Safety Engineering - HAZOP Study

Safety Engineering - HAZOP

• HAZOP stands for Hazard and Operability Study.
• HAZOP is a systematic technique for identifying hazards in plants or equipment.
• It aims to find problems with plant operability and identify hazards.
• HAZOP is a process to identify and assess risks in a plant or system.
• Each segment of the plant or equipment is examined for deviations from normal operating conditions.

Safety Analysis Methods

• Failure Modes and Effect Analysis (FMEA)
• Fault Tree analysis (FTA)
• Hazard and Operability Analysis (HAZOP)
• Job Hazard analysis (JHA)
• Markov Method
• Control Charts

HAZOP Study

• HAZOP is a systematic and thorough analysis used in plant design and operation.
• HAZOP methodology is not for problem solving; its aim is to identify possible problems and potential hazards.
• HAZOP study is for identifying plant or equipment hazards and operability problems.
• It examines each segment of a plant and looks at potential deviations from normal operating conditions.
• This includes pipelines, equipment, instruments, and other components.

When to Conduct HAZOP

• Project exploration/ preliminary project assessment
• Project definition stage
• Design and procurement stage
• During final stages of construction
• During plant commissioning
• During normal operation, sometimes after start-up

Documents Needed for HAZOP Study

• Preliminary HAZOP:
  • Process Flow Sheet or diagram (PFS or PFD)
  • Description of the Process
• Detailed HAZOP:
  • Piping and instrumentation diagram (P&ID)
  • Process Calculations
  • Process Data Sheets
  • Instrument Data Sheets
  • Interlock Schedules
  • Layout Requirements
  • Hazardous Area Classification
  • Description of the Process
• Diagrams such as P&ID and PFD are useful visual aids for the analysis.

HAZOP Study Features

• Subsystems of interest: Lines, valves, equipment, vessels, etc.
• Modes of operation: Normal operation, start-up, shut-down, maintenance/construction/inspection
• Trigger events: Human failure, Equipment/instrument/component failure, Supply failure, Emergency environment event.
• Effects within plant: Changes in chemical conditions, Changes in inventory, Change in chemical physical conditions.
• How are hazardous conditions detected?: During normal operation, Upon human failure, Upon component failure, In other circumstances
• Contingency actions: Improve isolation, Improve protection
• Corrective actions: Change of process design, Change of operating limits, Change of system reliability, Improvement of material, Change control system Add/remove materials.

Guide Words

• No, None: Negation of intention (No flow)
• More Of: Quantitative increase
• Less Of: Quantitative decrease
• As Well As (More Than): Qualitative increase
• Part Of: Qualitative decrease
• Reverse: Opposite of intention
• Other Than: Complete substitution

Process Elements

• Flow
• Composition
• pH
• Pressure
• Temperature
• Reaction
• Time
• Stirring Speed
• Maintain Level
• Particle Size
• Viscosity, etc.

Study Nodes

• The locations (on P&ID or procedures) where process parameters are investigated.
• The points where process parameters have a specific design intent.
• Locations where plant operation is scrutinized for deviations.

Intentions

• Define how a plant is expected to operate in the absence of deviations (problems).
• Describes the expected behavior of a piece of equipment or system.

Deviations

• Ways process conditions can depart from their design intent.
• Deviation is the departure from the design intent.
• A guide word plus parameter equals a deviation.

Causes

• Reasons a deviation might occur.
• Often starts by considering the most serious causes and consequences.

Consequences

• Results of a deviation.
• Can be trivial, important, or catastrophic.

Principles of HAZOP

• Focus on examining all potential deviations and combining with guide words.
• This ensures that all possible scenarios are considered.
• Emphasizes examining how deviations impact the overall system.

Safeguards

• Ways to mitigate or reduce the frequency of deviations.
• Five types:
• Identifying the deviation
• Compensating for the deviation
• Preventing the deviation from occurring
• Preventing further escalation
• Relieving the process from the hazard

HAZOP Procedure

• Divide the system into sections
• Select a study node
• Describe the design intent
• Select a process parameter
• Apply a guide word
• Determine causes
• Evaluate consequences
• Recommend action
• Record information
• Repeat the procedure

HAZOP Team

• Typically 5 to 7 members
• Includes design engineers, process engineers, operations supervisors, instrument design engineers, chemists, maintenance supervisors, safety engineers

HAZOP Study - Team Composition

• A team leader expert in HAZOP technique
• Existing plant professionals such as design and project engineers, plant superintendents, process supervisors, maintenance engineers, instrument engineers, and technical engineers
• This is a reference example only. Teams adapt their composition based on the specific process involved..

Process HAZOP Worksheet

• A table used to document the findings of a HAZOP study and guide discussions
• Includes sections for Study Node, Process parameter, Deviations, possible causes, possible consequences, and action required.

HAZOP Deviation Guide

• Table that lists typical deviation guide words for various process parameters.
• Lists a range of guide words (e.g., none, less, more, reverse, etc.)

Example of HAZOP Procedure (Example in the slides)

• Choose a study node
• Choose a process parameter: flow
• Apply a guide word: "NO"

HAZOP Advantages

• Easy to learn
• Stimulates creativity and generates ideas
• Systematic and thorough procedure
• Participants gain valuable knowledge of a process
• Readily acceptable to regulatory authorities

HAZOP Disadvantages

• Time-consuming
• Focusing on solutions too much
• Team discussions can be diverted into endless discussions
• Not effective where multiple-combination events have severe effects.

Explore the fundamentals of HAZOP (Hazard and Operability Study) and its importance in safety engineering. This quiz covers the systematic techniques for identifying hazards in plants, examining deviations, and assessing risks. Test your knowledge on HAZOP and related safety analysis methods.