does the code / law require the use of kirk keys ?

[ARCMASON]

We have just recently had an arc flash study completed and have been told by the certified NFPA 70 E master trainer that gave us the training that we could no longer open and close breakers in our medium voltage switch gear unless we are suited up for the job, even though the breakers are fully enclosed. We have breakers that are marked category dangerous which means on safe ppe exist to do this work energized. This leads into the question. We have double ended switch gear, each end has a transformer that takes the voltage from 12.47kv to 480 volts and on the primary side of the transfomer. The switches are rated for 600 amps on the transformer rating is 1000kva. I do not want to take out major sections of my plant in order to reset a breaker. The primary knife disconnects are kirk keyed with the main. I am thinking about utilizing a second key so that I can open the knife disconnect, since the primary side of the transformer is category 0 and the secondary side is cat dangerous. I have not been able to find any codes that require the use of kirk keys. I talked with the load switch manufactures and they say I can open and close the switch many times , with no problems. When I talk to the gear manufacture, they tell me they can not recommend bypassing the kirk key system. Ther switch manufacture sold the swith in this case to ABB who then created the assembly. The primary current of the transfomer under full load is less than 100 amps. I am looking for any commnets in regards to the arc flash, opening and closing the knife switch under load and any code requirements for the use of the kirk key system.

Thanks

 

[jim dungar]

Only the employer can decide what procedures and policies must be followed in the ESWP, the trainer only has an opinion.

 

[richxtlc]

Kirk interlocks are usually provided when a safety issue is presented, as in your case the knife switch is interlocked with the main circuit breaker to prevent you from opening the disconnect under load. This is to prevent the inductive kick-back that will result in a flash across the knife switch and a possible short circuit if the arcs cross. Even opening an unloaded knife switch on the primary can result in a similar event if the knife switch is not rated to de-energize a transformer. OSHA requires that you operate the equipment in a safe manner in accordance with the manufacturer's design specifications, bypassing the switch to get around an arc flash hazard is not within the parameters of the switch. If you want to make a safer operation of the switch try a remote tripping device, this will keep you at a safe distance when operating the switch no matter what the HRC category is.

 

[SG-1]

The short answer is no.

The kirk keys are provided to assure a specific sequence of events for the safe operation of the gear ( to prevent incidents ). There is no way the 12.47KV switch is CAT 0. A 120 volt receptacle is greater than CAT 0.

How will opening the switch ahead of the Main Breaker not interrupt power to the exact same thing that opening the Main Breaker will ?

I supect the switch was provided for isolation & to be opened after the Main Breaker, because the breaker is better able to interrupt any current that may be flowing, including fault current. The switch also has a view window to verify the contacts are open & the service is disconnected.

 

[zog]

We have just recently had an arc flash study completed and have been told by the certified NFPA 70 E master trainer

There is no such thing, there is no certification for 70E training, and certianally not a "master"

that gave us the training that we could no longer open and close breakers in our medium voltage switch gear unless we are suited up for the job, even though the breakers are fully enclosed.

Unless you have arc rated switchgear that is true, the enclosures are nto designed to contain an arc flash. Now "fully suited up", that all depends on the results of your analysis, you will need some PPE unless you operate these switches remotely outside the arc flash boundary.

We have breakers that are marked category dangerous which means on safe ppe exist to do this work energized.

Miigation is easy on this to get these down to a HRC 1 or 2, thats my job, I do it every day.

This leads into the question. We have double ended switch gear, each end has a transformer that takes the voltage from 12.47kv to 480 volts and on the primary side of the transfomer. The switches are rated for 600 amps on the transformer rating is 1000kva. I do not want to take out major sections of my plant in order to reset a breaker. The primary knife disconnects are kirk keyed with the main. I am thinking about utilizing a second key so that I can open the knife disconnect, since the primary side of the transformer is category 0 and the secondary side is cat dangerous.

Remote switching and racking is the perfect solution for this, or just mitigate the hazard.

I have not been able to find any codes that require the use of kirk keys. I talked with the load switch manufactures and they say I can open and close the switch many times , with no problems. When I talk to the gear manufacture, they tell me they can not recommend bypassing the kirk key system. Ther switch manufacture sold the swith in this case to ABB who then created the assembly. The primary current of the transfomer under full load is less than 100 amps. I am looking for any commnets in regards to the arc flash, opening and closing the knife switch under load and any code requirements for the use of the kirk key system.

Thanks

Depends on the type of switches you have and thier ratings, either way, not a good idea.

This "master certified trainer" should know some simple solutions to your issues and never should have left you with thee problems, nor should have the company that did your arc flash study. Sound to me like your plant has been getting training and engineering services from the low bidder.

PM me your info (If you like), I have already done a few mitigation projects for members of this forum with the same probelms you have.