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Structured brainstorm using guide words to identify hazards
(health, safety and environmental) and operations in a system.
Purpose
- Systematic identification of hazards
Requirements
- Process descriptions, drawings and operating procedure
Analysis Procedure
- Evaluate deviations from normal operation as potential hazards
Results
- Understand hazards and consequences for process sections
- Recommendations of safeguards as a protection against the hazards Screening Level Checklist What-if FMEA HAZOP Started Identification Human Error Analysis – Case Studies Thoughts
Intentions How the process operations are expected to occur
Hazard Departures from the design intentions
Causes Ways the hazard might occur
Consequences Results of the hazard
Safeguards Provisions^ for^ reducing^ the^ frequency^ or^ decrease^ the
severity of the consequence of the hazard
Actions Suggestions^ for^ the^ procedural^ changes,^ design^ changes
or further study
Screening Level Checklist What-if FMEA
Before going through details of the HAZOP procedure,
let’s review some relevant terminology:
HAZOP
Started Identification Human Error Analysis – Case Studies Thoughts
Define a system Explain design intension of the process section Select a process variable Apply guide words to the process variable to develop a meaningful hazard Examine the consequence of the hazard assuming all protection fails List possible causes of the hazard Identify existing safeguards to prevent hazard Assess acceptability of risk based on consequence, causes and protection Develop action items Repeat process for all guide words Repeat process for all process variables Repeat process sections Screening Level Checklist What-if
Over view of the Procedure
FMEA HAZOP
Started Identification Human Error Analysis – Case Studies Thoughts
- Flow
- Pressure
- Temperature
- Level
- Time
- Composition
- pH
- Speed
- Frequency
- Viscosity
- Voltage
- Mixing
- Addition
- Separation
- Reaction
What is meant by process variables?
Be aware not all combinations make sense!
Screening Level Checklist What-if FMEA HAZOP Started Identification Human Error Analysis – Case Studies Thoughts
Example of hazards resulting from process deviations
Process Variables
Flow, Temperature, Pressure
Guideword + Process Variable
Combinations
= No reaction
- High Temperature in reactor
= degradation of product
- Low pressure in storage tank
= f low out of reactor accelerated
Chemical A Chemical B Reactor PT PT Storage Tank Screening Level Checklist What-if FMEA HAZOP Started Identification Human Error Analysis – Case Studies Thoughts
• Hazards are detectable with careful review
• Engineering facilities are designed and operated to appropriate
standards
• Hazards can be controlled by a combination of equipment,
procedures
• This technique is conducted with openness and good faith by
competent analysts
Screening Level Checklist What-if FMEA
This technique makes some inherent
assumptions…
HAZOP
Started Identification Human Error Analysis – Case Studies Thoughts
Advantages
• Creative and open-ended
• Rigorous and structured
procedure
• Very versatile
• Identifies both safety and
operational hazards
• Can be time-consuming
• Critical that experienced
analysts are involved in
the process
• No distinction between
low and high probability
and consequence hazards
What-if FMEA
Disadvantages
Screening Level Checklist HAZOP
The aim of a HAZOP is to identify the cause of the process
deviation which could lead to hazards.
Started Identification Human Error Analysis – Case Studies Thoughts
