Human Machine Interfaces (HMIs) are the primary point of interaction between operators and automated systems. A poorly designed HMI can lead to operator confusion, increased error rates, and even safety incidents. Conversely, a well-designed HMI improves productivity, reduces training time, and enhances overall plant safety.
The High-Performance HMI Philosophy
The concept of High-Performance HMI design, championed by the ASM Consortium and documented in ISA-101, represents a paradigm shift from the traditional colourful, photo-realistic displays to simplified, information-rich screens that prioritise situational awareness.
Key principles include:
- Grey background with colour used only for status indication to reduce visual fatigue during 12-hour shifts
- Minimal use of animation to prevent distraction from critical information
- Clear hierarchy from overview screens to detail screens following a logical navigation structure
- Consistent colour coding across the entire SCADA/HMI system
Screen Layout Best Practices
When designing HMI screens, follow these guidelines:
- Overview screens should show the entire process at a glance with key performance indicators
- Navigation should be logical with no more than three clicks to reach any detail screen
- Alarm banners must be visible on every screen without obscuring process information
- Trend displays should be readily accessible for any process variable
- Use consistent placement for common elements such as navigation buttons, alarm summaries, and status bars
Alarm Management on HMI
Alarms are one of the most critical aspects of HMI design. Follow the ISA-18.2 standard for alarm management:
- Rationalise alarms to eliminate nuisance alarms that desensitise operators
- Use priority levels (critical, high, medium, low) with distinct visual indicators
- Implement alarm shelving for known conditions during maintenance or startup
- Log all alarm events for analysis and continuous improvement
Colour Standards
Adopt a consistent colour standard across your facility:
- Green: Running, open, energised, normal
- Red: Stopped, closed, de-energised, alarm
- Yellow/Amber: Warning, caution, transitioning
- Blue: Manual mode, maintenance, bypassed
- Grey: Inactive, disabled, out of service
Technology Considerations
Modern HMI development is moving towards web-based solutions that offer cross-platform compatibility. Technologies such as HTML5, SVG graphics, and responsive design enable operators to access HMI screens from tablets, phones, and remote workstations.
Training at EDWartens UK
Our HMI development courses at EDWartens UK cover the complete design lifecycle from requirements gathering to commissioning. Students learn to create professional HMI applications using Siemens WinCC and other industry-standard platforms, following high-performance design principles throughout.