Subject: Quantitative Risk Assessment

1. NAME MATRIC NO
MUHAMMAD HAFIZ BIN MOHD YATIM : KQD 160015
NORSIAH BINTI SUKARDY : KQD 160025
MARINA BINTI MUHAMAD : KQD 160022
MUHAMMAD IQBAL BIN MASRI : KQD 160039
NURUL FARHANA BINTI HAMDAN FADEL : KQD 160023
MOHAMAD ARIF BIN MUAHZIM : KQD 160016
KQD7005
ALOHA PROJECT
QUANTITATIVE RISK ASSESSMENT

2. 1/27
CONTENTS
1. INTRODUCTION..................................................................................2
2. ABOUT THE STUDY .................................................................. 2
3. ACCIDENTAL HEALTH RISK ASSESSMENT.......................... 4
3.1. Leaking Tank, Chemical Is Not Burning As It Escapes Into the
Atmosphere ............................................................................ 4
3.2. Leaking Tank, Chemical Is Burning and Forms a Pool Fire ... 5
3.3. BLEVE, Tank Explodes and Chemical Burns In A Fireball .... 7
4. ENVIRONMENTAL HEALTH RISK ASSESSMENT (EHRA) FOR
RESIDENTIAL AREA IN 1KM RADIUS ..................................... 8
5. FURTHER DISCUSSION.......................................................... 10
5.1 General................................................................................. 10
5.2 Accidental Health Risk Assessment..................................... 10
5.3 Environmental Health Risk Assessment (EHRA) for
Residential Area in 1km Radius ........................................... 13
6. RECOMMENDATIONS............................................................. 14
7. APPENDIX................................................................................ 18

3. 2/27
1. INTRODUCTION
Company : RXZ Sdn Bhd
Profile : Manufacturers several types of polymer resins
General
objective
: To conduct quantitative risk assessment study as part of
CIMAH report to be submitted to the Department of
Occupational Safety and Health (DOSH).
2. ABOUT THE STUDY
Objectives :
i. To assess and understand the impact of tank failure from –
a. Leaking tank, chemical is not burning and forms an evaporating
puddle
b. Leaking tank, chemical is burning and forms a pool fire
c. BLEVE, tank explodes and chemical burns in a fireball
ii. To propose recommendations on control / mitigation methods to reduce the
impact of in-situ and ex-situ exposures.
A Quantitative Risk Assessment for RXZ Sdn Bhd has been carried out by using
ALOHA. The information of the site data are as follows and were used for all there (3)
case studies (leakage with no fire, leakage with fire, BLEVE):
ITEM DETAILS REMARKS
Location : Bintulu Malaysia Reference from
Weather.com :
https://weather.com/wx/to
day/?lat=3.17&lon=113.0
4&locale=en_US&par=go
GPS : Latitude
Coordinate : 3.17°N
Time: 3h10m12s
Longitude
Coordinate :
113.03°E
Time: 113h1m48s

4. 3/27
ITEM DETAILS REMARKS
Wind : 6 km/h (3.72823 mph) from ESE ogle&temp=f
*Please refer appendixTemperature : 29 C
Humidity : 85%
Stability Class : B Auto-populated by
ALOHA to be aligned with
the temperature and
humidity entered.
The following quantitative risk assessment was performed for Tank 6 that contains
Methanol (Safety Data Sheet for Methanol referred throughout this study is available
at <www.sciencelab.com/msds.php?msdsId=9927227>). The details of the Tank 6 are
as follows:
Tank
Material
Stored
Volume
Tank
Geometry
Tank
Dimension
Bund
Area
T6
(Vertical)
Methanol 1,500
MT
Cylindrical 15m diameter x
15m height
70m x 40m
Assumption of the case area:
 The area and type of leak was assumed based on the probability of the incident
happen.
 The opening diameters is 1 cm with circular opening at 1 m height.
 The 1 m height is used because of many physical activities takes place in this
height i.e. forklift usage, physical maintenance, etc.
 Concrete ground type was used because of this setting takes place in an
industry.
 The maximum puddle diameter or area was depends on bunds area
measurement given, (70m x 40m = 2800m2
)

5. 4/27
3. ACCIDENTAL HEALTH RISK ASSESSMENT
The study was conducted by using ALOHA for 3 type of failures which were:
1. Leaking tank, chemical is not burning as it escapes into the atmosphere
2. Leaking tank, chemical is burning and forms a pool fire
3. BLEVE, tank explodes and chemical burns in a fireball
3.1. Leaking Tank, Chemical Is Not Burning As It Escapes Into the Atmosphere
ALOHA assessment was carried out under the following circumstances:
a) Scenario:
i. Flammable chemical escaping unintentionally/accidentally from tank
ii. No ignition source that will lead to fire during the spillage period
b) Potential impacts of spillage:
i. Downwind Toxic Effects
ii. Vapor cloud flash fire
iii. Overpressure from vapor cloud explosion
c) Result
i. *Please refer figure 1.1.1a for ALOHA output
ii. *Please refer figure 1.1.1b for ALOHA Threat Zone
iii. *Please refer figure 1.1.1c for ALOHA Source Strength
d) Discussion
i. Threat Zone
 Threat Zone was not produced because the effects of near-field
patchiness make dispersion predictions less reliable for short
distance.

6. 5/27
 Since the threat zone estimated to be less than 10 meters for
Toxic and Flammable Threat Zone, ALOHA was unable to
produce the threat zone as it need at least 50 meters to show
the relationship.
 In Overpressure Threat Zone, it shows that the all part of
emission released is under Low Explosive Limit, which lead to
no overpressure threat zone produced.
 *Please refer Chapter 3 for further explanation.
ii. Source Strength
 The graph displays the predicted rate at which the chemical
enters the atmosphere, limited for 1 hour release duration.
 From the graph, its shows the approximate release rate which
started at 0.7 pound/min and ended at 3.5 pound/min.
 From the source strength (table 1.a) shows that the maximum
average sustained release rate was 3.49 pounds/min.
3.2. Leaking Tank, Chemical Is Burning and Forms a Pool Fire
ALOHA assessment was carried out under the following circumstances:
a) Scenario:
i. Flammable chemical escaping unintentionally/accidentally from tank
ii. There’s an ignition source that lead to fire.
b) Potential impacts:
i. Thermal radiation from pool fire

7. 6/27
ii. BLEVE (if heat raises the internal tank temperature and causes the
tank to fail)
iii. Downwind toxic effects of fire byproducts (can’t be modeled by
ALOHA)
c) Result
i. *Please refer figure 1.2.1a for ALOHA output
ii. *Please refer figure 1.2.1b for ALOHA Threat Zone
iii. *Please refer figure 1.2.1c for ALOHA Source Strength
d) Discussion
i. Threat Zone
 Threat Zone was not produced due to stability of the
atmospheric setting.
ii. Source Strength
 The graph displays the predicted rate at which the chemical
enters the atmosphere, limited for 1 hour release duration.
 From the graph, its shows the approximate release rate which
started at 0.6 pound/min initially and stagnant at 8 pound/min
start from 21st
minute until the end.
 From the source strength (table 1.a) shows that the maximum
average sustained release rate was 8 pounds/min.

8. 7/27
3.3. BLEVE, Tank Explodes and Chemical Burns In A Fireball
ALOHA assessment was carried out under the following circumstances:
a) Scenario:
i. Flammable chemical escaping unintentionally/accidentally from tank
ii. There’s an ignition source that lead to fire.
b) Potential hazards:
i. Thermal radiation from pool fire
ii. BLEVE (if heat raises the internal tank temperature and causes the
tank to fail)
iii. Downwind toxic effects of fire byproducts (can’t be modeled by
ALOHA)
c) Result
i. *Please refer figure 1.3.1a for ALOHA output
ii. *Please refer figure 1.3.1b for ALOHA Threat Zone
d) Discussion
i. Threat Zone
 With circumstances of 100% percentage of Tank Mass in
Fireball, tank 6 Methanol will cause 643 meters of fireball
diameter with burn duration of 31 seconds.
 The area of the fireball derived from area formula shall be
324557.465m2
/ 0.3245km2
.

9. 8/27
4. ENVIRONMENTAL HEALTH RISK ASSESSMENT (EHRA) FOR
RESIDENTIAL AREA IN 1KM RADIUS
EHRA was handled by using ALOHA under the condition of fugitive release from
all the storage tanks each of 0.5 kg/s and the predominant wind speed is 2.0 m/s.
a) Scenario:
i. Flammable chemical escaping unintentionally/accidentally from tank
ii. There’s an ignition source that lead to fire.
b) Potential impacts:
i. Downwind toxic effects
ii. Vapor cloud flash fire
iii. Overpressure (blast force) from vapor cloud explosion
c) Notes:
i. 1. 0.5 kg/s is converted per minute, which is equal to 30 kg/min. From
the tank setting, the circular opening diameter is changed to 4.155 cm
to suit the fugitive release rate. The diameter of puddle is considered
with maximum puddle diameter or area was depends on bunds area
measurement given, (70m x 40m = 2800m2
).
ii. For fugitive release, the type of tank failure used is leaking tank,
chemical is not burning and forms and evaporating puddle.
d) Result
i. *Please refer figure 2.1a for ALOHA output
ii. *Please refer figure 2.1b for ALOHA Threat Zone
iii. *Please refer figure 2.1c for ALOHA Source Strength

10. 9/27
e) Discussion
i. Threat Zone
 Threat Zone for toxic area of vapor cloud is produced with only
yellow zone (ppm above 530ppm).
 However, the threat zone for Flammable Area of Vapor Cloud
and Blast Areas of Vapor Cloud Explosion was not produced
due to stability of the atmospheric setting.
ii. Source Strength
 The graph displays the predicted rate at which the chemical
enters the atmosphere, limited for 1 hour release duration.
 From the graph, its shows the approximate release rate which
started at 6 kg/min initially and capped at 30 kg/min start from
47th
minute until the end.
 From the source strength (table 1.a) shows that the maximum
average sustained release rate was 30 kg/min.

11. 10/27
5. FURTHER DISCUSSION
5.1 General
a) Threat Zone
i. Threat Zone was not produced because the effects of near-field
patchiness make dispersion predictions less reliable for short distance.
ii. Concentration patchiness defined that the gas concentrations cannot
be described as a bell-shaped curve (as the concept is been using in
Gaussian model).
iii. This shows that the gas distribution is very near to the source.
Since ALOHA uses concentration average, it affect ALOHA estimation to be
over/under estimate the concentrations. It shows that the emission is not well disperse
to a greater length as it depend on the stability, wind speed, and release details as
one of their aspect. It was supported because the setting had low wind speed. With
low wind speed the pollutant cloud was not mix quickly with the surrounding air which
makes the effect of near-field patchiness.
If the maximum distance to the toxic Level of Concern (LOC) concentration is
less than 50 meters, ALOHA will not show the threat zone, because concentration
patchiness makes the estimate unreliable near the source of the release (where
patchiness is most pronounced).
5.2 Accidental Health Risk Assessment
With reference to Appendix 1.1-1.3, based on the reading viewed on the 27th
of May
2017 Tank 6 will has the following impact in case of emergency:
In case of tank leakage, the methanol:

12. 11/27
i. Has low downwind toxic effects as the dispersion is less than 10 m due to
atmospheric condition.
ii. Has low flammable threat as the dispersion is less than 10 m due to
atmospheric condition.
iii. Has low overpressure effect as all parts of the cloud vapor is under LEL at
any time.
Elaboration:
Since the leakage affect takes place within the plant area (around 10m
radius), the worker might exposed to inhale experience the following symptoms
: slight irritation of the nose and eyes; head feels hot and face is flushed;
excitability and talkativeness; drunken behavior; staggering and lack of
coordination; headache; mental confusion and visual disturbance; tiredness.
However the affect will change to become more severe with different
atmospheric setting. For example, if the environment less stable with high wind
speed, it will increase the dispersion of the methanol leakage. This will certainly
affect the surrounding setting.
In case of pool fire:
i. Has low thermal radiation from pool fire with occurrence less than 10 m.
Elaboration:
As the tank leaks and contained in bund area, it will has a low thermal effect
to the surrounding. From the threat zone produced, it shows that the thermal
radiation has less than 10m. Therefore, since the thermal radiation will be
contained in the bund area (2800m2), the effect will be low toward the nearby
people. However, if the setting without the bund area and lower humidity, it will
affect has a different thermal radiation affect to the surrounding.

13. 12/27
In case of BLEVE:
i. Yellow zone (pain within 60 sec) with radius of 1.9km radius will affect the area
of 4.5961km2
ii. Orange zone (2nd
degree burns within 60 sec) with radius of 1.175km radius will
affect the area of 1.9311km2
iii. Red zone (potentially lethal within 60 sec) with radius of 0.875km radius will
affect the area of 2.4041km2.
Elaboration:
From the graph, the yellow zone will affect some human settlement ranges
from Parkcity Everly, Chin Lee Garden and Kampung Baru Serbuan Besar.
Therefore, for those are in this area might feel pain within 60 second of the
incident takes place. Followed by the orange zone will affect a minor human
settlement nearby Jalan Tun Razak. People in this area might experience
second degree burns within 60 second of the incident takes place. On the other
hand, the red zone does not affecting any human settlement. However, if
anyone are in this area during the incident might be dead within 60 second from
various reasons i.e. overpressure, high thermal radiation, etc.

14. 13/27
5.3 Environmental Health Risk Assessment (EHRA) for Residential Area in 1km
Radius
With reference to Appendix 2, Tank 6 will has the following impact in case of fugitive
release emergency:
i. Has low downwind toxic effects as the is very limited to yellow zone (greater
than 530 ppm) and travelled approximately 70m from the point source
Elaboration:
The low downwind toxic effects will has low impact to the people nearby as
the plant is located quite isolated from human settlement. However, with
different atmospheric setting (i.e. lower humidity, higher wind speed), it will has
significant toxic effect to the surrounding people that exposed to the chemical,
through inhalation.

15. 14/27
6. RECOMMENDATIONS
In Case Of Tank Leakage with No Fire
IN-SITU
1. Engineering control
a. Installation of proper early detection system (sensor) to ensure there’s
no unusual reading / condition occurs at any time.
b. Substitution of tank materials into durable material to ensure the
resistance of leakage due to foreign disturbances/knock-out.
c. Installation of relief valve to limit the pressure in a system or which can
build up for a process upset, instrument or equipment failure, or fire. The
pressure is relieved by allowing the pressurized fluid to flow from an
auxiliary passage out of the system (to reduce leakage)
d. Installation of blow-down drum – in the case of abnormal operating
condition, chemical inside the tank will be pumped into the underground
safe area (this system will be directly connected to the relief valve)
e. To scale down the tank and make it in series instead of one (1) batch to
ensure that the impact can be minimized – example: change the current
capacity from 1,500MT in one time into 3 batches of 500MT.
f. To install removal system (Local Exhaust Ventilation) to ensure no
trapped evaporated methanol from
g. Use suitably-rated electrical equipment – to ensure it will not be
contributing to fire hazards.
h. Implementation of permit to work system (PTW) to prevent hot-work
around the area (e.g., welding)
2. Administrative control
a. To ensure that all system and tank are in good condition at all time – this
can be delivered by proper management of system and tank service
maintenance
b. To identify specific and safe assembly point in case of accidents happen.
c. To ensure that there is no dust generation activities around the area by
undergoing good housekeeping.

16. 15/27
IN-SITU
3. Personal Protection Equipment (PPE)
a. To prepare self-contained breathing apparatus in the case of leakage
due to the high exposure to escapes methanol.
In Case Of Tank Leakage with Fire – Pool Fire
IN-SITU
1. Engineering control
a. Installation of tank grounding to remove – electrostatic charges which
can be the ignition source to fire.
b. Installation of inerting gas system to reduce oxygen concentration inside
the tank.
c. Redesigning the bund so to be able to contain all methanol in case of full
leakage
d. Installation of wall that is fire and explosion resistance
2. Administrative control
a. Implementation of ‘No-Smoking Policy’
b. Scheduled preventive maintenance
c. Training on spillage emergency response and plan
3. Personal Protection Equipment (PPE)
a. Fire proof coverall for the technicians and emergency response team in
the case of fire

17. 16/27
In Case Of Boiling Liquid Expanding Vapor Explosion – Fireball
IN-SITU
1. Engineering control
a. Installation of rupture disc / safety relief system to prevent over
pressurized which can lead to explosion.
b. Installation of blow-down drum – in the case of abnormal operating
condition, chemical inside the tank will be pumped into the underground
safe area (this system will be directly connected to the rupture disc
system)
c. Inerting gas to be introduced into the tank to ensure the level oxygen
concentration which can lead to fire (to avoid oxidation processes)
d. To scale down the tank and make it in series instead of one (1) batch to
ensure that the impact can be minimized
e. Installation of coolant to stabilize the temperature to its optimum level.
f. Installation of tank earthly-grounding to remove – electrostatic charges
which can be the ignition source to fire.
g. Explosion proof material for the tank.
2. Administrative control
a. Gas detection system must be duly checked.
b. Inventory control – to prevent storing for a long period of time and to
avoid high level of volume
c. Implementation of permit to work system (PTW) to prevent hot-work
around the area (e.g., welding)
3. Personal Protection Equipment (PPE)
a. To prepare self-contained breathing apparatus in the case of leakage
due to the high exposure to escapes methanol.

18. 17/27
In Case Of Leakage, Pool Fire and BLEVE
EX-SITU
1. Engineering control
a. Installation an early detection system / alarm system for the
neighboring
b. Implementation of proper traffic controls and route of entrance and
egress
c. Installation of sufficient barricading distance to ensure of no intruders
d. Implementation of engineering control via tree planting surrounding the
plant to reduce the magnitude impact towards the residence within the
zones
2. Administrative control
a. Information on hazards and risks from the plant to be distributed to the
local authorities, government agencies (police & firefighting agency)
and locals
b. Handbook on emergency plans and reactive precautionary.
c. Scheduled drills with the surrounding neighborhoods.
Additional recommendations -
IN-SITU
1. Engineering control
a. To isolate the bund from being place together with other chemicals in
batches to avoid any chain reactions.
b. To place every tank in a safe distance from each other
2. Administrative control
a. To do proper inventory for every chemicals – avoid keeping a huge
amount at one time.

19. 18/27
7. APPENDIX
Figure 1 – Meteorological information of Bintulu, Sarawak dated 27th
May 2017

20. 19/27
1.1.1a ALOHA Output
1.1.1b ALOHA Threat Zone
(Toxic Threat Zone)

21. 20/27
(Flammable Threat Zone)
Overpressure Threat Zone

22. 21/27
1.1.1c ALOHA Source Strength
1.2.1a ALOHA Output

23. 22/27
1.2.1b ALOHA Threat Zone
Thermal Radiation Threat Zone
1.2.1c ALOHA Source Strength

24. 23/27
1.3.1 ALOHA Output
1.3.2 ALOHA Threat Zone

25. 24/27
Mapped onto MyMaps
2.1a ALOHA Output

26. 25/27
2.1b ALOHA
Toxic Area of Vapor Cloud

27. 26/27
Flammable Area of Vapor Cloud
Blast Areas of Vapor Cloud Explosion

28. 27/27
2.1b ALOHA Source Strength
All ALOHA Threat Zone