visible disconnect blades

[muskiedog]

Visual Not Good.

Visual Not Good.

I had an incident where I was placing a temp sensor in a chiller used to cool UV curing system. Had eveything off but didn't check to verify no power. There was a back feed of the UV system when I went to attached the sensor got a nice surprise. Dropped my to the floor. Some how there was a Electronic board that had to verify that both where operational so that the uv curing system would not work with out the chiller in operation. I was putting the senor in after the chiller failed and the PVC pipe started sagging down from the rafter of the plant.

Always check.

 

[realolman]

Charlie,
Yes, the real question is why the window. It doesn't have any purpose if it can't be used to say the equipment is safe to work on.
Don

it does show you that the knife switch is open. I think I like that.
For whatever that's worth.

 

[RayS]

This will verify that power is off before you open downstream equipment to do the required voltage check. Unfortunate that some people will rely on this as the only check.

There was an article a while back about a guy killed when he relied on the visible blade position instead of checking in a MV switch. I believe it said part of the arc control was still making contact even though the blades were obviously not connected.

 

[George Stolz]

My coworker had just been hired, he'd been working for a very good EC in MA. In the first week, he blew up his strippers because he cut a ground and a white wire at the same time. Someone else had mistied a threeway, energizing what was supposed to be the neutral for the light.

Nobody's perfect. Misties happen. Maybe I'm visually impaired, but I've looked into a box not seeing a configuration problem that was plainly visible.

Not having seen the switch, I would not flatly trust my eyes (or rather, my lack of concentration to what I'm looking at.)

 

[Ragin Cajun]

That's why I just love my "tick tracer" to verify that the circuit is dead. One Christmas I gave all the electricians one as a gift. They use it all the time.

Have had 480 breakers with one pole that didn't open - OOPS!

Check all THREE phases, you never know . . .

 

[zog]

There is a great video from ERI called the Mark Standifer story where one blade of a 15kV disconnect swtich failed to open, he failed to visually verify all 3 blades open and his tic tracer was brolen so he did not do a voltage check. We see these switches fail on a regular basis, dont ever assume they have de-energized the circuit just because you opened the switch.

The window is there to verify all 3 blades open or closed for switching functions, not as a substitute for a voltage check. I cant believe we are even having this discussion, always do a live-dead-live test before working on any system, someone a few pages back quoted the NFPA 70E section regarding establishing an electrically safe working condition, that should have ended this discussion.

 

[don_resqcapt19]

Zog,

The window is there to verify all 3 blades open or closed for switching functions, ...

Switching functions on 30 and 60 amp safety switches that are only installed as local disconnects for equipment?
Don

 

[realolman]

I guess the window is about as good as you want it to be. It seems like a good thing, but several people have pointed out valid concerns.

Any of us are going to do what we feel comfortable with.

I suppose if you are in a position of being liable for what you tell people, you gotta tell them to check a rock with a meter before they touch it... but when it's you, yourself... you might just shut your eyes and touch it to the grounded box.... I hear that check is pretty reliable.

Not that I've ever done it, myself.

 

[zog]

Don,

I was refering to (and I thought the discussion was about) 5kV and 15kV disconnect switches. Those are the onlt ones I have seen with windows. Was I wrong in that assumption?

 

[don_resqcapt19]

Zog,

I was refering to (and I thought the discussion was about) 5kV and 15kV disconnect switches. Those are the onlt ones I have seen with windows. Was I wrong in that assumption?

I posted the original question after working on a portable water treatment unit that was made in Canada. The 30 and 60 amp, 480 volt SquareD safety switches had window kits intstalled. The kits are an option when you order the switch and I think you can also field intall them. I know that you are required to check voltage after locking out equipment, and wondered if the widows would eliminate the need to check for voltage? If you can't use the window to verify the lack of voltage (and I don't think that OSHA or 70E would permit the use of the window for that purpose), then what advantage is there in spending extra money to have the window? Maybe the rules are different in Canada?
Don

 

[George Stolz]

Perhaps it's to visually confirm after testing, leaving, and returning?

 

[zog]

Sorry Don, I didnt read close enough. I agree, whats the point of spending the money? I am pretty familiar with canadain regs, and I dont know of anything that would allow a visual as a replacement for a voltage check. Canada, if anything, is usually ahead of the US for electrical safety standards. (They know thier safety and beer up there)

 

[Coyote]

Why not check to see if dead circuit?
Better than dead electrican!

 

[zog]

Well per OSHA and the 70E to lockout a switch you must make a visual verification that all 3 blases of a switch are open (Or drawout circuit breakers are in the disconnect position).

You still must do a voltage check to consider the equipment in an electrically safe working condition, however for the visual the window would allow this without opening the door to do a visual, reducing the chance of an arc flash. So I guess that would be the reason for the windows.

 

[tomP]

How about nonelectrical work? The window would allow you to check the position of the switch, after lockout, without an electrician having to come do a voltage check. This is quite often the circumstance in industry. We have people checking/working on equipment or product quite often without the luxury of an electrician checking voltage for them. They follow a lockout procedure posted on the main electrical panel and a window might help verify a switch is open. As for an electrician I for one would check voltage before work would begin.

 

[realolman]

Seems to me Hazardous energy proceedures should require a check if you're going to tag it off even for non-electrical stuff.

 

[don_resqcapt19]

For non-electrical lock-outs we use a try-lock-try system. All motors have a local jog button that bypasses all interlocks. You go to the motor, push the jog button and see it move, then go to the MCC and lock out the starter, return to the job button and push it again and see nothing happen. {lock outs are remote from the motor per 430.102(B) Exception (b)}
Don

 

[tomP]

Seems to me Hazardous energy proceedures should require a check if you're going to tag it off even for non-electrical stuff.

I'm all for that it would mean we would have to hire at least another 20 or 30 electricians. Then we would have to have more of other trades to check their energy sources, pneumatic,hydraulic, heat,etc Of course product price would be so high nobody would buy.

don_resqcapt19
You go to the motor, push the jog button and see it move, then go to the MCC and lock out the starter, return to the job button and push it again and see nothing happen.

O.K. I work in the auto industry, how could we make that feasible when there are forty robots and various other automation in one "work area".
No, I am not being a smart a.. I will always try to learn a new and better way to do things.
At the present time it is part of my responsibility to provide a lock out guide to anyone, who is going to enter a work area, of the proper way to MAKE IT SAFE to work there. Mine is not the only step in this process as there are other checks made of the procedure I write, but it is an awsome responsibility.

 

[realolman]

Then we would have to have more of other trades to check their energy sources, pneumatic,hydraulic, heat,etc

I'm a union guy and I do them all.

You have to neutralize them all, including counter weighted members.

There are supposed to be papers in a book "Hazardous energy control" for each piece of equipment detailing how to do that....How do you do that?

 

[tomP]

I'm a union guy and I do them all.

You have to neutralize them all, including counter weighted members.

There are supposed to be papers in a book "Hazardous energy control" for each piece of equipment detailing how to do that....How do you do that?

Do your union guys like machine repair millwright pipefitter etc. use a voltage tester to determine if voltage is present? Remember the original question was what good would a "window" be. So the other people READ: non electricians, could tell the switch was open. A very important part of any lockout procedure.
Those "papers in a book" are an example of of the procedures I write.
I think the "window" would be of little use to us electricians, but may be of help to others who do not have a means to check voltage in their back pocket.