E-Stop & Safety Relay Question

We have a line of equipment where half of it is controlled from one control panel and half from a second control panel. We will have an e-stop in each panel and then a couple a each end of the line. We typically just keep the e-tops separate but I would like to tie them in together so that any e-stop would stop the whole line and not just half of it. We also want to be able to run half the line if the other half is shut down for maintenance.

Is there a good/recommended way to do this? I was thinking about having a safety relay in each cabinet and then have two sets of contacts on each e-stop - set for each safety relay and all four e-tops would be wired in series to the safety relays. Then any of the 4 e-stops would drop out both safety relays. Seems like maybe there is a better way though.

you could do a single relay, and have the E-Stops tied in series with the coil


using the other set of contacts from each, tie this back into the controls to indicate which stop is made, either through a plc/hmi or some indicator lights that the operators can see relatively easy

The hitch I see in the plan is that if you want to be able to run each half separately then Scott's plan runs into the issue when you shut down power (assuming you lock out for maintenance) to the half with the relay in it that the other half goes down with an e-stop.

Your solution would work (if you only need a single channel e-stop chain). My concern is how do you prevent 'old timers' from hitting the e-stop on the side they are doing maintenance "just to be sure it won't move."

I don't remember coming across a preferred method for doing this.

You may need to check your regulations - I'm not familiar with them but over here the following is one of the requirements :-


The emergency stop function must be available and operational at all times, regardless of the operating mode.


This would seem to preclude tying the E-stops from two sections together but then expecting to seperate them functionally for maintenance on 1 section .
Paul

my two cents.
What you are suggesting is not allowed with a control relay, interlocking relay.
You have a SINGLE assembly line split into 2 control systems due to the size (i'm assuming this). they should already be tied together if they are to run as a single line. when you tie the lines together with safety relay, they both run or they both stop. No running 1/2 while the other is down for maintenance.
lots of risk assessments and planning here for this to work.

What you might be able to do is use a safety plc and have it programmed.
my project had multiple stations. any error upstream of the fault would stop
and allow anything downstream, to keep running.

you will have to check with your state, local, company safety guys.
regards,
james