arc flash worst case scenario

[pistolpigg]

So just for argument's sake if you were to press a start button on an automatic starter disconnect combo you'd have to put a suit on if its arc flash analysis deemed it to have that incident energy?

 

[raider1]

So just for argument's sake if you were to press a start button on an automatic starter disconnect combo you'd have to put a suit on if its arc flash analysis deemed it to have that incident energy?

Correct, so one way to mitigate the hazard without having to wear arc flash rated PPE would be to install a remote start button that was located outside of the arc flash boundary.

Chris

 

[zog]

Correct, that is why you have those remote switching devices.

 

[pistolpigg]

Or use a big stick to press the button lol. So even with that don't someone got to put ppe on to turn off so it can be locked out? Almost sounds like we need to come up with a means of remote lockout

 

[raider1]

Or use a big stick to press the button lol. So even with that don't someone got to put ppe on to turn off so it can be locked out? Almost sounds like we need to come up with a means of remote lockout

Yes, you must wear the appropriate PPE to verify the absents of voltage as part of a lockout/tagout policy if you are within the arc flash boundary and the restricted approach boundary.

Chris

 

[jim dungar]

Yes, you must wear the appropriate PPE to verify the absents of voltage as part of a lockout/tagout policy if you are within the arc flash boundary and the restricted approach boundary.

Chris

Absence of voltage does not have to be confirmed for all OSHA mandated LOTO procedures. For example, a local disconnect, between the starter and the motor, maybe Locked Out for changing a motor belt without ever 'opening' the disconnect enclosure.

 

[raider1]

Absence of voltage does not have to be confirmed for all OSHA mandated LOTO procedures. For example, a local disconnect, between the starter and the motor, maybe Locked Out for changing a motor belt without ever 'opening' the disconnect enclosure.

Correct, I was thinking of the LOTO procedure as part of establishing an electrically safe work condition and not a LOTO for mechanical reasons. I should have clarified that.

Chris

 

[pistolpigg]

Absence of voltage does not have to be confirmed for all OSHA mandated LOTO procedures. For example, a local disconnect, between the starter and the motor, maybe Locked Out for changing a motor belt without ever 'opening' the disconnect enclosure.

But to operate that handle would you not have to have ppe ?

 

[jim dungar]

But to operate that handle would you not have to have ppe ?

Now we are back to your company's Electrical Safe Work Practices requirements.
Your company needs to evaluate the risk once they know the 'worst case' outcome. As I have said before, NFPA70E purposely does not address this level of detail.

 

[pistolpigg]

Now we are back to your company's Electrical Safe Work Practices requirements.
Your company needs to evaluate the risk once they know the 'worst case' outcome. As I have said before, NFPA70E purposely does not address this level of detail.

This is where the confusion lies and had made everything more complicated at most facilities all of them are more or less scared by the arc flash program and this fear of the worst case explosion at any interaction is causing most places to go with an overkill policy for the most mundane actions such as a mechanic or a production worker changing a belt or checking clearances is now requiring an electrician to operate a disconnect in the arc flash ppe.

 

[jim dungar]

This is where the confusion lies and had made everything more complicated at most facilities all of them are more or less scared by the arc flash program and this fear of the worst case explosion at any interaction is causing most places to go with an overkill policy for the most mundane actions such as a mechanic or a production worker changing a belt or checking clearances is now requiring an electrician to operate a disconnect in the arc flash ppe.

There is nothing in NFPA70E that would prohibit a non-electrician from becoming a qualified worker for a specific task.

I agree that many people do not want any 'employee' judgment to be made concering NFPA70E required PPE. I wonder what they do about PPE for fall protection when working on a 10ft ladder in the middle of an office - where do they tie off? How about an extension ladder, how do they get to the top to secure it in place? When using cleaning products in the restrooms, are respirators always required or is risk considered?

 

[kwired]

There is nothing in NFPA70E that would prohibit a non-electrician from becoming a qualified worker for a specific task.

I agree that many people do not want any 'employee' judgment to be made concering NFPA70E required PPE. I wonder what they do about PPE for fall protection when working on a 10ft ladder in the middle of an office - where do they tie off? How about an extension ladder, how do they get to the top to secure it in place? When using cleaning products in the restrooms, are respirators always required or is risk considered?

I have wondered about fall protection when using ladders for years. How do you tie off on a step ladder or secure the extension ladder before you get to the top?

I have also wondered why equipment is not required to contain the potential flash which would mean it is safe to operate a switch mounted on the enclosure? Most places that have high incident energy levels also have full time trained people that know there is a hazard. But there are enough smaller facilities that still have pretty hazardous levels of incident energy available that don't have full time trained people and at some time or another someone will likely operate a disconnect for any reason imaginable.

 

[zog]

I have also wondered why equipment is not required to contain the potential flash which would mean it is safe to operate a switch mounted on the enclosure? .

Simple answer, cost. There is a standard for arc rated enclosures and rated gear is becoming more common but it is a large cost adder. 10 years ago I did some testing on what was involved to retrofit old gear to meet the new standards and concluded is was not economically feasable to do so.

 

[kwired]

Simple answer, cost. There is a standard for arc rated enclosures and rated gear is becoming more common but it is a large cost adder. 10 years ago I did some testing on what was involved to retrofit old gear to meet the new standards and concluded is was not economically feasable to do so.

Would you agree that some older equipment maybe was better at protecting the operator? I have seen old panels that you about needed a crane to lift the dead front, but today an equivelant panel - one man can lift the cover without being a body builder. Much lighter gauge cans and covers in general today - mostly because of cost I assume.

 

[zog]

Would you agree that some older equipment maybe was better at protecting the operator? I have seen old panels that you about needed a crane to lift the dead front, but today an equivelant panel - one man can lift the cover without being a body builder. Much lighter gauge cans and covers in general today - mostly because of cost I assume.

Yes, I agree for the most part but some older designs also included vents in switchgear doors.

 

[Jraef]

I'm trying to figure out why and how it would logical to have to put a hrc four requirement to operate a disconnect for a motor when its load is disconnected by a motor starter or a drive. Seems like a lot of overkill for operating a device that has no load for example.

OK, how about this in your scenario.

Cables pulled into an enclosure that was going to have an 800A CB main disconnect for a 500HP soft starter, meggered after installation. Couldn't get the back panel installed with the cables in the box, so contractor pulled the cables back into the conduit temporarily. After installing the back panel with the soft starter and 800A CB, cables were pulled back in and terminated on the breaker lugs. Just as I was closing the doors of the cabinet, electrician in the switchgear room closed the feeder that delivered power to this unit. Cables had not been re-meggered after being pulled back into the cabinet, they had apparently nicked the insulation and one went to ground. Explosion blew me back but out of shear luck, the mechanical catch on the disconnect handle latch had just clicked and held the door closed long enough to direct the blast up and down instead of right at me.

In that scenario, the MAIN BREAKER WAS OPEN, there was ZERO load connected. All it needed was an arc flash event inside the conduit feeding the enclosure, the mechanical expansion of the vaporized copper was almost enough to have killed me.

Just FYI, copper expands 67,000 times it's volume in an arc flash event like that. To get a visualization of that, if you put a penny on the middle of the 50 yard line of the new Cowboys stadium and expanded it 67,000 times, it would blow the roof off of that stadium!