Abbreviations (acronyms) used in Functional Safety

Greek Letters

β: Beta factor for common cause failures (for DU failures)

βD: Beta factor for common cause failures (for DD failures)

λDD : Rate of Dangerous Detected failures (failures per hour)

λDU : Rate of Dangerous Undetected failures (failures per hour)

λSD : Rate of Safe Detected failures (failures per hour)

λSU : Rate of Safe Undetected failures (failures per hour)

From A to L

BPCS: Basic Process Control System  (also DCS)

CC: Common Cause

CCF: Common Cause Failure

Cpt: Coverage of Proof Tests  (also PTC)

DC: Diagnostic Coverage [λDD / (λDU + λDD)]

DCS: Distributed Control System  (also BPCS)

DTT: De-energized To Trip

E/E/PE: Electrical, Electronics, and Programmable Electronic

ESD: Emergency Shut Down

ETT: Energized To Trip

EUC: Equipment Under Control

FAT: Factory Acceptance Tests

FC: Fail Close (valve close when power/air failure)

FE: Final Element  (actuator subsystem)

F&G: Fire & Gas

FIT: Failures in Time (failures per billion hours; λ=FIT x 1E-9)

FMEA: Failure Mode and Effect Analysis

FMEDA: Failure Modes, Effects, and Diagnostic Analysis

FO: Fail Open (valve open when power/air failure)

FST/FVST: Full Valve Stroke Test

GUI: Graphic User Interface

HAZID: Hazard Identification study

HAZOP: Hazard and Operability study

HFT: Hardware Fault Tolerance

HIPPS: High Integrity Pressure Protection System

HMI: Human Machine Interface

HP: High Pressure

ICSS: Integrated Control & Safety System

IEC: International Electrotechnical Commission

IPL: Independent Protection Layer

IS: Intrinsically Safe

LT: Life Time of the SIF  (also MT)

From M to Z

MDT: Mean Detection Time (MTTR=MDT+MRT)

MooN: M out of N (architecture)

MOV: Motorized Valve

MPRT: Maximum Permitted Repair Time

MRT: Mean Repair Time (MTTR=MDT+MRT)

MT: Mission Time of the SIF  (also LT)

MTBF: Mean Time Between Failures

MTTF: Mean Time To Failure

MTTFS: Mean Time To Fail Spuriously

MTTR: Mean Time To Restore (MTTR=MDT+MRT)

NC: Normally Closed

NO: Normally Open

PFD: Probability of Failure on Demand

PFDavg : Average Probability of Failure on Demand

PFH: Probability of Dangerous Failure per Hour

PFS: Probability of Failing Safely

PHA: Process Hazard Analysis

PL: Performace Level (for machinery)

PLC: Programmable Logic Controller

PRV: Pressure Relief Valve

PST: Process Safety Time

PST/PVST: Partial Valve Stroke Test

PTC: Proof Test Coverage  (also Cpt)

PTD: Proof Test Duration (hours with bypass activated)

RBD: Reliability Block Diagram

RO: Restriction Orifice

RRF: Risk Reduction Factor

SAT: Site Acceptance Tests

SFF: Safe Failure Fraction

SIF: Safety Instrumented Function

SIL: Safety Integrity Level

SIS: Safety Instrumented Function

SOV: Solenoid Valve or Shut-off Valve

SRS: Safety Requirements Specification

STR: Spurious Trip Rate

TBD: To Be Defined

TI: Test Interval


Measures of:

B: Combustion, Flame

F: Flow

L: Level

P: Pressure

R: Radiation

S: Speed, Frequency

T: Temperature

V: Vibration

Z: Position

For equipment:

C: Compressor

P: Pump

R: Relay

S: Switch

T: Transmitter

XV: Valve

XY: Solenoid Valve

For setpoint:

H: High

HH: High High

L: Low

LL: Low Low


PT-10: Pressure Transmitter

FSL-25: Flow Switch for Low Trip/Alarm

FSLL-26: Flow Switch for Low Low Trip/Alarm

ZSO-100: Proximity Switch for Open position

ZSC-100: Proximity Switch for Closed position

XV-100: Safety Valve

P-100A: Pump

VSHH-200: High High Vibration Switch

Related links:

Glossary of Terms: