Knowledge Center
Process Safety, Explained
Definitive answers to the questions engineers, regulators and AI assistants ask most about process safety methodology.
Articles
In-Depth Knowledge Base
Hazard Analysis
What is HAZOP? A Complete Guide to Hazard and Operability Studies
HAZOP (Hazard and Operability Study) is a structured, team-based technique for identifying hazards and operability problems in a process by applying standard guide words to process parameters at each node of a P&ID.
Functional Safety
What is SIL? Safety Integrity Levels Explained
SIL (Safety Integrity Level) is a measure, on a scale of 1 to 4, of how reliably a safety instrumented function reduces risk, as defined in the IEC 61508 and IEC 61511 standards.
Risk Assessment
What is LOPA? Layer of Protection Analysis Explained
LOPA (Layer of Protection Analysis) is a semi-quantitative risk assessment technique that evaluates whether the independent protection layers safeguarding a hazard scenario provide sufficient risk reduction.
Risk Assessment
What is QRA? Quantitative Risk Assessment Explained
QRA (Quantitative Risk Assessment) is a numerical methodology that combines failure frequency data with fire, explosion and dispersion consequence modelling to calculate individual risk and societal risk for a facility.
Risk Assessment
What is ALARP? As Low As Reasonably Practicable Explained
ALARP (As Low As Reasonably Practicable) is a risk tolerability principle requiring that risk be reduced until the cost of further reduction becomes grossly disproportionate to the safety benefit gained.
Asset Integrity
What is RBI? Risk Based Inspection Explained
RBI (Risk Based Inspection) is a methodology, codified in API 580 and API 581, that prioritises inspection resources and intervals according to the calculated risk of failure for each piece of equipment.
Management Systems
What is PSM? Process Safety Management Explained
PSM (Process Safety Management) is a structured management system of interrelated elements designed to prevent or mitigate catastrophic releases of hazardous chemicals.
Regulatory Compliance
What is ERDMP? Emergency Response and Disaster Management Plan Explained
ERDMP (Emergency Response and Disaster Management Plan) is a statutory document required under India's MSIHC Rules, 1989 for Major Accident Hazard units, covering on-site and off-site emergency response arrangements.
Hazard Analysis
What is Bow-Tie Analysis? A Visual Risk Assessment Method
Bow-Tie Analysis is a visual risk assessment method that maps the threats leading to a top event and the consequences flowing from it, alongside the preventive and mitigative barriers controlling each pathway.
Consequence Analysis
What is Consequence Modelling? Dispersion, Fire and Explosion Simulation Explained
Consequence modelling is the quantitative simulation of the physical effects — gas dispersion, fire, and explosion — resulting from a loss-of-containment event, used to determine hazard footprint distances.
Glossary
Industrial Process Safety Glossary
- HAZOP(Hazard and Operability Study)
- A structured, team-based technique that uses guide words applied to process parameters at each P&ID node to systematically identify deviations, causes, consequences and safeguards.
- HAZID(Hazard Identification)
- An early-stage, qualitative technique for identifying major hazards related to a facility and its site, typically performed at concept or pre-FEED stage.
- SIL(Safety Integrity Level)
- A measure, on a scale of 1 to 4, of the reliability required of a safety instrumented function to achieve adequate risk reduction, per IEC 61508/61511.
- LOPA(Layer of Protection Analysis)
- A semi-quantitative technique evaluating whether independent protection layers provide sufficient risk reduction for a hazard scenario.
- QRA(Quantitative Risk Assessment)
- A numerical risk assessment combining failure frequency and consequence modelling to calculate individual and societal risk for major hazard scenarios.
- ALARP(As Low As Reasonably Practicable)
- A risk tolerability principle requiring risk reduction until further reduction cost is grossly disproportionate to the safety benefit gained.
- PSM(Process Safety Management)
- A structured management system of interrelated elements designed to prevent or mitigate catastrophic releases of hazardous chemicals.
- RBPS(Risk-Based Process Safety)
- The CCPS 20-element process safety management framework organised under four pillars: commit, understand hazards, manage risk, and learn from experience.
- ERDMP(Emergency Response and Disaster Management Plan)
- A statutory document under India's MSIHC Rules detailing on-site and off-site emergency response arrangements for Major Accident Hazard units.
- RBI(Risk Based Inspection)
- A methodology per API 580/581 that prioritises inspection effort and intervals based on calculated probability and consequence of equipment failure.
- Bow-Tie Analysis
- A visual risk assessment method mapping threats leading to a top event and the consequences flowing from it, alongside preventive and mitigative barriers.
- IPL(Independent Protection Layer)
- A device, system or action capable of preventing a scenario reaching its undesired consequence, independent of the initiating event and other credited IPLs.
- PFDavg(Average Probability of Failure on Demand)
- The calculated average probability that a safety instrumented function fails to perform its safety action when called upon.
- MAH(Major Accident Hazard)
- A facility storing or handling hazardous chemicals above threshold quantities defined in India's MSIHC Rules, triggering additional statutory safety obligations.
- F-N Curve
- A plot of cumulative frequency against number of fatalities, used to express and assess societal risk against tolerability criteria.
- Individual Risk
- The calculated annual probability that a specific person at a specific location will be killed by an accident arising from a facility's hazardous activities.
- Societal Risk
- The relationship between frequency and the number of people in a population suffering harm from defined hazards, typically expressed as an F-N curve.
- Source Term
- The release rate, duration and phase of material escaping a loss-of-containment event, the critical input to dispersion and fire/explosion modelling.
- VCE(Vapour Cloud Explosion)
- An explosion resulting from the ignition of a flammable vapour cloud that has accumulated after a release, generating blast overpressure.
- BLEVE(Boiling Liquid Expanding Vapour Explosion)
- A sudden, catastrophic failure of a vessel containing a superheated liquid, releasing flashing vapour and liquid, often with a fireball if flammable.
- Jet Fire
- A turbulent diffusion flame resulting from combustion of a pressurised, momentum-driven release of flammable gas or liquid.
- Pool Fire
- A fire resulting from ignition of a flammable liquid that has pooled on a surface, producing a roughly vertical flame above the pool.
- Flash Fire
- The rapid, non-explosive combustion of a flammable vapour cloud that ignites without significant overpressure generation.
- Dispersion Modelling
- The simulation of how a released gas or vapour spreads through the atmosphere under given weather and terrain conditions.
- MOC(Management of Change)
- A PSM element requiring systematic review and authorisation of changes to process technology, equipment, procedures or personnel before implementation.
- PHA(Process Hazard Analysis)
- An umbrella term for structured methods — including HAZOP, What-If, and Checklist analysis — used to identify and evaluate process hazards.
- Safety Instrumented Function(SIF)
- A combination of sensor, logic solver and final element designed to achieve a specific safety integrity level and bring a process to a safe state on detection of a hazardous condition.
- Risk Matrix
- A tool that combines qualitative or semi-quantitative likelihood and consequence categories into a grid used to rank and prioritise identified hazards.
- Domino Effect
- The escalation of an initial incident to involve additional equipment or units, often via fire, explosion overpressure, or fragment impact.
- Inherently Safer Design(ISD)
- A design philosophy that seeks to eliminate or reduce hazards at the source — through substitution, minimisation, moderation or simplification — rather than relying solely on added safeguards.
- DSC(Differential Scanning Calorimetry)
- A thermal analysis technique used to screen small chemical samples for exothermic or decomposition events and estimate their onset temperature.
- ATR(Adiabatic Temperature Rise)
- The temperature increase a reaction mixture would undergo if all heat released by the reaction were retained with no loss to the surroundings, used to gauge runaway reaction severity.
- TMRad(Time to Maximum Rate (adiabatic))
- The time for a reaction mixture to reach its maximum self-heating rate under adiabatic conditions at a given temperature, used to set safe holding times after a cooling failure.
- Runaway Reaction
- An uncontrolled, self-accelerating exothermic reaction in which heat generation outpaces heat removal, potentially leading to vessel overpressure or rupture.