to the substation?
In the above example the change in arc flash hazard was due entirely to the distance of the run (1000') and the change in fault current due to the added impedence
The only way to check an arc flash hazard report is to do a study. I would ask my consultant for some fixes to reduce the arc flash hazards and see what they say.
1. Was your sister facility built at the same time?
This can change the equipment used for example the relaying schemes could be diffrent or the service size could be diffrent. If they are diffrent in any way your comparison based upon voltage levels are not valid. While doing an arc flash study for a dam circa 1950 I found a class 4 panel the feeder for this panel was coming from a class 0 panel. The point of this example is that voltage or even fault current do not have nearly the effect that the protection has on the Arc flash hazard.
2. Is your sister facility closer to the substation?
In the above example the change in arc flash hazard was due entirely to the distance of the run (1000') and the change in fault current due to the added impedence
The only way to check an arc flash hazard report is to do a study. I would ask my consultant for some fixes to reduce the arc flash hazards and see what they say.
- Location
- Illinois
- Occupation
- retired electrician
I would assume that "extreme danger" would mean that the incident energy exceeds 40 cal/cm^2...the maximum for level 4 PPE.
Don
Don
Seguridad
Member
- Location
- Villahermosa, Tabasco, Mexico
Arc Flash Hazard Analysis is Critical
Arc Flash Hazard Analysis is Critical
We have done several arc flash studies in our facilities; you would be surprised of the levels of incident energy we found.
For example in one facility we had the following results: 480 V there was from 0.2 up to 192 cal/cm2, in 220 V from 0.1 up to 47 cal/cm2, in 13.8 kV from 3 and up to 249 cal/cm2. We brought down several of these values, but we could not change the 192 cal/cm2 and many stayed over 30 and up to 55 cal/cm2.
I shake when I see some people using the 70E tables instead of having a proper hazard assessment done.
Arc Flash Hazard Analysis is Critical
We have done several arc flash studies in our facilities; you would be surprised of the levels of incident energy we found.
For example in one facility we had the following results: 480 V there was from 0.2 up to 192 cal/cm2, in 220 V from 0.1 up to 47 cal/cm2, in 13.8 kV from 3 and up to 249 cal/cm2. We brought down several of these values, but we could not change the 192 cal/cm2 and many stayed over 30 and up to 55 cal/cm2.
I shake when I see some people using the 70E tables instead of having a proper hazard assessment done.
ron
Senior Member
- Location
- New York, 40.7514,-73.9925
I'm not surprised to see varying results between buildings. As mentioned earlier, lower available fault current at a particular piece of equipment, and possibly an associated different upstream OCPD, will result in VERY different incident energy results.
If you get the Sister building report, you can compare a particular piece of equipment by using the calculated 3 phase bolted fault current, the calculated arc flash fault current, the settings of the upstream protective device (OCPD), and the clearing time of that device.
I've had 208V equipment calculate to be DANGEROUS (>40 cal/cm^2), because of low fault current and OCPD's that were not set low enough to clear it.
Will the consultant produce "remedies" as part of their report if they are possible? Sometimes it is as easy as producing a coordination study and reducing the OCPD settings where possible/needed. We sometimes, with owners agreement, compromise selectivity (not on emergency circuits) in order to result in lower incident energy values.
If you get the Sister building report, you can compare a particular piece of equipment by using the calculated 3 phase bolted fault current, the calculated arc flash fault current, the settings of the upstream protective device (OCPD), and the clearing time of that device.
I've had 208V equipment calculate to be DANGEROUS (>40 cal/cm^2), because of low fault current and OCPD's that were not set low enough to clear it.
Will the consultant produce "remedies" as part of their report if they are possible? Sometimes it is as easy as producing a coordination study and reducing the OCPD settings where possible/needed. We sometimes, with owners agreement, compromise selectivity (not on emergency circuits) in order to result in lower incident energy values.
Last edited:
bphgravity
Senior Member
- Location
- Florida
I see 100 cal/cm? clothing advertised, but I don't see how that is possible.
ron
Senior Member
- Location
- New York, 40.7514,-73.9925
There is a lot of PPE rated >40, but at this time NFPA 70E only acknowledges PPE up to 40 cal/cm^2. So I do not identify a PPE rated @ >40 until a national standard like 70E recognizes it. If it calculates at >40, then I say "dangerous" no rating.
ron said:
If it is >40, there is an excellent chance that PPE won't make any difference. One breath of air and your lungs are cooked and they will not exchange any oxygen for you in that state. I would not work on anything >40. But, that is only my opinion.
I would add that above 40 cal/cm^2, arc blast (pressure) may be the more important hazard (particularly because of high-speed shrapnel thrown out by the blast). As I understand the testing methods, they do not consider resistance to this, but only heat rise. I'm with dlhoule; I consider that an event > 40 cal/cm^2 may not be survivable, and can't recommend working there.
zog
Senior Member
- Location
- Charlotte, NC
"So I do not identify a PPE rated @ >40 until a national standard like 70E recognizes it"
Earlier editions of the 70E did recognize these, HRC 5 was for Ei of 40-100cal/cm2. Further research has shown that the human body cannot survie the pressures from an arc with Ei of >40cal/cm2 so thats why the 2004 70E classifies these as "Dangerous".
If you were subjected to a 100cal/cm2 arc a 100cal/cm2 flash suit would simply allow for a open casket instead of a closed casket.
Earlier editions of the 70E did recognize these, HRC 5 was for Ei of 40-100cal/cm2. Further research has shown that the human body cannot survie the pressures from an arc with Ei of >40cal/cm2 so thats why the 2004 70E classifies these as "Dangerous".
If you were subjected to a 100cal/cm2 arc a 100cal/cm2 flash suit would simply allow for a open casket instead of a closed casket.
Seguridad
Member
- Location
- Villahermosa, Tabasco, Mexico
Arc Flash PPE
Arc Flash PPE
The 70E committee stopped clothing suggestions at 40cal/cm2 with the argument that over 40 cal/cm2 the hazard was the blast. I heard that they had a responsibility issue, especially since they promoted quite a lot the use of the tables and so many people are looking into those damn tables instead of making hazard assessments.
The truth is that the blast does not have a relationship with the flash; this is to say that at higher incident energy (cal/cm2) does not mean that you will get a higher shock wave (psf). This is a new variable, which is independent.
The general public is starting to understand cal/cm2 today, after more than 6 years of being general public information. We cannot put out a new issue like that on the table, not until the first one is clear. In the meantime the blast hazard should be explored as much as it was the flash hazard from 1982 until 1995 before any standards arise from those studies.
Today, most people die because of burns, caused by the arc flash (incident energy), so today we need to protect the skin to help the person have a normal life. Although bones, muscles and other organs can be damaged in the blast, in most cases those can be healed.
Arc Flash PPE
The 70E committee stopped clothing suggestions at 40cal/cm2 with the argument that over 40 cal/cm2 the hazard was the blast. I heard that they had a responsibility issue, especially since they promoted quite a lot the use of the tables and so many people are looking into those damn tables instead of making hazard assessments.
The truth is that the blast does not have a relationship with the flash; this is to say that at higher incident energy (cal/cm2) does not mean that you will get a higher shock wave (psf). This is a new variable, which is independent.
The general public is starting to understand cal/cm2 today, after more than 6 years of being general public information. We cannot put out a new issue like that on the table, not until the first one is clear. In the meantime the blast hazard should be explored as much as it was the flash hazard from 1982 until 1995 before any standards arise from those studies.
Today, most people die because of burns, caused by the arc flash (incident energy), so today we need to protect the skin to help the person have a normal life. Although bones, muscles and other organs can be damaged in the blast, in most cases those can be healed.
Seguridad said:
I do not say you are wrong, but do you have reliable statistics to back up that portion of statement. It has been my understanding that there have been a number of deaths from inhaling the super heated air, where there has been very little burn damage to the skin. Anyway you want to look at this; if it is over 40 I am not working it.
zog
Senior Member
- Location
- Charlotte, NC
"The general public is starting to understand cal/cm2 today"
The 70E is changing to Joules/cm2, I have argued your point that cal/cm2 is finally being understood by the industry so why change it, but, they want everything to be metric.
FYI: 1 cal = 4.1868 Joules
The 70E is changing to Joules/cm2, I have argued your point that cal/cm2 is finally being understood by the industry so why change it, but, they want everything to be metric.
FYI: 1 cal = 4.1868 Joules
hutch75
Member
- Location
- Detroit, MI
Arc Flash Study
Arc Flash Study
I am responsible for Arc Flash compliance in 29 Manufacturing locations in the US and Canada, and have just completed my first two study's, and am striving to complete seven locations each year over the next four years. In reviewing proposals from vendors for this work, and having two under my belt(3 million sq feet each), I have the following questions on your initial study:
1. What software did they use to prepare this data? We have standardized on SKM
2. How much field data collection did your vendor do? Did he verify all breaker settings, buss/feeder lengths, and buss plug fuse information?
3. How was your final report presented, and was it signed by a PE?
4. Since you are in Canada, and the CEC and Ministry of Labor have not formally adopted NFPA 70e(yet) what propmted the study?
Arc Flash Study
I am responsible for Arc Flash compliance in 29 Manufacturing locations in the US and Canada, and have just completed my first two study's, and am striving to complete seven locations each year over the next four years. In reviewing proposals from vendors for this work, and having two under my belt(3 million sq feet each), I have the following questions on your initial study:
1. What software did they use to prepare this data? We have standardized on SKM
2. How much field data collection did your vendor do? Did he verify all breaker settings, buss/feeder lengths, and buss plug fuse information?
3. How was your final report presented, and was it signed by a PE?
4. Since you are in Canada, and the CEC and Ministry of Labor have not formally adopted NFPA 70e(yet) what propmted the study?
- Location
- Illinois
- Occupation
- retired electrician
Maybe the NFPA should move from the US to a country where they use the metric system!!!
Don
Seguridad
Member
- Location
- Villahermosa, Tabasco, Mexico
Arc Flash Studies
Arc Flash Studies
I agree in that cal/cm2 is the standard today, since studies and PPE are selected that way. Joules was adopted because they wanted to have metric and US system, so cal/cm2 is metric and joules from the US system. Anyway, we all use the cal/cm2 for incident energy and for other measurements in the US they use inches and so forth.
1) SKM I believe it is the best option for engineers.
2) I believe most of the data should be given by the company; it just makes sense since they know their system better. The vendor should tell them what they need, maybe using a spreadsheet with all electrical equipment fields needed to perform study.
3) Reports are presented in a way that allows the company to take actions. One part of the report explains the findings, such as incident energy levels per bus, another part of the report gives reengineering suggestions to bring down those levels and both of the reports include the PPE (personal protective equipment) suggestions per bus. I prefer this to be reviewed by Oberon Company (manufacturer of PPE) or a knowledgeable distributor or consultant of them, since they know the products better and can give you suggestions based on their tested layering systems and BIRG ? (Burn Injury Reduction Guide) data, which is unique to their PPE and protective systems. Remember that the ATPV (arc thermal Protection Value) of the suits, is based on a 50% probability of enough energy going through the material (textile or shield) to cause a second degree burn, so only knowing the other probabilities, don to 1% you would be able to choose the safest PPE.
4) I am in Mexico, but I know that most companies outside the US, that decide to adopt this standard, do that because most Occupational Health and Safety departments/ministries, etc. have some safety standard that states that the employer should perform a hazard assessment and provide adequate PPE to the employee. This can only be accomplished in the electrical safety field, by implementing NFPA 70E, since there is no similar standard in the entire world.
Good luck with your studies and have fun, plenty of new issues will arise, and it is great, because we all need to realize about the importance of electrical safety and protect our workers correctly. We have been with our eyes closed for too long, is time to take action; Prevent instead of Healing.
Arc Flash Studies
I agree in that cal/cm2 is the standard today, since studies and PPE are selected that way. Joules was adopted because they wanted to have metric and US system, so cal/cm2 is metric and joules from the US system. Anyway, we all use the cal/cm2 for incident energy and for other measurements in the US they use inches and so forth.
1) SKM I believe it is the best option for engineers.
2) I believe most of the data should be given by the company; it just makes sense since they know their system better. The vendor should tell them what they need, maybe using a spreadsheet with all electrical equipment fields needed to perform study.
3) Reports are presented in a way that allows the company to take actions. One part of the report explains the findings, such as incident energy levels per bus, another part of the report gives reengineering suggestions to bring down those levels and both of the reports include the PPE (personal protective equipment) suggestions per bus. I prefer this to be reviewed by Oberon Company (manufacturer of PPE) or a knowledgeable distributor or consultant of them, since they know the products better and can give you suggestions based on their tested layering systems and BIRG ? (Burn Injury Reduction Guide) data, which is unique to their PPE and protective systems. Remember that the ATPV (arc thermal Protection Value) of the suits, is based on a 50% probability of enough energy going through the material (textile or shield) to cause a second degree burn, so only knowing the other probabilities, don to 1% you would be able to choose the safest PPE.
4) I am in Mexico, but I know that most companies outside the US, that decide to adopt this standard, do that because most Occupational Health and Safety departments/ministries, etc. have some safety standard that states that the employer should perform a hazard assessment and provide adequate PPE to the employee. This can only be accomplished in the electrical safety field, by implementing NFPA 70E, since there is no similar standard in the entire world.
Good luck with your studies and have fun, plenty of new issues will arise, and it is great, because we all need to realize about the importance of electrical safety and protect our workers correctly. We have been with our eyes closed for too long, is time to take action; Prevent instead of Healing.
Seguridad
Member
- Location
- Villahermosa, Tabasco, Mexico
Arc Blast
Arc Blast
I say this based on the 70E committee hearings and some testing conducted at Kinectrics. Arc blast is being studied as we speak; I believe we will here more about it after the 2008 Edition of 70E comes out.
Most of the deaths are because of burn injuries on the skin (usually higher than 60% of the skin). There are cases of hot air being inhaled, causing internal burns in the respiratory system and subsequently death, but those are definitively not the majority.
Be safe...
Arc Blast
dlhoule said:[/COLOR]
I do not say you are wrong, but do you have reliable statistics to back up that portion of statement. It has been my understanding that there have been a number of deaths from inhaling the super heated air, where there has been very little burn damage to the skin. Anyway you want to look at this; if it is over 40 I am not working it.
I say this based on the 70E committee hearings and some testing conducted at Kinectrics. Arc blast is being studied as we speak; I believe we will here more about it after the 2008 Edition of 70E comes out.
Most of the deaths are because of burn injuries on the skin (usually higher than 60% of the skin). There are cases of hot air being inhaled, causing internal burns in the respiratory system and subsequently death, but those are definitively not the majority.
Be safe...
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