1.
HAZOP
Designed by
Hossam A. Hassanein

2.
Goals
 Basic understanding of HAZOP
 HAZOP requirements
 How it works
 Case study
 HAZOP team
 Advantage & disadvantage
2

3.
 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 a deep hole and, one of your tire blows. You hit the brake, but
due to slippery road and your car tire thread was thin, the car skidded
and was thrown off the road.
Scenario
3
What is the
cause of the
accident?
What is the
consequence
of the event?
What can we
do to prevent
all those
things to
happen in the
first place?
What other
possible
accidents
might happen
on the road
trip?
Can we be
prepared
before the
accident
occurs?
Points to
Ponder

4.
Definition
HAZOP
(Hazard &
Operability)
Study
- Is structured technique, which may be applied
typically to a chemical production process,
identifying hazards resulting from potential
malfunctions in the process
4

5.
History
5
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.

6.
ICI Six Levels
6
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

7.
REMEBER
7
HAZOP is an
identifying technique
and not intended as a
means of solving
problems

8.
Features of HAZOP Study
8
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

9.
Features of HAZOP Study
9
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

10.
Features of HAZOP Study
10
How would hazardous conditions
detected ?
During normal operation Upon human
failure
Upon component failure In other
circumstances
Contingency actions Improve isolation Improve protection

11.
Documents Needed for
HAZOP Study
11
Preliminary
HAZOP
– Process Flow Sheet or digram ( 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

12.
Process Flow Diagram (PFD)
12
Is a diagram commonly used
in chemical and process
engineering to indicate the
general flow of plant processes
and equipment.
The PFD displays the
relationship
between major equipment of a
plant facility and does not
show minor details such as
piping details and designations

13.
Process Flow Diagram (PFD)
Example
13

14.
P&ID
14
A Piping and
Instrumentation
Diagram - P&ID, is a
schematic illustration of
functional relationship
of piping,
instrumentation and
system equipment
components.
P&ID represents the
last step in process
design.

15.
P&ID Example
15

16.
HAZOP Procedure
16
Possible
Causes
Process
Deviations
Possible
Consequences
List of guide words
for generation of
process deviations

17.
Definitions
17

18.
Study Nodes
The locations (on piping
and instrumentation
drawings and
procedures) at which
the process parameters
are investigated for
deviations.
18

19.
Intention
The intention defines
how the plant is
expected to operate in
the absence of
deviations at the study
nodes.
19

20.
Deviations
Is a way in which the
process conditions may
depart from their
design/process intent
20

21.
Causes
These are the reasons
why deviations might
occur
21

22.
Consequences
The results of the
deviation, in case it
occurs.
22

23.
Safeguards
Facilities that help to
reduce the occurrence
frequency of the
deviation or to mitigate
its consequences.
23

24.
A short word to create
the imagination of a
deviation of the
design/process intent.
Guide Words
24

25.
Guide Words Used (most
7 used)
25
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

26.
HAZOP Deviation Guide
26
No,
Not,
None
Less,
Low,
Short
More,
High,
Long
Part of As Well As,
Also
Other Than Reverse
Flow No Flow Low Rate High Rate Missing
Ingredient
Misdirection,
Impurities
Wrong
Material
Backflow
Pressure Open to
Atmosphere
Low Pressure High
Pressure
___________
_
___________
_
___________
_
Vacuum
Temperature Freezing Low
Temperature
High
Temperature
___________
_
___________
_
___________
_
Auto
refrigeration
Level Empty Low Level High Level Low Interface High
Interface
___________
_
___________
_
Agitation No Mixing Poor Mixing Excessive
Mixing
Mixing
Interruption
Foaming,
Extra Phase
___________
_
Phase
Separation
Reaction No Reaction Slow
Reaction
Runaway
Reaction
Partial
Reaction
Side
Reaction
Wrong
Reaction
Decompositio
n
Time
Procedure
Skipped or
Missed Step
To Short,
To Little
Too Long,
Too Much
Action
Skipped
Extra Action
(Shortcuts)
Wrong Action Out of Order,
Opposite
Speed Stopped Too Slow Too Fast Out of Synch ___________
_
Web or Belt
Break
Backward
Special Utility Failure External Leak External
Rupture
Tube Leak Tube Rupture Startup,
Shutdown,
Maint
___________
_
Process
Variable
Guide
Words

27.
Process Parameters
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
27
Process parameters may generally be classified into the following groups:

28.
Examples of Process
Parameters
28
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

29.
Simply How does it work?
29
NODE: Pipe after pump and splitter
PARAMETER: Flow rate
GUIDE WORD: Less (less than normal
value)
DEVIATION: less flow than normal
CAUSE: of deviation, can be more than one
CONSEQUENCE: of the deviation/cause
ACTION: initial idea for correction/
prevention/mitigation
A group members
focus on the same
issue

30.
The HAZOP Process
30
Monitor Actions For Completion
Agree Actions To Be Taken
Apply Risk Ranking
Associate Consequences
Identify Causes
Choose Deviation OR Parameters & Guide Words
Select Equipment Node

31.
31
Case
Study

32.
Case Study 1: Preliminary
HAZOP on Reactor
32
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

33.
Case Study 1: Preliminary
HAZOP on Reactor
33
Guide Word Deviation Causes Consequences Action
No No Cooling Cooling water
valve malfunction
Temperature
increase in reactor
Install high
temperature alarm
(TAH)
Reverse Reverse cooling
flow
Failure of water
source resulting in
backward flow
Less cooling,
possible runaway
reaction
Install check valveMore More cooling flow Control valve
failure, operator
fails to take action
on alarm
Too much cooling,
reactor cool
Instruct operators
on procedures
As Well As Reactor product in
coils
More pressure in
reactor
Off-spec product Check
maintenance
procedures and
schedules
Other Than Another material
besides cooling
water
Water source
contaminated
May be cooling
ineffective and
effect on the
reaction
If less cooling,
TAH will detect. If
detected, isolate
water source.
Back up water
source?
Cooling
Water

34.
Case Study 2: Shell & Tube
Heat Exchanger
34
Using relevant guide words, perform
HAZOP study on shell & tube heat
exchanger

35.
Case Study 2: Shell & Tube
Heat Exchanger (Answer 1)
35
Guide Word Deviation Causes Consequences Action
Less Less flow of
cooling water
Pipe blockage Temperature of
process fluid
remains constant
High Temperature
Alarm
More More cooling flow Failure of cooling
water valve
Temperature of
process fluid
decrease
Low Temperature
Alarm
More of More pressure on
tube side
Failure of process
fluid valve
Bursting of tube Install high
pressure alarm
Contamination Contamination of
process fluid line
Leakage of tube
and cooling water
goes in
Contamination of
process fluid
Proper
maintenance and
operator alert
Corrosion Corrosion of tube Hardness of
cooling water
Less cooling and
crack of tube
Proper
maintainence

36.
Case Study 2: Shell & Tube
Heat Exchanger (Answer 2)
36
Guide Word Deviation Causes Consequences Action
None No cooling water
flow
Failure of inlet
cooling water valve
to open
Process fluid
temperature is not
lowered
accordingly
Install Temperature
indicator before
and after the
process fluid line
Install TAH
More More cooling water
flow
Failure of inlet
cooling water valve
to close
Output of Process
fluid temperature
too low
Install Temperature
indicator before
and after process
fluid line
Install TAL
Less Less cooling water Pipe leakage Process fluid
temperature too
low
Installation of flow
meter
Reverse Reverse process
fluid flow
Failure of process
fluid inlet valve
Product off set Install check valve
Contamination Process fluid
contamination
Contamination in
cooling water
Outlet temperature
too low
Proper
maintenance and
operator alert

37.
HAZOP Team
5to7members
Design Engineer
Process
Engineer
Operations
Supervisor
Instrument
Design Engineer
Chemist
Maintenance
Supervisor
Safety Engineer
(team leader)
37

38.
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
38

39.
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.
39

40.
Division Into Sections
Guideline
40
Choices of lines–P&ID must be
divided logically. Not too many
sections.
Each section should contain
active components, which gives
rise to deviations. e.g piping
which contains control valves can
give rise to flow deviations, heat
exchangers can cause Temp.
deviations.
Materials in section – contain
significant amount of hazardous
materials.
Section based on process and
states of materials. Only 1
process operation per 1 section.
Define each major process
component as a section.
Define one line section between
each major process component.
Define additional line sections for
each branches off the main
process flow.
Define a process section at each
connection to existing equipment.
Define only one process section
for equipment in identical service.
Define only one line at the end of
a series of components if there
are no other flow paths.
Define only one additional line
section if there are alternative
flow paths, regardless of how
many branches there are.

41.
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