Seeking idea on long E-Stop Chain

[rsdoran]

You can use the cable type and run it 50-100 feet with no problems, and series several for the 300 feet you mentioned. Try to keep them in line of sight i.e. after any turns place on separate system. This method would mean 4-6 actual estops with an indicator light to specify which has been used.

Safety monitoring may be necessary but I believe estops should be maintained for 2 reasons. First, someone needs to look at the area the estop was engaged to determine why, an operator is not the only that may activate an estop; ex: forklift driver sees jamm on conveyor, hits estop gets back on lift and drives off.

Second, an estop should never reset a system; therefore the person that will be starting the system should know when it is appropriate to do so i.e. should know where it was estopped and why, verify manual reset then restart system.

Just my thoughts.

I think Steve was thinking the same way I would, using spring return type Stops can allow the system to either start on its own or allow an operator to restart without determining why it was stopped.

 

[Rich1955]

using spring return type Stops can allow the system to either start on its own or allow an operator to restart without determining why it was stopped.[/QUOTE]


I would not like to have my fingers in there if someone else could start it back up that could not see me.

 

[JohnW]

We are doing a conveyor job at the moment, 28 conveyors each between 30 and 150 metres long total site length about 500 metres. We are using Guardlogix PLCs and safety devicenet modules. A total of 128 e-stops. Each one is connected to a devicenet module 1791DS IB12 and they are linked back on devicenet to one of 2 Guardlogix PLCs The PLCs will stop the conveyors using safety devicenet output modules and send indication to SCADA as to which e-stop push has operated. The PLCs have safety rated communication over Ethernet.

 

[stevebec]

How about adding a NO contact and voltage divider pair of resistors to each e-stop and feeding all of them into a 1 wire bus connected to an analog input on the PLC. If each voltage divider is different, then the input voltage to the PLC uniquely identifies the stop that was pushed.

 

[russrmartin]

Rich's solution is the best

Rich's first solution is the best, I'm positive your manager will agree. For the price of a few estop switches, you can have a lighted Estop PB, which is perfect. I'm sure you have regulatory E-stop Pm's, and noting that the light is functional when pressed simply becomes part of the PM. A second contact is nice if you want to soft interlock the string, but it's a cost that I doubt management will want to pay for.

Russ

 

[jimtech67]

you could add contacts to each e-stop button. Instead of having every single aux contact go to the PLC, batch them together.

Connect about 5 aux contacts in series. When an e-stop button is pressed you will know which section to look in.

 

[brucechase]

Rich's first solution is the best, I'm positive your manager will agree. For the price of a few estop switches, you can have a lighted Estop PB, which is perfect. I'm sure you have regulatory E-stop Pm's, and noting that the light is functional when pressed simply becomes part of the PM. A second contact is nice if you want to soft interlock the string, but it's a cost that I doubt management will want to pay for.

Russ

With this solution, if the existing system only uses a contact from the e-stop back to the relay, then to get a lighted e-stop, you will still have to pull some wires. If you are going to pull wires and your risk assesment mandates a safety e-stop, then the only solution is to use 2 sets of contacts from the e-stop back to your safety relay and then an auxiliary set for either plc indication or a mounted light.