HMIs (or “Human Machine Interfaces”) have been around now for a few decades and although they give us an idea of what’s going on in the PLC (“Programmable Logic Controller”) or PAC (“Programmable Automation Controller”), they can be, at times more than a bit frustrating.
Some areas of frustration can stem from:
Depending on the style and type of HMI (DCS or computer-based, or “panels” or text displays), navigation can come from either hardware buttons (function keys) right on the HMI bezel or programmed “buttons” within the HMI application.
Panel hardware navigation keys can be quite restrictive as there are a limited amount of options you can have, however with most brands of HMI, you can either programmatically change the buttons depending on what screen or display your user is on or you can still use software buttons in conjunction with hardware buttons to give operators more options.
Navigation can become critical if an operator is forced to switch back and forth between displays when trying to deal with a process upset or malfunction, costing them time and increasing the level of stress they’re already experiencing.
Improper Level Structure
If you’re familiar with one of the many standards surrounding HMI visualization such as “Abnormal Situation Management” (ASM) or ANSI/ISA-101.01 or other “High Performance” HMI guidelines, you’re probably aware of the display “Level” structure where graphic displays are structured in Levels (usually 1-4) with high level overviews being “Level-1” and high detail displays being “Level-3” or “Level-4” depending on the level of detail.
The advantage of this architecture is that operators can keep a pretty good eye on their process (or equipment) if a Level 1 or 2 display is well designed. When things “go south” or when an upset happens, the operator can dive deeper into Level 3 or 4 displays to get a better understanding of the issue and take action to resolve it much quicker.
Two things can happen if this isn’t done effectively, 1) the operator can miss critical events if the overviews don’t have the ability to issue an alert in the area of concern, or 2) the operator is left trying to “hunt” around a bunch of detailed displays to find the information they’re looking for. Either way, the result isn’t going to be good for either the process OR the operator.
Alarms are critical to the operation, but meaningful alarms and their proper handling are essential to the efficient operation of a process that is running at its optimal peak.
A few things come into play here.
“Alarm Flooding”, which is when events within the plant are configured as alarms to which there may not even be an action associated with it, resulting in an alarm (audible or otherwise) being displayed on the HMI and rendering all other valuable alarms useless because the operator has either lost track of what is relevant or just “tuned out” the alarms flooding into the system.
The other is the effective handling of the alarms. Operations need to be able to “acknowledge” alarms to stop them from flashing or ringing an audible alarm but also to indicate operators in other areas that someone is currently dealing with that alarm. If alarms aren’t acknowledged across multiple HMIs in a “distributed” system then other operators are forced to simply hit “Acknowledge All” on the alarm page to “clean up” their alarm summary. This can easily result in a level of complacency and/or a loss of communication between operations personnel.
Many books have been written on the subject of Alarm Management such to say much work can be done in this area to increase effectiveness of alarms, but too many facilities simply ignore this area because they think that Alarm Rationalization exercises are only for large systems or they are too intimidated by the task. Don’t wait, just start somewhere. Small incremental changes are better than no change at all.
Unclear Data Representation
You’ve probably heard different people talk about information vs data. Data is just that, “data”. A pile of numbers on a screen are “data”. Equipment statuses that turn red or green are “data”. Even a bar graph can just be “data”. Unless data is given context, it cannot become information.
Information is critical to an operator’s success and is at the bottom line of profitability of any organization. Unless people are given the context to know when the data they’re looking at is something that requires their attention, it will be useless to them. This lies at the heart of predictability.
Context can be provided in many ways; is the value trending upwards or downwards?; does the status show something normal or undesirable?; is the value within optimal constraints or encroaching on the level of inefficiency leading to a loss of profitability?
Let’s be clear, even large, multinational Vendors and System Integrators struggle with this. Why? To be blunt, it comes at a cost, and the cost is quite often scrutinized most at the project level. It then becomes Operations’ problem to either find funding to improve or just live with it.
Many other circumstances can play a part in lowering the effectiveness and raising the level of frustration to operators such as ambient lighting (and noise), hardware obsolescence and functionality (or lack thereof). I won’t even get into the topic of color as, by now, everyone should know that the misuse of color in HMI graphics is what simply makes marginally “good” graphics into just plain bad graphics.
By now there is enough good, statistical information (notice how I didn’t say “data”) on the topic of human behavior to assist anyone in producing efficient, operable graphical interfaces. Interestingly enough, the online retail community learned years ago that unless the public masses (the majority) “likes” what they see and find it “easy” to navigate, as well as find the information they’re looking for, they’ll simply go elsewhere. Plant operators don’t have that “luxury” but, that being said, if you’re experiencing high personnel turnovers, maybe they do…?
AccuBytes Inc has over 20 years of experience helping clients optimize their Industrial Control Systems (ICS) including graphical interfaces and assisting in productivity and, in the end, profitability. Contact us for help relieving some of the frustration.