Safety Rated Keyswitch ? Safety Gate Application ?

[milmat1]

Folks,
Do you know of a safety rated key switch ? Not the big key disconnect switches, but a switch that will simply provide an input to my safety controller.

I have a machine safety application where we have several safety gates at entry points. Beyond the standard gate switch and locking mechanism, we need to add the system described here:


After an entry request is initialized using a push button, and we unlock the gate. We want up to 4 "Keys" that each person entering the area will take with them. These keys can be a key from an actual key switch (safety rated). Or coded magnet sensor or even RFID.

The requirement is that all 4 "keys" (pucks) must be returned to the interchange unit before the safety system can be reset.

I cannot find a simple key switch that is safety rated, other than the large high current shutoff switches.


Anyone have experience with this type of entry system ?

 

[the_msp]

https://www.castell.com/product/x/

 

[the_msp]

https://www.castell.com/product/ks/

 

[parky]

Yes castell, the idea is as you require there is a master station where all keys are kept, this contains one key that operates the safety, when turned off it releases the other keys there are many combinations that could be used for example perhaps one interlock but many access points i.e. vessels all keys have to be returned to the master station before it can be enabled. or in the case of seperate areas i.e. two master stations etc. no keys should be able to interchange, the "slave" keys if you like can only be released when the master is unlocked this cannot be locked again until all keys have been returned & set to correct Locked mode. If that makes sense.

 

[dogleg43]

AB, Telemecanique, and most other vendors make them.

 

[parky]

@ Dogleg, those are not returnable types like the OP requested, it seems apparent that the castel type multiple key is the type the OP needs, When I was in the game these were rather chuncky tho.
The trapped key are the ones that I think are needed, the reason for them being reasonably large is the nature of their robustness, should be ideal for the US market as most equipment I have worked on is twice as large as we find in Europe & I have worked on a lot from the US.

 

[dogleg43]

@ Dogleg, those are not returnable types like the OP requested, it seems apparent that the castel type multiple key is the type the OP needs, When I was in the game these were rather chuncky tho.
The trapped key are the ones that I think are needed, the reason for them being reasonably large is the nature of their robustness, should be ideal for the US market as most equipment I have worked on is twice as large as we find in Europe & I have worked on a lot from the US.

Ok, thanks for the info. Learn something every day.

 

[JordanCClark]

AB's version is the trapped key.

https://www.rockwellautomation.com/...-switches/trapped-key-interlock-switches.html

 

[dogleg43]

Just curious, as I’ve not known about this type of guard switch before. What are examples of machines or processes that would require this type of protection?

Why only 4 keys? How do you keep a 5th or 6th person from being involved?

I did a lot of safety work over the years so this application really intrigues me. Thanks in advance for anyone’s insight.

 

[parky]

If you are talking about the Castel system an example is a project I did in the 90's it was 5 batching tanks plus a set of 3 CIP tanks. there were two castel systems so I will only describe the main batching.
There were 5 if you like slave keys the castel interlock was the 5 keys plus the master key, the five keys need to be inserted & turned this then mechanically allowed the master key in the bank to be turned on thus enabling the safety system. the only way for a key to be released was to switch the master key to the off position, this de-energised the safeties so the plant was safe to work on.
Each of the 5 keys (all are coded so & stamped) cannot be placed in any other position, the operator/engineer would operate the master key to the off position (note: if I remember correctly the master key even in the off position cnnot be removed) and then twist the required key to release it, then they could use that key to unlock the guard/tank access hatch or guard. once opened then this key is trapped so cannot be removed, when the guard/hatch is closed & locked (notice these slave key locks do not have any electrical connection to the controls) so they were in this case purley mechanical, when locked the key is released & put back in the castel lock array this enables the master key that can be switched back on to enable the safeties.
Before people start about how do you know which one is open there was an sensor (in our case magnetic safety switch did not have to be but it was a standard) to indicate the gate/hatch was open.
I I believe these keys are unique so it is impossible to swap or use another key, it means that any access to safety controlled areas can only be done in the above manner. In the plant above it allowed more than one operator to open a safety guard/hatch.
I have seen systems tht contained more than one bank so that each area could be isolated.
The only downfall is if a key is lost then you either need to replace the whole lot with a spare system if you have one or order a new one by giving the supplier the original order spec but I presume this new unit wouls then have different unique keys so that should someone try to use a key off the old system it will not work.

 

[Puddle]

We have a few machines with this type of key system. Some of them are very old (1970ish) and had no safety at all as part of the original design and look as though they were designed to run from an overhead leather belt. Some of the pulleys actually still use leather belts to allow it to slip if the machine jams.
They've since had guards fitted around the entire machine, but I don't think there's even a safety relay in the panel. The machine must be stopped for more than one minute to release the keys and the keys are locked into the guard once opened. This means that the machine must be stationary before a guard can be opened and cannot be restarted until all guards are closed. The keys are not individually unique, but the pattern is unique to the machine which means you can't take another key and run the machine with a guard open, like you can with the Guardmaster switches.

 

[parky]

I think it depends on how you order the system if keys are individual, as I say it was in the 90's and the blue chip company I was working for spare no exspense when implementing projects so perhaps the individual key pattern may be a special build for them, Because they are 90% mechanical & only contain one form of safety electrical isolation i.e. positive guided contacts on the master key makes them ideal in a area that could contain a lot of water or steam etc. again the normal "BOX" for the keys is probably painted steel but in this case it was stainless each key had a tag and etched tag on the key position as well as on the mechanical interlock of the guards/vessel lids so it was almost idiot proof.
I don't know if the interlock was a special for them or it had extra metal tab done by the installers so that the AB safety type magnetic switch only became true once the interlock on that tank had been locked, this was to ensure that the PLC system could indicate it had been locked.

 

[slp530]

https://fortress-safety.com/

 

[JankyPLC]

We also use Fortress Keys, as do many of the vendors who we've bought equipment from and have had good success. Sounds like they do sell what you need.

 

[dogleg43]

I am trying to process the information here about why this is needed and don’t really get it yet.Is this an overkill by OSHA and safety departments?

Am I correct that part of the idea is that 4 or 5 people (or steps) have to be in agreement for the process to continue or the machine to cycle.