Safety hardware or program

what kind of hardware or software would you use for long conveyor E-stops that was requested to install many locations along the conveyor?

how i can i reduce the wiring?

Would pull cord switches work?? Some of those support long cable lengths.

customer wanted E-stops

dani90 said:

customer wanted E-stops

Click to expand...

Not sure of code requirements in Canada.
However pull cords are probably the better option as they can be reached from both sides of the conveyor system and can be activated at any position.

If you use E-Stops they must be placed on either side of the conveyor at a maximum spacing of 6ft apart.

In either case a minimum requirement for the circuit should be a safety monitoring relay.

Should you choose the E-Stop route the IDEC tamper proof "safe break action" X series E-Stop PB's and safety monitoring relays are my go to product. IMHO extremely well designed and reliable.

There is no software that would satisfy safety requirement. Pull cords are appropriate for long conveyor.

What safety rating is your customer looking to achieve? You probably can't get Sil3/PLe if you Daisy chain all the estops together back to the safety relay.

Pull cord is "simpler" but if the customer wants estops, and you want to simplify wiring, then a safety PLC might be your friend here. That way you know which button has been pushed, instead just that one has, somewhere.

If you get something like the buttons below, then I think you just need to run 24v and Ethernet to each estop. The IO could communicate back over Profinet/Profisafe or EIP/CIP Safe (not supported by the link here)
http://w3.siemens.com/mcms/industri...Pages/default.aspx?tabcardname=emergency-stop

Or you can run the estops back to safety IO in an IO rack.

it amused me when l saw this, as in aust we call them lanyard switches (pull cord switches).
Amusing because what do your bosses expect along a conveyor, 1 -stop every 5 feet.
Show the boss how stupid he is then take his job.
But then if you need this advise l think you both need the sack.
Go the gaqunter

dani90,

you must do the following.

1. define what are the safety requirements in Canada?
2. detail your conveyor from end to end.
how many conveyor sections, how many e-stops, are e-stops on both sides and wired in series?
3. get with management, engineering, safety, maintenance, and operators to discuss the project and how the system will work.
4. Do a risk assessment.

depending on your answers, you may be able to use a safety plc for e-stops and interface it with the production plc.

for example.
lets say there is 50 e-stops.
at e-stop 30, someone pulls the e-stop cord.
stations 1-29 stop after current operation is complete and do not move.
stations where the e-stop was pulled stop immediately.
stations associated with estops 31-50 keep running.
correct the issue at estop 30 and reset the system
press the system reset / restart.

this is what we did several years ago.
james

It pains me to say this (bad experiences V1.0) but Asi Safe is ideal for conveyors.

Nick

A pull-cord is an emergency stop, and one that is suited to the application.
Because a pullcord covers a longer section it by itself reduces your wiring.
We do use pull-cords for all conveyors. I do believe that customers expect there to be pull-cords.
I have never before heard that someone demand buttons instead of pullcords. Maybe your customers only know bad installations of pullcords, where the line was slack and difficult to activate. Modern pullcords cannot be slack, they activate also if the wire is not tightened to the the correct level.

One thing that can decide the matter is if there are specific safety standards for your area of business (f.ex. mining, food, foundries, whatever..). If there is, you can present the standard and say that it is not up to a customer to decide, unless they want to bypass the standard.

Pull cords can also have a two in one functionality depending on installation. They can be an e-stop and a barrier for people to stay away from moving equipment.