Industrial Control Panel Accessed by a Ladder

[Johnshealey]

A suggestion was made to relocate an industrial control panel from roughly eye-level to be mounted to an overhead moving crane. The purpose of the change was to save money on expensive flexible servo motor cables and to simplify installation. The overhead option would require a ladder to access it.

The industrial controls included servo motor drives, with a maximum of 480 VAC inputs. The control panel design includes an interlocked disconnect switch for power and is operable with the enclosure door open or closed (NFPA 79 handle). The controls are all "dead front" and so might be considered to be not "exposed live parts".

Some concerns I have with the proposal were (from NFPA 79):

11.1.1 "All control equipment shall be located and mounted so as to facilitate ... accessibility and maintenance of the equipment."
11.5.1 Working Space: Condition 1: 3 feet "in the direction of access to live parts".

So, the accessibility is certainly reduced. All components are "finger safe", so my guess is that we can get away with this. Any comments?

 

[petersonra]

is a crane covered by nfpa79?

personally, I don't have a huge problem with the suggestion being made. But like many of these kind of suggestions without more information on this specific installation I would not say yea or nay.

It might be appropriate to have a permanent platform somewhere the crane can be moved to so the control panel can be more easily accessed. Maybe a temporary platform can be moved to the crane for servicing.

I don't think I would want to be the guy trying to work on such a control panel off a ladder.

 

[Johnshealey]

Bob - thanks for your reply

Bob - thanks for your reply

This crane is really an overhead "hoist" used to move barrels or racks from station to station in an electroplating tank line. The height would be about 10 ft off of the ground. The travel of the hoist is usually 50 to 100 feet. The control enclosure would be accessed very rarely. I don't really like the proposed change, but it would save time and money during installation. My question is really if there's a code violation in this design change.

 

[petersonra]

This crane is really an overhead "hoist" used to move barrels or racks from station to station in an electroplating tank line. The height would be about 10 ft off of the ground. The travel of the hoist is usually 50 to 100 feet. The control enclosure would be accessed very rarely. I don't really like the proposed change, but it would save time and money during installation. My question is really if there's a code violation in this design change.

you keep changing the story.

I would not accept the idea of someone working off a ladder over a open tank of acid. period.

In any case, i don't think it would meet the requirements for working space.

(3) Height of Working Space. The work space shall be
clear and extend from the grade, floor, or platform to a height
of 2.0 m (61⁄2 ft) or the height of the equipment, whichever is
greater.

I think you need to provide some place where there is open space below the hoist so it can be worked on safely. A permanent access platform would probably be best, but a lift would work as well if you have one.

Is there a way you can add a permanent platform with railings to the hoist itself?

 

[Johnshealey]

Thank-you again, Bob. Here's another change to the story, which I meant to imply: I'm not in favor of this proposal; in fact, it's a reversion to an old practice that I spent a lot of time changing. I'd be delighted to find a code article that would definitively support my argument against it; maybe 11.5.1.3 is it. I may have been hung up with 11.5.1 including references to "live parts" and the requirement to be able to "step back" three feet. Obviously, one can't do that when on a ladder. I'm not sure my controls could be considered to be "live parts", however. Your suggestion of Paragraph 11.5.1.3 is helpful; it defines the requirements for working space height, with no reference to "live parts".

There's no chance of putting in a working platform. The argument for the proposed design change was to save money, which would be overwhelmed by the cost of a platform. These "hoists" are often so light that they couldn't support a person on a platform that moved with the hoist.

 

[petersonra]

Thank-you again, Bob. Here's another change to the story, which I meant to imply: I'm not in favor of this proposal; in fact, it's a reversion to an old practice that I spent a lot of time changing. I'd be delighted to find a code article that would definitively support my argument against it; maybe 11.5.1.3 is it. I may have been hung up with 11.5.1 including references to "live parts" and the requirement to be able to "step back" three feet. Obviously, one can't do that when on a ladder. I'm not sure my controls could be considered to be "live parts", however. Your suggestion of Paragraph 11.5.1.3 is helpful; it defines the requirements for working space height, with no reference to "live parts".

There's no chance of putting in a working platform. The argument for the proposed design change was to save money, which would be overwhelmed by the cost of a platform. These "hoists" are often so light that they couldn't support a person on a platform that moved with the hoist.

I think you are obsessed with applying NFPA79 to something it may not apply to. In fact, NFPA79 actually applies to nothing unless the company decides it does. It is not like the NEC where legislation forces you to abide by it. It is just a voluntary standard.

I think a good argument can be made that the standard itself would allow the standard to apply but your company would have to then adopt it for it to apply.

The electrical code requires working space and is something that an actual law requires be obeyed. I would be looking there first.

Personally I am not sure how this arrangement saves money. You still have to have some kind of festoon type arrangement with pricey cables for the power wiring whether it feeds the drive or feeds the motor from a drive.

 

[Jraef]

Every overhead crane I have ever worked on has a control panel or two, or 5, on it. Bob's right, NFPA79 doesn't apply unless someone says it does. NFPA 79 applies to industrial machines. If you have a copy, look at appendix C for examples of where it applies.