Estop Circuit Reset

Is a series of 4 e stop mushroom pushbuttons a true estop if it does not reset and does not use a safety relay?
When any of these buttons are pushed the safety rated red allen Bradley contactor opens above the motors normal contactor.
Do all estop circuits have to have a reset circuit to be classified as a estop?

So are you saying that as soon as the e-stop pushbutton is pulled back out, the machine starts?

Not enough information.
Your circuit may reach category 1 or performance level c if it is set up properly. But only if setup properly.
Go to this web page:
http://www.dguv.de/ifa/en/pra/en13849/index.jsp#

Download this report:
BGIA Report 2/2008e

Read it and you will then be able to tell if your circuit is good enough for safety.

wire them all in series, and wire them to a master control relay. If any one is pushed, then the mcr opens and kills all control power. When you reset the e-stop, the system has to be restarted.

wire them all in series, and wire them to a master control relay. If any one is pushed, then the mcr opens and kills all control power. When you reset the e-stop, the system has to be restarted.

Click to expand...

And at best it will only be a category 1 system

You make it hard wired and added in your plc program. What do mean by a level 1 system?

Check out this PDF. Don't confuse the type of Stop with the category of the safety circuit.

A Category 1, while generally safe, can fail (and 'fail' means failure to stop the machine) if only one part fails to work as normal.

The whole point of safety is confidence that, once started, the machine can be stopped. The next point that it won't be allowed to start if any of the safety components are faulty.

You can't rely on components that, in order to turn off, depend on a spring. Springs break.

The higher categories are used as it is more possible that a machine can harm or kill an operator. Read carefully and take the examples to heart.

bernie_carlton said:

... The next point that it won't be allowed to start if any of the safety components are faulty...

Click to expand...

This is already a property of Category 4 safety system, not even of Category 3.

It depends upon your local legislation, here in the EU a E/Stop should have a positive locking action which in turn needs a positive action to reset it, automatic resets are,nt normally used for emergency stop circuits. so in essance, wired into a pilz unit with a reset circuit, unless it,s a safety plc you can,t wire them into there and use normal logic to control it !!

I,d do alot of reading upon on the subject purely because it,s safety and you could be dealing with somebodys life !!

Regards

JV

Tim Ganz said:

Is a series of 4 e stop mushroom pushbuttons a true estop if it does not reset and does not use a safety relay?
When any of these buttons are pushed the safety rated red allen Bradley contactor opens above the motors normal contactor.
Do all estop circuits have to have a reset circuit to be classified as a estop?

Click to expand...

the basic principle of a safety system is to protect people.
the level of protection is as per the PDF that Bernie has directed you to.
Depending on what category you need.
Consider your contactor - the red series is fine but what happens if the contracts weld closed - how do you stop the motor or drive system.
ask yourself questions
If someone could get cought - how badly (risk analisys)
If the E/stop button fails - how do you Know it has failed
If a contactor fails - what can you do.
Dont forget mechanical / stored energy (Hydraulics Pnuematics)

At the end of the day there are many specialists that will assist you with safety systems, they are also insured to do so.
this is a better approach.




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