Isa Standards

ISA Standards Reference for Industrial Automation

ISA-5.1: Instrumentation Symbols and Identification

Tag Number Structure

[Area].[Functional ID].[Loop Number][Suffix]

Functional ID = [First Letter: measured variable] + [Succeeding Letters: function/modifier]

Examples from project:
  11301.PDI.076A   = Area 11301, Pressure Differential Indicator, loop 076, suffix A
  11301.SALL.020A  = Area 11301, Speed Alarm Low-Low, loop 020, suffix A
  11301.FIC.056A   = Area 11301, Flow Indicating Controller, loop 056, suffix A
  11301.CLWW.1A1   = Area 11301, Conveyor (equipment tag), unit 1A1

First Letter (Measured/Initiating Variable)

Common Tag Combinations

Flow: FE (element), FT (transmitter), FI (indicator), FIC (indicating controller), FCV (control valve), FAH (alarm high), FAL (alarm low), FAHH (alarm high-high), FALL (alarm low-low), FSH (switch high), FSL (switch low), FQI (quantity indicator/totalizer), FR (recorder)

Level: LT, LI, LIC, LCV, LAH, LAL, LAHH, LALL, LSH, LSL, LSHH, LSLL, LG (gauge glass)

Pressure: PT, PI, PIC, PCV, PAH, PAL, PAHH, PALL, PDI (differential indicator), PDIC, PDT, PSH, PSL, PSV (safety valve), PG (gauge)

Temperature: TE (element), TT, TI, TIC, TCV, TAH, TAL, TSH, TSL, TR (recorder), TW (thermowell)

Position/Valve: ZT (position transmitter), ZI, ZIC, ZAH (open alarm), ZAL (closed alarm), ZSH (open switch), ZSL (closed switch), ZSHH, ZSLL

Speed: ST, SI, SIC, SAH, SAL, SAHH, SALL

Current (Electrical): II (current indicator), IIC (current indicating controller), IAH, IAHH

Vibration: VI (vibration indicator), VAH, VAHH

Equipment Tags (Non-ISA, Plant-Specific)

Tag Naming Variations by Region/Vendor

ISA-88: Batch Control (S88)

Physical Model Hierarchy

Enterprise
  +-- Site
       +-- Area
            +-- Process Cell
                 +-- Unit
                      +-- Equipment Module (EM)
                           +-- Control Module (CM)

Mapping to DCS Engineering

Control Module Types (Standard Templates)

• Motor CM: Start/Stop, feedback, interlock, mode selection
• On/Off Valve CM: Open/Close, position feedback, interlock
• Modulating Valve CM: Analog output, position feedback, PID output
• PID Loop CM: AI input, PID algorithm, AO output
• Analog Input CM: Scaling, filtering, alarm limits
• Digital Input CM: State detection, alarm on state

ISA-95: Enterprise-Control Integration

Equipment Hierarchy (extends ISA-88 upward)

Enterprise > Site > Area > Work Center > Work Unit

Relevance to Tag Naming

Tags should encode the hierarchy. Example: 11301.FIC.056A

• 11301 = Area identifier (maps to ISA-95 Area)
• FIC = Function (ISA-5.1)
• 056 = Loop number (unique within area)
• A = Suffix (parallel instance)

ISA-18.2: Alarm Management

Alarm Priority Distribution (Guideline)

Alarm Tag Properties for Bulk Engineering

Each alarm tag requires: Priority, Setpoint (limit), Deadband, On-delay, Off-delay, Alarm class (Process/Safety/Equipment), Shelving capability.

Naming Convention for Alarms

{Area}.{Variable}{AlarmType}.{Loop}{Suffix}
  PAH  = Pressure Alarm High
  PAHH = Pressure Alarm High-High
  PAL  = Pressure Alarm Low
  PALL = Pressure Alarm Low-Low

In Freelance EAM: XA1 = primary alarm, XA2 = secondary alarm

ISA-101: Human Machine Interfaces

Display Hierarchy

High-Performance HMI Principles

• Gray backgrounds (not black)
• Analog representations (bar graphs, sparklines, not just numbers)
• Minimal animation (no rotating equipment, no flowing pipes)
• Color reserved for abnormal states (alarms, deviations)
• Consistent navigation (plant hierarchy)
• Situational awareness focus