Trapped Keys are a great way to safely secure your systems -- especially if you don't want
to spend the time, effort and money on wiring up a bunch of electronic interlocks.
Trapped Keys eliminate the need for all of that hassle.
And they're simple.
When you pull the key out, it deactivates the contact module below it which you could
use to turn a machine off.
You then take that key down to where ever the gate is and insert it into the mating
module which releases this gate actuator so you can pull the gate slider out.
The cool thing about this is I didn't have to run any wires to the gate -- did I?
This guy is purely mechanical.
If I take it apart you can see that the modules are mechanically coupled by these interlocking
fingers.
So that means the remote gate can now be a few feet away, a hundred yards away, or even
a few buildings away from the main stations electrical panel . Since we don't have to
spend money, time and effort running wires, it can be anywhere!
And no one can restart the system until we latch this gate, which releases the key below
it, and return the key to the main station which activates the contacts below it, so
the system can now start back up.
And since this is modular, I can just keep adding modules like this.
Now multiple people can pull these keys to go work on different parts of the system and
everybody is safe because the system can't be re-started until ALL the keys are returned
to the main station which activates the contacts which re-starts the system.
By the way, this is important to understand.
Keys are always removed from bottom to top, this one, then this one, then this one ... and
returned from top to bottom.
A lower module always activates the module above it.
Suppose we repeat the previous example: take this key from the main station and insert
it into this remote door station key module to release the gate slider so we can safely
enter the secured area -- well, what's to keep someone - who doesn't know any better
- from walking by after I have entered the secured area and pushing the slider back in,
removing the key and putting it back in the main station and re-starting the system -- with
me still in the secured area?
That would be a huge safety issue.
Can we prevent it?
Sure.
We just insert a Padlock module here at the door station.
Now you pull the key to release the contacts, insert it here which releases the padlock
module above it.
You pull the padlock key out which reveals a hole where you can put a padlock -- that
releases the gate latch.
Now, as long as you have the padlock key with you, no one can pull this key and use it to
restart the system.
Inserting the gate latch releases the padlock module.
Removing the padlock and pushing the key back in releases the gate key which then goes back
to the main station so we can restart the system without any risk of someone being left
in the cage.
There is also a Safety Key version of this.
It does the exact same thing, but the key isn't captive -- you take the key with you.
It saves you the trouble of having to keep track of a padlock.
But it's the same end result -- as long as you have the safety key with you -- no one
can pull this key to restart the system.
Putting the gate latch back to release the safety key module.
Insert the safety key and now we can take the gate key back to the main station so we
can re-start the system.
Again, without any risk of someone being left in the cage.
This optional Safety Key module is identified by "C" serial numbers to remind you it's different
- he doesn't have a mating module, contacts or a gate actuator -- it's just a single module
and a single key.
The regular Gate Keys have "A" serial numbers and come in matched pairs.
One module you pull the key out to lockout the module below it and activate the module
above it, the mate for this is just the opposite, you push the key IN to activate the module
above it and lockout any module below it.
The first one is called a '01' module, the second one is a "10" module.
I like to think of it as OI and IO where the first letter tells me how to activate the
module.
This one I pull the key Out to activate the module above and this one I push the Key IN
to activate the module above.
The modules look identical, so look for the code on the side to tell the difference.
What if you need to limit access to the main station's electrical panel -- maybe it's in
a secure control room that only limited personnel have access to and you want the gate keys
down on the shop floor near the machine where everybody can use them.
That's where this optional key module set comes in handy.
It's just a key module pair with no gate actuator or contact modules.
You put the 01 module here and the 10 module here so pulling this key shuts down the system,
and inserting the key here releases the gate keys.
This module set has "B" serial numbers on the keys to remind you it's different.
And since B serial numbered keys are not compatible with the "A" serial numbered gate keys, this
guy can't be used to bypass the key transfer station and open the gates.
He can only be used with his mate to release the keys here.
And of course that special B key can't be removed until all the keys in the system have
been returned from top to bottom.
This special Key Module set can also be used to sequence gate opening.
We just put the 01 module here and its mate down at the next gate with an extra gate module.
Now, this gate slider module releases the key module above it which you can now carry
down to its mate at the next station to release that gate.
That's cool because it forces us to open gates sequentially -- again without the need for
fancy wiring or electronic interlocking.
Could you do that again?
Yep.
You can string these along as many as you want.
And there's no penalty for the number you use or the distance covered, because there
is no expensive wiring connecting them all together.
This contact module we have been using in these examples releases the contacts when
the key above it is pulled.
What if we don't want the key released until commanded to do so.
Maybe we need to wait for a machine to spin down or stop moving before allowing access.
Is there a way to do that?
Of course!
Instead of a contact module at the main station, we use a solenoid version.
Now this key can't be extracted until something like a PLC, a safety relay or even a manual
switch provides 24 volts to deactivate the solenoid.
You can now pull the key above it, and the one above that just like before.
The Solenoid contact module has a manual override just in case you need access during a power
outage.
Just take a pair of needle nose pliers and rotate this guy to the Override position to
move the solenoid interlock out of the way.
These gate key sets are available in 1, 2, 3, 4, or 5 gate sets, with regular contacts,
or with contacts with a solenoid interlock.
And whether you use them in parallel or sequentially or even a mix of the two, it all avoids the
hassle and expense of wiring and maintaining a bunch of electronic interlocks.
And remember -- since these are mechanical, they aren't bothered by things that typically
give electronic sensors trouble: temperature swings, noise, dirt, fog, steam, moisture,
etc.
Not a problem for trapped keys.
The bottom line is Trapped keys are: Secure, Durable, Reliable, Easy to install and maintain,
you don't need to install or maintain expensive wiring and they are incredibly flexible and
adaptable to help you meet your safety needs.
Please keep in mind ... safety is up to you and how you use these things will determine
how safe your system is.
Hopefully this little primer video will give you a better understanding of your options.
Check out the companion Trapped Keys helpful hints video for details on how to install
these and some other helpful hints and tricks that will make your life easier.
As always, if you have any questions at all, please contact AutomationDirect's free award
winning technical support -- they will be happy to help you out.