HAZOP CASE STUDY
The full HAZOP study requires a committee composed of a cross-section of experienced ' plant, laboratory, technical, and safety professionals. One individual must be a trained HAZOP leader and serves as the committee chair. This person leads the discussion and must be experienced with the HAZOP procedure and the chemical process under review. One individual must also be assigned the task of recording the results, although a number of vendors provide software to perform this function on a
personal computer. The committee meets on a regular basis for a few hours each time. The meeting duration must be short enough to ensure continuing interest and input from all committee
members. A large process might take several months of biweekly
meetings to complete the HAZOP study. Obviously, a complete
HAZOP study requires a large investment in time and effort, but
the value of the result is well worth the effort.
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The HAZOP procedure uses the following steps to complete an analysis:
1. Begin with a detailed flow sheet. Break the flow sheet into a number of process units. Thus the reactor area might be one unit, and the storage tank another. Select a unit for study.
2. Choose a study node (vessel, line, operating instruction).
3. Describe the design intent of the study node. For example, vessel V-1 is
designed to store the benzene feedstock and provide it on demand to the reactor.
4. Pick a process parameter: flow, level, temperature, pressure, concentration, pH, viscosity, state (solid, liquid, or gas), agitation, volume, reaction, sample,
component, start, stop, stability, power, inert.
5. Apply a guide word to the process parameter to suggest possible deviations. A list of guide words is shown in Table 10-3. Some of the guide word process
parameter combinations are meaningless, as shown in Tables 10-4 and 10-5 for process lines and vessels.
6. If the deviation is applicable, determine possible causes and note any protective systems.
7. Evaluate the consequences of the deviation (if any).
8. Recommend action (what? by whom? by when?)
9. Record all information.
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10. Repeat steps 5 through 9 until all applicable guide words have been applied to the chosen process parameter.
11. Repeat steps 4 through 10 until all applicable process parameters have been considered for the given study node.
12. Repeat steps 2 through 11 until all study nodes have been
considered for the given section and proceed to the next section on the
flow sheet.
The HAZOP procedure to complete an analysis:
5. Apply guide word to the process parameter to suggest possible deviations
Lembar Kerja Proses HAZOP
Hazards and Operability Review Project
Name:
Date: Page of
Process :
Section: Ref.
Drawing:
Item Study
node
Process Parameter
Deviations (guide words)
Possibl e
causes
Possible consequence s
Action Required
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Kata Panduan/ guide words
Kata panduan dasar pada HAZOP:
Kata Panduan Arti Contoh
No (not, none) None of the design intent is achieved
No flow when production is expected
More (more of, higher)
Quantitative increase in a parameter
Higher temperature than desired
Less (less of, lower) Quantitative decrease in a parameter
Lower pressure than normal As well as (more
than)
An additional activity occurs Other valves closed at the same time (logic fault or human error)
Part of Only some of the design intention is achieved
Only part of the system is shut down
Reverse Logical opposite of the design intention occurs
Back-flow when the system shuts down
Other than (Other) Complete substitution – another activity takes place
Liquids in the gas piping
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Kata panduan/guide words …… lanjutan
Guide-word Meaning
Early/ late The timing is different from the intention
Before/ after The step (or part of it) is effected out of sequence
Faster/ slower The step is done/not done with the right timing
Where else Applicable for flows, transfer, sources and destinations
The guide words SOONER THAN, LATER THAN, and WHERE ELSE are
applicable to batch processing.
Deviation
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Deviation Column Tank/Vessel Line
Heat
Exchanger Pump
High Flow X
Low/no Flow X
High Level X X
Low Level X X
High Pressure X X X
Low Pressure X X X
High Temp. X X X
Low Temp. X X X
High Concen. X X X
Low Concen. X X X
Reverse Flow X
Tube Leak X
Tube Rupture X
Leak X X X X X
Rupture X X X X X
Parameters
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Flow Frequency Pressure Viscosity Temperature Voltage
Level Information Time Mixing
Composition Addition
pH Separation
Speed Reaction
Studi kasus – Shell & Tube Heat Exchanger
Gunakan petunjuk kerja yang relevan, lakukan studi HAZOP study pada shell & tube heat exchanger
Process fluid
Cooling water
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HAZOP on Heat Exchanger – Answer 1
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 Contaminati
on of process fluid line
Leakage of tube and
cooling water goes in
Contamination of process fluid
Proper
maintainance and operator alert
Corrosion Corrosion of tube
Hardness of cooling water
Less cooling and crack of tube
Proper
maintainence
HAZOP on Heat Exchanger – Answer 2
Guide Word Deviation Cause 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 (whether it is
crucial have to check?)
CONTAMINATIO N
Process fluid contaminatio n
Contamination in cooling
water
Outlet
temperature too low
Proper
maintenance and operator alert
Hazard & Operability Studies
Example
Consider the simple process diagram below. It represents a plant where substances A and B
react with each other to form a new substance C.
If there is more B than A there may be an explosion.
A
B
V1
V2 V3
V4
V5
A < B = Explosion C
Guide Word
Deviation Possible Causes Consequences Proposed Measures NO, NOT No A Tank containing A is empty.
V1 or V2 closed.
Pump does not work.
Pipe broken
Not enough A = Explosion
Indicator for low level.
Monitoring of flow
MORE Too much
A
Pump too high capacity Opening of V1 or V2 is too large.
C contaminated by A. Tank overfilled.
Indicator for high level.
Monitoring of flow
LESS Not enough
A
V1,V2 or pipe are partially blocked. Pump gives low flow or runs for too short a time.
Not enough A = Explosion
See above
AS WELL AS Other substance
V3 open – air sucked in Not enough A = Explosion
Flow monitoring based on weight REVERSE Liquid
pumped backwards
Wrong connector to motor Not enough A = Explosion
A is contaminated
Flow monitoring
OTHER THAN
A boils in pump
Temperature too high Not enough A = Explosion
Temperature (and flow) monitoring.
Preliminary HAZOP Example
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
19 T
C
Cooling Coils Monomer
Feed
Cooling Water to Sewer
Cooling Water In
Thermocouple
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