consequence assessment of pipeline explosion in farashband...
TRANSCRIPT
Consequence Assessment of Pipeline
Explosion in Farashband
Gas Refinery by Phast Software
Presenter: Amin Avazpour
Dalan Gas Field Production Superintendent
Outline:
• Introduction
• Modeling
• Results and Figures
• Conclusion
• References
Impacts on People, Process and
Facilities , Environment and
Finances is being assessed in
Consequences Modeling
Many things can go wrong on a hazardous industrial facilities, leading
to an unintended release of hazardous materials or an uncontrolled
release of energy.
Consequence assessment is a
methodical examination of the direct
undesirable impacts of a loss of
containment of material or energy.
Introduction:
• Applications:
• design of new facilities: suggest optimal separation distances
• risk assessment of a facility for safety case
• emergency planning and land use planning: estimate impact distances for
• major accident scenarios
• Highly technical area, requiring detailed process safety expertise
PHAST version 7.3 Software (DNV Corp.) was adopted in
order to model the accident. PHAST examines the progress
of a chemical process incident from initial release through
formation of a cloud or pool to final dispersion calculating
concentration, fire radiation, toxicity and explosion
overpressure.
Modeling:
• Whole aim of this study is consequence assessment of explosion
caused by leakage occurred at the critical pipeline system
located in unit-4500 of Farashband Gas Refinery during the
start-up of the plant after annual Overhaul by PHAST. High
pressure (more than 100bars), makes the estimation of
probable explosion consequence more important.
Plant Description :
• Farashband Gas Refinery is located in Fars Province and is a subsidiary of South Zagros Oil and Gas production Company
• The major Process of the Refinery is to Dehydration of Gas and Stabilization of Gas Condensate which is produced in Aghar and Dalan Gas Fields and is transported to the Refinery.
• Climate
• Farashband has hot and humid weather. The temperature of this district
in the hottest month of the year is about 49 degrees centigrade
(August) and in the coldest month of the year is about 8 degrees
centigrade (December).
• The maximum humidity in Farashband is 67 percent in December and
its minimum humidity is about 46 percent in May.
Average value of essential weather variable for Farashband Gas Refinery
Atmospheric temperature 9.85◦C (The average of the minimum temperature
of the 6 colder months).
Relative humidity 64% (the average of the relative humidity for the 6
same months).
Solar radiation 0.50 kW/m2
Wind speeds (based on probable wind speed
of location)
1.5/D, 5/D and 1.5/F
Wind Condition:
For gas dispersion modeling detailed wind and weather data
were obtained from a local weather station and these were
used to define two representative weather conditions to be
used in the modeling.
These being Pasquill-Gifford categories D5 (atmospheric
stability class D with 5m/s wind speed) and F 1.5 (stability F
with 1.5 m/s wind).
D5 represents the most commonly found condition on the site
occurring >65% of the time and F 1.5 a worst case for gas
dispersion (stable conditions with low wind speed).
Gas Analysis Used For Modeling
AREA ACF (MOL%)
N2 6.82
CO2 1.42
C1 88.499
C2 1.52
C3 0.44
IC4 0.13
NC4 0.19
IC5 0.11
NC5 0.10
totalC6 0.38
totalC7 0.26
totalC8 0.10
totalC9 0.02
totalC10 0.01
C11+ 0.001
H2S(PPM) 138
SP.GR 0.64
MOL.WT (gr/mol) 18.42
PRESSURE (BAR) 101
TEMP. (c) 47
RATE (mm/day) 12.17
Figure shows the late Explosion Overpressure in adjacent of equipment.
Category 1.5F and 1.5D have overlap to each other but category 5D has a
40m delay for its maximum overpressure. 0.02068bar over pressure that
is one of the critical thresholds for unsafe distance occur in 500m distance
downwind of explosion
Figure shows the distance of late explosion in which the radii of circles for
various wind speed categories are between 1250 to 1320m downwind.
Figure on top shows the dose radii of jet fire and the other figure shows
that the lethality radius of jet fire which is about 360m.
Explosion radiation vs distance of jet fire showed in this figure. Level of
radiation varies between 360 to 380 KW/𝑚2 for wind speed categories.
Figure shows late explosion worst case distance due to modelling.
The radius of following circle is about 1300m.
Figure shows the flash fire envelop distribution due to explosion.
Category 5D has the smallest radius of flash fire and 1.5F includes the
largest zone between the other categories.
Conclusions:
1- Paying attention to HSE issues during Overhauls will cause to prevent from
losing huge cost of untimely shutdown and production interruption.
2- Consequence assessment will provide a good time for engineering analysis to
perform complete cost assessment for future remediation technique such as
pipeline intelligent pigging and inspection tests for replacing or maintenance of
the pipelines.
3- In safety issues radiations of 20.0 kW/m2 and 37.5 kW/m2 is very important
because the radiation of 20.0 kW/m2 cause damage to human, and 37.5kW/m2
cause damage to equipment and cause Annie's death, from the PHAST result the
radius of 37.5 kW/m2 is about 400m.
4- Concentration of released fluid reaches to 22000ppm in 900m far from
explosion for category 1.5F. This result clearly shows that pipeline explosion can
be extremely mortal for personnel that are working in mentioned distance.
References:
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Conference, 1998, pp. 1–7.
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