Safety ESTOP Circuits

[j13s]

Hello,
Should ESTOP circuits de-energise the control circuit or the power circuit to a motor?
I want to put multiple ESTOPs to a safety relay which will not allow actuation of the motor. I am leaning towards the power circuit being de-energised but am wondering if it it safety-rated to do as part of the control circuit. Please advise.
Thanks and stay safe.

 

[JesperMP]

The safety relay shall definitely cut off the power to the motor.
The question is if it is enough with a single contactor being disconnected.
If the risk or injury is severe enough, then double contactors with feedback to the safety relay may be required.

When doing risk assessments and chosing risk avoidance method according to EN ISO 13849-1, then you calculate a Performance Level required (PLr) that the safety system must achieve.
For example PLr=c is the highest level with a single contactor but with diagnostics.
PLr=d is the next level with redundant contactors, and PLr=e is the highest level with redundant contactors and diagnostics at such a high level that it will catch any perceivable hardware error.

I always say this when such questions pop up:
Whenever safety is involved, do not dabble with it without the responsibilities being defined, and in particular your own responsibility in writing. If you have any part of the responsibility, then you need to be acquainted with safety standards and methods.
If an accident happens, you can get in serious trouble when all fingers are pointing at you.

 

[j13s]

Thank you very much.

 

[PLCnovice61]

This is the classic what should l do, as jesperMp advised but different standards may be applicable.
The big thing is it an "emergency stop" or just a "stop" that is the major difference.
People make the major mistake of insisting a "EStop" when realistically it should be just a stop.

Read up in the Aust standards what you need re Estop, or just a normal top.

Estops are way over said and in most cases aren't required, but if they are by standards needed, you need to know how to wire them correctly to put them in.

Normal PLC's as a basic input/control aren't allowed if you call it an "emergency stop, EStop" you need hard wired control maybe via a safety controller/PLC.

After re reading, l see you have a safety relay lets hope that's what it is and hopefully you have proved it is working.
But by the side, please take no notice what l or anyone here says,
" READ THE APPLICABLE AUSTRALIAN STANDARD REGARDING WHAT IS REQUIRED AND FOLLOW THAT TO THE LETTERT" now if you do that you can't be wrong.

 

[jdbrandt]

This is the classic what should l do, as jesperMp advised but different standards may be applicable.
The big thing is it an "emergency stop" or just a "stop" that is the major difference.
People make the major mistake of insisting a "EStop" when realistically it should be just a stop.

Read up in the Aust standards what you need re Estop, or just a normal top.

Estops are way over said and in most cases aren't required, but if they are by standards needed, you need to know how to wire them correctly to put them in.

Normal PLC's as a basic input/control aren't allowed if you call it an "emergency stop, EStop" you need hard wired control maybe via a safety controller/PLC.

After re reading, l see you have a safety relay lets hope that's what it is and hopefully you have proved it is working.
But by the side, please take no notice what l or anyone here says,
" READ THE APPLICABLE AUSTRALIAN STANDARD REGARDING WHAT IS REQUIRED AND FOLLOW THAT TO THE LETTERT" now if you do that you can't be wrong.

+1 to that.
An internet message board is the most wrong place to learn about ESTOPS ... not counting GOOGLE Searches.