This document provides an overview of Hazard and Operability Studies (HAZOP). It discusses that HAZOP is a systematic technique used to identify potential problems in chemical process facilities. The document outlines the history and development of HAZOP since the 1970s. It then describes the key aspects of conducting a HAZOP study, including assembling a multidisciplinary team, identifying deviations using guide words, evaluating causes and consequences, and developing recommendations. The document also notes some limitations of the HAZOP methodology.

1. HAZOP
HAZARD & OPERABILITY
presented by
Artina Deka_19056
(8th Sem)

2. INTRODUCTION
Safety is a top priority in the chemical industry .
Several structured process hazard analysis (PHA) methodologies have
been developed :
• HAZOP
• What-If (What If Checklist)
• Failure modes and affects analysis (FMEA)
• Fault-tree analysis (FTA)
• Event-tree analysis (ETA)
• Cause–consequence analysis
• Bow-tie analysis.
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3. HISTORY
• HAZOP has its origins in the 1970s, developed by
the Imperial Chemical Industries (ICI)
• But it really became a standard after an explosion
in a chemical plant producing nylon intermediate
in the United Kingdom that killed 28 people and
injured dozens of others .
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Inductive: bottom-up methods that start from known causes and identify possible effects .
Deductive : top-down methods that start from known effects and seek possible causes

5. • The GDP has doubled
since 1980, while the
number of accidents has
remained essentially
constant, which
demonstrates that the
commitment to safety has
improved with time
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6. HAZOPS
• HAZOP is a systematic approach to determine potential
problems that may be uncovered by reviewing the safety of
designs and revisiting existing processes and operations in
chemical, pharmaceutical, oil and gas, and nuclear
industries.
• The ultimate purpose was to eliminate any cause leading
to major accidents, including fire, explosions, and toxic
releases.
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GUIDE WORD

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The HAZOP is a hierarchical procedure, consisting in the following steps :
1. selection of a section of the plant/process and explanation of the design intent.
2. definition of the purpose of the HAZOP and boundaries of the study
3. formation of the HAZOP multidisciplinary team.
4. identification of the important parameters to be studied
5. Development of a list of deviations by combining guide-words and parameters
6. For each deviation, identify potential causes, consequences, frequency of deviation,
and risk management strategies
7. Reporting.
HAZOP STUDY

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CAUSES
Typical causes of a deviation belong to the following components of a system:
• hardware (equipment, piping, instrumentation, construction, and materials)
• software (specifications, instructions, and procedures)
• human (management, operations, and maintenance)
• external (services, natural events, and intentional malicious actions).

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CONSEQUENCES
 Documentation

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The final HAZOP STUDY REPORT include:
• summary
• conclusions and outputs
• scope and objectives
• worksheets
• marked-up design representation
• list of the drawings and documentation referred to
• historical information used in the HAZOP analysis.

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After the study
HAZOP issues are categorized as:
• significant hazard
• minor hazard
• standards/operability issues
• deferred problems
• line diagram errors.

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The safeguard should help to reduce the occurrence frequency of the deviation or to mitigate its
consequences and, in principle, can be categorized into five categories:
a. Inherent: by minimizing or possibly eliminating the hazard
b. Spatial: for reducing the hazardous effects (distance and segregation)
c. Passive: process and equipment design features that reduce frequency or consequence without
the active functioning of any device or requiring human input (e.g., storage tank dike and fence)
d. Active: safety controls, alarms, and interlocks to detect and respond to deviations
e. Procedural: management approaches to prevent incidents or minimize the consequences (e.g.,
policies ,operating procedures, training, administrative checks, etc.).
SAFEGUARD

20. HAZOP
LEVEL
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PROCESS DEVELOPMENT
Identifies basic hazards of materials and operations and assembles information on previous
hazard experiences.
PROCESS DEFINITION
Examines process items on draft flowsheets, identifies problematic designs, assesses
strategy versus relevant hazards, and establishes prevention and protection systems and
alarms.
PROCESS DESIGN
Reviews and confirms the detailed flowsheets–P&ID with suggestions to improve process safety and
operability (front end engineering design [FEED] stage)

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PROCUREMENT & CONSTRUCTION
Verifies hardware and implementation of suggested actions. Examines operating and emergency
procedures.
COMMISSIONING
Appraises operating team’s ability to commission the research and development (R&D)
laboratory experiments . Reviews pre startup safety, including cleanliness and purging tests,
and confirms compliance with company and legislative standards.
OPERATION & DECOMISSIONING
Confirms action items identified in previous reviews were addressed post-start up. Verifies that
operation matches the considerations made in the previous studies.

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•Study Leader - This person leads the study and should have experience with HAZOP studies
already.
•Recorder / Scribe - This person documents everything about the study including causes,
consequences, actions, deviations, and more.
•Process Designer - This person provides details about the intent of designs.
•Operator - This person will operate the process.
•Specialist - This person provides specialized technological knowledge about the process.
•Maintainer - This person offers information and details about the maintenance of equipment or
other machinery.
Assembling a Team
Operability of this method requires a team of experts in areas such as operations, maintenance,
instrumentation, engineering, process design, etc.

24. LIMITATIONS OF HAZOP
1. The procedure is meticulous and time consuming
2. It is unwarranted for systems where the risk is slight.
3. It relies on heuristics rather than algorithms.
4. Multiple deviations complicate the analysis
5. Ignore minor hazards such as less-obvious chemical reactivity hazards arising from loss of control of
intended chemical reactions, self-reacting materials, and chemical incompatibility.
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Hazard pictograms (symbols)
Hazard pictograms alert us to the presence of a hazardous chemical.

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REFERENCES
https://hsseworld.com/wp-content/uploads/2021/01/HAZOP-GUIDE-TO-BEST-PRACTICE-IChemE-
THIRD-EDITION.pdf
https://onlinelibrary.wiley.com/doi/10.1002/cjce.24520