Voltage test or touch screen

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bure961

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Farmingham, MA
I NEED SOME HELP WITH THESE TWIST LOCK OUTLETS AND CABLES THAT SUPPLY POWER TO ELECTRICAL EQUIPMENT. WE HAVE A TOUCH SCREEN THAT TURNS ON/OFF OUR EQUIPMENT. WHEN TURNING THE POWER OFF FROM TOUCH SCREEN OUR WORKERS CAN THEN TURN THE TWIST LOCK TO REMOVE THE 240V SINGLE PHASE BEFORE REMOVING THE CABLE TO THE EQUIPMENT [MOTOR- LIGHTS ]. LOOKING AT THE TOUCH SCREEN IS THE ONLY WAY TO SEE IF THE EQUIPMENT IS OFF. THERE IS NO VOLTAGE TEST TO CONFIRM POWER IS OFF BEFORE REMOVING CABLE , MOTOR AND LIGHTS ARE NOT VISABLE. WORKERS ARE NOT ALLOWED IN PANELS. THIS COMPANY WAS TOLD BY MANUFACTURE THIS METHOD IS SAFE BECAUSE THE TWIST LOCK TURNS POWER OFF BEFORE REMOVING CABLE. HOW DO WE SHOW COMPANY THAT A VOLTAGE TEST IS NEEDED BEFORE WORK CAN BE CONE ?
 
130615-1243m EDT

bure961:

Can you clarify what the problem is?

At the twist lock outlet do you need to know that the twist lock outlet is dead before you are supposed to be allowed to remove the plug? Or is the problem something else?

Possibly the best solution is to have a lockout switch at the outlet that disconnects power to the outlet. This makes lockout mechanical, and being locked out visible at the outlet.

I would not trust any electronically controlled lockout where a mechanical one can be employed.

.
 
bure961 said:
I NEED SOME HELP WITH THESE TWIST LOCK OUTLETS AND CABLES THAT SUPPLY POWER TO ELECTRICAL EQUIPMENT. WE HAVE A TOUCH SCREEN THAT TURNS ON/OFF OUR EQUIPMENT. WHEN TURNING THE POWER OFF FROM TOUCH SCREEN OUR WORKERS CAN THEN TURN THE TWIST LOCK TO REMOVE THE 240V SINGLE PHASE BEFORE REMOVING THE CABLE TO THE EQUIPMENT [MOTOR- LIGHTS ]. LOOKING AT THE TOUCH SCREEN IS THE ONLY WAY TO SEE IF THE EQUIPMENT IS OFF. THERE IS NO VOLTAGE TEST TO CONFIRM POWER IS OFF BEFORE REMOVING CABLE , MOTOR AND LIGHTS ARE NOT VISABLE. WORKERS ARE NOT ALLOWED IN PANELS. THIS COMPANY WAS TOLD BY MANUFACTURE THIS METHOD IS SAFE BECAUSE THE TWIST LOCK TURNS POWER OFF BEFORE REMOVING CABLE. HOW DO WE SHOW COMPANY THAT A VOLTAGE TEST IS NEEDED BEFORE WORK CAN BE CONE ?
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Why would you need to have a voltage test to unplug something?
 
My take from OP description is he has a machine supplied by a cord and plug. They are looking at the screen to verify the machine is not under load before unplugging the cord, maybe not a requirement but not a bad practice either. I think his real question there is that someone thinks they need to verify there is no voltage within the equipment after unplugging the supply cord.
 
bure961 said:
I NEED SOME HELP WITH THESE TWIST LOCK OUTLETS AND CABLES THAT SUPPLY POWER TO ELECTRICAL EQUIPMENT. WE HAVE A TOUCH SCREEN THAT TURNS ON/OFF OUR EQUIPMENT. WHEN TURNING THE POWER OFF FROM TOUCH SCREEN OUR WORKERS CAN THEN TURN THE TWIST LOCK TO REMOVE THE 240V SINGLE PHASE BEFORE REMOVING THE CABLE TO THE EQUIPMENT [MOTOR- LIGHTS ]. LOOKING AT THE TOUCH SCREEN IS THE ONLY WAY TO SEE IF THE EQUIPMENT IS OFF. THERE IS NO VOLTAGE TEST TO CONFIRM POWER IS OFF BEFORE REMOVING CABLE , MOTOR AND LIGHTS ARE NOT VISABLE. WORKERS ARE NOT ALLOWED IN PANELS. THIS COMPANY WAS TOLD BY MANUFACTURE THIS METHOD IS SAFE BECAUSE THE TWIST LOCK TURNS POWER OFF BEFORE REMOVING CABLE. HOW DO WE SHOW COMPANY THAT A VOLTAGE TEST IS NEEDED BEFORE WORK CAN BE CONE ?
Click to expand...

kwired said:
My take from OP description is he has a machine supplied by a cord and plug. They are looking at the screen to verify the machine is not under load before unplugging the cord, maybe not a requirement but not a bad practice either. I think his real question there is that someone thinks they need to verify there is no voltage within the equipment after unplugging the supply cord.
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My take is that if they are using a the plug/receptacle as the disconnecting means it has to be within sight of the motor. he seems to be claiming its not.

I suppose one could use a voltage tester on the plug after it was unplugged but that seems sort of redundant.

Personally, I think using a twist lock style plug for this makes sense. The power is disconnected once the twist is made and before the plug is removed from the receptacle so it is about as safe as it can get.

If there is some concern that the equipment is shutdown before unplugging it, make the guy go look at it and make sure it is off first.

I am not sure I get the concern.

I am also unclear as to why they are unplugging the cord, or how often. It seems like they might be doing it as part of operating the equipment, as opposed to repair or maintaining it.
 
They make covers to put on cord caps that can then be locked with your usual LOTO equipment to prevent someone from energizing whatever may be supplied by that cord. Question is once disconnected via cord and plug does a person still need to verify there is no voltage in the equipment before working in this equipment? I guess it doesn't hurt anything to do so, but in almost every case is not all that necessary to do so either.
 
kwired said:
They make covers to put on cord caps that can then be locked with your usual LOTO equipment to prevent someone from energizing whatever may be supplied by that cord. Question is once disconnected via cord and plug does a person still need to verify there is no voltage in the equipment before working in this equipment? I guess it doesn't hurt anything to do so, but in almost every case is not all that necessary to do so either.
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A couple of possible exceptions to this would be if there is control wiring linking the equipment being maintained to other equipment, and that control wiring is powered from the other side. But to check this you would have to look at all wiring on your side rather than just the main connections.
Or if the equipment is connected in some way to other equipment or stray current source and by unplugging the cord you have removed the EGC, allowing the metal of what you are working on to rise above ground.
 
GoldDigger said:
A couple of possible exceptions to this would be if there is control wiring linking the equipment being maintained to other equipment, and that control wiring is powered from the other side. But to check this you would have to look at all wiring on your side rather than just the main connections.
Or if the equipment is connected in some way to other equipment or stray current source and by unplugging the cord you have removed the EGC, allowing the metal of what you are working on to rise above ground.
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Good points, but if a machine is powered by a cord and plug, then chances are other connections for controls are also cord and plug connected, so wouldn't it make sense that one needs to disconnect all plugs, as well as all air, water, steam etc. before the machine is deemed safe to work on? If all potential electric power sources are visibly disconnected do you still have to get the meter out in case one of them is miraculously conducting to a source? I do not claim to be expert on 70E but it seems to me if I have a fairly simple machine with only one supply cord and I have the plug in my hand then there is very little chance there is power in the unit unless it also has some internal power source of some kind.
 
I don't think i explained it right . sorry for misleading you guys . my question is after repairs of equipment and the plug has to be put back into its female twist lock that could be powered should there be a voltage test on this recept.? the only way to do this is to open a control panel to test for power. the plug it self has a number of small prongs [ 8 PRONGS ] that suppy power 240 and 24v to the equipment when plug in.
 
bure961 said:
I don't think i explained it right . sorry for misleading you guys . my question is after repairs of equipment and the plug has to be put back into its female twist lock that could be powered should there be a voltage test on this recept.? the only way to do this is to open a control panel to test for power. the plug it self has a number of small prongs [ 8 PRONGS ] that suppy power 240 and 24v to the equipment when plug in.
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I see no reason to.
 
130616-2019 EDT

What I view as a possible problem is the need for a lockout switch. In the original post it seems the plug is performing the function of a disconnect. So if the socket remains powered, then while someone is working on the equipment another person could come along and plug the plug back in and hurt someone working on the equipment. If there is a physically lockable, padlock, disconnect switch preceding the socket, then conventional lockout procedures can be employed.

.
 
gar said:
130616-2019 EDT

What I view as a possible problem is the need for a lockout switch. In the original post it seems the plug is performing the function of a disconnect. So if the socket remains powered, then while someone is working on the equipment another person could come along and plug the plug back in and hurt someone working on the equipment. If there is a physically lockable, padlock, disconnect switch preceding the socket, then conventional lockout procedures can be employed.

.
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There are also lockable covers that can be placed over the cord cap that can be used to lock out the equipment, same lockout rules apply.
 
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