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Inherent Safer Design

Inherent Safety Index Assessment

Quantitative inherent safer design scoring that lets you compare design options

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Technical overview

Inherent Safety
Index Assessment

Inherent safer design is easy to endorse in principle and hard to act on at a decision gate, because safer is rarely self evident when two process routes each trade one hazard for another. Inherent safety index methods turn that qualitative judgement into comparable and defensible numbers, scoring the chemical, process, and structural hazard contributions so that design alternatives can be ranked on inherent risk rather than intuition. Our team selects the index matched to your design stage and the available data. We use the Heikkila ISI and PIIS for early route and concept selection, and INSET tools together with the Dow Fire and Explosion Index and Chemical Exposure Index where the flowsheet supports quantification of fire, explosion, and toxicity. We document the scoring basis so the chosen option withstands later scrutiny. The result turns inherent safer design from an aspiration into a selection criterion you can defend, captured before the design is frozen.

Inherent Safety Index Assessment Overview
Engineering process

Inherent Safety Index Assessment workflow

ISD Index Methodology Selection

Select ISD index method per project stage, Dow Fire & Explosion Index (FEI) for unit level, Dow Chemical Exposure Index (CEI) for toxic, Mond Index for refined screening, INSET (Inherent SHE Evaluation Tool), i IS Index (Heikkila Hurme), align with CCPS / IChemE ISD guidance.

Process Data & Inventory Compilation

Compile process data per index, material flammability / reactivity / toxicity, inventory per node, process temperature / pressure, equipment type and arrangement, align with HMB and P&ID source documents.

Index Calculation & Risk Banding

Calculate index per node, F&EI (material factor × general process hazard × special process hazard), CEI (toxic dispersion concentration × distance), apply banding (low / moderate / intermediate / heavy / severe) per Dow / Mond reference scales.

ISD Principle Application

Apply ISD principles, Minimise (inventory reduction), Substitute (less hazardous material), Moderate (temperature / pressure / dilution), Simplify (process simplification), identify design options per node and quantify index reduction.

Option Evaluation & Trade Off Analysis

Quantify capex / opex impact per option, compare against index reduction and downstream LOPA / SIL / FERA credit, conduct trade off analysis with non ISD risk reduction options (engineering safeguards), align with ALARP gross disproportion.

ISD Recommendation Register & Integration

Issue ISD recommendation register with risk rank, capex / opex estimate, and implementation timeline, integrate with FEED decision making and HAZOP/SIL workflow, align with CCPS RBPS Inherently Safer Design element.

Inherent Safety Index Assessment Scope
Scope of work

Every deliverable from basis to handover

Complete Inherent Safety Index Assessment scope covering every calculation, drawing, specification, and construction support activity.

Selection of the index method for each design stage
Scoring of inventory, condition, and complexity
Analysis of the energy and toxicity components
Comparison of materials and process routes
Sensitivity and uncertainty assessment
Aggregation and decision support
Integration with your stage gate process
Engineering outcomes

Outcomes of Inherent Safety Index Assessment

Inherent Hazard Index Reduction
  • Enables objective comparison of design options
  • Identifies the drivers of inherent hazard
  • Supports stage gate decisions
  • Hardens your inherent safer design culture
CCPS, Dow Fire Index, and Mond Index Defence
  • Follows CCPS inherent safer design and EPSC guidance
  • Documents the quantitative inherent safer design basis
  • Supports dialogue with the regulator and the insurer
  • Underpins an ALARP demonstration
Design Option Comparison Quality
  • Strengthens design dialogue across your teams
  • Embeds inherent safer design in stage gate reviews
  • Supports the inherent safer design baseline used in MOC
  • Improves the rigour of your design selection
Hazard Reduction at Minimum Capex
  • Targets capex toward inherently safer options
  • Reduces the safeguard burden through a lower base hazard
  • Supports licensing and technology selection
  • Optimises insurance loadings
Standards & references

Codes & standards we work to

Heikkila ISIINSET ToolkitPIISCCPS ISDEPSC ISDDow F&EI / CEI
When to engage

Triggers that signal the need

A technology selection decisionEvaluation of FEED optionsProcess route selectionA stage gate reviewA licensor comparisonAn inherent safer design culture programme
Industries served

Where Inherent Safety Index Assessment applies

Oil & Gas, Upstream

Wellheads, separators, gas compression, FPSO topsides, produced water systems.

UpstreamOffshoreFPSO
Refineries & Petrochemicals

Distillation columns, reactors, heat exchangers, storage spheres, LPG handling.

RefiningPetrochemical
LNG & Gas Processing

Cryogenic exchangers, liquefaction trains, BOG compressors, storage and sendout.

LNGCryogenic
Specialty Chemicals

Reactive systems, batch reactors, solvent handling, runaway reaction scenarios.

ReactiveBatch
Power Generation

Boilers, HRSGs, steam headers, hydrogen systems, ammonia SCR units.

PowerHydrogen
Pharma & Food

Sterile vessels, CIP/SIP, pressure fermenters, solvent recovery, spray dryers.

PharmaFood & Bev
What we deliver

Tangible deliverables

  • Inherent safety index scoring for each design option
  • A comparison and ranking report
  • A sensitivity analysis
  • A decision support narrative
  • A stage gate input package
  • An inherent safer design baseline for MOC
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