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difference between stop and emergency stop

Thread Starter: RAJKIRAN Started: 5/15/2012 2:28 PM Replies: 11

5/15/2012, 2:28 PM

RAJKIRAN

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Dear Expert,

what is the main difference between stop and emergency stop ?

also what are other stop we can use in logic?

Rajkiran Patil

Executive Project Eng r.- Process Automation

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5/15/2012, 2:36 PM

AMAZINGAHMED

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If we are talking about machines here, then emergency stop means that everything has to stop immediately (motors,valve,etc..)

Stop means that the machine should stop in sequence, or stop in zero position to be ready to start again immediately on pressing start button

The more you know, The more you know you don't know

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5/15/2012, 2:45 PM

Ayman Elotaify

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RAJKIRAN wrote:

Dear Expert,

what is the main difference between stop and emergency stop ?

also what are other stop we can use in logic?

Hello,

A very general question which I expect you will recieve a hill of answers about it.

Stop signal or Stop Pushbutton:

It is a command which should be executed in the system at normal operation.

Emergency Stop signal or Emergency Stop Pushbutton:

It is a command which should be executed in the system at ab-normal operation.

There are some conditions should be fullfilled in order to make a standard stop or Emergency stop signals like type of contacts, accessability of emergency stop buttons to maintanance personnel, it should have attractive colors (Red+Yellow) to attract the eyes to it, It should not cleared easily (i.e. may need to rotate the button or may need a key to re-run machine again ...etc.

Here's a useful white paper about emergency stop:

http://www.eao.com/global/en/Catalogues/whitepaper/EAO_E-Stops_White_Paper.pdf

Hope it helps.

=== Edited by Ayman Elotaify @ 5/15/2012 2:48 PM [GMT ] ===

Ayman Elotaify
MISC Egypt
www.miscegypt.com

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5/15/2012, 2:59 PM

Amit_86

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Hello Rajkiran,

I think Google is the best to search answer of those question.

Here in Step7 if you create the Thread then it of no mean.

Well,

Step7 doesnot understand/Care of those Signals.

it understand only 0 or 1.

But yet i found something for you.

www.eao.com/global/en/Catalogues/.../EAO_BR_Emergency_stop_EN.pdf

Check it out there.

=== Edited by Amit_86 @ 5/15/2012 3:02 PM [GMT ] ===
My internet is too slow

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5/15/2012, 3:15 PM

manmeet

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Its upto you (or operational people) to define it. Once the defination is created you just need to programme it. There is no standards as to what is stop and what is E.stop and how shall you programm it.

Generally E.stop sonditions shouldn't be programmed (though you can withdraw your outputs) that is E.stop conditions shall not depend on PLC logic. E.Stop conditions shall be hard wired, withdraw power from everything.

On lighter side:

Stop is like: Walking out of a Mall through normal (general purpose) door.

E.Stop like: Running out of Mall through Emergency Exit.

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5/15/2012, 4:04 PM

Marko Bursic

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Look for new standards EN ISO 13849-1 and EN/IEC 62061.
Each machine has to be equiped with stop that really disables the machine and prevents from starting again, this is so called emergency stop. We do use safety modules that are certified for monitoring and activation of E-stop, this can't be done with normal PLC, except with those that are safety PLC. In our applications we do use cascade delayed emergency stop, when the operator pushes red mushroom the process stops, servo motors and others are decelerating with quick stop ramp, then all the drives are disconnected from main power supply.

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5/15/2012, 5:56 PM

Mike J

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Amit_86 wrote:

I think Google is the best to search answer of those question.

Hi Amit

I think Google is the worst place. He has to ask the customer or the process/machine/system responsible what are the definitions and what does Stop and Emergency Stop means/requires

By the examples from the colleagues, even an Emergency Stop must follow some requirements. For exemple, for a generator you cannot simply switch the excitation off.

Mike J

Energy Automation products: Sicam, Siprotec, Digsi

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5/15/2012, 6:04 PM

Aret

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Regular stop is normal procedure as stated above. It allows (like a start) to operate machine.

Emergency stop bears defensive role - it should protect people from injury and equipment from breaking. In my practice E stop can be done with PLC. The reason is - E stop is also a sequence of actions. Generally you can't cut off power supply of all actuators and say "Now it's safe". What you really need - stop safely as fast as possible. But safety is priority. E stops can be also divided into classes - "clean" allows you to stop without any damage, but if this one is not fast enough you may bump into more strict defense sequence, thus decreasing stop time, but allow some equipment damage.

Overall E.Stop should provide minimum damage (not necessary no damage). Sequence should be provided by machine manufacturer and industry standards (which are different in different countries).

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5/15/2012, 7:14 PM

Marcjan

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Hello,

The only right answer you can get from your local safety regulations (if there are, have seen places where they don't seem to care about safety).
There are a lot off answers writen here that are through, but even in Europe where all regulations should be the same, are diferences.

So find loccaly the rules about machine safety and you know.

Regards,

Marcjan

Problem solved?
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5/31/2012, 10:04 PM

Marko Bursic

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Aret wrote:

Regular stop is normal procedure as stated above. It allows (like a start) to operate machine.

Overall E.Stop should provide minimum damage (not necessary no damage). Sequence should be provided by machine manufacturer and industry standards (which are different in different countries).

For my opinion, you may not use regular PLC, however with delayed E-Stop you can do everything you want with plc sequence as safety module will disconnect drives no matter if your sequence has finished or not, you set delay time on module such that is bigger then your stop sequence, and then cut-off.

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