Lockable Safety Switch

alexbeatle

Member
Join Date
Feb 2010
Location
San Francisco
Posts
188
Hello,

I'm looking to install a separate lockable cam switch in conjunction with the AB 440r-S13R2 relay to be used as part of the Estop Zone to the safety PLC. This will prevent people from using other Estops in the same zone for the lockout, forcing to lockout at the specific switch.

Is there a safety specific rating or NFPA70e compliance for such switch?

Thank you.
 
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Is this lockable switch for en E-stop function ?!
It sounds so the way you describe it:
This will prevent people from using other Estops in the same zone for the lockout, forcing to lockout at the specific switch.
If it is, you can definitely not do something to prevent people from using it.
A key for resetting the E-stop would be OK, but not for activating the E-stop.

Also the "for the lockout, forcing to lockout" sounds suspicious to me. An E-stop is not device for disconnecting energy sources ("lockout") before accessing a dangerous area for maintenance or the like.

What are you trying to achieve ? What is the problem you want to solve ?
 
Is this lockable switch for en E-stop function ?!
It sounds so the way you describe it:

If it is, you can definitely not do something to prevent people from using it.
A key for resetting the E-stop would be OK, but not for activating the E-stop.

Also the "for the lockout, forcing to lockout" sounds suspicious to me. An E-stop is not device for disconnecting energy sources ("lockout") before accessing a dangerous area for maintenance or the like.

What are you trying to achieve ? What is the problem you want to solve ?

I'm trying to create a lockout point for the moving equipment, but to keep the PLC and the +24VDC logic on for troubleshooting.

As for the "An E-stop is not device for disconnecting energy sources ("lockout") before accessing a dangerous area for maintenance or the like". Aren't safety cell gates part of the E-Stop zones, which can be locked-out?
 
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I worked a short stint in a paper converting plant and I was told to add lockable operators to some "e-stop" buttons. I told them it was stupid, after finding out that the "e-stop" buttons weren't even really safety relay inputs. They made me do it anyway. I did find lockable operators from Allen-Bradley, and installed them. I quit that job not long after that. They had operators using that as a lockout point to apply locks before performing adjustments to deadly pinch points on this machinery. Screw that. If you aren't locking out the main disconnect, it is not a lockout in any true sense.
 
Thats maintenance. LOTO procedure.
Local electrical and pneumatic padlockable disconnects.
You can keep control voltages on, as long as it cannot initiate any risks.
 
I worked a short stint in a paper converting plant and I was told to add lockable operators to some "e-stop" buttons. I told them it was stupid, after finding out that the "e-stop" buttons weren't even really safety relay inputs. They made me do it anyway. I did find lockable operators from Allen-Bradley, and installed them. I quit that job not long after that. They had operators using that as a lockout point to apply locks before performing adjustments to deadly pinch points on this machinery. Screw that. If you aren't locking out the main disconnect, it is not a lockout in any true sense.

My Estops are inputs to the GuardMaster circuitry, which drops the safety contractors (drops power to the motion actuators), leaving the PLC and the 24VDC on. Hence, no motion can occur during an EStop.

I'm looking to install something like this on my panel.:
https://www.awc-inc.com/a/datasheets/0000/0000/3058.pdf, which will be an input to a 440R — Guardmaster Safety Relay, which in turn will be part of the EStop zone.
 
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If you aren't locking out the main disconnect, it is not a lockout in any true sense.
Using the main disconnect is one way, but then you dont have 24V for troubleshooting as the OP requests.

We actually split the supply voltage before the main disconnect. So the control voltage has its own disconnect (and plenty signage everywhere). Exactly for the purpose of troubleshooting.
 
Sounds like just another attempt by production to minimize the amount of time it takes to safely lockout a machine. I do not know Canadian rules but I’m sure it would would be acceptable to OSHA.
 
My Estops are inputs to the GuardMaster circuitry, which drops the safety contractors (drops power to the motion actuators), leaving the PLC and the 24VDC on. Hence, no motion can occur during an EStop.

Still NOT a lockout.

You must not use an estop device in this way to remove hazardous energy [period--full stop].

Don't believe us? See Control of hazardous energy — Lockout and other methods. CSA Standard Z460.

Good article on the subject: machinerysafety101.com Using-e-stops-in-lockout-procedures.
 
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