Pilot Lights

Is green or red "ON" or "OFF"? What about "Run", "Running", OPEN", "OPENED", "CLOSE" AND "CLOSED"? What conventions do you follow? I've seen green and red used both ways in the field.

The common way is RED for negative operation.and GREEN for positive
operation.
You also can use other colors like blue or yellow if you wamt to color
your panel.
Its not conventions to use RED for On operation or GREEN for fault.

In the US, check publication NFPA 79 fo recommended meaning of colors in lights and control switches.

Hi,

try this link:
domino.automation.rockwell.com/appl...D80886C9EC26F91685256BCE004C53AD?OpenDocument


regards

Rolf

As mentioned allready it depends on what part of the world you are in. Here in the US we have used green for on / running and red for stopped and most common alarm conditions. Here lately we have gotten alot of overseas stuff that request exact opposite. We even had a spec from a Egypt LNG project that mandated red for stop, green for run on electrical and the exact opposite for instrumentation. I wish we could all get together and have one accepted standard because it is a real pain to change out a bunch of pilot light lenses and LEDs on a EEXd enclosure when you get caught up in the confusion.

In the US, for motor and power control, RED is hot or on, GREEN is safe or off, this is typical on motor control centers and circuit breaker indicators.

Check with applicable regulatory agencies (NENA, OSHA, IEEE, etc) for your area.

Regardless of any published spec, it still depends on what is reasonable and safe for the users and the process.

It depends on the situation, the process, the environment, the relevant meaning of the color in terms of the information being imparted, and the decisions made as a result of seeing those colors.

Generally, GREEN means ON.
However, it can also mean "OK to GO" or "SAFE"... in this case, is the device ON? Or is it OFF? It might very well be that the device must be OFF for the "OK to GO" or "SAFE" condition to exist.

In some situations, a string of lights might indicate the particular status of a set of valves, motors, whatever. It might be the case that all of those devices must be in a particular state before an operator can proceed with a particular action.

If the required status of the various devices is a particular combination of ON, OFF, OPEN, CLOSED, then is it better to show all GREEN if the combination is as required? Or should the lights indicate GREEN = ON/OPEN and RED = OFF/CLOSED?

An operator can make a decision much more easily if all colors are to be GREEN (for example) before proceeding. A RED would instantly show a missing condition. The operator coulds then look to see what the particular missing condition is.

If there is a multitude of various colors then it becomes very hard to quickly discern that there is a problem.

It depends.

As you can see, you'll never get a straight answer to this question, as there are two competing schools of thought. Both use the basic principle of "Green is go, red is stop", but

Electicians think in terms of safefy. "Go" to them means that it is safe to work on. This means that the device is NOT energized when green. "Stop"/Red means it's not safe; that the device is energized.

Operators think in terms of activity. "Go" to them means that something is running. So for them, Green means running, and red means stopped.

And so you'll see both types out in the field. You may even see both types in THE SAME SYSTEM!! The switchgear graphics will be Red=On/Green=Off, while the system graphcs screen wil be Red=Off/Green=On.

Confusing? Absolutely!

There's been all kinds of ideas thrown out over the years to end the confusion (at least for the operators - electrician's have NFPA, so those standards are set in stone). Probably the best alternative uses grey for "Inactive" and the color of choice (usually a bright one) to indicate "Active" (and another color to indicate "Trouble"). In this way, your eye is drawn to the active objects and can see at a glance (once you get used to how things are supposed to look) if everything is good.

But it's not a standard.

There is no universal standard, and you would do well to check with the customer or the plant's existing systems to find out what they are using. I prefer Green = ON, Green = OPEN, Amber = CLOSED, Amber = WARNING, Red = FAIL. I try to avoid blue and white lights because visibility isn't good.

The electric power industry tends to use Red for ON or OPEN indicating an unsafe condition, and Green for OFF or CLOSED indicating a safe condition. This is not universal in this industry, nor is it common in many other industries.

In my experience most operators intuitively like Green for ON and Red for STOP because of traffic lights.

Here are a few more.
Red, white and blue lights for phases OK, white for 24VAC control power OK, green for on, red for off, amber for fault.
Loosly based on IEC.
beerchug

UL 508A 67.2.2 The color red shall only be used for operators for stop, off, or emergency stop operations.

NFPA 79 10.2.2.1 Start or On The preferred color of start or on shall be GREEN,except that BLACK,WHITE, or GRAY shall be permitted. RED shall not be used for start or on.


NFPA 79 10.3.2 Machine Indicator Lights and Icons
RED----Danger
YELLOW(AMBER)-----Warning/Caution
GREEN----Safe
BLUE-------Mandatory action
CLEAR,WHITE,GRAY,BLACK------No specific meaning assigned

Another observation: If the panel indications are too dense (too many indicators, too many different colors) the operator will often not be able to distinguish important information. Alarm colors (red, etc.) should be used sparingly to avoid diluting their importance.

In our operation we use green for operational and red for fault condition.
The one problem that no one here seems to agree on is whether the E-Stop Mushroom should be lit red when the E-Stop has been hit or if it should be red when it is not hit. I prefer it to be lit when it is not hit so the operator can find it easier in an emergency. I would like to know which way others are using.

A light should indicate an action...therefore if a red light is used on an ESTOP then the light should indicate that ESTOP is active...ie its been pushed. Its just as easy to have the light on to show it as it is off...as long as just the pushbutton that was pressed is the only one lit. I have used pole/flashing lights in zones (on conveyors) to KNOW where/when an ESTOP was pushed. Of course when you have to work with 5 miles of conveyor in a distribution plant you need all the help you can get to know why the line is d

Since I am in the US I attempt to follow NFPA code, many may not consider it a standard BUT if not used its possible you will be in violation of local codes...which the company could be fined for. Companies have a tendency to fire a person or person(s) when they get fined because of something that person or person(s) did or did not do.

Traffic lights were mentioned and in the US I think their method is applied because its easily understood.
GREEN= GO, RUN, RUNNING...machine is operating or ON
RED= STOP....Machine is not operating or OFF
AMBER= Warning, slow down or stop...a safety issue

The other colors can be indicative of anything that doesnt mean STOP, GO or Warning. I use BLACK for buttons like JOG or FORWARD/REVERSE..just depends on situation.

There is an IEC standard that relates to colours of indicator lights and displays on SCADA screens, ( I have a copy in the office and will find the number of it when I return to the office next week).

Basically:
Green is safe, stopped, open, off etc.
Red is a fault condition
White is normal operation, ie running with no fault

Amber and Blue can have other meanings applied.
The reference to traffic lights is common but is misleading, a mimic screen or indicator light is displaying a status, the traffic light is issuing a command. The green and red traffic lights will also have different meanings to pilots than to drivers.