Indeed, the IE is based on the MCC bus.
After many conversations with my Arc Flash consulting engineer, we're kind of stuck at having the same IE at the stabs where the bucket joins the MCC so the bucket (line side) IE must be the MCC bus IE. Anyone locking out at the MCC will be exposed to high levels should a fault occur behind the bucket while in the act of locking out no matter how small the bucket. Maybe I'm wrong??
This is a major source of confusion for us in industry as it affects the whole arc flash program, PPE, operator training, etc.
I have investigated arc flash incidents where the stab to disconnect wiring acted as a fuse and extinguished the arc flash limiting the damage to a blown off door and arc damage within the bucket(size 1, 600V L to L fault). I also had an arc flash from a size 2 bucket travel into the bus below the bucket, it burned almost completely through 2 1200 amp copper busses and blew the back panel off. The bucket was scarred and door blown open but the major damage was at the bottom of the MCC. Both incidents occured during remote start commands from the control room. Electricity is a dangerous thing...
If forced into a corner, I will have everyone gear up to the IE posted on the label, further cornering would make me gear everyone up to the highest IE in the switchroom based on the previous 2 experiences. I feel like a cat in a room full of rocking chairs. There's no safe position!

480V switchgear, ITE/BBC/ABB k-line to be exact.

Here is another one, lucky for them they were using remote racking and no one was hurt. 1st photo is the RRS unit which still was able to function and rack the breaker back out that was arcing, perhaps saving the entire line-up from damage, an operator would have been burned and ran away.

The 2nd photo is the remains of the breaker after the incident.

Admittedly, I know of no serious injuries from safety switches.

I agree with your line of questioning and your premise, Haze. The problem that I see has two parts.

First, I agree with Canuck here:



Especially given stuff like this from here: http://www.arcflashforum.com/showthread.php?t=709&page=4



And this story: http://www.labelprinters.org/blog/2009/12/new-york-personal-injury-attorney-says.html#links

So how do you defend the choice of cutoff from a legal position?
While my own judgment may say that you are correct, am I willing to bet my livelihood on it? Better yet, am I willing to be my kids’ livelihood on it? I would like to leave my kids better off tomorrow than they are today (I have four). That being said, I don’t think that leaving them a world where they get up and put on fire rated bubble wrap before leaving the house every morning is better. In fact, as a dad, I have often stood by and watched them do stuff that I knew could injure them. On a few occasions, I have encouraged them. (Ok, maybe more than a few.)

The second part of the problem is with the standards themselves. Ok, so if we got the standards changed, then we could back up our call with the standard.
Zog has said many times that he feels like the goal of the 70E committee is to prohibit ALL live work. And if you spend more than a few minutes with just about anyone on these standard committees, you will know that he is probably right, and that changing them to make them easier to work is not likely to happen. They want to have the safest safety standard they can. And they are right as well, from their perspective.

Back to square one??

See the note under Table 130.7(C)(11). ATPV is "the incident energy on a material or a multilayer system of materials that results in a 50% probability that sufficient heat transfer through the tested specimen is predicted to cause the onset of a second-degree skin burn injury based on the Stoll curve". EBT is "the incident energy on a material or material system that results in a 50% probability of breakopen".

If you barely match the PPE with the IE, then yes, you have 50% of being burned if the worst case happens (provided the worst case is properly modeled by calculations).

See also [url="http://www.e-hazard.com/ASTMF18-65-Double-Hump-Taskforce-PPT-10-09-Hugh-Mikhail.pdf"]this paper[/url] by Hugh Hoagland (referenced by himself in [url="http://www.arcflashforum.com/showthread.php?t=672&page=2"]this thread[/url]), with probability curves of second-degree burn hazard vs IE. The paper itself is about layered protection systems, but for the present discussion it doesn't matter. Look on page 3: in red you have test points (0=no burn, 1=yes burn), in gray you have the probability curve, and in green you have the rating for a 50% probability. If you wanted a 15% probability of being burned, then you'd expose that same garment to an IE of 40 cal/cm^2 only. Note you can't get to 0% probability on that graphic.

Thank you.

PPE required???



I hate to see this one die...
For your comments:

Normal operation of the equipment require only standard issue PPE (HRC 2).

normal operation of the equipment includes:

* Lockout of 480/600 V disconnect on MCC including field disconnect.
* Lockout of 480/600 V molded case, secondary breaker (i.e. non-main breaker).
* Resetting overload on a 480/600 V starter.
* Lockout of 4160 V starter (on disconnect only).
* Operation of breakers and fused disconnects rated below 25 kV
I don't know if I support any or all of this but we're looking at this as a policy.

One large organization in my area uses a "Risk Matrix" approach to this problem. They have created categories similar to those used in 70E. Equipment is labeled with a category based on the worst case. The worst case hazard category on the label can then be decremented for low risk tasks according to a look-up table.

Is FR PPE required for all deadfront operations

Oh boy the good old 83rd. I remember when Lt. Col Diaz, and Lt. Col. Ullmann were the commanders. Personally Lt. Col. Ullmann was the best in my tenure there at the NOSC. Hope that the next commander is better than the outgoing commander for all of you NOSCeteers out there.

On a side note. I want to know who the fk came up with that gay A statement of NOSCeteer

Anyone know?

I think I know who you are talking about, are you in Cali?

Yes, there is a 50% probability of a 2nd degree burn if one just matches the PPE to the IE. But, the code is not designed to eliminate injuries, just to reduce them to acceptable levels. A 2nd degree burn will completely heal without scarring. So this appears to be a risk that NFPA is willing to accept. They established the risk level at 50% when they could have gone for 20%.

I do think MCC buckets are generally different than an MCC bus, especially on smaller buckets. There is a short cable that attaches from the bus to the line side of the disconnect. That cable will significantly reduce let through current, and hence IE. Which is why I speculated that some amperage rating might be appropriate.

I have 30 years in the petrochemical industry. I have seen a lot of faulty equipment, L to G and L to L, but I have never seen it blow off doors. Perhaps because most load centers were fed by only 1500KVA xfrms and fault currents were usually never more than 42KA. But I have seen the photos where it has happened.

Liability is almost a meaningless concept today. You win a lawsuit because McDonalds sold you a cup of coffee that was 'too' hot and you spilled it on yourself. GF breakers set at the lowest level, but the equipment trips off line when the water cooler kicks in. If an employee is injured on the job, to a good extent, you've already lost. I have testified at arbitrations for settlements. At the end the Arbitrator would get us together and say things like, "... the man has three children, he is outstanding member in his church, and he is scarred..it doesn't matter who is at fault..." Yes you need a program to show a good faith effort, but in the end it doesn't matter.

While I agree with those that say the best defense is to prevent the accident, and it is, at the same time I have lived the 'american dream' for 30 years. Its one of merger, aquisition, productivity, right sizing, and now it global relocation. Walk in to a Penny's or a Walmart, and ask yourself, what percentage of the goods sold here are made in the USA.

You want you sons to be safe, and not to suffer because of your loss. What about their suffering all their life as they try to edge out a living wage, relocate from State to State chasing the last manufacturing job left. Paying that ever increasing tax burden that deprives them of the standard of living we, or your parents, enjoyed. I hear this arguement in the same voice regarding national security. "... I would rather have every liberty taken away and to know my children are safe..." Its very different than what it would have been 50 years ago, "... I would rather my children die fighting for liberty than to live under tyranny..." I don't mean to get political or philosophical but I see our country at a turning point, and NFPA is just one of many burdens. Any country that loses its manufacturing based is going to have a two tiered class system between the rich and the poor without a middle class.

I lived this situation in chemical plant. We had 6 electricians and 120 operators. When we introduced Arc Flash we looked at the cost burden to equip and train the 120 operators who only did simple tasks like LO/TO safet switches or MCC buckets for equipment cleaning. The union contract required 4 sets of clothing per year. To add 120 more people to the annual bill was $60K/yr. The site was already struggling financially. So we decided to just meet the code as it was written. Only the electricians switched switchgear anyway. Would we have been safer to equip and train the 120 operators - that goes without question. Two years later the site closed completely due to foreign competition.

You see you 10 year old climbing a tree to build his own tree house. If he falls he will get hurt. You wife asks what to do. You tell her, let him continue, its a risk, but he has to learn to also enjoy life and the freedoms of choice. You accept a certain degree of risk to enjoy the freedoms it brings.

US based industry is not that far removed from the child climbing the tree. If we try to eliminate every risk that exists, we can tolerate things like stairs, chairs, coffee pots, paper, tools, etc. Taking a shower involves risk.
What we want to do is to focus on those risks that have high probability of injury with a degree of frequency.

I am sure I can find a photo of the child with a broken leg who fell out of the tree. But do we really want to live in a world where a 10 year can't climb a tree?

Sorry for the rant. I'm letting other emotions leak into the discussion.

Thought I would add this link:

http://finance.yahoo.com/tech-ticker/u. ... p,TM,xli,F,^DJI,^GSPC&sec=topStories&pos=8&asset=&ccode=

Who's going to pay...

Hello Haze10
You make many valid points in your argument against excessive regulation however it’s here to stay …
If you’ve watched the news today, you may have heard about the Continental Airlines welder and his supervisor who were charged in the Concorde crash in France. A piece of the Continental aircraft fell off during takeoff and subsequently caused the tire failure on the Concorde. This is how far we’ve gotten and this is also why Arc Flash is making our collective lives interesting. Liability is implied now that the civilized world has found the courts. Even Toyota is going to take it on the chin from the class action suits by plaintiffs who “potentially could have suffered from unintended acceleration� of their vehicle.

With respect to Arc Flash – we need to be sure the workers remain safe from obvious dangers and also we need to maintain a high level of due diligence or we’ll be on the wrong side of the courtroom. We will lose our some of our competitive advantage to countries with less restrictive safety laws however we can gain it back through productivity and creative engineering. All arc flash hazards can be engineered out to some degree or policies can be put in place to mitigate the risk.

I’m not real happy with the direction my company is headed with our program but I will do my part to make it work. I have an elevated sense of insecurity when I look at the potential for legal action due to an arc flash incident. Countering this is the need to be productive; this is why my company wants to perform some tasks without following the posted IE. Lockout should be one of them as long as it’s a safe thing to do. My thought is that if the risk of an arc flash is any more than “remote� then gear up to the IE. Risk ranking matrices work if there is a large enough pool of statistics available to back up the matrix assumptions. I still haven’t found any actual incidents where a non-electrician was locking something out and experienced an arc flash. I’m sure it’s happened but how often? Air France and Toyota have highly paid actuaries who said the odds of further incidents are “remote� but there they are in court…

It’s tough to decide how to approach the issues at hand but I can tell you that deep pockets and a company willing to spend are the only things that make me sleep easier at night. Working for a company that doesn’t accept today’s legal liabilities is not an option.

Well said Canuck

Canuck, well written. But we are still left with the concept of defining 'remote'. The janitor who switches off the hall lights from the QO panel breaker would have a 'remote' probability of an incident, but we are still left with some who argue the risk is unacceptable.

Another link: Talks about the shifting balance of US manufacturing. But as you read it, ask yourself if the balance is equal on the employee pay scale and what effect that balance will have on society.


http://finance.yahoo.com/banking-budgeting/article/108745/radical-shifts-take-hold-in-us-manufacturing?sec=topStories&pos=6&asset=&ccode=



"...For chemical makers, the recession has intensified an exodus from the U.S. that has been going on for at least a decade, amid rising energy costs, environmental concerns and growing demand in developing countries. In the past year, Dow Chemical, has closed, or announced plans to close, six plants producing ethylene-related chemicals in Louisiana and Texas.

"The chemical industry is leaving the United States, and it won't be back," said Peter Huntsman, chief executive of Texas-based chemical giant Huntsman Corp., which plans to report fourth-quarter earnings on Feb 19. "When demand picks back up, they'll build new capacity overseas -- in the Middle East, Singapore and China."

Huntsman, he said, is expanding its capacity in the Mideast and China to make chemicals used in products like insulation and high-speed railway construction. It now has about a third of its capacity in the U.S., down from more than four-fifths a decade ago. That capacity is increasingly focused on producing more-specialized chemicals, such as epoxies that can be used in building airplanes...."

Remote

This is only my opinion….

Is this the extent Arc Flash will end up?
“The janitor who switches off the hall lights from the QO panel breaker would have a 'remote' probability of an incident�
Mirriam Webster defines REMOTE as: “separated by an interval or space greater than usual�.
Wordnet defines REMOTE as: “very unlikely�

For us in the Arc Flash world, applying REMOTE is a daily occurrence. We assume always that the arc flash will not occur when our workers are out in the field doing their jobs. Electrical equipment is operated millions (billions?) of times daily throughout North America and arc flash incidents do occur on a daily basis. Some incidents sputter, others take lives. NFPA 70e and CSA Z462-08 were implemented to protect workers from the dangers (however remote). I would like to think that the odds of a worker having an incident are well above the 500,000 man-hour mark. Therefore any equipment that worker is exposed to must have an MTBF of greater than 500,000 hours to be considered safe to operate. What is the statistical MTBF on a breaker? What happens if the equipment doesn’t meet the acid test? In my view, we would need to train the workers to use the proper PPE and/or engineer the IE levels down to a manageable point (<1.2 cal/cm).

A good parallel to arc flash regulations is the invention of the seat belt. The seat belt has saved countless lives since its inception. The seat belt was universally reviled as restrictive and dangerous when it was introduced – I see a startling similarity here!

As far as jobs going to third world countries – only the strong will survive. I feel sorry for those people who lose their jobs to foreign plants. I can count myself as one of them but I also am smart enough to realize the fact that the plant was old, the workers were highly paid, and we were inefficient.
Attracting Greenfield plants to economically depressed areas should be a priority for all levels of government. The plants are efficient, have small highly trained workforces, and pay well. This is good! It’s also the price of progress in the G-8 countries. China may be the newest member and have poor safety but it is a powerhouse that imports goods from the western world. We make those goods!

http://internationaltrade.suite101.com/article.cfm/top_chinese_exports_imports

This is a good article illustrating how 120/240 volt circuits with system characteristics less than 125 kva can become dangerous.
Remember the janitor turning off the breaker? Maybe he should wear AF PPE?
http://www.etap.com/support/articles/electrical-safety-measures-2009/etap-arc-flash-esm.pdf

Canuck, the article doesn't offer much help. It suggests using the normal 3 phase equations for single phase systems. Although it says these equations will be conservative, I think that is overstating it. I think that if you look at some slow speed films and the physics of the arc and what happens with the arc plasma, single phase systems behave very differently, and would be less likely to sustain itself. This is largely because single phase systems will experience a system zero at some point, whereas a 3-phase system will not have a total zero current point. Couple this with the plasma helping to re-strike the arc on the other phases by reducing the resistance of the air, and you have got a system where arc sustainment becomes much more likely for 3-phase systems.

Also speaking as someone who has burned many holes in screwdrivers and side-cutters , the low voltage (120V), single phase arc doesn't extend very far or last very long.

The basic tenant of electrical energy
3P power: KVA=VxIx1.73 (Sqrt 3)
1P power: KVA=VxI

Although very general, we should expect a reduction in 1P power by a factor of 1.73.

As Dean mentioned the 1P arc has a greater tendency to self extinguish because of the zero cross over.

I always say 'follow the money'. This is a Safety Auditing company putting out this supplement. The same can be said of NFPA. Do you ever see who the board members are? Almost all have a vested interest in selling products into the market place, for the very regulations they specify. Its more than coincidence.

Maybe we need the entire country to dress in FR so they can operate their microwave at home.

Actually the article was written by a real engineer at ETAP.
Not to muddy the waters or anything but if the engineers who are in NFPA and other decision makers would agree that "normal operation of electrical equipment" was inherently not risky, we'd be much better off. I still think it's a good article - look at the raised hackles!