Door Interlock Actuator - Safety Rated

Timeismoney08

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Jul 2012
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If I have a cell where the doors are monitored with a sufficient level of guarding, is it required to run the locking signal to the door on a safety controller or relay?

I was thinking as long as it is monitoring and nothing harms anyone during an immediate stop, the unlock signal could be sent via a PLC once I say everything is safe.

Is this the case? and if not, how would you recommend unlocking the doors?
 
Without knowing your machine, it does sound as that the door protects against dangerous movements.
It may be that it is enough to monitor the door with safety sensors, and shutdown the dangerous moving parts via a safety relay or a safety PLC.
But it may be necessasry to hold the door locked until the dangerous parts have come to a complete stop. In that case there must be an actively held lock via a safety relay or safety PLC.
The PLC can only be part of this for signalling to the user, or for interlocking for protection of the machine, but not for protecting humans against danger.

Anyway, someone must do a full risk assessment, decide safety categories, design the safety system accordingly, validate the achieved safety, and document the whole thing.
 
JesperMP said:
Without knowing your machine, it does sound as that the door protects against dangerous movements.
It may be that it is enough to monitor the door with safety sensors, and shutdown the dangerous moving parts via a safety relay or a safety PLC.
But it may be necessasry to hold the door locked until the dangerous parts have come to a complete stop. In that case there must be an actively held lock via a safety relay or safety PLC.
The PLC can only be part of this for signalling to the user, or for interlocking for protection of the machine, but not for protecting humans against danger.

Anyway, someone must do a full risk assessment, decide safety categories, design the safety system accordingly, validate the achieved safety, and document the whole thing.
Click to expand...

Correct, I was saying if the application was killed immediately, all control power was dropped immediately and everything was setup as if the cell could be protected with everything outside of the locking part, could we then send the signals to lock the door via a normal non-safety rated PLC.


Thanks for the replies!
 
The safety system have to do 2 things:
1. Remove/engage energy to the system via the safety relay.
2. Allow/disallow access to the dangerous area via the safety relay.
The safety relay takes care of both of these so that the wrong situation cannot happen.

There are much more to this, and I think you should get advice from someone who is proficient in safety, or you should get some training in safety.
If you design this and an accidence happens, you can get into serious trouble !
 
JesperMP said:
Without knowing your machine, it does sound as that the door protects against dangerous movements.
It may be that it is enough to monitor the door with safety sensors, and shutdown the dangerous moving parts via a safety relay or a safety PLC.
But it may be necessasry to hold the door locked until the dangerous parts have come to a complete stop. In that case there must be an actively held lock via a safety relay or safety PLC.
The PLC can only be part of this for signalling to the user, or for interlocking for protection of the machine, but not for protecting humans against danger.

Anyway, someone must do a full risk assessment, decide safety categories, design the safety system accordingly, validate the achieved safety, and document the whole thing.
Click to expand...

JesperMP said:
The safety system have to do 2 things:
1. Remove/engage energy to the system via the safety relay.
2. Allow/disallow access to the dangerous area via the safety relay.
The safety relay takes care of both of these so that the wrong situation cannot happen.

There are much more to this, and I think you should get advice from someone who is proficient in safety, or you should get some training in safety.
If you design this and an accidence happens, you can get into serious trouble !
Click to expand...


Understood and thank you!
 

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