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 Post subject: how do you treat disconnects
PostPosted: Sun Apr 24, 2016 8:18 pm 
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Joined: Tue Jan 19, 2010 2:35 pm
Posts: 132
We have a client who works in an industrial facility. In the plant, there are several fused and non fused disconnects that are located at equipment. For example, they have several larger 480 volt 3 phase welders. Each of the welders has a disconnect. Sometimes the work means having to disconnect a welder (for repair) from its disconnect. The safety person has some concerns about this. He thinks because the line side of the disconnect is still energized, that they are exposed to shock. However, this is what they're doing. Shut off the disconnect and open it. Check the line side for power (this acts as the meter test) and check between all three phases and to ground for all three phases. Then re-check the meter on the line side. Then lock off the switch. They also wear Class 00 gloves plus the leathers. Can anyone point to something in the 70E Standard that they're violating? Are there steps missing? By the way, most of the disconnect switches are 30 to 200 amps and are NEMA 1. Plus the disconnect are the type where the blades become visible if pulled and there are no other sources of power inside the disconnects.


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 Post subject: Re: how do you treat disconnects
PostPosted: Mon Apr 25, 2016 4:24 am 

Joined: Fri Nov 06, 2015 1:05 am
Posts: 25
Location: Evansville IN
While I cant immediately point to mis-step in the Team Members action, You have not provided enough information.
What other PPE is TM wearing
Is an electrical hazard label located on said disconnect?
Is the TM trained in electrical safe work practices?
Is proper clearance around panel?
Is the TM de-terminating the wires within this panel?
Are the supply side terminals covered or could they be an old type disconnect that leave exposed wires and lugs?
Is this just a Lock out(control of hazardous energy)?
Is the TM using a properly rated meter(Cat Level)?


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 Post subject: Re: how do you treat disconnects
PostPosted: Mon Apr 25, 2016 6:19 am 
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Joined: Tue Jan 19, 2010 2:35 pm
Posts: 132
Thanks for your questions, they are good ones and I've answered below in italics:
While I cant immediately point to mis-step in the Team Members action, You have not provided enough information.
What other PPE is TM wearing - No arc flash equipment but they do wear gloves and leather covers as well as safety glasses, ear protection and cotton work long sleeves shirts and long pants made with cotton.
Is an electrical hazard label located on said disconnect? Not an arc flash label, just the factory label that came with the disconnect plus a voltage label that was added by the plant.
Is the TM trained in electrical safe work practices? - They are qualified per the employer, I have watched them work and I agree, they are qualified to do this particular level of electrical work.
Is proper clearance around panel? yes, there is 36" in front of the disconnects
Is the TM de-terminating the wires within this panel? Yes they disconnect the wire in order to remove the welder for maintenance.
Are the supply side terminals covered or could they be an old type disconnect that leave exposed wires and lugs? There are a variety of older and new disconnects. Most have barriers, but I think a few don't have barriers.
Is this just a Lock out(control of hazardous energy)? Yes, and even though no one else gets into the disconnects, they still apply their own lock.
Is the TM using a properly rated meter(Cat Level)? Yes, they do use good quality Fluke meters.


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 Post subject: Re: how do you treat disconnects
PostPosted: Mon Apr 25, 2016 6:39 am 

Joined: Mon Apr 06, 2015 9:51 am
Posts: 5
We had a lot of discussions about this and also had a consultant contact OSHA about this and other items(working in an MCC with unit off, but the bus live). We learned the OSHA unofficial interpretation, although not written, "near" is the restricted approach boundary. I believe disconnecting wires is considered work, and assuming you are within 12"(480 volt) of the line side of the disconnect and the terminals are not covered, you are doing live work. I don't know what it will take to de-energize the line side of the terminals, but I would doubt it would be of greater risk to de-energize than work it live if you are at a manufacturing plant or construction yard. Inconvenient yes, but OSHA doesn't care about incovenient.

Remember arc flash consists of both a shock hazard and a flash hazard, even if you are outside of the shock hazard region, you may not be out of the flash hazard area, and I am not sure how well those little paper covers reduce the arc flash hazard.


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 Post subject: Re: how do you treat disconnects
PostPosted: Mon Apr 25, 2016 7:24 am 
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Joined: Thu Oct 18, 2007 7:10 pm
Posts: 261
Location: NW USA
seems pretty cut and dry; taking voltage measurements is interacting with exposed energized conductors in a fashion that could draw an arc.

The worker should have Arc Flash PPE rated for the calculated exposure.


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 Post subject: Re: how do you treat disconnects
PostPosted: Mon Apr 25, 2016 9:25 am 
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Joined: Tue Oct 26, 2010 9:08 am
Posts: 2174
Location: North Carolina
wilhendrix wrote:
We have a client who works in an industrial facility. In the plant, there are several fused and non fused disconnects that are located at equipment. For example, they have several larger 480 volt 3 phase welders. Each of the welders has a disconnect. Sometimes the work means having to disconnect a welder (for repair) from its disconnect. The safety person has some concerns about this. He thinks because the line side of the disconnect is still energized, that they are exposed to shock. However, this is what they're doing. Shut off the disconnect and open it. Check the line side for power (this acts as the meter test) and check between all three phases and to ground for all three phases. Then re-check the meter on the line side. Then lock off the switch. They also wear Class 00 gloves plus the leathers. Can anyone point to something in the 70E Standard that they're violating? Are there steps missing? By the way, most of the disconnect switches are 30 to 200 amps and are NEMA 1. Plus the disconnect are the type where the blades become visible if pulled and there are no other sources of power inside the disconnects.


No lock. Initially during the unwiring procedure it may be required but perhaps not after that.

LOTO under OSHA is somewhat messy in regard to out of service equipment. Locks are required as long as the equipment is actively undergoing maintenance and the locks need to be unique to the LOTO procedure. However if equipment is not under maintenance whether this means that the part is taken out of service and sent off and requires several months for rebuild or if the equipment is taken out of service for other reasons (such as shutting something down for demolition or that won't be in production and it is desirable to no longer maintain it), then the LOTO locks MUST come off. Prior to this of course it needs to be secured so that it can't go back in service, which usually means unwiring it, installing blanks for valving or disconnecting piping, etc.

Some plants often have "out of service" or "construction" locks for this purpose and the reverse case also applies. So during startup/commissioning first the construction locks go on. Then the locks are taken off one by one as the equipment is commissioned and put in service until all the construction locks have been removed and the equipment is now "in service" and being maintained at which point standard LOTO locks apply.

Finally during operation of the disconnects if the equipment is maintained properly then arc flash does not apply but it certainly applies for testing for absence of voltage and potentially opening/closing the door on the disconnect. There was no mention of this and I don't know how big your incident energy is so no way to tell if you need anything here or not but my suspicion is that you do.


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 Post subject: Re: how do you treat disconnects
PostPosted: Mon Apr 25, 2016 9:49 am 
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Location: North Carolina
wilhendrix wrote:
What other PPE is TM wearing - No arc flash equipment but they do wear gloves and leather covers as well as safety glasses, ear protection and cotton work long sleeves shirts and long pants made with cotton.


This is rated up to 1.2 cal/cm2 for incident energy. Untreated cotton can catch fire and cause a severe burn. Unlike with welding an arc flash happens so fast that the victim will NOT have time to get away. There are fire retardant versions (called arc rated) of shirts and pants that are treated cotton that are rated from about 6 cal/cm2 all the way to 12 cal/cm2. This is basically the same thing as a "welders" shirt and pants except that the material has been tested with a simulated arc to verify the maximum thermal energy that it can withstand while still providing adequate protection to the worker. Since this is a welding shop anyways if you just switch to those for shirts and pants it will work for both purposes.

I have personally "tested" these against welding slag. They do burn but they don't sustain a flame so you just get holes where the molten metal burned through.

Quote:
Is an electrical hazard label located on said disconnect? Not an arc flash label, just the factory label that came with the disconnect plus a voltage label that was added by the plant.


Arc flash label is required by National Electrical Code as of 2002. OSHA cited General Motors for this I think around 2008. The manufacturers DO not apply this label and you can't get them to do it. The issue is that the required label depends on the current available from the upstream power source which is site specific. So the end user is required to put these labels on.

Quote:
Are the supply side terminals covered or could they be an old type disconnect that leave exposed wires and lugs? There are a variety of older and new disconnects. Most have barriers, but I think a few don't have barriers.


Barriers don't matter except in that they may change the equipment from not exposed to exposed wiring which then mandates shock protection PPE. This is somewhat independent of arc flash concerns. Since you've got to get at the lugs at some point all that it changes is whether or not opening the doors exposes anything and makes opening the door itself potentially hazardous.

Quote:
Is this just a Lock out(control of hazardous energy)? Yes, and even though no one else gets into the disconnects, they still apply their own lock.


OSHA has about a dozen different "LOTO" procedures. They are all similar but not exactly identical. Be aware that in the case being discussed there are three to be aware of : Subchapter J, Subchapter O, and Subchapter S. This is different from construction (1926) and generation/transmission/distribution (Subchapter R, multiple sections).

Subchapter J is the "general" or "mechanical" LOTO. This would be used for instance if you locked out a ventilation fan to work on the fan shroud. It is the one that is most familiar to most people and can be used in lieu of Subchapter O but is specifically prohibited to be used as a replacement for Subchapter S.

Subchapter O is for minor servicing and adjustment, generally a "production" lockout. It doesn't require locks at all...just that there is a written procedure that is followed. This would be the case for instance when someone shuts off a welder to reposition a work piece. No lockout is typically used for this activity.

Subchapter S is for electrical work. It is nearly identical to Subchapter J except that all the workers doing this work need to be qualified workers, a test for absence of voltage is required, and in some cases personal protective grounding is required.

Quote:
Is the TM using a properly rated meter(Cat Level)? Yes, they do use good quality Fluke meters.


The brand name is immaterial. Fluke makes meters that are NOT rated for the service and older meters (more than about 10-15 years old) weren't rated for a specific category anyways. Depending on what you are doing typically you would need either a CAT III or CAT IV meter and these are subdivided by voltage. For industrial 480 V systems I recommend using either CAT III/1000 V or CAT IV/600 V meters. These are the highest rating available and even though the specifications look different they have exactly the same test requirements. The "category" rating by itself is some kind of meaningless confusing terminology when in reality the key is the transient test that the meter is designed to withstand.

If you get this wrong if a transient (voltage surge) occurs while the probes are on the wires the meter can start an arc flash and explode causing major injuries to the person using the meter. It is rare that this happens but most larger plants had about one incident every 10 years or so up until the category rating system came along.


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 Post subject: Re: how do you treat disconnects
PostPosted: Tue Apr 26, 2016 3:46 pm 
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Joined: Tue Jan 19, 2010 2:35 pm
Posts: 132
Thank you all for your thoughtful replies. It's clear you all took your valuable time to answer and I really appreciate that. Thank you again,


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