Solution for Trapped Key Safety Upgrade

[mc62182]

HI guys I wanted to get some ideas. I am trying to figure out a way to lock out a machine with a trapped key setup that isolates power and drops out an MSR then only unlocks the doors when the key is removed then also somehow requires the operator to take the key without using an exchange station. The customer does not want to make the operator walk around to an exchange station but still ensure the key is a requirement to unlock the machine.

I have read alot of manufacturer info but don't think this is a possibility as the trapped key when turned off and removed would need a set of contacts or some other means to initiate a door unlock signal.

Any ideas?

 

[keshik]

I would take a look at the Fortress Interlocks mGard stuff. http://www.fortressinterlocks.com/ProductRange/2 You can connect the exchange station right to the guard door bolt.

 

[mc62182]

Thanks, I have used the Fortress before but the customer is asking for no exchange station and only wants the one key on the HMI panel. I really don't know if it can be done the way it has been proposed.

The 440T AB rotary switches can isolate power but there is no requirement to remove the key unless you have an exchange station as mentioned.

Any good ideas with other relays or switches to the circuit? I'm just trying to think outside the proverbial box here.

 

[cjd1965]

Hi I am unclear of your exact needs but I would

1. Stick to certified devices (cover your a$$)
2. Call a vendor such as fortress, if they don't make it, it is unlikely it is available
3 Does the customer have a similar set up at their plant you can go and look at?
4 Just because someone asks for a solution it doesn't mean it is the best or safest one

Good Luck

 

[ianingram]

The customer does not want to make the operator walk around to an exchange station but still ensure the key is a requirement to unlock the machine.

Any ideas?

You don't have to have an exchange station.
You can exchange the key at the gate entry point

The "A" key is at the operator control station (key switch), the "B" key is removed at the gate entry lock

Does this picture help?

 

[ianingram]

The 440T AB rotary switches can isolate power but there is no requirement to remove the key unless you have an exchange station as mentioned.

Its true that the B key does not have to be removed BUT it does have to be rotated to unlock the gate.

If the operator does not remove the key, then isn't that just a training/procedure issue

 

[Timbert]

Something doesn't sound right.

Let's say you use solenoids to unlock access if the key is turned. If the operator is the only person working on the equipment, then wouldn't they have to walk around the machine even if a key is not required to unlock the door? So, they wouldn't be saving any effort there.

Now, if more than one person is working on it. It would save walking around the machine. Of course doing so would be very dangerous because the person exposing themselves to danger isn't in control of the equipment.

It comes back to the hazard analysis. You could have the trapped key both disable power and unlock the doors. But know you have to consider what if the operator doesn't take the key and someone else comes along. If you force the operator to take the key that isn't an issue.

The weakest link is always the operator maintaining sole control of the key.

 

[kiwi sparky]

Use the spring loaded ejector keys
http://www.ab.com/en/epub/catalogs/3377539/5866177/3377559/6387374/5189323/Accessories.html
When they turn key to isolate safety the key pops out in your hand forcing you to take it with you. Use auxiliary contacts on trapped key to unlock solenoids on gates

 

[Timbert]

Use the spring loaded ejector keys
http://www.ab.com/en/epub/catalogs/3377539/5866177/3377559/6387374/5189323/Accessories.html
When they turn key to isolate safety the key pops out in your hand forcing you to take it with you. Use auxiliary contacts on trapped key to unlock solenoids on gates

Thanks, Sparky, I thought they made spring-ejectors for them I was looking at the lock side for the spring, not on the key itself. Doh!