Centralized MCC Rooms, Network controlled Motors and Emergency Stop Circuits

Curious to everyone's approach when using motors that are controlled over a network versus traditional hard-wiring. I'm more of a software guy, but certainly want to understand proper E-stop design considerations.

For stand-alone equipment, I think it's pretty simplistic. E-Stops on your machine shuts everything down. But I work in the world of large processing plants where everything is integrated and everything is spread out over large areas. Now that MCCs are being networked(well the popularity of Ethernet/IP is rising), you no longer can drop the control signal to the motor from within the local control panel where the E-Stop is located. So it seems to me you need to extend your E-stop circuit over some large distances to properly integrate it into the centralize MCC areas. Of course, the motors in an MCC center can be part of different PLC systems/E-stop circuits so it seems you would have an inter-wearing of E-stop circuits routed within the MCC to properly isolate the motors in an E-stop situation. I assume this isn't a new issue as motors have been controlled using various networks for years (DeviceNet, ControlNet....etc) so there should already be "standard/best practices" correct?

I was reviewing a Rockwell designed MCC (mainly for educational purposes)that will use networked drives and motor starters, but I didn't see a provision for E-stop circuits.

Seems to me, it would be easier to have a control panel in the MCC room dedicated to handling incoming/outgoing E-Stop circuit terminations to/from the various plant areas. The control panel would have relays to separate 120VAC E-stop circuit voltage from the Drive/Motor Starter 24VDC circuit E-stop provisions (contactors, safe-offs...)

How is this actually being handled by everyone?

I buy all Rockwell MCC's with ethernet and in the past Devicenet.

I spec drives and soft starts to have the safe torque option so EStops can be handled over the network.

The Plc Kid said:

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I spec drives and soft starts to have the safe torque option so EStops can be handled over the network.

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I'll have to look into that, but can you expand?

When you say "over a network", does that mean it must be programmed? If I hit an e-stop in area A, and all area A motors need to be shutdown, how does that hardware E-stop signal translate into a proper "stop" signal over the network? Is that something that must be programmed in the your logic, and thus potentially a risk if it is missed?

I dont think that the conveyor/Material Handling industry has escaped hardwired estops. I would expect to see long runs of 120v wire that touches local actuators/buttons/pullcords, and goes back to the MCC rooms for positive motor/drive control. As of 5 years ago that was the standard.

-Not done that in a while.

Yes you must have a guardlogix full or compact somewhere to control the CIP safety over ethernet.

I use guradlogix PLCs for each major process line and use the Safety POint IO modules to take EStop PB signals. The switch in you rockwell MCC can pass that CIP safety message to the correct safey component like the safe torque off module for a drive in Column 2 bucket # 3 for example.

All programming for safety is done in the safety routine of the guardlogix.

Most of my equipment now has zero hard wired safey components.

Ok Kid, I am not familiar with safty PLCs and such so that didn't cross my mind. That makes sense.

But in the case where you just have a safety relay, I woud imagine that signal must reach the safe-torque off board through an electrical contact to achieve the same effect. Off to the manual I go!

Paully's5.0 said:

Ok Kid, I am not familiar with safty PLCs and such so that didn't cross my mind. That makes sense.

But in the case where you just have a safety relay, I woud imagine that signal must reach the safe-torque off board through an electrical contact to achieve the same effect. Off to the manual I go!

Click to expand...

Yep you can wire the safety relay to drive IO to trigger the safe torque off function.

If you only have 1 or 2 it would be worth wiring but for a lot of them it makes sense to use a safety PLC.

Get rid of the MCC

Depending on application and environment go for a decentralised system like Eaton Rapidlink on ASi bus. Have your drives, starters etc local to the pump, motor. Hang your Estops on ASi safe and use it to shutdown your motors. If you are in process you can also hang your process valves etc off it too. Cut down on the expensive metalwork and cabling too.

Cheers,

Lee

Outrage said:

Get rid of the MCC

Depending on application and environment go for a decentralised system like Eaton Rapidlink on ASi bus. Have your drives, starters etc local to the pump, motor. Hang your Estops on ASi safe and use it to shutdown your motors. If you are in process you can also hang your process valves etc off it too. Cut down on the expensive metalwork and cabling too.

Cheers,

Lee

Click to expand...

That's a great solution for many industries and a pure nightmare for others. As with anything else in automation there really is no one size fits all.

Outrage said:

Get rid of the MCC

Depending on application and environment go for a decentralised system like Eaton Rapidlink on ASi bus. Have your drives, starters etc local to the pump, motor. Hang your Estops on ASi safe and use it to shutdown your motors. If you are in process you can also hang your process valves etc off it too. Cut down on the expensive metalwork and cabling too.

Cheers,

Lee

Click to expand...

Customer gets what they want...