Emergency Stop Button
- Thread starter TheJay
- Start date
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Yes BAS, that's a switch-disconnector suitable for emergency switching off, that will achieve a category 0 emergency stop.
OK - fair enough.
I'm surprised that it qualifies as any category, given that it can be locked on.
What is it about these which means they are not emergency stop devices:
?
I'm surprised that it qualifies as any category, given that it can be locked on.
What is it about these which means they are not emergency stop devices:
?
Last edited:
Ah, I hadn't spotted that it can be locked on. That's a can of worms, not really addressed in standards. Occasionally someone proposes to ban devices that can be locked on, but then someone mentions ventilation, lighting, and other applications where it can be dangerous to switch something off.
I'm a bit puzzled by your remark about "qualifies as any category"; the stop categories are those defined in IEC 60204-1. Category 0 simply means stopping by removal of power, i.e. without any electrical braking.
I'm a bit puzzled by your remark about "qualifies as any category"; the stop categories are those defined in IEC 60204-1. Category 0 simply means stopping by removal of power, i.e. without any electrical braking.
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It's the "emergency" bit that I'm surprised about - really it should not be possible to lock any form of e-stop device on.
I agree that there are applications where turning off might cause danger. Ventilation could be either - in a fire you might well want to stop fans pumping/dragging air in/out PDQ - you're never going to get a one-size-fits-all. You might even, sadly, have to deliberately choose to endanger some people in order to save a larger number elsewhere.
But if a device is there because you might need an e-stop then to me it seems counter-intuitive that that device could be lockable. I would have thought the answer would be to separate the functions of emergency stopping and isolation for other reasons. Is there any reason, per se, why an emergency stop device should not have a break glass, as alarms often do?
I agree that there are applications where turning off might cause danger. Ventilation could be either - in a fire you might well want to stop fans pumping/dragging air in/out PDQ - you're never going to get a one-size-fits-all. You might even, sadly, have to deliberately choose to endanger some people in order to save a larger number elsewhere.
But if a device is there because you might need an e-stop then to me it seems counter-intuitive that that device could be lockable. I would have thought the answer would be to separate the functions of emergency stopping and isolation for other reasons. Is there any reason, per se, why an emergency stop device should not have a break glass, as alarms often do?
Remember that there are things that need to be turned on, or started, in an emergency, and perhaps locked on until that emergency has been dealt with. I agree that if the purpose of the device is for emergency stopping then it should not be lockable in the on position.
As for break-glass enclosures, they impede access to the device, and hence are not compliant to the Machinery Directive. Several studies have shown that people don't like breaking the glass, so they might not operate the device when they really should.
As for break-glass enclosures, they impede access to the device, and hence are not compliant to the Machinery Directive. Several studies have shown that people don't like breaking the glass, so they might not operate the device when they really should.
Anyway, back to the question - what actually is wrong/non-compliant with either of those NVR switches?
Why are they permitted in other potentially life/death situations, such as when someone needs to activate an alarm, or open an emergency exit?
Education education education.
I rather doubt that any amount of education would appreciably alter the way people react (or don't) 'in the heat of the moment' in the face of some sort of emergency.
Kind Regards, John
Those flap switches usually fail the latching tests, and always fail the robustness tests. They are just a hindrance to operating the stop button underneath them.
Activating an alarm is not usually a situation in which milliseconds count, stopping a machine can be.
As for education, if that worked we wouldn't need break-glass enclosures would we?
Activating an alarm is not usually a situation in which milliseconds count, stopping a machine can be.
As for education, if that worked we wouldn't need break-glass enclosures would we?
Ah - I thought those big round red bits were the buttons.
Where's the number for Specsavers?
I can't see it!
Under the big red thing and the yellow flap is usually a perfectly good magnetic motor starter.
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