High Performance HMI: Saving Seconds to Save Systems

1. Introduction & Context

For decades, the standard for SCADA and DCS graphics was to recreate the plant’s Piping and Instrumentation Diagram (P&ID) on the screen. Tanks were bright blue, pipes were green, spinning pumps were animated with yellow flames, and every value was displayed as a raw number. During normal operations, this looks impressive. However, during a massive plant upset or an alarm flood, a screen full of 50 flashing neon colors creates catastrophic cognitive overload, destroying an operator’s ability to respond quickly.

2. The Core Issue

Abnormal Situation Management (ASM) relies heavily on how quickly a human operator can identify a deviation from normal and take corrective action. Traditional graphic design masks failures. If an operator stares at a screen with 15 red pumps (indicating “off” or “tripped”) and 30 green pumps (indicating “running”), a critical pump turning red blends perfectly into the background noise.

The Solution: High Performance HMI (ISA-101) The ISA-101 standard radically redesigns the interface to prioritize situational awareness and response time:

1. The Grayscale Baseline: The entire background, static pipes, and inactive equipment are rendered in muted, low-contrast grays.
2. Color for Abnormalities Only: Color is strictly reserved for alarms and abnormal states. If the screen is entirely gray, the plant is operating perfectly. If a single bright red or orange indicator appears, the operator’s eye is drawn to it instantly, cutting recognition time from minutes down to milliseconds.
3. Analog Context over Digital Numbers: A raw number like “145 PSI” requires the operator to mentally remember if 145 is good or bad. High-Performance HMI replaces raw numbers with analog moving-pointer bars (often called “bullet graphs” or “radar plots”) that visually show the current value relative to the normal operating band and the alarm limits.

3. Actionable Takeaways

• Strip the Decoration: Remove spinning fans, 3D shading on tanks, and bright background colors from HMI screens. If an element doesn’t convey actionable data, it is a dangerous visual distraction.
• Implement Analog Indicators: Embed normal operating ranges visually into your interface. An operator should be able to look at a tank level bar from across the room and instantly know if it’s within the optimal band without reading the numerical value.
• Reserve Color for Crisis: Implement a strict hierarchy of color. Use a specific hue (like deep red) only for critical Level 3 alarms, ensuring it is never used for a normal “Stop” indicator.