Is that light supposed to be blinking?

If finding an alarm on your HMI is like playing Where’s Waldo, you might want to reevaluate some of your operator display graphics. A process upset is no time to try and remember what a flashing light means.

07/30/2013


Do you ever get the feeling that trying to find what’s in alarm on your HMI graphics is a bit like playing the “Where’s Waldo” game? There are so many things blinking and so many colors on the screen that you can’t tell which one just went into alarm. Is it an important alarm? Could be, but how can you tell since five alarms just came in at about the same time? Conventional wisdom suggests that people work by pattern recognition and can easily spot what just changed on the screen. There is some truth to that, provided they were looking at the screen when it happened, but if several things changed at the same time, they may not figure out quickly enough which one is the most important.

There are several paradigms at work here: pattern recognition, alarm philosophies that try to make everything important, the desire to get the operator’s attention during events, the need for color to differentiate process fluids, black background vs. colored background, the need for color or animation to define equipment states, and of course, let’s not forget red = run, green = stop. Or is it green = run, red = stop? In some places, it depends on what part of the facility you’re in. All of these have led us to build confusing graphics that do more to prevent the operator from reacting to alarms than to facilitate addressing them.

Some of the sophisticated HMI capabilities available today have led to truly bad and sometime downright silly graphics that suggest a designer felt compelled to use every possible option. I’ve seen operator screens that are detailed to the point of using shading to make things look three dimensional or so detailed that you can tell if a tank is made of rolled metal or ceramic bricks. I’ve seen engineers spend hours building an animation that has a truck drive up to a loading rig and then drive off when it’s done. I still remember going into one plant where some of the graphics were on a magenta background and they were built by an operator!

The Abnormal Situation Management Consortium (ASM) has spent about 20 years studying factors that affect operators’ ability to prevent and respond to abnormal situations in a plant. The organization has released extensive guidelines on how to create graphics that improve operator performance, but attractiveness is secondary. Their recommendations begin with the assumption that operators have to watch those monitors for many hours at a time while maintaining a high level of alertness for events that might not happen all that often.

Operators who like flashy video game graphics find screens that follow ASM’s recommendations gray and boring. They say things like,

• You’re just not used to our cool graphics. I can find anything on them instantly.
• All the gray just blends together.
• How do we know what’s running?
• How do I know which valves are open?
• How will we know if the level is starting to get low or the pressure is starting to get high?
• I don’t want to click through that many pages.

What I don’t hear from them is, “How will I know something is in alarm?” It’s immediately obvious that once the only thing on the screen that’s red is an alarm, then seeing one is going to be easy. Not so immediately obvious is the fact that the graphics are easier to look at for a shift. I have one customer that decided to change the backgrounds on his existing graphics from black to light gray just to see if it made a difference. He didn’t change any of the colored elements on the screens, and one of the first benefits he noticed was that the lights in the control room didn’t have to be as dim.

The other was that looking at the new scheme resulted in reduced eye strain, partially from lower contrast on screen and partially from having a better lit room. The next step is to start de-coloring the stuff on the screen, in particular the old red = run, green = stop indications. Then he’ll be ready for the really big leap, alarm rationalization. But that’s a topic for another time.

So have you tried to adopt any of the ASM guidelines? How have your operators responded? Are they fighting the change or seeing the benefits?

This post was written by Bruce Brandt. Bruce is a technology leader at MAVERICK Technologies, a leading system integrator providing industrial automation, strategic manufacturing, and enterprise integration services in the manufacturing and process industries. MAVERICK delivers expertise and consulting in a wide variety of areas including industrial automation controls, distributed control systems, manufacturing execution systems, operational strategy, and business process optimization. The company provides a full range of automation and controls services – ranging from batch control process consulting to outage planning services and plant safety audits. Additionally MAVERICK offers industrial and technical staffing services, placing on-site automation, instrumentation and controls engineers.



David , NY, United States, 08/07/13 02:04 PM:

Hard to imagine anyone that would confuse red and green as suggested above. What color are traffic lights in other parts of the world?
Mark , IL, United States, 10/28/13 04:11 PM:

Something like 5-10% of the male population has some red/green deficiency color blindness. Most learn to cope by shade, position, and in other ways. Some don't even know they have this color blindness until the day when there is no other way to tell, other than to miss the signal or alarm. If that is a mission-critical moment, it might not end well.
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