PPE for 480V and 4160V and above?

[powerpete69]

I wanted to bring this up for what seems to be a grey area.
I wanted to get a feeling for what other people are doing.
For our 480V substations pull out breakers and our 4160V pull out breakers, we have a general safety rule that you wear a 40 calorie moon suit whether you are turning the breaker off, turning it on, racking it in or racking it out. In other words, if you are going to touch that breaker, you wear the moon suit regardless if its racked in or out or regardless if the arc flash sticker reads 1 calorie or 40 calories. It's easy to make mistakes in the arc flash model programs.
We go by this rule and several of our contractors use this rule whether they are on our site or not.
What are the electrical guys on this site doing when they operate these devices?

It's my understanding that NFPA 70E is not quite this strict, but most of these guys operating these switches have families and just aren't willing to risk it which makes perfect sense to me. Lot of arc flash videos out there with massive explosions.
What about downstream MCC's with non pullout breakers? What are electrical guys wearing when they operate those breakers?

 

[mayanees]

Pete,

PPE for the 70E-compliant method is determined by either the PPE Categories method (130.7(C)(15)(a) or (b), or by the Incident Energy Analysis method as posted on the arc-flash label. If the equipment is labeled you have to use that method.

The tasks that require PPE are determined by table 130.5(C), Estimate of the Likelihood of Occurrence of an Arc Flash Incident.

You can operate the switches without PPE, as long as the condition of the equipment is what 70E defines as Normal. This is a case where the equipment is being used as intended by the manufacturer. But for racking breakers in or out you must wear PPE rated for the task.

So although your method sounds safe, you could be putting yourself at risk in a case where the incident energy level is above 40 calories and your suit is only rated for 40.

Oh and by the way, my experience with the forum is that there's not a whole lot of discussion around PPE usage. I've probed before as to what everyone's wearing prior to purchasing my latest PPE and I got crickets

 

[powerpete69]

Gotcha, thanks for your input.
The word "Normal" above is the gray area. A normal condition to most is a breaker in excellent or new condition. However, when they are 50 years old, we don't know what condition they are in. Have they been serviced? Have they been lubricated? Are they full of dust? In there a mouse lying across the terminals? Etc.
That's why we say to suit up no matter what. If there is a .1% of a incident, we can't have it per company policy.
Thanks for the code references above, I will take a good look.

 

[mayanees]

Normal is defined in 70E.

 

[powerpete69]

I see they make and sell PPE suits at a rated 65 calorie and a rated 100 calorie for situations exceeding 40 calories.

 

[mayanees]

I see they make and sell PPE suits at a rated 65 calorie and a rated 100 calorie for situations exceeding 40 calories.

The best way to use PPE is to dress in layers to achieve an increased IE level. Undershirt, shirt and coat are ideal.

 

[wbdvt]

The best way to use PPE is to dress in layers to achieve an increased IE level. Undershirt, shirt and coat are ideal.

Only if they are from the same manufacturer and the manufacturer has tested the combinations to determine what the incident energy level is that the combo will protect to.

 

[twm22]

I applaud the use of PPE at the 0.1% probability, but one would be wise to remember that overusing PPE is known to cause collateral mistakes: body overheating, lack of dexterity, reduction in vision and hearing, loss of pre- and post-job time. Of course, a motivated person will do what's required, but the culture must be strong.

In the Navy nuclear culture, safety factors were typically 4X, so I've lived the extensive requirements often considered best practices, and greater (and gladly complied). But as one's education increases and the statistics show a poor cost/befit (either at management or shop floor level), compliance can be affected negatively. Sadly, I think much of the negative comes from the top, based on needed investment of time and money.

 

[iceworm]

My experience is all industrial, about 50 years worth. Arcflash started to get noticed about 20 years ago. Arcflash classes started about 10 years ago. I have been to several - even taught some of the beginning classes.

I'm not even close to where you are in several areas.

Note:
Most of my clients require ordinary work clothes shall consist of arcflash rated shirt and pants, 4 - 8 cal/cm2, safety glasses, hardhat. Any outer layer, such as a jacket, will be arcflash rated. No, they don't check their underwear.

For our 480V substations pull out breakers and our 4160V pull out breakers, we have a general safety rule that you wear a 40 calorie moon suit whether you are turning the breaker off, turning it on, racking it in or racking it out. In other words, if you are going to touch that breaker, you wear the moon suit regardless if its racked in or out or regardless if the arc flash sticker reads 1 calorie or 40 calories.

For operating Circuit Breakers, or disconnect switches (fused, or unfused), with doors closed, ordinary work clothes. For rack-in/rack-out, arcflash gear commensurate with the calculated arcflash, by the arcflash study. If the calculation is 25, that is what they wear, if 40, then that is what they wear.

If greater than 40cal/cm2, then they don't do it. Isolate, remote racking are two options. And I hear rumbling of, "Remote racking is too expensive, and we can't take the equipment down for an isolation. Bullpucky of the first water. If it is a transformer secondary, then pulling the secondary main is in fact isolating the switchboard. It is okay to open the transformer primary.

If the issue is a switchboard fed by a low impedance transformer with an insanely high Short Circuit Current, buy and install trip units with maintenance switches.

I'll discuss the cutoff at >40cal/cm2 later.

It's my understanding that NFPA 70E is not quite this strict, but most of these guys operating these switches have families and just aren't willing to risk it which makes perfect sense to me.

Interesting. My first question is, "How do they manage to drive to work?" The statistical risk of injury while driving to work is much is much higher than being involved in an arcflash incident. I'm not saying to ignore the work safety. I'm saying mitigate the risk to acceptable levels. In my mind that would be Zero incidents of death, zero incidents of crippling injury.

Lot of arc flash videos out there with massive explosions.

Yeah, that is a problem.. I have been to two 70E classes (maybe more) that consisted of endless pictures/videos of arcflash incidents. And that is useless. We already got it that the work can be dangerous. We got that after the first two videos/pictures. What we want to know is how do we mitigate the risk. We are going to do the work. We need to do it with low risk. Showing us endless pictures to burn up the 16 hour class we have asked you for doesn't help.

Part 1 (more later)

 

[iceworm]

Part 2:

It's easy to make mistakes in the arc flash model programs.

This one bothers me - a lot. You don't trust the arcflash study? Then get it reviewed. Or, consider having someone at the company go to school to where they could do the review. This should be a mandatory thing. If any of the arcflash calcs look the least bit odd - ask for the data, and check that, then get the calc redone.

Interestingly, most of the errors I have found are the other direction - arcflash is calculated way to high. I consider these somewhat deadly. The crew knows when an arcflash is high. And that makes them ask, "How many of the others are bogus?" And I think that breeds complacency - and that is deadly.

However, when they are 50 years old, we don't know what condition they are in. Have they been serviced? Have they been lubricated? Are they full of dust? In there a mouse lying across the terminals?

And Here Is The Problem:

Yes, there is an arcflash issue. But you are not going to fix it buying arcflash gear. Because, this is a maintenance problem. Deferred maintenance is a killer. I have a client that has a bunch of 45 year old switchgear. And it works great. The CBs get pulled every few years (I recall it is a 5 year schedule) - cleaned lubricated, tested, trips calibrated.

"We can't do that, it is too expensive." Wait, what was that you said about probability of incidents? Well, yes you can, or you are out of business.

That's why we say to suit up no matter what. If there is a .1% of a incident, we can't have it per company policy.

This one bothers me. 0 .1% is 1:1000. With a moderately large sized plant, 1000 switch operations/year is reasonable. Statistically that is one incident a year. That is insane. Oh, we meant we must be better than that. Okay, let's make it 0.01%. That is 1 incident per 10 years. That is still way too much.

My thinking is to mitigate to less than 1 incident per 100 years, injury is serious, non-life threatening, non-crippling. This are statistical averages. 1:100 years is equivalent to the incident is likely to occur within the lifetime of the plant.

I see they make and sell PPE suits at a rated 65 calorie and a rated 100 calorie for situations exceeding 40 calories.

Yes, there are suits with these high rating. I am absolutely not in favor of them. My research shows that wearing a Haz Cat 4 suit, rated 40cal/cm2 in a 40 cal/cm2 incident leaves the worker with survivable 2nd degree burns.

Now let’s put the worker in a 100cal/cm2 suit and push the incident up to 65cal/cm2. My research indicates the body is not burned up and is pretty recognizable – just crushed from the pressure blast.

And, of course, as mentioned by twm, there is the issue of collateral mistakes due to the clumsy suit.

My solution – don’t do the work hot. Yes, you can. It is just money.

Yes, there will be plenty on here that will disagree with me - and that is okay


the worm

 

[hillbilly1]

Sure you can get suits above 40 cal, but it’s just the difference between an open casket and a closed casket. The concussion blast would most likely kill you at that point.

 

[jim dungar]

Now let’s put the worker in a 100cal/cm2 suit and push the incident up to 65cal/cm2. My research indicates the body is not burned up and is pretty recognizable – just crushed from the pressure blast.

Arc Blast effect is something the industry is not yet addressing. however, from my research it is not directly related to the arc flash incident energy level. Personally I have calculated many locations which have >40cal.cm^2 levels with the available fault current is so low that the protective device does not operate very fast. Definitely no killing shock wave, but definite burning if the worker stays in place for more than 2 secs.

 

[powerpete69]

Fascinating comments and points. We definitely got more than crickets today!!!

Incidentally, the type of work I am referring to is turning breakers on or off, racking in or out. Unfortunately the bus is hot for this, no way around it unless you want the utility to turn off the electricity grid. But in that case, there is still arc flash possibility on their end!

 

[iceworm]

Arc Blast effect is something the industry is not yet addressing. however, from my research it is not directly related to the arc flash incident energy level. Personally I have calculated many locations which have >40cal.cm^2 levels with the available fault current is so low that the protective device does not operate very fast. Definitely no killing shock wave, but definite burning if the worker stays in place for more than 2 secs.

Yes, there are arcflash calculations where the time is several seconds to trip. You are correct I did not specifically note that those were not part of the discussion.

 

[iceworm]

Fascinating comments and points. We definitely got more than crickets today!!!

Incidentally, the type of work I am referring to is turning breakers on or off, racking in or out. Unfortunately the bus is hot for this, no way around it unless you want the utility to turn off the electricity grid. But in that case, there is still arc flash possibility on their end!

(bold is by the worm)
Following is Personal Opinion - Thoroughly backed up by my reasoning.

So, you are saying the design is such that the switchboards were installed such that they can not be isolated for maintenance. And, by inference, some are 50 years old and have never been cleaned. And (by inference) some, perhaps all, of the breakers have never have maintenance pulled. And (by inference) in the last 50 years nobody stood up and said, "Things have changed in the last XX years. We got to fix this poorly designed equipment. It is freekin' dangerous."

Seriously, 50 years ago, 1970, the effects of poor design that did not allow maintenance were well known. Yeah, I was working then. That would have been about the time I learned to not stick my screwdriver into a live 480V panel - not even one fed with a 75KVA xfm.

I'm saying that being a "UTILTY" is not a magic bullet that allow deferred maintenance.

Here is my distilled translation:
We have 50 year old gear, with no maintenance records, so we are going to have Joe get into a 40cal suit and go open the CB. If there is an incident, he is protected - right? Hey, the probability is only 1 in a 1000 - that is pretty good odds. By the way how many switches do we expect to have this year? Oh, 2000, hummmm

pp - It is not you I'm looking at. It is the 50 years of managers before you that kept saying, "Yep, we're good. We will just keep on doing what we been doing."

I have had more than one conversation about doing work hot. They usually go something like this:

Manager: OSHA says we can work "continuous process" hot. We don't have to shut down.​

Me: Yep it says that alright. I'm a little fuzzy of exactly what does this "continuous process" mean. What does it cost to shut down the process for four hours?​

Ma: $100,00​

Me: So sending in Joe with a HazCat 4 suit for four hours cost us $70 an hour, say $300. But if we shut down for four hours it costs $100,300.​

Ma: Yep.​

Me: Alright, I'd like an email detailing we would rather send Joe in with a suit and not spend the $100K for a shutdown?​

Ma: (*&^%$*&^(^*&)(*​

***​

I understand that eventually the cost gets high enough to that the work will get done. Look at Live-Line/Bare-Handed work. That is only about the money. I'm pretty sure that if I were offered that kind of money, I'd be standing in line to do it.

The issue I have is: I don't know how much money is enough to decide to do hot work, (possibility of seriously injuring hot work - not the mild sunburn kind).
$1000 - no
$10K - likely not
$100K - closer
$1M - maybe yes
$10M - yep, we are doing it.

Like it or not - it is always about the money.

*** No, we never got an email.
Yes we either figured out how to reduce the risk.
Or , we scheduled a shutdown - and did a bunch of stuff requiring a shutdown


the worm

 

[powerpete69]

Worm
In our case, the drawout breakers and their relays are tested, serviced, cleaned, lubricated, etc every three years like clockwork. Sometimes the entire breaker is even completely taken apart into a hundred plus pieces and re-zinc'd and re-tinned. This is done on the 4160V side and the 480V substation side. Still, we error on the cautious side.

I am just saying that in general, there are some gear out there that hasn't been serviced in years. Contractors I talk with say they won't thru switches without at least 40 calorie full suits because they aren't always certain of the gear's present condition. That's their company policy which isn't the worst thing in my opinion.

I do appreciate your very spirited responses!!!

 

[powerpete69]

I would also be careful with taking arc flash stickers as gospel law.
Some arc flash models have over 2000 buses. A lot of things can get confused with this much information. Also, remember that every "engineer" is not as good as you think. A lot of pretenders out there, a lot of people just learning. Some are experts, some are not. Its the same in any industry.
Here's where the arc flash analysis can get convoluted:

The engineer receives all the single lines in CAD. Are the single lines in CAD he received for sure accurate? Some drawings are 30 plus years old sometimes. The engineer builds the model. Did he get all 10,000 details exactly correct? Likely not. Did he match every breaker correctly with every single setting especially the instantaneous settings? Likely not.
Did he get every arc flash setting correct for Include main breaker or exclude main breaker? Maybe.
As far as checking, that would be nice but unfortunately these arc flash jobs are bid out. If a company bids the job for the head of engineering to check all 10,000 details, they would simply not get the job.

Once you get thru all that, someone has to actually put the 2,000 stickers on all the gear. In older factories, the labeling of the gear is very obscure. Is the engineer the one who actually installs the stickers? Likely not, his electrical designer probably does it. Does this guy accurately install all 2,000 labels on the correct gear. Hopefully, but not for sure.
With all this said, hopefully all the arc flash stickers are correct. Is it possible that some are not correct? With all the variables above, yet it is possible that every arc flash sticker is not correct.
And yes, typically the arc flash label is overcautious, but sometimes it is under labeled putting worker in more danger.

Per my opinion and experience, take each arc flash label with a grain of salt.
The arc flash ratings will be highest at the secondary of a substation transformers. The bigger the transformer, the larger the arc flash potential. As it goes down stream thru breakers and wires, the arc flash energy falls with each breaker. Until you get to a smaller transformer like a 150 KVA feeding a 208V panel for example. Then the arc flash jumps up again on the secondary of that transformer, then tends to fall again thru each breaker downstream. However, there is still much discussion in process on these lower voltage transformers.

Here's an example. If you see a 1 calorie sticker on the secondary of a 4160V to 480V, 2000 KVA transformer, a bell should ring in your head that something might not be right. I would expect that to be more around 40 calories give or take 25% or so.

 

[iceworm]

...In our case, the drawout breakers and their relays are tested, serviced, cleaned, lubricated, etc every three years like clockwork. Sometimes the entire breaker is even completely taken apart into a hundred plus pieces and re-zinc'd and re-tinned. This is done on the 4160V side and the 480V substation side. ...

Interesting. I did not get that from:

A normal condition to most is a breaker in excellent or new condition. However, when they are 50 years old, we don't know what condition they are in. Have they been serviced? Have they been lubricated? Are they full of dust? In there a mouse lying across the terminals? Etc.
That's why we say to suit up no matter what. ...

 

[powerpete69]

A normal condition to most is a breaker in excellent or new condition. However, when they are 50 years old, we don't know what condition they are in. Have they been serviced? Have they been lubricated? Are they full of dust? In there a mouse lying across the terminals? Etc.
That's why we say to suit up no matter what. ...

My apologies. That quote is more from the owner of a company that services breakers. Servicing these big boy breakers is their sole profession. So they don't always know what shape the breakers are in when they get a new client. So the owner's philosophy is to suit up no matter what....due to the paragraph above.

 

[mayanees]

Here's an example. If you see a 1 calorie sticker on the secondary of a 4160V to 480V, 2000 KVA transformer, a bell should ring in your head that something might not be right. I would expect that to be more around 40 calories give or take 25% or so.

40 cals is what I would expect to see at the secondary of a 480 Volt, 750 kVA transformer. A 2 MVA unit would be closer to 120 calories at an 18" WD, 80 cals at 24".