Here we go again: Stack light colors

TConnolly

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Apr 2005
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Production has finally decided that stack lights might be a good idea if used for signaling to help with machine up time. The idea has been kicked around for a while with some in favor of it and some opposed against it. Par for the course, some mysterious bit of corporate dynamics has kicked off the big bang and the idea gained traction at cosmic inflation theory speeds and has "do it now dammit" task that people who didn't like buzzers and flashing lights last week now want completed next week.

No one can agree on the colors. Until they do I can't do much to implement it, but the clock is ticking. So here is what I suggested:

  • Red = machine is operating, i.e., don't open the door (which is locked anyways) and stick your hand in there.
  • Green = machine has stopped cycle, you can now open the door.
  • Amber = Alarm condition exists that requires the operator attention.
But there are camps that think red should be alarm and other who say green means the machine is running. I'm not aware of any published standard. Looking for input or a standard number.
 
I like

Green = Machine is running Properly
Amber = Non Shutdown alarm condition exists
Red Solid = Machine not running
Red Falshing = Shutdown alarm Condition Exists
 
As a rule, I tend to agree with PLC KID.

Green means everything is good. Running, no problems.
Yellow means some kind of non-critical fault exists that should be dealt with when you have a chance.
Red means an acknowledged alarm still exists
Flashing Red means unacked (new) alarm/critical fault exists.

When the machine is not running because it's been intentionally turned off, all of the lights are off.

In the US, we tend to think of green being good and red being bad. Your suggestions tend more toward the European philosophy of red being not-safe, green being safe. In the US, our natural inclinations toward a red light is that it means something is wrong...
 
I guess how you use the colors is more along the lines of what you want to represent.

From your descriptions you are using the stack light as an "OK to Enter" indicator.

That changes with the Amber light.

So I guess my first question would be exactly what are you trying to convey with the light.

Generally for me Stack Lights are long distance indictators. And below is how I have seen them used the most. I have seen where the non standard colors (blue, orange, white) have had special meaning just to the process.

Green= machine running
Red= Fault
Yellow= machine stopped by operator

On alot of our panels we use multi color lights ( 5 different colors on same pilot light)

Our Standard here is:

Green = Auto Ready no faults ready to start
Green Flashing = Auto Run with no issues
White= sytem Off and in Setup mode
White Flashing= error with Setup
Yellow= Manual Ready with no faults present
Yellow flashing= Manual Running with no faults
Blue= Batch complete
Blue Flashing= batch completing
Red= Sytem stopped by fault
Red Flashing= Sytem detected fault but has not stopped yet (material low etc)
 
We use pretty much the same setup as The PLC Kid posted:

Red = Critical alarm
Amber = Non-critical alarm (ie, hopper getting low on product)
Green = Machine is running with no problems

I also use a flashing green = Machine guards are all in place and machine is ready to start.

The key is setting a pattern and sticking with it. Once the operators learn what the lights on one machine mean, they expect them to mean the same thing on another machine.
 
I agree with you
In Ozz (following European standards)
RED - stopped/safe/open
GREEN - running/good/closed
AMBER - alarm/fault
Pretty hard to convince some people though - even with the standard in hand.
Everyone wants something different.
The 'old school' is green running/good - red BUGGER!
 
Due to the confusion between red and green, we chose purple as the standard for our HMI alarms. Anything purple means something is wrong...

My opinion lies with the majority in contradiction to the land down under. RED=Bad, Green=Good. But you seem to be talking mainly about interlocked safety doors, with which I have no experience. I can see where Green meaning "Go ahead on in there!" makes sense, and red means "Stop, Don't touch this handle!"

Do they make purple stacklights?
 
Do they make purple stacklights?

Yes they do but I am not sure who does them. I saw them in a Cotton Mill I worked at while I was in college. They used the purple to say the loom was down for maintenance.

Couldn't say if they special ordered them. This was back in 1992 so the fact I remeber them is impressive to me...lol
 
Due to the confusion between red and green, we chose purple as the standard for our HMI alarms. Anything purple means something is wrong...

Of course, up here (near Manhattan, KS -- home of the KSU Wildcats!), purple would mean everything is WONDERFUL!!! Nothing wrong with purple up here. Red or orange, on the other hand...

;)
 
Flashing Red = Stopped, E-Stop Active or non-recoverable fault during run

Red = Stopped, machine is not running

Amber = Stopped, alarm or recoverable fault during Run mode

Green = Running normally

Flashing Green = Startup cycle running, if the machine has a long enough startup to notice


There are of course some varients on this, but generally that's what I've used. I've also seen Blue used to indicate low parts hoppers or full scrap bins, which I liked.

I've also got one machine where we track all these various times in the PLC and I post them on the HMI. Ops asked for it a few years ago, but I don't know that anyone pays much attention to it now.
 
It kind of surprizes me that NFPA79 and IEC60204 haven't started shifting away from green and red, give the 7-10% incidence of red/green color-blindness among males. I kind of like the purple idea.

Keith
 
NFPA 79 gives different meanings to the colors based on what the purpose is.

For safety of persons or environment:
Red - Danger, Yellow/Amber - Warning/Caution, Green - Safe

For Condition of Process:
Red - Emergency, Yellow/Amber - Abnormal, Green - Normal

For State of Equipment:
Red - Faulty, Yellow/Amber - Abnormal, Green - Normal

I'm referencing NFPA-79 2002, table 10.3.2. I have the newer standard at work, and if memory serves, it hasn't changed.

So it sounds like Alaric is thinking in terms of personnel safety, but the corporate borg is thinking in terms of "Condition of Process" or "State of Equipment."
 

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