line monitoring for ‘nc’ emergency push buttons

[murugappan]

We have requirement of line monitoring of Emergency pushbuttons connected to UCP. Please explan how the wirirng configuration will be

What toy of E pushbutton ( no of contacts 2NO +2NC) I need o buy ?

Regards

Ayyappan

 

[ScottyUK]

You need to buy the type specified by the qualified engineer who designed the emergency stop system. I wouldn't like to think my life depended on a safety system designed by someone who didn't know how to specify the correct switch for the purpose.

 

[murugappan]

My query is E -stop is connected in NC contact meaning it is fail safe. what is the other advantage of adding a line monitoring to a fail safe wiring ?
when there cable breakage the system will trip
Please see the attachment, one vendor suggested to use EOL and In line resistor to monitor, expert comments please

 

[controlnovice]

There is no attachment to your post...

If there are multiple causes that affect the system trip, a line monitor will help you or operations identify exactly what shut the system down.

So, if there are 68 items that can cause a system shutdown, you will know that it was the E-Stop that shut down the unit if it was pushed (or line break).

Assuming the line monitoring goes to a PLC/DCS that records history or a Sequence of Events recorder.....

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This is normally the space where people post something insightful.

 

[ScottyUK]

Have a look at the safety relays made by Pilz and others. These relays actively monitor the stop circuit to reduce the probability of a fail-to-danger situation. More sophisticated than an EoL resistor.

 

[roydm]

You have several pushbuttons. If the system shuts down how do you know which button it was?

If you use a button with 1 NC and 1 NO you can wire the NO contact back to the control panel and read it with an analog input or simple Voltmeter
One way I have seen on a 2 kilometer conveyor was to have a series resistor at each switch feeding one side of the NO switch with 1V, 2V, 3V, 4V etc when a switch was pulled by the Voltage feeding back the operator knew which switch was pulled, if 2 switches were pulled it would display the closest one first. A 4 core cable was used daisy chaining from switch to switch.

Of course if all your switches are close you can wire them all back to a common location and monitor them with a PLC inputs, whatever you do don't compromise the ability of the switches to interrupt the power to the safety shutoff device.

 

[murugappan]

Thanks all for sharing your ideas and views