Wiring Up 7 Emergency Stops on a Conveyor

Yeah we took off the wires on the PLC, and they keep running I was thinking. Then I thought, it can be that they either didn't activate either the input or the output for the stoppers as well. I would think they would need some kind of activation in the ladder. I do know how to check the program some, but the only computer with the software on it is in Chinese lol; working on getting one in English.
 
Without the ladder or Logic drawing of the plc controls it is not possible to properly assess what is not working.

I have to say that my own experience has been that true "emergency stops" are not simply a plc input, but system over-rides that "stop" the system safely.

What you seem to have is a series of local stop switches, more properly classified as operator start/stops. They do not appear to be "man-safe" emergency stops.
 
Hey Greg,

Something a little odd about the whole section not working. Could it be as simple as a control cable not plugged in to join sections? Just thought i would throw it out there.
 
Yeah we looked into that; wasn't it.

>Something a little odd about the whole section not working.
>Could it be as simple as a control cable not plugged in to
>join sections? Just thought i would throw it out there.
 
Man not sure how I didn't see this before. I was looking at the diagram and noticed that this schematic is for the rack and not the conveyor. So they sent me the wrong one. Another thing is most of these new lines the stops were never connected in the control box. The cables are run there, but they are just not connected to anything. And the one that was connected to the PLC, the PLC for the numbers 22/23 screws are not lighting up at all like the other old lines are.
 
So this conveyor has been running for 2-3 years and its ES suddenly doesn't work or never work? I can see 2x 3series of ES there, so which one works?

Assuming this is 24VDC ES, for now you can check each ES first by push and release each one of them (will the open/close status changed or not).

if it is working properly, then check your looped connection from/to PLC IO module (means you check 2 groups of 3series ES signal to PLC). if it is also working properly, then check your PLC program (does the signal comes or not. I assume this chain of ESs never work if there is something wrong with the program, unless someone force the IO value and forgot to normalize it).

And also get a PLC guy to check this one.
 
Yeah hasn't worked since they installed, the lines but we have a new manager and he wants them all working. I saw that all but one line were never hooked up. they ran all the cables from the E.STOPS to the control box, but all they did was tie the cable back in the box never connected them to anything. Like I said before this is still new to me haven't done much with the electrical side of it.
 
Well I appreciate you guys taking the time to help me but from what we found out was the program needs to be changed in order for them to work right. They are going to call in a programmer to fix the program.
 
Hi Greg

Sounds like a good idea, hopefully he is local. You can get a local technician to correct your problem for less cost in many different ways. However, since it is a Safety circuit your issue needs to be carefully assessed and properly corrected. Good luck Sir, hope it works out for you.
 
Hi Greg

Haven't seen a follow-up on your problem and I've been off-line for a while, so I'll throw my hat in the ring...

Short of a safety PLC or safety relay, your e-stops MUST be hard-wired. This means directly interrupting your motor control circuit. If you want any button to shut off all motors, your two strings of three must be wired as one string of six. Not knowing how your motors are wired is an issue for me. If they're cascading, stopping the first will stop them all IF there are no parallel start signals.

If you want your PLC to monitor your e-stops individually, you can add a 2nd dry contact to each button and have each button as an individual indicator of an e-stop condition.

Hope this helps...
BillyMac
 
Yeah we had to swap some weirs around, add a few relays, and adjust the program a bit to get it in order. Thanks for everyone's help it has been resolved.
 
When installing the E-Stop Safety Chain it is important to install a dual circuit that terminates at a Safety Relay or a Safety Controller such as the type manufactured by Banner. Having two circuits, run in series and running through all of the associated E-Stop switches with both contacts in the switch in a normally closed state, the ability to stop the conveyor safely as well as being in compliance with OSHA are both met. The PLC cannot be used as a safety device but can be used to monitor the status of the safety device (safety relay such as a Allen Bradley MSR127T in combination with a Banner IM-T-9A Interface module) by programming the PLC to report when the E-Stop circuit(s) have been disrupted.
 
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