Racking out Breakers

[dancassidy]

At this facility ( a pulp and paper mill) we often lock out sections of the process by means of low voltage power circuit breakers. Our policy is to open and rack out the breaker and to lock it in the disconnected position. This eliminates any possibility that a breaker failure could allow the circuit to remain energized, but it also presents some problems of its' own... The act of racking the breaker out and back in exposes the employee to an arc flash hazard (the style and vintage of breakers involved are racked with the door open), and repeated racking in and out causes wear on the racking mechanisms.

Some have suggested that we should stop racking out these breakers, and instead open the breaker and lock it in the connected position. The breakers have provisions for this - when the breaker is open, a tab can be pulled out from the front of the breaker which has a slot for padlocks. When the tab is pulled out and locked, the breaker can not be closed. Their argument is that this is no different from locking out a disconnect or molded case breaker with a locking mechanism...you can't see what is going on inside, so you open the switch, test for voltage, and trust that it will stay open.

We have talked with the manufacturer, and they will not commit to recommending this method of lockout, although the device is designed to allow it. I would appreciate any feedback from others who may have faced this issue.

 

[zog]

Re: Racking out Breakers

You are doing the right thing, for the right reasons, your electricians just need to wear the proper PPE for arc flash.

 

[69boss302]

Re: Racking out Breakers

I have faced this issue many times, and win some loose some. But, now with what you stated about the new evidence readily available on arc flash, it justifies this even more.

You need to get into a moon suit to rack out these breakers in accordance with NFPA 70E and even though you see the breaker racked out you are required to take voltage readings on the equipment you are working on to verify it de energized, utilizing all applicable safety precautions as if it were still energized.

Provided, and usually, you can show that the breaker lockout is not just some kind of electrical interlock and it has a physical means to keep the breaker from closing, this meats OSHA standards for lockout. Using this means you still (not something extra, you had to do this before anyway) need to check for voltage using all applicable safety precautions.

On thing that happened to me once to really help me get my point across. The plant VP for maintenance and engineering was standing next to me while one of my guys was racking out an old (just say even before I was born) Westinghouse 480 VAC breaker. We could hear a little tinkling noise that came from behind the breaker. Needless to say I knew right away what happened and the VP said "Wt was that?" At the same time the electrician said "Oh S**T!". I then explained to the VP how now we would have to de energize the entire switchgear, which meant turning off half the building, and we would have to go in and pick up all the fingers and springs inside the switchgear, hopefully we would find them all and they would not be broken and put the connectors back together. He didn't believe me until the breaker was all the way out and I asked him if he was willing to reach in that live switchgear with all the dust and cob webs (Oh they didn't believe in switchgear maintenance either), and pick up the pieces and put them back on those stabs all the way in the back. He simply shook his head walked away, and said "Let me know when your ready to turn it off". Just after we got it all back together he asked me, "How can we avoid this?"

 

[kiloamp7]

Re: Racking out Breakers

dancassidy - We have hundreds of low-voltage draw-out (LVDO) ckt bkrs at our facility.

In most cases, they are feeders that supply many other O/C devices downstream. So frequently, the lockout/tagout is done at the downstream O/C device.

There are ocasional instances where we do need to "LOTO" at the LVDO gear itself. Usually, we rack the bkr out & lock it. Once in a while, we lock the bkr, but leave it racked in.
It all depends on that particular scenario & how comfortable the parties involved are.

By the way, I do not believe that we have implemented arc flash programs as well as we probably should have.

[ September 16, 2005, 10:11 PM: Message edited by: kiloamp7 ]

 

[realolman]

Re: Racking out Breakers

It would feel better to have the breaker out.

[ September 18, 2005, 08:25 AM: Message edited by: realolman ]

 

[templdl]

Re: Racking out Breakers

The drawout air and power breaker that I'm familiar with can not be racked out nor can they be racked in when they are in the closed position. The line and load stab assembly in the rear are not load break anyway. When completely removed there is a set of shutters that coverup the stabs. If you had an unqualified person doing the job I would imagine that some way could be found to get their fingers into trouble. It's the same with medium voltage motor starters, MCC buckets, and medium voltage switchgear breakers.

 

[zog]

Re: Racking out Breakers

NFPA 70E 2004 edition 120.1 Process of achieving an electrically safe working condition. (3) Whenever possible, visually verify that all blades of the disconnecting devices are fully open or that drawout type circuit breakers are withdrawn to the fully disconnected position.

2 reasons for this:
1) You cannot see the contacts due to the arc chutes, so no visual verifiaction can be made unless you rack it out.
2) The main line contacts are only open about an inch or so (depending on tyoe and vintage), this distance is sufficient for 480V but not for the transients that occur on the system, a higher voltage from a lightning strike or switching transient may just across the oipen contacts.