liminfoHMI Design Guide
Free reference guide: HMI Design Guide
About HMI Design Guide
The HMI Design Guide provides a comprehensive reference for designing effective Human-Machine Interfaces in industrial process control. It covers the ASM (Abnormal Situation Management) screen hierarchy from Level 1 Overview (full plant status with KPIs on a single screen) through Level 2 Area (P&ID-based zone displays), Level 3 Unit (individual equipment control), to Level 4 Diagnostic (trends and detailed parameters). The guide follows ISA-101 principles for HMI philosophy documentation and style guide standardization.
Color design is covered in depth with industry-standard specifications: background color recommendations (ASM medium gray #707070-#999999 to reduce eye fatigue and improve alarm distinction), ISA-18.2/EEMUA alarm priority colors (Emergency red #FF0000, High orange #FF8C00, Medium yellow #FFD700, Low blue #4169E1), equipment status colors (Running green #00B050, Stopped gray #808080, Fault red), and fluid identification colors per KS A 0503. The guide also details font specifications (sans-serif at 12-20pt for 1920x1080), button sizing (minimum 20x20mm for touch), and multi-monitor configurations.
Advanced topics include alarm management per EEMUA 201 (target less than 6 alarms/hour/operator, alarm flood threshold at 10 alarms/10 minutes), faceplate design for motors (run/stop/fault states with current and runtime feedback) and valves (open/close with position percentage), trend screen design (maximum 6-8 pens with zoom and cursor), user permission levels (Viewer through Admin with 15-minute auto-logout), audit trail requirements (1-year minimum retention with tamper-proof DB), and HMI performance optimization (less than 200 tags per screen, less than 2-second screen transition).
Key Features
- ASM-compliant screen hierarchy design from Level 1 Overview to Level 4 Diagnostic with layout specifications
- ISA-18.2/EEMUA alarm color coding with priority levels, flashing for unacknowledged alarms, and shelving guidelines
- Equipment status and fluid color standards including running/stopped/fault states and KS A 0503 pipe identification
- Faceplate design templates for motors (run/stop/auto/manual) and valves (open/close/position feedback)
- EEMUA 201 alarm management KPIs: target less than 6 alarms/hour, flood detection, and rationalization methods
- ISA-101 HMI standard guide covering philosophy documents, style guides, graphic libraries, and usability testing
- User permission hierarchy (5 levels from Viewer to Admin) with auto-logout, password policy, and audit trail requirements
- Performance optimization guidelines: less than 200 tags/screen, 1-second refresh rate, less than 2-second screen transitions, under 50% CPU
Frequently Asked Questions
What is the recommended background color for industrial HMI screens?
The ASM (Abnormal Situation Management) guideline recommends medium gray (#707070 to #999999, RGB 128,128,128 to 160,160,160) as the background color. This reduces eye fatigue during long shifts and provides optimal contrast for alarm colors. Avoid black (eye strain, OLED burn-in), white (glare, poor alarm distinction), and blue (insufficient color contrast). The gray background allows alarm colors like red, orange, and yellow to stand out clearly.
How should alarm colors be organized according to ISA-18.2?
ISA-18.2 and EEMUA standards define a four-level alarm priority color scheme: Emergency uses red (#FF0000), High priority uses orange (#FF8C00), Medium priority uses yellow (#FFD700), and Low priority uses blue (#4169E1). Unacknowledged alarms should flash, acknowledged alarms should be steady (non-flashing), and alarms that have returned to normal should have their color removed. This consistent color coding helps operators quickly identify the most critical situations.
What are the EEMUA 201 benchmarks for alarm performance?
EEMUA 201 recommends an average of less than 6 alarms per hour per operator during normal operations, with a maximum of 10 alarms in any 10-minute period. During steady state, the target is less than 1 alarm per 10 minutes. An alarm flood (more than 10 alarms in 10 minutes) indicates a problem. Improvement methods include removing unnecessary alarms, applying deadbands, using alarm delays, implementing state-based alarming, and conducting alarm rationalization reviews.
What is the ASM screen hierarchy and how should I implement it?
The ASM hierarchy has four levels: Level 1 (Overview) shows the entire plant status with KPIs on a single screen for immediate situation awareness. Level 2 (Area) provides zone-specific P&ID-based displays. Level 3 (Unit) offers individual equipment control and settings. Level 4 (Diagnostic) contains detailed trends and parameters. Operators should reach any target screen within 3 clicks, with consistent navigation bars and breadcrumb location indicators.
How should I design a motor faceplate for HMI?
A motor faceplate should display: status (Running/Stopped/Fault with color coding), command buttons (Start/Stop), operating mode (Auto/Manual/Local), feedback values (current draw, accumulated runtime), and alarms (overload, ground fault). The start button should be green and the stop button red. Include a confirmation dialog for critical commands. For the valve faceplate, show open/close status, position percentage, command buttons, and alarms for excessive torque or travel time timeout.
What font and button sizes should I use for industrial HMI?
Use sans-serif fonts (Arial, Verdana) for readability. At 1920x1080 resolution: titles 16-20pt, body text 12-14pt, tag values 14-16pt bold, units 10-12pt. Text must be at least 5mm tall at 1m viewing distance and 10mm at 2m. For touch interfaces, buttons should be minimum 20x20mm with at least 5mm spacing between them. Use 3D effects to indicate button press states, and gray out disabled buttons.
How should I implement user permissions and audit trails?
Use five permission levels: Level 1 (Viewer) for monitoring only, Level 2 (Operator) for operational commands, Level 3 (Supervisor) for setpoint changes, Level 4 (Engineer) for parameter modifications, and Level 5 (Admin) for system configuration. Enforce 15-minute auto-logout, 8+ character alphanumeric passwords, and log all operator actions. Audit trail records must include timestamp, user, action, tag, old value, and new value, stored in a read-only database for a minimum of 1 year.
What are the key ISA-101 requirements for HMI design?
ISA-101 requires: (1) an HMI philosophy document defining design principles, (2) a style guide standardizing colors, fonts, symbols, and layouts, (3) a screen hierarchy design following ASM guidelines, (4) a standardized graphic symbol library for consistency across all screens, and (5) usability testing with operators. Performance targets include situation awareness within 1 minute, 50% reduction in operator errors compared to baseline, and alarm response times meeting priority-based benchmarks.