Introduction Types of HAZOP HAZOP team Process HAZOP Procedure HAZOP Reporting and review Conclusions
Risk Assessment
9. HAZOP
Stein Haugen Marvin Rausand
[email protected] [email protected]
RAMS Group
Department of Production and ality Engineering
NTNU
(Version 0.1)
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Introduction Types of HAZOP HAZOP team Process HAZOP Procedure HAZOP Reporting and review Conclusions
Slides related to the book
Risk Assessment
Theory, Methods, and Applications
Wiley, 2011
Homepage of the book:
http://www.ntnu.edu/ross/
books/risk
MARVIN RAUSAND
STATISTICS IN PRACTICE
Risk Assessment
eory, Methods, and Applications
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Introduction Types of HAZOP HAZOP team Process HAZOP Procedure HAZOP Reporting and review Conclusions
What is HAZOP?
A Hazard and Operability (HAZOP) study is a structured and systematic
examination of a planned or existing process or operation in order to identify
and evaluate problems that may represent risks to personnel or equipment,
or prevent eicient operation.
The HAZOP technique was initially developed to analyze chemical process
systems, but has later been extended to other types of systems and also to
complex operations and to soware systems.
A HAZOP is a qualitative technique based on guide-words and is carried out
by a multi-disciplinary team (HAZOP team) during a set of meetings.
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Introduction Types of HAZOP HAZOP team Process HAZOP Procedure HAZOP Reporting and review Conclusions
HAZOP objectives
I
Identify all deviations from the way a system is intended to function:
their causes, and all the hazards and operability problems associated
with these deviations.
I
Decide whether actions are required to control the hazards and/or the
operability problems, and if so, identify the ways in which the
problems can be solved.
I
Identify cases where a decision cannot be made immediately, and
decide on what information or actions are required.
I
Ensure that actions decided are followed up.
I
Make operator aware of hazards and operability problems.
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Introduction Types of HAZOP HAZOP team Process HAZOP Procedure HAZOP Reporting and review Conclusions
When to perform a HAZOP? - 1
The HAZOP study should preferably be carried out as early in the design
phase as possible – to have influence on the design. On the other hand; to
carry out a HAZOP we need a rather complete design. As a compromise,
the HAZOP is usually carried out as a final check when the detailed design
has been completed.
A HAZOP study may also be conducted on an existing facility to identify
modifications that should be implemented to reduce risk and operability
problems.
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Introduction Types of HAZOP HAZOP team Process HAZOP Procedure HAZOP Reporting and review Conclusions
When to perform a HAZOP? - 2
HAZOP studies may also be used more extensively, including:
I
At the initial concept stage when design drawings are available
I
When the final piping and instrumentation diagrams (P&ID) are
available
I
During construction and installation to ensure that recommendations
are implemented
I
During commissioning
I
During operation to ensure that plant emergency and operating
procedures are regularly reviewed and updated as required
– From Kyriakdis (2003)
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Introduction Types of HAZOP HAZOP team Process HAZOP Procedure HAZOP Reporting and review Conclusions
HAZOP history
I
The basis for HAZOP was laid by ICI in 1963 and was based on
so-called “critical examination” techniques
I
First guide: “A Guide to Hazard and Operability Studies”, ICI and
Chemical Industries Associations Ltd. 1977.
I
First main textbook: Kletz, T. A.: “Hazop and Hazan – Identifying and
Assessing Process Industry Hazards”, Institution of Chemical Engineers.
I
See also: Kletz, T. A.: “Hazop – past and future”. Reliability Engineering
and System Safety, 55:263-266, 1997.
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Introduction Types of HAZOP HAZOP team Process HAZOP Procedure HAZOP Reporting and review Conclusions
Standards and guidelines
I
IEC 61882. “Hazard and operability studies (HAZOP studies) –
Application guide”. International Electrotechnical Commission, Geneva.
I
Crawley, F., M. Preston, and B. Tyler: “HAZOP: Guide to best practice.
Guidelines to best practice for the process and chemical industries”.
European Process Safety Centre and Institution of Chemical Engineers,
2000
I
Kyriakdis, I.: “HAZOP – Comprehensive Guide to HAZOP in CSIRO”,
CSIRO Minerals, National Safety Council of Australia, 2003
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Introduction Types of HAZOP HAZOP team Process HAZOP Procedure HAZOP Reporting and review Conclusions
Types of HAZOP
I
Process HAZOP
•
The HAZOP technique was originally developed to assess plants and
process systems
I
Human HAZOP
•
A “family” of specialized HAZOPs. More focused on human errors than
technical failures
I
Procedure HAZOP
•
Review of procedures or operational sequences Sometimes denoted
SAFOP – SAFe Operation Study
I
Soware HAZOP
•
Identification of possible errors in the development of soware
Only Process HAZOP and Procedure HAZOP are covered in this
presentation.
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Introduction Types of HAZOP HAZOP team Process HAZOP Procedure HAZOP Reporting and review Conclusions
Team member responsibilities
I
HAZOP team leader
Responsibilities:
•
Define the scope for the analysis
•
Select HAZOP team members
•
Plan and prepare the study
•
Chair the HAZOP meetings
I
Trigger the discussion using guide-words and parameters
I
Follow up progress according to schedule/agenda
I
Ensure completeness of the analysis
The team leader should be independent (i.e., no responsibility for the
process and/or the performance of operations)
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Introduction Types of HAZOP HAZOP team Process HAZOP Procedure HAZOP Reporting and review Conclusions
Team member responsibilities
I
HAZOP secretary
Responsibilities:
•
Prepare HAZOP work-sheets
•
Record the discussion in the HAZOP meetings
•
Prepare dra report(s)
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Introduction Types of HAZOP HAZOP team Process HAZOP Procedure HAZOP Reporting and review Conclusions
Team members
I
HAZOP team members
The basic team for a process plant may be:
•
Project engineer
•
Commissioning manager
•
Process engineer
•
Instrument/electrical engineer
•
Safety engineer
Depending on the actual process the team may be enhanced by:
•
Operating team leader
•
Maintenance engineer
•
Suppliers representative
•
Other specialists as appropriate
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How to be a good HAZOP participant
I
Be active! Everybody’s contribution is important
I
Be to the point. Avoid endless discussion of details
I
Be critical in a positive way – not negative, but constructive
I
Be responsible. Shee who knows should let the others know
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HAZOP meeting - 1
Proposed agenda:
1. Introduction and presentation of participants
2. Overall presentation of the system/operation to be analyzed
3. Description of the HAZOP approach
4. Presentation of the first node or logical part of the operation
5. Analyze the first node/part using the guide-words and parameters
6. Continue presentation and analysis (steps 4 and 5)
7. Coarse summary of findings
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HAZOP meeting - 2
Focus should be on potential hazards as well as potential operational
problems
Each session of the HAZOP meeting should not exceed two hours.
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Introduction Types of HAZOP HAZOP team Process HAZOP Procedure HAZOP Reporting and review Conclusions
HAZOP recording
The findings are recorded during the meeting(s) using a HAZOP work-sheet,
either by filling in paper copies, or by using a computer connected to a
projector (recommended).
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HAZOP work-sheet
The HAZOP work-sheets may be dierent depending on the scope of the
study – generally the following entries (columns) are included:
1. Ref. no.
2. Guide-word
3. Deviation
4. Possible causes
5. Consequences
6. Safeguards
7. Actions required (or, recommendations)
8. Actions allocated to (follow-up responsibility)
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Introduction Types of HAZOP HAZOP team Process HAZOP Procedure HAZOP Reporting and review Conclusions
Prerequisites
As a basis for the HAZOP study the following information should be
available:
I
Process flow diagrams
I
Piping and instrumentation diagrams (P&IDs)
I
Layout diagrams
I
Material safety data sheets
I
Provisional operating instructions
I
Heat and material balances
I
Equipment data sheets Start-up and emergency shut-down procedures
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Introduction Types of HAZOP HAZOP team Process HAZOP Procedure HAZOP Reporting and review Conclusions
HAZOP procedure
1. Divide the system into sections (i.e., reactor, storage)
2. Choose a study node (i.e., line, vessel, pump, operating instruction)
3. Describe the design intent
4. Select a process parameter
5. Apply a guide-word
6. Determine cause(s)
7. Evaluate consequences/problems
8. Recommend action: What? When? Who?
9. Record information
10. Repeat procedure (from step 2)
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Introduction Types of HAZOP HAZOP team Process HAZOP Procedure HAZOP Reporting and review Conclusions
HAZOP procedure
The HAZOP procedure may be illustrated as follows:
Apply all relevant
combinations of guide-
words and parameters.
Any hazards or
operating problems?
Select a study node
Divide section
into study nodes
Need more
information
Record consequences
and causes and
suggest remedies
NOYES
NOT SURE
HAZOP report
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Modes of operation
The following modes of plant operation should be considered for each node:
I
Normal operation
I
Reduced throughput operation
I
Routine start-up
I
Routine shutdown
I
Emergency shutdown
I
Commissioning
I
Special operating modes
– Based on Kyriakdis (2003)
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Process HAZOP work-sheet
No.
Guide-
word
Element
Deviation
Possible
causes
Conse-
quences
Safeguards Comments
Actions
required
Action
allocated to
Design intent: Material:
Source:
Activity:
Destination:
Part considered:
HAZOP team: Meeting date:
Drawing no.: Rev no.:
Date:
Study title: Page: of
– Source: IEC 61882
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Work-sheet entries - 1
I
Node
A node is a specific location in the process in which (the deviations of)
the design/process intent are evaluated. Examples might be:
separators, heat exchangers, scrubbers, pumps, compressors, and
interconnecting pipes with equipment.
I
Design intent
The design intent is a description of how the process is expected to
behave at the node; this is qualitatively described as an activity (e.g.,
feed, reaction, sedimentation) and/or quantitatively in the process
parameters, like temperature, flow rate, pressure, composition, etc.
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Work-sheet entries - 2
I
Deviation
A deviation is a way in which the process conditions may depart from
their design/process intent.
I
Parameter
The relevant parameter for the condition(s) of the process (e.g.
pressure, temperature, composition).
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Work-sheet entries - 3
I
Guideword
A short word to create the imagination of a deviation of the
design/process intent. The most commonly used guide-words are: no,
more, less, as well as, part of, other than, and reverse.
In addition, guidewords such as too early, too late, instead of, are used;
the laer mainly for batch-like processes. The guidewords are applied,
in turn, to all the parameters, in order to identify unexpected and yet
credible deviations from the design/process intent.
Guide-word + Parameter → Deviation
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Work-sheet entries - 4
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Cause
The reason(s) why the deviation could occur. Several causes may be
identified for one deviation. It is oen recommended to start with the
causes that may result in the worst possible consequence.
I
Consequence
The results of the deviation, in case it occurs. Consequences may both
comprise process hazards and operability problems, like plant
shut-down or reduced quality of the product. Several consequences
may follow from one cause and, in turn, one consequence can have
several causes
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Work-sheet entries - 5
I
Safeguard
Facilities that help to reduce the occurrence frequency of the deviation
or to mitigate its consequences.
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Safeguard types
1. Identify the deviation (e.g., detectors and alarms, and human operator
detection)
2. Compensate for the deviation (e.g., an automatic control system that
reduces the feed to a vessel in case of overfilling it. These are usually
an integrated part of the process control)
3. Prevent the deviation from occurring (e.g., an inert gas blanket in
storages of flammable substances)
4. Prevent further escalation of the deviation (e.g., by (total) trip of the
activity. These facilities are oen interlocked with several units in the
process, oen controlled by computers)
5. Relieve the process from the hazardous deviation (e.g., pressure safety
valves (PSV) and vent systems)
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Process parameters - 1
Process parameters may generally be classified into the following groups:
I
Physical parameters related to input medium properties
I
Physical parameters related to input medium conditions
I
Physical parameters related to system dynamics
I
Non-physical tangible parameters related to batch type processes
I
Parameters related to system operations
– From Statoil Guideline HMS-T/99142
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Process parameters - 2
The parameters related to system operations are not necessarily used in
conjunction with guide-words:
I
Instrumentation
I
Relief
I
Start-up / shutdown
I
Maintenance
I
Safety / contingency
I
Sampling
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Examples of process parameters
Flow Composition pH
Pressure Addition Sequence
Temperature Separation Signal
Mixing Time Start/stop
Stirring Phase Operate
Transfer Speed Maintain
Level Particle size Services
Viscosity Measure Communication
Reaction Control
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Guidewords
The basic HAZOP guide-words are:
Guide-word Meaning Example
No (not, none)
More
(more of, higher)
Less
(lessof, lower)
As well as
(more than)
Part of
Reverse
Other than
(other)
None of the design intent is achieved
Quantitative increase in a parameter
Quantitative decrease in a parameter
An additional activity occurs
Only some of the design intention is
achieved
Logical opposite of the design intention
occurs
Complete substitution - another activity
takes place
No flow when production is expected
None of the design intent is achievedNone of the design intent is achievedNone of the design intent is achievedNone of the design intent is achievedNone of the design intent is achievedLower pressure than normal
Higher temperature than designed
Other valves closed at the same time
(logic fault or human error)
Only part of the system is shut down
Back-flow when the system shuts down
Liquids in the gas piping
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Additional guidewords
Guide-word Meaning
Early / late
Before / after
Faster / slower
Where else
The timing is different from the intention
The step (or part of it) is effected out of sequence
The step is done/not done with the right timing
Applicable for flows, transfer, sources and destinations
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Guideword & parameter - 1
Some examples of combinations of guide-words and parameters:
I
NO FLOW
Wrong flow path – blockage – incorrect slip plate – incorrectly fied
return valve – burst pipe – large leak – equipment failure – incorrect
pressure dierential – isolation in error
I
MORE FLOW
Increase pumping capacity – increased suction pressure – reduced
delivery head – greater fluid density - exchanger tube leaks – cross
connection of systems – control faults
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Guideword & parameter - 2
I
MORE TEMPERATURE
Ambient conditions – failed exchanger tubes – fire situation – cooling
water failure – defective control – internal fires
– Many more examples in Kyriakdis (2003)
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Introduction Types of HAZOP HAZOP team Process HAZOP Procedure HAZOP Reporting and review Conclusions
What is a procedure HAZOP?
A procedure HAZOP is an examination of an existing or planned operation
(work) procedure to identify hazards and causes for operational problems,
quality problems, and delays.
I
Can be applied to all sequences of operations
I
Focus on both human errors and failures of technical systems
I
Best suited for detailed assessments, but can also be used for coarse
preliminary assessments
I
Flexible approach with respect to use of guide-words
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Procedure
I
Breakdown of operation (work) procedure to suitable steps
I
Define intention of each step
I
Establish boundary conditions
else as
conventional Process HAZOP
I
Apply guide-words to intention and boundary conditions for each step.
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Introduction Types of HAZOP HAZOP team Process HAZOP Procedure HAZOP Reporting and review Conclusions
Guidewords
Guide-word Meaning
No (not, none)
More
(more of, higher)
Less
(lessof, lower)
As well as
(more than)
Part of
Reverse
Other than
(other)
None of the design intent is achieved
Quantitative increase in a parameter
Quantitative decrease in a parameter
An additional activity occurs
Only some of the design intention is achieved
Logical opposite of the design intention occurs
Complete substitution - another activity takes place
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Alternative guidewords - 1
Guide-word Meaning
Unclear
Step in wrong
place
Wrong action
Incorrect
information
Step omitted
Step
unsuccessful
Interference effects
from others
Procedure written in confusing and ambiguous fashion
Procedure will lead to actions out of correct sequence or
recovery failure
Procedure action specified is incorrect
Information being checked prior to action is incorrectly specified
Missin step, or steps too large, requiring too much of the operator
Step likely to be unsuccessful due to demands on operator
Procedure-following performance likely to be affected by other
personnel carrying out simultaneous tasks (usually when co-located)
– Adapted from
B. Kirwan
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Alternative guidewords - 2
Parameter Guide-word / deviation
Time
Sequence
Procedure
Measurement
Organization
Communication
Personnel
Too early, too late
Wrong sequence, omissions, wrong action
Not available, not applicable, not followed
Instrument failure, observation error
Unclear responsibilities, not fitted for purpose
Failed equipment, insufficient/incorrect information
Lack of competence, too few, too many
Position
Wrong position, movement exceeding tolerences
Power Complete loss, partly lost
Weather
Above limitations - causing delayed operation
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Introduction Types of HAZOP HAZOP team Process HAZOP Procedure HAZOP Reporting and review Conclusions
Report contents
Summary
1. Introduction
2. System definition and delimitation
3. Documents (on which the analysis is based)
4. Methodology
5. Team members
6. HAZOP results
– Reporting principles
– Classification of recordings
– Main results
Appendix 1: HAZOP work-sheets
Appendix 2: P&IDs (marked)
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Review meetings
Review meetings should be arranged to monitor completion of agreed
actions that have been recorded. The review meeting should involve the
whole HAZOP team. A summary of actions should be noted and classified
as:
I
Action is complete
I
Action is in progress
I
Action is incomplete, awaiting further information
– Based on Kyriakdis (2003)
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HAZOP Results
I
Improvement of system or operations
– Reduced risk and beer contingency
– More eicient operations
I
Improvement of procedures
– Logical order
– Completeness
I
General awareness among involved parties
I
Team building
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Advantages
I
Systematic examination
I
Multidisciplinary study
I
Utilizes operational experience
I
Covers safety as well as operational aspects
I
Solutions to the problems identified may be indicated
I
Considers operational procedures
I
Covers human errors
I
Study led by independent person
I
Results are recorded
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Success factors
I
Accuracy of drawings and data used as a basis for the study
I
Experience and skills of the HAZOP team leader
I
Technical skills and insights of the team
I
Ability of the team to use the HAZOP approach as an aid to identify
deviations, causes, and consequences
I
Ability of the team to maintain a sense of proportion, especially when
assessing the severity of the potential consequences.
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Pitfalls and objections
I
Time consuming
I
Focusing too much on solutions
I
Team members allowed to divert into endless discussions of details
I
A few of the team members dominate the discussion
I
“This is my design/procedure”
– Defending a design/procedure
– HAZOP is not an audit
I
“No problem”
I
“Wasted time”
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