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 Post subject: Throwing Live Disconnects
PostPosted: Tue Oct 27, 2020 2:58 pm 
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Joined: Mon Jun 11, 2018 12:02 pm
Posts: 12
Location: Slave Lake, Alberta
During a recent safety presentation on lockout at a company I am working for, it was stressed that a disconnect must NEVER be thrown live.

This is counter to my experience where serious injury occurred to one individual because another individual was convinced NEVER to throw a disconnect live, so there was a disastrous (nearly fatal) delay while they were trying to communicate on a busy radio channel to tell the operator to stop the line.

All disconnects in this installation also have a secondary safety function of early break handle switches which operate through the PLC to ensure a stop command is issued before the knives actually pull out. Is this relevant since control circuits are never an assurance of a safety function?

Although I have seen evidence of disconnects exploding, it is my understanding that a properly designed, installed, closed and maintained disconnect switch must be rated to reduce and contain the arc when disconnected live at full load? Obviously, the closed and properly maintained state can also be questionionable.

Is it ever acceptable to throw a disconnect live? OR Is it ever acceptable to have a company policy to throw a disconnect live to prevent a fatality? Comments?

Note: Obviously the incident I referred to above was initiated because of a LOTO procedural failure. Unfortunately, these procedural failures are still far too common. In this particular case, the wrong disconnect had been locked by a new hire.


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 Post subject: Re: Throwing Live Disconnects
PostPosted: Wed Oct 28, 2020 1:42 pm 

Joined: Thu Apr 18, 2019 11:42 am
Posts: 30
Did they give a reason? All of the OEMs make load break rated disconnect switches.

Mike


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 Post subject: Re: Throwing Live Disconnects
PostPosted: Mon Nov 02, 2020 9:08 am 
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Joined: Tue Jan 13, 2009 5:00 pm
Posts: 540
"Live" generally means energized, whether under conditions of load or not. This is not the word to use here, since you are speaking of operating a disconnect under load. Unless designed and rated for this duty, such an operation is guaranteed to arc and fault.


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 Post subject: Re: Throwing Live Disconnects
PostPosted: Mon Nov 02, 2020 9:34 am 
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Joined: Tue Jan 19, 2010 2:35 pm
Posts: 144
Generally speaking, disconnects are supposed to be used to disconnect power, they are not supposed to be used to shut off an operating load. But that's under normal circumstances. Shutting off a disconnect with a load is nothing when weighed against someone being injured or worse.


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 Post subject: Re: Throwing Live Disconnects
PostPosted: Mon Nov 02, 2020 4:29 pm 
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Joined: Tue Jul 01, 2014 8:40 am
Posts: 98
Hi Dave, greetings from Ontario. I am not sure what you mean by "throwing a disconnect switch live" Could you please explain?


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 Post subject: Re: Throwing Live Disconnects
PostPosted: Thu Nov 05, 2020 9:30 am 
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Joined: Mon Jun 11, 2018 12:02 pm
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Location: Slave Lake, Alberta
Apologies for the lack of clarity. "Live" would be any unspecified but potentially energized state up to and including full load motor starting condition where the motor is drawing near the equivalent of locked rotor current. The assumption is that in an emergency situation, the person operating the disconnect would not have time to determine what state the equipment was at, but just needed to stop it as quickly as possible and the disconnect was much closer than any E-stop button.


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 Post subject: Re: Throwing Live Disconnects
PostPosted: Mon Nov 09, 2020 7:27 am 
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Joined: Tue Jul 01, 2014 8:40 am
Posts: 98
Hi Again Dave. A couple of things here. Now that you have clarifierd that you are referring to a disconnecting means under load as opposed to "Live". Does this company have a Lockout Program including procedures? as part of the Program or even "An Electrically Safe Work Condition" - Article 4.2 of CSA Z42 specifically Clause 4.2.5. Have a look at sub clause [b]b) After properly interrupting the load current, open the disconnecting device(s) for each source. Basically a controlled shutdown. This is so that you complete the opposite when recommissioning to avoid start up under load

Rgarding the disconnecting means offering any protection from an arc flash. I suggest that you have Jim send you his video on "Doors Blowing Open" It is excellent and a great training tool

I hope that this helps out

Thanks


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 Post subject: Re: Throwing Live Disconnects
PostPosted: Mon Nov 09, 2020 7:32 am 
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Joined: Sun Sep 23, 2007 5:00 pm
Posts: 122
Location: Calgary, Alberta, Canada
It has been awhile since I have posted.

Lots of myths and misinformation out there from bad training, arc flash hazard incident energy analysis study reports that should NOT include any recommendations on policies, practices and procedures.

Does you company have an Electrical Safety Program? If yes does it include the mandatory Risk Assessment Procedure?

Under normal operating conditions we operate energized electrical equipment with NO arc flash and shock PPE, and no Energized Electrical Work Permit is required.


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 Post subject: Re: Throwing Live Disconnects
PostPosted: Mon Nov 09, 2020 9:03 am 
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Joined: Tue Jan 13, 2009 5:00 pm
Posts: 540
I'm not believing some of the replies here. A colleague is being electrocuted, so you ask him to stand by while you consult the rule book, perform a risk assessment, fill out an energized work permit, get approval, and perform LOTO?

The only question here is this: Can the disconnect be opened with a reasonable chance of not increasing the number of victims?


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 Post subject: Re: Throwing Live Disconnects
PostPosted: Mon Nov 09, 2020 1:01 pm 
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Joined: Mon Jun 11, 2018 12:02 pm
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Location: Slave Lake, Alberta
Thanks very much for all the information. This may not have been the best place to clarify my question since it is more of a question of what is the legal and ethical thing to do.

For those of you who queried about Electrical Safety Programs with Risk Assessment Procedures, it would be a severe violation of OH&S code in our jurisdiction if we didn't have one. The company policy and training is very specific - NEVER throw a disconnect under load under any circumstances. Don't even think about it.

However my question is based on a number of incidents in the last few years where employees made unintentional errors in lockout procedures or violated all of their training and company safety policies by not locking out at all. In some cases they unintentionally put themselves in harms way and were nearly injured or killed. In at least one case of knowingly violating safety training and policy the employee was dragged into the machine and killed. Other employees (not electricians) trained in our safety programs did NOT throw disconnects within easy reach but were calling on busy radio channels for operators to stop the process or racing to get to an E-Stop button several feet away to stop the machinery.

Several answers suggest that my question should be posed differently.

Before awareness of Arc Flash issues, no one would question throwing the disconnect in these or any other case and in my experience, we would stand by the disconnect, ready to throw it during testing and commissioning without any question about the safety. In the distant past, I have personally thrown disconnects under load hundreds of times without incident.

Now that we are all aware of the risk of Arc Flash and doors being blown open, is there ever an ethical, moral or legal argument to throw a disconnect to save another, because there is obviously a risk that this could lead to becoming a second victim.

To re-phase my question: What is the safety training and policy in your company? a) NEVER throw a disconnect under load even to save a life. b) Advise employees that it is their personal choice to risk throwing a disconnect under load in order to save a life. c) THROW a disconnect if that is the quickest means to save a life. d) Your plant has E-Stops within easy reach of every disconnect so this question is irrelevant. e) Your employees never violate safety policy and never make mistakes in lockout procedures.


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 Post subject: Re: Throwing Live Disconnects
PostPosted: Mon Nov 09, 2020 1:20 pm 
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Joined: Tue Jan 13, 2009 5:00 pm
Posts: 540
Perhaps a survey question Jim? Already written.


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 Post subject: Re: Throwing Live Disconnects
PostPosted: Tue Nov 10, 2020 5:05 am 

Joined: Tue Nov 10, 2020 4:55 am
Posts: 1
Hi guys
I work in the utility company of Ireland, ESB. For HV substations a disconnect is only to be operated off load (as it is not rated for load current making or breaking) so as to isolate the circuit for maintenance or repair etc. The breaking and making is done by a circuit breaker. For LV a disconnect can be just a disconnect or isolator which is not load rated or it can be called a disconnect switch which is rated to make and interrupt the load.
So why can't you either install a load rated disconnect switch or else install an LV circuit breaker (MCCB or ACB depending on load rating).


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 Post subject: Re: Throwing Live Disconnects
PostPosted: Sun Nov 15, 2020 3:48 pm 
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Joined: Mon Sep 17, 2007 5:00 pm
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Location: Scottsdale, Arizona
stevenal wrote:
Perhaps a survey question Jim? Already written.

Done! Great conversation. That part about saving a life is difficult. I often state it is human nature to try to help people in harms way even it means putting yourself at risk. For legal/safety reasons there should be a policy prohibiting this which is why I selected option 1 (yes I vote too :D ) but I'm sure when faced with the difficult situation of saving someone, many might ignore it. A difficult choice.


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