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)
| Letter | Variable | As Succeeding Letter |
|---|
| A | Analysis (pH, O2, conductivity) | Alarm |
| B | Burner, Combustion | User's choice |
| C | User's Choice | Control |
| D | User's Choice | Differential |
| E | Voltage (EMF) | Sensor/Element |
| F | Flow Rate | Ratio/Fraction |
| G | User's Choice | Glass/Gauge |
| H | Hand (Manual) | High |
| I | Current (Electrical) | Indicate |
| J | Power | Scan |
| K | Time, Schedule | Time Rate of Change |
| L | Level | Light/Low |
| M | User's Choice | Middle/Intermediate |
| N | User's Choice | User's choice |
| O | User's Choice | Orifice/Restriction |
| P | Pressure, Vacuum | Point (test) |
| Q | Quantity | Totalize/Integrate |
| R | Radiation | Record |
| S | Speed, Frequency | Switch/Safety |
| T | Temperature | Transmit |
| U | Multivariable | Multifunction |
| V | Vibration, Mechanical Analysis | Valve/Damper |
| W | Weight, Force | Well/Probe |
| X | Unclassified | Unclassified |
| Y | Event, State, Presence | Relay/Compute |
| Z | Position, Dimension | Actuator/Driver |
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)
| Code | Equipment Type | Example |
|---|
| K | Kiln/Equipment | 11301.K.9 |
| N | Pump | 11301.N.3A |
| F | Feeder | 11301.F.4 |
| WG | Weighing belt | 11301.WG.8 |
| SR | Screen/Separator | 11301.SR.9A |
| CL/CLWW | Conveyor (weigh) | 11301.CLWW.1A1 |
| KC | Crusher | 11301.KC.F.4 |
| EL | Elevator | 11301.EL.AA |
| Z | Silo/Storage | 11301.Z.2A |
Tag Naming Variations by Region/Vendor
| Convention | Format | Example |
|---|
| ISA Pure | FIC-101A | American standard |
| European (this project) | 11301.FIC.101A | Area.Function.LoopSuffix |
| Siemens/KKS | +FIC101A= | German power plant standard |
| DeltaV path | FIC-101A/PV | With parameter path |
| Honeywell | FIC101A.PV | With point parameter |
ISA-88: Batch Control (S88)
Physical Model Hierarchy
Enterprise
+-- Site
+-- Area
+-- Process Cell
+-- Unit
+-- Equipment Module (EM)
+-- Control Module (CM)
Mapping to DCS Engineering
| ISA-88 Concept | DCS Implementation | Example |
|---|
| Control Module | Function block instance | Motor block, valve block, PID loop |
| Equipment Module | Sequence/SFC | Reactor filling sequence |
| Unit | Process unit with sequences | Reactor R-101 |
| Process Cell | Group of units | Production Line A |
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:
- = Area identifier (maps to ISA-95 Area)
- = Function (ISA-5.1)
- = Loop number (unique within area)
- = Suffix (parallel instance)
ISA-18.2: Alarm Management
Alarm Priority Distribution (Guideline)
| Priority | Percentage | Response Time |
|---|
| Critical (1) | ~5% | Immediate |
| High (2) | ~15% | < 5 minutes |
| Medium (3) | ~30% | < 30 minutes |
| Low (4) | ~50% | Next round |
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
| Level | Name | Content | Quantity |
|---|
| 1 | Plant Overview | Entire plant, KPIs | 1-3 |
| 2 | Area Overview | One process area | 5-20 |
| 3 | Unit Detail | One unit operation | 20-100 |
| 4 | Faceplate/Detail | One control loop | Auto-generated |
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