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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.
Hazard Analysis
How HAZOP Works for Pharmaceutical Batch Reactors
HAZOP on pharmaceutical batch reactors examines each process step — charging, heating, reaction, holding, and discharge — as a distinct node in time, since the same vessel presents different hazards at different stages of the batch cycle.
Functional Safety
How SIL Assessment Works for Petrochemical Safety Instrumented Systems
SIL assessment for petrochemical facilities typically results in multiple safety instrumented functions at different integrity levels across a single unit, since high-consequence scenarios like large hydrocarbon releases demand higher SIL ratings than lower-consequence deviations.
Risk Assessment
How QRA Works for Refinery Major Accident Hazard Units
QRA for a refinery must cover a large set of credible major accident scenarios across crude and product storage, process units, and pipeline interconnections, integrated into facility-wide individual and societal risk figures for safety report and land-use planning submissions.
Asset Integrity
How Risk Based Inspection Works for Aging Refinery Assets
RBI for aging refinery assets ranks equipment by calculated risk of failure, combining active damage mechanism assessment with consequence of failure, so turnaround inspection scope and interval can concentrate on the equipment items that actually carry the highest risk.
Consequence Analysis
How Consequence Modelling Works for Ammonia Releases in Fertilizer Plants
Consequence modelling for ammonia releases in fertilizer plants requires heavy-gas dispersion modelling for refrigerated or pressurised storage failures, since ammonia vapour is denser than air at typical release temperatures and behaves as a slumping cloud rather than a passive plume.
Hazard Analysis
How HAZID Works for Green Hydrogen Facility Siting
HAZID for green hydrogen facilities identifies siting and layout hazards early, driven by hydrogen's wide flammability range, low minimum ignition energy, and high buoyancy, so that electrolyser, compression, and storage placement can account for these hazards before detailed design is finalised.
Consequence Analysis
How Fire and Explosion Risk Assessment Works for Hydrogen Storage
Fire and Explosion Risk Assessment for hydrogen storage must account for hydrogen's near-invisible flame, high flame speed in congested or confined layouts, and tendency toward deflagration-to-detonation transition under certain conditions, which differ materially from hydrocarbon fire and explosion behaviour.
Hazard Analysis
How HAZOP Works for Multi-Product Specialty Chemical Plants
HAZOP for multi-product specialty chemical plants must account for the fact that the same equipment train handles different chemistries across campaigns, so hazard findings valid for one product's process conditions may not hold for the next campaign using the same vessels.
Regulatory Compliance
How ERDMP Works for Fertilizer Ammonia Facilities
ERDMP for fertilizer ammonia facilities must plan for toxic release scenarios in addition to fire and explosion, requiring evacuation and shelter-in-place distances derived from toxic dispersion modelling alongside the more conventional thermal and blast planning distances.
Management Systems
How Process Safety Management Works for Multi-Product Chemical Plants
Process Safety Management for multi-product chemical plants places particular weight on the management of change element, since the frequency of recipe, raw material, and equipment allocation changes in these facilities is far higher than in dedicated single-product plants.
Consequence Analysis
How Thermal Hazard Testing Works for API Synthesis Routes
Thermal hazard testing for API synthesis uses calorimetric techniques to characterise the exothermic behaviour of a reaction before it is scaled up from laboratory to plant scale, where reduced surface-area-to-volume ratio makes heat removal proportionally harder.
Risk Assessment
How LOPA Works for Batch Process Scenarios
LOPA for batch process scenarios must account for sequence-dependent hazards and a higher reliance on operator action as an initiating event or protection layer, since batch operations involve manual steps like charging and valve alignment that continuous processes typically automate.
Functional Safety
How SIL Assessment Works for Pharmaceutical Reactor Safety Systems
SIL assessment for pharmaceutical batch reactors must account for demand modes that occur only during specific process stages, such as an emergency cooling function only relevant during the reaction hold, rather than a continuously-active protection layer.
Risk Assessment
How QRA Works for Specialty Chemical Complexes
QRA for specialty chemical complexes must account for changing hazardous inventory and chemistry across production campaigns, often requiring a bounding or worst-case-campaign approach rather than a single fixed inventory assumption used in continuous-process QRA.
Management Systems
How Management of Change Works as a Process Safety Control
Management of Change (MOC) is a process safety management element requiring that any modification to process technology, equipment, procedures, or personnel is reviewed and authorised before implementation, so that new hazards introduced by the change are identified and controlled.
Functional Safety
What is a Safety Requirements Specification (SRS)?
A Safety Requirements Specification (SRS) is the document defining the functional and integrity requirements a Safety Instrumented Function must meet, produced after SIL determination and before detailed Safety Instrumented System design begins.
Risk Assessment
What is Fault Tree Analysis? A Deductive Risk Assessment Method
Fault Tree Analysis (FTA) is a deductive, top-down technique that models the logical combinations of equipment failures and human errors that could lead to a defined top event, used to calculate that event's overall frequency.
Risk Assessment
What is Event Tree Analysis? Modelling Outcomes After an Initiating Event
Event Tree Analysis (ETA) is an inductive, forward-looking technique that models the range of possible outcomes following an initiating event, based on whether each subsequent safeguard succeeds or fails.
Regulatory Compliance
What is a Safety Case? Demonstrating Control of Major Accident Hazards
A Safety Case is a structured document demonstrating that major accident hazards at a facility have been identified and that risks are being controlled to a tolerable level, typically required for facilities notified as Major Accident Hazard installations.
Hazard Analysis
What is Inherently Safer Design? Reducing Hazards at the Source
Inherently Safer Design (ISD) is 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 to control an inherently hazardous condition.
Management Systems
What is a Pre-Startup Safety Review (PSSR)?
A Pre-Startup Safety Review (PSSR) is a documented check confirming that construction and equipment match design intent, safety procedures are in place, and hazard analysis recommendations have been addressed before a new or modified facility is started up.
Management Systems
What is Mechanical Integrity in Process Safety Management?
Mechanical integrity is the Process Safety Management element ensuring that safety-critical equipment — pressure vessels, piping, relief systems, instrumentation — is designed, fabricated, installed, and maintained to remain fit for purpose throughout its operating life.
Hazard Analysis
What Triggers a Process Hazard Analysis Revalidation?
Process Hazard Analysis revalidation is triggered either by a scheduled interval, commonly every five years, or by an unscheduled event such as a significant management of change, a near-miss revealing an unaddressed hazard, or a change in applicable regulatory requirements.
Consequence Analysis
What is Domino Effect Analysis in Major Hazard Facilities?
Domino effect analysis assesses how an initial incident — typically a fire, explosion, or toxic release — can escalate to affect neighbouring equipment or units through thermal radiation, blast overpressure, or fragment impact, extending the scale of consequences beyond the originating event.
Hazard Analysis
What is a Hazard and Risk Register?
A hazard and risk register is a structured, maintained record of identified hazards, their assessed risk, and the status of any recommended risk reduction action, serving as the ongoing link between hazard analysis studies and their real-world closure.
Risk Assessment
What Makes a Protection Layer 'Independent' in LOPA?
A protection layer qualifies as independent in LOPA only if it is capable of preventing the scenario's consequence regardless of the initiating event and regardless of the success or failure of any other protection layer credited for the same scenario.
Functional Safety
What is Demand Mode in Safety Instrumented Function Design?
Demand mode describes how frequently a Safety Instrumented Function is called upon to act; low-demand mode functions are assessed using average probability of failure on demand (PFDavg), while high-demand or continuous mode functions are assessed using probability of dangerous failure per hour.
Management Systems
What is a Process Safety Audit and How Does it Differ from a Hazard Study?
A process safety audit assesses whether a facility's actual management systems, procedures, and physical condition comply with its own standards and applicable regulations, distinct from a hazard analysis study, which identifies hazards inherent to a process design.
Risk Assessment
What is a Consequence Severity Category in Risk Ranking?
A consequence severity category is a qualitative or semi-quantitative ranking — such as minor, serious, major, or catastrophic — assigned to the credible outcome of a hazard scenario, used as an input to risk matrices and as an initial screening step before more detailed quantitative assessment.
Regulatory Compliance
What is Threshold Planning Quantity Under India's MSIHC Rules?
Threshold Planning Quantity (TPQ) is the quantity of a hazardous chemical above which a facility becomes subject to Major Accident Hazard notification and associated statutory obligations under regulations such as India's MSIHC Rules, 1989.
Functional Safety
What is Proof Testing in Functional Safety?
Proof testing is a periodic test performed on a safety instrumented function to reveal dangerous failures not detected by automatic diagnostics, restoring the function's assumed failure rate and keeping its calculated probability of failure on demand valid over its operating life.
Hazard Analysis
What Makes an Effective Barrier in Bow-Tie Analysis?
An effective barrier in Bow-Tie analysis is a control — physical, procedural, or human-action — that is specific, independent, and verifiable, capable of genuinely preventing a threat from causing the top event or limiting consequences once it occurs.
Functional Safety
What is Common Cause Failure Analysis in Safety Instrumented Systems?
Common cause failure analysis assesses whether multiple redundant elements of a safety instrumented system could fail simultaneously from a shared cause — such as a shared power supply, calibration error, or environmental condition — undermining the risk-reduction benefit that redundancy is intended to provide.
Functional Safety
What is Voting Architecture in SIL Design?
Voting architecture describes the configuration of redundant sensors or final elements in a safety instrumented function, expressed as MooN (M-out-of-N), determining how the system tolerates individual element failures versus how often it produces spurious trips.
Regulatory Compliance
What is Consent to Operate and How Does Process Safety Documentation Support It?
Consent to Operate is the statutory authorisation issued by a pollution control board or equivalent regulator permitting a facility to operate, subject to compliance conditions that, for hazardous chemical facilities, commonly include process safety documentation such as safety reports and emergency plans.
Hazard Analysis
What is What-If Analysis? A Lighter-Weight Hazard Identification Technique
What-If Analysis is a qualitative hazard identification technique in which a review team poses structured 'what if' questions about a process to uncover hazards and operability concerns, often used as a lighter-weight alternative to HAZOP for lower-complexity or lower-hazard processes.
Hazard Analysis
What is Checklist Analysis in Process Hazard Review?
Checklist Analysis is a hazard identification technique that compares a process or facility against a standardised list of known hazards and required safeguards drawn from codes, standards, and prior experience, verifying known concerns are addressed rather than discovering novel scenarios.
Management Systems
What is Process Safety Information (PSI)?
Process Safety Information (PSI) is the foundational Process Safety Management element comprising the technical data on process chemistry, technology, and equipment that hazard analysis studies, operating procedures, and management of change reviews all depend on being accurate and current.
Risk Assessment
What is a Risk Matrix and How Is It Used in Process Safety?
A risk matrix is a tool that combines qualitative or semi-quantitative likelihood and consequence categories into a grid, used to rank and prioritise identified hazards for further, more detailed assessment.
Risk Assessment
What is an Independent Protection Layer (IPL)?
An Independent Protection Layer (IPL) is a device, system, or action capable of preventing a scenario from proceeding to its undesired consequence, independent of the initiating event and of other IPLs credited for the same scenario in a LOPA study.
Comparisons
Side-by-Side Method Comparisons
HAZOP vs HAZID
HAZOP vs HAZID: What Is the Difference?
HAZID is a qualitative, facility-wide hazard identification study performed early at concept or pre-FEED stage, before detailed design exists. HAZOP is performed later, once P&IDs are available, and examines process deviations node-by-node in much finer detail. HAZID informs layout and siting; HAZOP informs safeguarding decisions.
LOPA vs QRA
LOPA vs QRA: What Is the Difference?
LOPA (Layer of Protection Analysis) is a scenario-based, order-of-magnitude technique typically applied per HAZOP finding to judge whether existing safeguards are adequate. QRA (Quantitative Risk Assessment) is fully quantitative, models consequences with specialist software across an entire facility, and produces individual risk contours and societal risk F-N curves used for land-use planning and ALARP demonstration.
SIL Assessment vs LOPA
SIL Assessment vs LOPA: What Is the Difference?
LOPA (Layer of Protection Analysis) is the risk assessment step that determines how much additional risk reduction a scenario needs, often expressed as a target SIL. SIL assessment is the subsequent engineering step that determines and verifies whether a designed Safety Instrumented Function (sensor, logic solver, final element) actually achieves that target Safety Integrity Level per IEC 61508/61511.
API 580 vs API 581
API 580 vs API 581: What Is the Difference?
API 580 provides the qualitative and semi-quantitative Risk Based Inspection (RBI) methodology and program management framework. API 581 provides the detailed quantitative risk calculation methodology — probability of failure and consequence of failure models — used to implement an API 580-aligned RBI program with calculated risk numbers.
PSM vs PSSR
PSM vs PSSR: What Is the Difference?
PSM (Process Safety Management) is the overarching management system of interrelated elements that prevents catastrophic chemical releases across a facility's entire lifecycle. PSSR (Pre-Startup Safety Review) is one specific PSM element — a checklist-driven review confirming a process is safe to start up after new construction or a significant management-of-change modification.
Bow-Tie Analysis vs HAZOP
Bow-Tie Analysis vs HAZOP: What Is the Difference?
HAZOP is a detailed, node-by-node hazard identification technique that systematically generates process deviations, causes, consequences, and safeguards. Bow-Tie Analysis is a visual risk communication method that maps a single major hazard's threats, barriers, and consequences in an intuitive diagram, typically used downstream of HAZOP to communicate major accident hazard scenarios to non-specialist audiences.
HAZID vs QRA
HAZID vs QRA: What Is the Difference?
HAZID is a qualitative, early-stage technique that identifies which major hazards exist at a facility; QRA is a fully quantitative technique, performed later once design details are available, that calculates numerical individual and societal risk from those hazards.
PHA vs HAZOP
PHA vs HAZOP: What Is the Difference?
Process Hazard Analysis (PHA) is an umbrella term covering several structured hazard identification methods — including HAZOP, What-If Analysis, and Checklist Analysis — while HAZOP is one specific, systematic technique within that broader category.
RBI vs RCM
RBI vs RCM: What Is the Difference?
Risk Based Inspection (RBI) is a methodology for prioritising inspection effort and intervals on static equipment based on calculated risk of failure, while Reliability Centered Maintenance (RCM) is a methodology for determining the most effective maintenance strategy for equipment — commonly rotating and active equipment — based on its specific failure modes and consequences.
DSC vs Adiabatic Calorimetry
DSC vs Adiabatic Calorimetry: What Is the Difference?
Differential Scanning Calorimetry (DSC) is a rapid, small-sample thermal screening test that detects whether a reaction mixture has any exothermic or decomposition event in a given temperature range, while adiabatic calorimetry is a more detailed, slower test that closely simulates a real cooling-failure scenario to measure realistic runaway reaction severity.
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.
- PHA Revalidation
- The periodic review of a previously completed process hazard analysis to confirm it remains valid, typically triggered by an elapsed time interval or accumulated process changes.
- SRS(Safety Requirements Specification)
- The document defining the functional and integrity requirements a Safety Instrumented Function must meet, produced after SIL determination and before detailed SIS design.
- Proof Test
- A periodic test performed on a safety instrumented function to reveal dangerous failures not detected by automatic diagnostics, restoring its assumed failure rate.
- Common Cause Failure(CCF)
- A failure affecting multiple redundant elements of a safety system simultaneously from a shared cause, reducing the risk-reduction benefit that redundancy would otherwise provide.
- Voting Architecture
- The configuration of redundant sensors or final elements in a safety instrumented function, expressed as MooN (M-out-of-N), determining how failures are tolerated versus how spurious trips occur.
- What-If Analysis
- A qualitative hazard identification technique in which a review team poses structured 'what if' questions about a process to uncover hazards and operability concerns, often used as a lighter-weight alternative to HAZOP.
- Checklist Analysis
- A hazard identification technique that compares a process or facility against a standardised list of known hazards and required safeguards drawn from codes, standards, and prior experience.
- Consequence Severity Category
- A qualitative or semi-quantitative ranking (e.g. minor, serious, major, catastrophic) assigned to the credible outcome of a hazard scenario, used as an input to risk matrices and LOPA.
- Escalation Scenario
- A hazard scenario in which an initial loss of containment or fire triggers failure of neighbouring equipment via thermal radiation, overpressure, or fragment impact, extending the incident's consequences.
- Fault Tree Analysis(FTA)
- A deductive, top-down technique that models the logical combinations of equipment failures and human errors that could lead to a defined top event, used to calculate its frequency.
- Event Tree Analysis(ETA)
- An inductive, forward-looking technique that models the range of possible outcomes following an initiating event, based on whether each subsequent safeguard succeeds or fails.
- Safety Case
- A structured document demonstrating that major accident hazards at a facility have been identified and that risks are being controlled to a tolerable level, typically required for Major Accident Hazard installations.
- Consent to Operate
- The statutory authorisation issued by a pollution control board or equivalent regulator permitting a facility to operate, subject to compliance conditions that may include process safety documentation.
- Threshold Planning Quantity(TPQ)
- The quantity of a hazardous chemical above which a facility becomes subject to Major Accident Hazard notification and associated statutory obligations under regulations such as India's MSIHC Rules.
- Node
- A defined section of a P&ID with a consistent design intent, used as the unit of examination in a HAZOP study.
- Basic Process Control System(BPCS)
- The control system managing normal process operation, distinct from and not to be relied upon as a substitute for a Safety Instrumented System unless it independently meets IPL qualification criteria.