Walkways directly through Electrical Equipment setback zone

[Automation-Tim]

I am having a difficult time either finding it spelled out directly in code or insinuated in some paragraph buried deep in OSHA, IBC or NEC. Is there something in writing that would not allow a normal walkway or foot traffic in an industrial plant to be directed directly through an area that would normally be reserved for large electrical equipment door swing, arc blast zone or set back required for the equipment. Additionally, directly across this large electrical equipment in question, approximately 6-7 feet, is another control panel at 480VAC/80A FLA facing in. To sum it up, high powered electrical equipment and control panel on both left and right sides of a route that is intended for employee's to walk to and from.

I see that the NEC, in Art. 100 talks about indoor and outdoor electrical equipment spacing requirements but it falls short of spelling out that when closed and area is free and clear, should that space be intended for normal foot traffic?

I'm not sure if this is a building code topic or electrical safety topic.

Can anyone shed some light?

Tim

 

[jim dungar]

If foot traffic was not allowed in front of electrical equipment, you would not be able to install panelboards in most hallways.

 

[charlie b]

There is no reasonable expectation that a piece of electrical distribution equipment will suddenly explode without there being some evolution in progress (i.e., turning or or off a breaker, performing maintenance on the panel's interior, racking in or out a switchgear breaker, doing thermographic evaluations of a panel's interior, etc.). During such activities, steps will be taken to isolate the area from casual passers by. The rest of the time, it is considered safe for anyone to stand or walk in front of the equipment.

 

[iceworm]

... a normal walkway or foot traffic in an industrial plant to be directed directly through an area that would normally be reserved for large electrical equipment door swing, arc blast zone or set back required for the equipment.

... directly across this large electrical equipment in question, approximately 6-7 feet, is another control panel at 480VAC/80A FLA facing in. To sum it up, high powered electrical equipment and control panel on both left and right sides of a route that is intended for employee's to walk to and from.

As Jim and Charlie said - No regulatory issues.

That being said, I am not a fan of having process equipment in close proximity to substation/distribution equipment. But it is a design issue and generally driven by "the money". Heated footprint is expensive. Designers get pushed to pound the equipment in as close as practicable.

Then there is your definition of "normal foot traffic". Consider Charlie's post about operations/maintenance activities.
1000 people per day walking through headed for a high-rise office building is somewhat different than the operations/maintenance personnel using the walkway for their "normal activities'.

In the case of the 1000 office workers, I would likely be concerned about damage to the equipment/inadvertent operation than personnel injury. Still, it is a design issue

 

[jim dungar]

That being said, I am not a fan of having process equipment in close proximity to substation/distribution equipment.

I am trying to think of the last 'process' floor that did not have a motor control center or multi-motor control panel on it.

 

[ggunn]

If foot traffic was not allowed in front of electrical equipment, you would not be able to install panelboards in most hallways.

Neither would you be able to walk up to one to reset a breaker.

 

[Automation-Tim]

I do agree that the space in front of electrical equipment needs to remain clear for inspection, servicing, testing or repair just as Art. 100 implies. With added electrical equipment, including Isolation transformers, and addition equipment tends to compress the space for normal employee foot traffic out on a plant floor. The electrical equipment is not enclosed into a separate room that is under locked and key, its on a side wall with other CNC machines in close proximity of the equipment. To me, and this is just my opinion, the space has become compressed and with added machining equipment, plasma cutter and additional transformer, this space has become a higher electrical hazard and it seems to go against the natural and inherent feeling to allow regular foot traffic to flow directly through the space. That is my dilemma, I can't find anything that backs up that gut feeling of a potential safety concern in the event of an arc blast of enclosed electrical equipment or transformers. I agree that if a Qualified Technician is inspecting or servicing the gear it should by blocked off to prevent normal flow. Now the issue becomes an emergency escape route for a room within that vicinity that qualifies as using that walkway as an escape route.

 

[iceworm]

I am trying to think of the last 'process' floor that did not have a motor control center or multi-motor control panel on it.

Well, it is just possible that "large electrical equipment" is closer in nature to "substation/distribution equipment" than an MCC. Of course I work oil patch and medium/heavy industry. MCC in the middle of process floor is not real common.

 

[iceworm]

That is my dilemma, I can't find anything that backs up that gut feeling of a potential safety concern in the event of an arc blast of enclosed electrical equipment or transformers

The transformers - what is the magnitude, 75kVA dry, or 1MVA oil filled. Take a look at NFPA 70E. It contains guidance about arc-flash safety. If there is no arc-flash data posted, perhaps it is time to suggest an arc-flash study be done.

 

[Jraef]

My concern is for when someone DOES need to service the equipment. Once ANY door is opened, you have exposed the area to the Limited Approach Boundary, which may extend up to 3.5ft in front of 480V equipment. So if someone has to work live, can they cordon off that walkway without pushing employee traffic into other hazardous work / traffic areas? That's the thing I see that gets left off of the table most often. I was just at a food plant where this was happening: the MCCs were along the wall that had the yellow floor tape "safe zone" for walking where you were out of the way of fork lift traffic. When the MCCs were being worked on live, they put the chains up to keep people out of the Limited Approach Boundary, which meant they were pushed out into the fork lift traffic lane. It's just an accident waiting to happen, but because this is an older facility designed before we thought of such things, they don't have a lot of choices without rearranging the factory floor. What they probably need to do is to have a traffic director stationed there while the electrical work is being done. I mentioned that to the electrical supervisor, but he said "not my job"... The reality is, it IS, because he is a supervisor. OSHA would not accept that as an excuse if something happened.