liminfoHAZOP Reference
Free reference guide: HAZOP Reference
About HAZOP Reference
This HAZOP Reference is a searchable cheat sheet for Hazard and Operability Study methodology used in process safety engineering. It covers all seven standard guide words (NO/NOT, MORE, LESS, REVERSE, PART OF, AS WELL AS, OTHER THAN) with detailed application examples, typical causes, and consequences for each deviation.
The reference includes process deviation types (flow, temperature, pressure, level), a complete 5x5 risk matrix with severity and likelihood ratings per IEC 61882, Safety Integrity Level (SIL) definitions per IEC 61511/61508, SIL determination methods (risk graph, LOPA), and Independent Protection Layer (IPL) credit values for BPCS, alarms, PSV, SIS, and other safeguards.
Designed for process safety engineers, HAZOP facilitators, chemical engineers, plant operators, and HSE professionals who need quick reference to guide word meanings, risk ranking criteria, SIL/LOPA calculations, HAZOP worksheet formats, team composition guidelines, and real-world analysis examples for reactors, storage tanks, and heat exchangers.
Key Features
- All seven HAZOP guide words with definitions, application examples, causes, and consequences
- Process deviation types for flow, temperature, pressure, and level with cause-consequence chains
- 5x5 risk matrix with five severity levels (negligible to catastrophic) and five likelihood ratings
- SIL 1-4 definitions with PFD ranges, risk reduction factors per IEC 61511/61508
- SIL determination methods: risk graph, risk matrix, and LOPA with IPL credit values
- HAZOP node selection criteria, standard worksheet format per IEC 61882, and team composition guide
- Real-world HAZOP examples for CSTR reactor, atmospheric storage tank, and shell-and-tube heat exchanger
- Filterable by category: Guide Words, Deviation Types, Risk Matrix, SIL, Node/Recording, Application Examples
Frequently Asked Questions
What are the seven HAZOP guide words?
The seven standard HAZOP guide words are: NO/NOT (complete negation), MORE (quantitative increase), LESS (quantitative decrease), REVERSE (opposite direction), PART OF (partial achievement), AS WELL AS (additional activity or component), and OTHER THAN (completely different from design intent). Each is applied to process parameters like flow, temperature, pressure, and level.
How does the HAZOP risk matrix work?
The 5x5 risk matrix combines severity (1-Negligible to 5-Catastrophic) with likelihood (A-Extremely Unlikely to E-Frequent). The intersection determines risk ranking: H (High, immediate reduction required), M (Medium, reduce as reasonably practicable), or L (Low, current measures adequate). This follows the ALARP principle.
What are SIL levels and how are they determined?
Safety Integrity Levels (SIL 1-4) define required reliability for safety instrumented systems per IEC 61511. SIL 1: PFD 10^-1 to 10^-2 (RRF 10-100), SIL 2: PFD 10^-2 to 10^-3 (RRF 100-1000), SIL 3: PFD 10^-3 to 10^-4 (RRF 1000-10000). SIL is determined via risk graph, risk matrix method, or LOPA.
What are IPL credits in LOPA?
Independent Protection Layers (IPLs) each receive PFD credit values: BPCS (10^-1), alarm with operator action (10^-1), PSV (10^-1 to 10^-2), rupture disc (10^-1 to 10^-2), SIS (10^-1 to 10^-3 depending on SIL), blast wall (10^-1 to 10^-2), dike (10^-2 if fully enclosed). IPLs must be independent, effective, and auditable.
How do I select HAZOP analysis nodes?
Select nodes by major equipment (reactor, column, heat exchanger, tank), where process conditions change (temperature, pressure, phase), and where design intent can be clearly defined. Optimal node size covers 1-2 P&ID sheets. Mandatory nodes include reaction processes, hazardous material storage/transfer, high pressure/temperature sections, and utilities.
What does a standard HAZOP worksheet include?
Per IEC 61882, the HAZOP worksheet has 14 columns: Node, Design Intent, Guide Word, Deviation, Causes, Consequences, Existing Safeguards, Severity, Likelihood, Risk Ranking, Recommendations, Action By, Due Date, and Status. The worksheet systematically documents each deviation analysis and tracks follow-up actions.
Can you show a HAZOP example for a chemical reactor?
For an exothermic CSTR (80 degrees C, 5 bar, 2 hr residence): Deviation MORE TEMPERATURE caused by cooling water failure leads to runaway, overpressure, and rupture. Existing safeguards are TIC, TAH, PSV. Severity 4, Likelihood C gives Risk M. Recommendation: add independent SIS at SIL 2. Deviation NO FLOW (Feed A) from pump failure causes unreacted B accumulation and runaway on restart.
Is this HAZOP reference free to use?
Yes, this HAZOP cheat sheet is completely free with no account required. All guide words, risk matrix criteria, SIL definitions, and analysis examples are searchable and filterable by category in your browser. It is part of liminfo.com's collection of free process safety engineering reference tools.