HAZOP
Designed by
Hossam A. Hassanein
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Goals
Basic understanding of HAZOP
HAZOP requirements
How it works
Case study
HAZOP team
Advantage & disadvantage
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Scenario What is the
cause of the
accident?
You and your family are on a road trip by using a car in the middle of
the night. You were driving at 100 km/h and, it was raining heavily. The
car hits aCan
deep
we behole and, one of your tire blows. You hit the brake, but
prepared What is the
due to slippery
before theroad and your car tire threadconsequence
was thin, the car skidded
accident off the road.
and was thrown of the event?
occurs?
Points to
Ponder
What other What can we
possible do to prevent
accidents all those
might happen things to
on the road happen in the
trip? first place?
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Definition
- Is structured technique, which may be applied
typically to a chemical production process,
identifying hazards resulting from potential
HAZOP malfunctions in the process
(Hazard &
Operability)
Study
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History
Initially prepared by Dr.
H G Lawley and
associates of ICI at
Wilton in 1960’s .
In 1977, Chemical
Industries Association
published the edited
version.
ICI expanded the
procedure called
HAZARD STUDY levels
1 to 6.
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ICI Six Levels
Project exploration / preliminary project assessment
Project definition
Design and procurement
During final stages of construction
During plant commissioning
During normal operation, some times after start-up
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REMEBER
HAZOP is an
identifying technique
and not intended as a
means of solving
problems
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Features of HAZOP Study
Subsystems of interest line and valve, etc Equipment, Vessels
Modes of operation Normal operation
Start -up mode
Shutdown mode
Maintenance /construction / inspection
mode
Trigger events Human failure
Equipment /instrument/component
failure
Supply failure
Emergency environment event
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Features of HAZOP Study
Effects within plant Changes in chemical conditions
Changes in inventory
Change in chemical physical
conditions
Corrective actions Change of process design
Change of operating limits
Change of system reliability
Improvement of material containment
Change control system Add/remove
materials
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Features of HAZOP Study
How would hazardous conditions During normal operation Upon human
detected ? failure
Upon component failure In other
circumstances
Contingency actions Improve isolation Improve protection
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Documents Needed for
HAZOP Study
– Process Flow Sheet or digram ( PFS or PFD )
Preliminary
– Description of the Process
HAZOP
– Piping and Instrumentation Diagram (P & ID)
– Process Calculations
– Process Data Sheets
– Instrument Data Sheets
Detailed – Interlock Schedules
– Layout Requirements
HAZOP – Hazardous Area Classification
– Description of the Process
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Process Flow Diagram (PFD)
Is a diagram commonly used The PFD displays the
in chemical and process relationship
engineering to indicate the between major equipment of a
general flow of plant processes plant facility and does not
and equipment. show minor details such as
piping details and designations
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Process Flow Diagram (PFD)
Example
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P&ID
A Piping and
Instrumentation
Diagram - P&ID, is a
schematic illustration of P&ID represents the
functional relationship last step in process
of piping, design.
instrumentation and
system equipment
components.
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P&ID Example
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HAZOP Procedure
List of guide words
for generation of
process deviations
Possible Process Possible
Causes Deviations Consequences
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Definitions
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Study Nodes
The locations (on piping
and instrumentation
drawings and
procedures) at which
the process parameters
are investigated for
deviations.
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Intention
The intention defines
how the plant is
expected to operate in
the absence of
deviations at the study
nodes.
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Deviations
Is a way in which the
process conditions may
depart from their
design/process intent
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Causes
These are the reasons
why deviations might
occur
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Consequences
The results of the
deviation, in case it
occurs.
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Safeguards
Facilities that help to
reduce the occurrence
frequency of the
deviation or to mitigate
its consequences.
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Guide Words
A short word to create
the imagination of a
deviation of the
design/process intent.
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Guide Words Used (most
7 used)
Guide Words Meaning
No Negation of the design intend
Less Quantitative Decrease
More Quantitative Increase
Part of Qualitative Decrease
As Well As Qualitative Increase
Reverse Logical opposite of the intend
Other Than Complete Substitution
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HAZOP Deviation Guide
Guide No, Less, More, Part of As Well As, Other Than Reverse
Process Words Not, Low, High, Also
Variable None Short Long
No Flow Low Rate High Rate Missing Misdirection, Wrong Backflow
Flow Ingredient Impurities Material
Open to Low Pressure High ___________ ___________ ___________ Vacuum
Pressure Atmosphere Pressure _ _ _
Freezing Low High ___________ ___________ ___________ Auto
Temperature Temperature Temperature _ _ _ refrigeration
Empty Low Level High Level Low Interface High ___________ ___________
Level Interface _ _
No Mixing Poor Mixing Excessive Mixing Foaming, ___________ Phase
Agitation Mixing Interruption Extra Phase _ Separation
No Reaction Slow Runaway Partial Side Wrong Decompositio
Reaction Reaction Reaction Reaction Reaction Reaction n
Skipped or To Short, Too Long, Action Extra Action Wrong Action Out of Order,
Time Missed Step To Little Too Much Skipped (Shortcuts) Opposite
Procedure
Stopped Too Slow Too Fast Out of Synch ___________ Web or Belt Backward
Speed _ Break
Utility Failure External Leak External Tube Leak Tube Rupture Startup, ___________
Special Rupture Shutdown, _
Maint
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Process Parameters
Process parameters may generally be classified into the following groups:
Physical parameters related to input medium properties
Physical parameters related to input medium conditions
Physical parameters related to system dynamics
Non-physical tangible parameters related to batch type
processes
Parameters related to system operations
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Examples of Process
Parameters
Flow Pressure Composition Addition Separation Time
pH Signal Start/stop Operate Maintain Services
Communication Temperature Mixing Stirring Transfer Phase
Speed Particle size Measure Control Level Viscosity
Reaction Sequence
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Simply How does it work?
NODE: Pipe after pump and splitter
PARAMETER: Flow rate
GUIDE WORD: Less (less than normal
value)
DEVIATION: less flow than normal
A group members
CAUSE: of deviation, can be more than one
focus on the same
CONSEQUENCE: of the deviation/cause
issue
ACTION: initial idea for correction/
prevention/mitigation
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The HAZOP Process
Select Equipment Node
Choose Deviation OR Parameters & Guide Words
Identify Causes
Associate Consequences
Apply Risk Ranking
Agree Actions To Be Taken
Monitor Actions For Completion
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Case
Study
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Case Study 1: Preliminary
HAZOP on Reactor
Cooling Water Refer to reactor system shown.
The reaction is exothermic. A cooling system is
provided to remove the excess energy of
reaction. In the event of cooling function is lost,
the temperature of reactor would increase. This
would lead to an increase in reaction rate
leading to additional energy release.
The result could be a runaway reaction with
pressures exceeding the bursting pressure of
the reactor. The temperature within the reactor is
measured and is used to control the cooling
water flow rate by a valve.
Perform HAZOP Study
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Case Study 1: Preliminary
HAZOP on Reactor
Cooling
Water
Guide Word Deviation Causes Consequences Action
No
Reverse
More
Other
As WellThan
As No
MoreCooling
Reverse
Another
Reactor cooling
cooling
material
flowin
product Cooling
Failure
Control
Water water
of waterin
source
valve
More pressure Temperature
Less
Too
May cooling,
much
be
Off-spec cooling
cooling,
product Install
less high
Instruct
If
Check check
cooling, valve
operators
flow
besides
coils cooling valve
source malfunction
failure, resulting in
contaminated
reactor operator increase
reactor inand
possiblecool
ineffective reactor
runaway temperature
on
TAH procedures alarm
will detect.
maintenance If
water backward
fails to takeflow
action reaction
effect on the (TAH)
detected,
procedures isolate
and
on alarm reaction water source.
schedules
Back up water
source?
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Case Study 2: Shell & Tube
Heat Exchanger
Using relevant guide words, perform
HAZOP study on shell & tube heat
exchanger
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Case Study 2: Shell & Tube
Heat Exchanger (Answer 1)
Guide Word Deviation Causes Consequences Action
Less
More
More of Less
More flow
More of flow
cooling
pressure on Pipe
Failure
Failureblockage
of cooling
ofof
process Temperature of
Bursting of tube High
Low Temperature
Temperature
Install high
Contamination Contamination of Leakage tube Contamination of Proper
Corrosion cooling water
Corrosion of tube
tube sidefluid line Hardness
water of
valve
fluid cooling
valve water Less cooling
process fluid and Proper
Alarm
pressure alarm
process and process fluid maintenance and
cooling water remains
crack constant
of tube
decrease maintainence
goes in operator alert
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Case Study 2: Shell & Tube
Heat Exchanger (Answer 2)
Guide Word Deviation Causes Consequences Action
None
More No
Morecooling water
cooling water Failure
Failure of
of inlet
inlet Process
Output offluid
Process Install
Install Temperature
Temperature
Less
Reverse Less
Reversecooling water
process Pipe
Failureleakage
of process Process
Product fluid
off set Installation
Install checkofvalve
flow
Contamination flow
Process fluid
flow cooling water
water valve
Contamination
cooling in
valve temperature
Outlet
fluid is not
temperature
temperature indicator
Proper before
indicator before
fluid flow fluid inlet valve temperature too meter
contamination to open
cooling
to closewater lowered
too low and
and after
after the
maintenance and
process
low
accordingly process
fluid line fluid
operator alertline
Install TAH
Install TAL
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HAZOP Team
Design Engineer
5 to 7 members
Process
Engineer
Operations
Supervisor
Instrument
Design Engineer
Chemist
Maintenance
Supervisor
Safety Engineer
(team leader)
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HAZOP Advantage
Easy to learn
Stimulates creativity and generates ideas
Systematic and through procedure
Participants gain valuable knowledge of process
Readily acceptable to regulatory authorities
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HAZOP Disadvantage
Time consuming
Focusing too much on solutions
Team members allowed to divert into endless
discussions of details
HAZOP is poor where multiple-combination events
can have severe effects.
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Division Into Sections
Guideline
Each section should contain
active components, which gives
Choices of lines–P&ID must be rise to deviations. e.g piping Materials in section – contain Section based on process and
divided logically. Not too many which contains control valves can significant amount of hazardous states of materials. Only 1
sections. give rise to flow deviations, heat materials. process operation per 1 section.
exchangers can cause Temp.
deviations.
Define additional line sections for
Define each major process Define one line section between Define a process section at each
each branches off the main
component as a section. each major process component. connection to existing equipment.
process flow.
Define only one additional line
Define only one line at the end of
Define only one process section section if there are alternative
a series of components if there
for equipment in identical service. flow paths, regardless of how
are no other flow paths.
many branches there are.
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