Key Interlocking

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mboutal

Member
Location
Columbia, SC
Hello Everyone,
I hope you are all doing well.
I am new here :angel: , and this is my first question :? - Key Interlocking -
How you can create a key scheme from a given logic table.
For example:
If I have a G-T-M-M-G-T-G application with the following logic table.

Condition

GenTieMainMainGenTieGen
State 1OpenOpenClosedOpenOpenClosedOpen
State 2OpenOpenOpenOpenOpenClosedClosed
State 3ClosedOpenOpen OpenOpenClosedOpen
State 4ClosedClosedOpenOpenOpenOpenClosed
State 5ClosedClosedOpenOpenClosedOpenOpen


Please help and provide step by step if you can, I need to understand how the process works.

Thank you,
 

Strathead

Senior Member
Location
Ocala, Florida, USA
Occupation
Electrician/Estimator/Project Manager/Superintendent
Hello Everyone,
I hope you are all doing well.
I am new here :angel: , and this is my first question :? - Key Interlocking -
How you can create a key scheme from a given logic table.
For example:
If I have a G-T-M-M-G-T-G application with the following logic table.

Condition
GenTieMainMainGenTieGen
State 1OpenOpenClosedOpenOpenClosedOpen
State 2OpenOpenOpenOpenOpenClosedClosed
State 3ClosedOpenOpenOpenOpenClosedOpen
State 4ClosedClosedOpenOpenOpenOpenClosed
State 5ClosedClosedOpenOpenClosedOpenOpen


Please help and provide step by step if you can, I need to understand how the process works.

Thank you,


You got me! You have three generators all feeding the same sources? I must admit the logic chart you sent just sends my head in to a spin. It would be easier for me to understand if you posted a riser diagram and a narrative on the intention of the states. I am sure there are some rain man types here who will grasp it from the above though. :angel:
 

mboutal

Member
Location
Columbia, SC
You got me! You have three generators all feeding the same sources? I must admit the logic chart you sent just sends my head in to a spin. It would be easier for me to understand if you posted a riser diagram and a narrative on the intention of the states. I am sure there are some rain man types here who will grasp it from the above though. :angel:

Sorry the state 5 should have only 2 Gens Closed- and the third open!
 

Fulthrotl

~Autocorrect is My Worst Enema.~
They have a nice application guide and their tech support will work out something custom for you.

yup. old school customer service.

the only way i could see doing this......

you used a transfer panel with five arrays, and you'd only free the keys
for one status with the primary key.

you could do it easily that way.
 
Last edited:

Besoeker

Senior Member
Location
UK
You got me! You have three generators all feeding the same sources? I must admit the logic chart you sent just sends my head in to a spin. It would be easier for me to understand if you posted a riser diagram and a narrative on the intention of the states. I am sure there are some rain man types here who will grasp it from the above though. :angel:
A single-line power circuit diagram might help clarify what the arrangement is intended to achieve. From that it would be easier (IMO) to propose how to provide interlocking.
 

mpoulton

Senior Member
Location
Phoenix, AZ, USA
I think there may be some states missing from the table. There's no state shown where Main 2 is ever closed. It might be helpful to envision the logic by producing a table of prohibited states, too. That's mostly what a trapped key interlock does - it prohibits certain combinations of states rather than prescribing certain allowable states. The system can allow the operator to enter unexpected or undesirable states as long as it prohibits the dangerous ones. A table showing prohibited combinations would clarify the logic.
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
Another major consideration is what series of operations is allowed in going from one state to another.
If the all open state (plant shut down temporarily) is allowed something like the following would meet the specification if not the intent:
1. Each switch is in the open position unless its key is inserted and turned.
2. There are five key banks, each released by the same key.
3. Sequence:
A. Return all keys to the initial state bank. Enter state zero, all off.
B. Remove state key from initial bank.
C. Insert key into desired state bank and remove its switch keys.
D. Insert switch keys into switch locks and turn, producing the new state.

If you instead have to transition from one state to another one switch at a time, avoiding forbidden states, I do not think this job is really suitable for Kirk Key control. The best the latter could do us avoid unsafe states but could not force you to go by the shortest route from one state to another without a shutdown.
If there is a sequence that is always in one of the 5 states and all states can be reached by a path that changes only one switch at a time, then a key system might be able to keep you only in allowed states but would not help you to figure out how to get to the state you want.
 

templdl

Senior Member
Location
Wisconsin
Hello Everyone,
I hope you are all doing well.
I am new here :angel: , and this is my first question :? - Key Interlocking -
How you can create a key scheme from a given logic table.
For example:
If I have a G-T-M-M-G-T-G application with the following logic table.

Condition

GenTieMainMainGenTieGen
State 1OpenOpenClosedOpenOpenClosedOpen
State 2OpenOpenOpenOpenOpenClosedClosed
State 3ClosedOpenOpen OpenOpenClosedOpen
State 4ClosedClosedOpenOpenOpenOpenClosed
State 5ClosedClosedOpenOpenClosedOpenOpen


Please help and provide step by step if you can, I need to understand how the process works.

Thank you,
I have had to interpreted and order k-k intlks on numerous occasions and found it best to use a oneline with all of the devices to be interlocked with the k-k intlks illustrated and carefully go through and understand the interlocking sequences remembering that a k-k either prevents operation or allow it. A key may remain captive and not removable to lock out a device or the key may be only operated to the on position with the key in place and held captive in the on position and able to be removede when the device is in the off position.
You may have multiple keys on a device.

You have an involved key sequence and ordering the locks should be done with caution as any errors in specifying the locks is quite costly.
 

Fulthrotl

~Autocorrect is My Worst Enema.~
If you instead have to transition from one state to another one switch at a time, avoiding forbidden states, I do not think this job is really suitable for Kirk Key control. The best the latter could do us avoid unsafe states but could not force you to go by the shortest route from one state to another without a shutdown.

agreed.
you won't be able to go from one state to another without opening all positions.
not in a way that wouldn't be amazingly confusing to someone needing to do this in a hurry, without instruction
or understanding of the function, which is often the case.

the way i see it.....

seven unique kirk locks.

five transfer lock arrays.

first stage has two captive keys
second stage has two captive keys
third stage has two captive keys
fourth stage has three captive keys
fifth stage has two captive keys.

there is only ONE stage select key.

you put that key in the stage you wish, and it frees the keys for that stage.
put them in the locks they fit, close them, and off you go.

changing stage?

open the switches, retrieve the keys, put them back in their captive locks,
move the stage select key to the stage you wish, get the keys out for that
stage, enable them, and close devices, ties, whatever.

understand that you will have multiple kirk keys for a specific device with this strategy,
however, they will be locked in transfer stations. there will be only one stage select key.

to the OP... if you do a key control strategy like this make absolutely sure of the function
before ordering. kirk company will most likely make you sign a letter acknowledging
that there are multiple keys in existence for a specific lock. you'll get the transfer station
with the keys locked in it. you won't be able to pull them all out at once to check stuff.
 
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