480VAC and NFPA70E

[CtrlSystemsEng]

I have an enclosure (72Hx68Wx18D in.) containing 2x40 HP VFD's fed with 480VAC/200A. Given the increasing (and real) concerns regarding Arc Flash hazards and associated NFPA70E requirements, we are confronted with major hurdles in order to service this enclosure. From time to time, we do need to service this enclosure under live voltage to access the VFD's HIM module for motor manual override purposes. Suiting up with the required NFPA70E gear (Nomex, faceshield, gloves) is not an issue, but rather obtaining a hot work permit which can take up to hours or days for approval.

We could get around the approval process if we were to provide a fixed and permanent barrier between the "qualified" personnel and electrical enclosure's interior.

One thought was to mount a clear plastic sheet within the enclosure so that it covers all 120VAC and 480VAC devices. Small cutouts would be made in this sheet to permit access to the HIM module. The thought was that a "compliant" clear plastic sheet would satisfy the barrier plane between the qualified personnel and the voltage devices as dictated by NFPA70E. The plastic sheet would be fabricated from the same material as the polycarbonate faceshield so that it satisfies the fire rating requirement. Envisioning this arrangement, you would open the enclosure's door, then this clear barrier would be within the enclosure and covering the devices. We'd obviously need to defeat the flanged disconnect switch to open the door without shutting the system down.

I've looked around, but cannot find anything off the shelf that provides a solution like this. There are a couple of companies that manufacture "blankets", but this would be too cumbersome for our installation.

We're stuck with the approval process, so coming up with an engineered solution is presently our only option. Hope someone has some ideas.

Thanks

 

[electricpete]

I don't have any solution ideas. At our plant "hot work permit" is associated with welding or high temperatures, not work near energized circuits. Do you have a different definition of hot work permit?

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[CtrlSystemsEng]

electricpete, generally speaking, your definition of a hot work permit is probably more correct. Likewise, when dealing with Class 1 Div 1, 2 areas. My particular situation is at a customer's site, and it is they who define hot work in the context of working on energized equipment.

 

[jraef]

Remotely mount the VFD display if at all possible. This is becoming a big issue, the ramifications of NFPA70E are filtering down into a lot of ordinary day-to-day tasks that equipment designers didn't account for.

As to the "clear plastic barrier" idea, the reason why you don't see it as a commercial product is because it is a problem yet to be solved. In the past if you permanently installed any "plastic" barrier like that, it just needed to be tested to UL94V for fire resistance, i.e. like Lexan. Now, how are you going to know that the barrier is going to stop an arc flash? Someone has to test it, and how do you test something that is field installed? What if the installer makes a mistake, such as too generous of a space on the edges, an arc flash happens and someone gets hurt? Are the blood sucking leaches lawyers going to sue the poor schmuck electrician who installed it wrong, or are they going to sue GE for making the Lexan and said it could be used for that?


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[Zogzog]

Hot work permit = tasks like welding
Energized Electrical Work Permit = elecrical work, as referenced in the 70E.

Now to your barrier idea, that will revove the shock hazard and PPE requirements but will not remove the arc flash hazard and PPE requirements unless the system is tested and rated as an arc rated enclosure, we both know that won;t happen.

For routine taks like this you are allowed to create a standing EEWP

 

[CtrlSystemsEng]

Thanks for all of your inputs. I was never really a proponent of the barrier implementation for exactly the reasons cited by jraef. We are currently pursuing obtaining a standing EEWP per Zogzog's recommendation. We are hopeful that our customer will be receptive to that strategy.

Thanks again.

 

[panter]

Hello everyone,
what acronym EEWP mean ?

 

[xnuke]

Energized Electrical Work Permit.

xnuke
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