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HAZ29_122
Failure of Above-ground Storage Tanks (AST) :
a new methodology for assessing consequences
Authors: Chris Robinson 1, Mark Scanlon 2, Euan Stoddart 1, Kunle Fajuyitan 1, Tristan Vye 1
Organisations: 1 MMI Thornton Tomasetti2 Energy Institute
Correspondence: CRobinson@ThorntonTomasetti.com | 01904 428721 | 07979 656988
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Failure of Above-ground Storage Tanks (AST)
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Failure of Above-ground Storage Tanks (AST)Project Brief
EI Containment Systems Working Group
“Develop failure mode analysis
assessment tool for above ground
storage tanks”
Objective: Improve predictive
risk assessment for
catastrophic AST
failure
Clarity in
required risk
reduction
measures
Consistency in
predictive risk
assessments
COMAH
Safety
Regulations
Failure of Above-ground Storage Tanks (AST)Project Brief
EI Containment Systems Working Group
“Develop failure mode analysis
assessment tool for above ground
storage tanks”
Phase 1: • Focus: catastrophic primary
containment failure modes
and the factors that affect
vulnerability
• FMECA
Phase 2-4: • Phase 2: develop methodology
for assessing consequences of
AST failure
• Phase 3: calibrate the
methodology
• Phase 4: determine overtopping
fractions in methodology
Risk = frequency of event x consequence of event
Failure of Above-ground Storage Tanks (AST)
How will the new methodology work
[fatalities per year] [events per year] [fatalities]
Phase 2-4: • Methodology for assessing
consequences of different
failure scenarios
Phase 1: • FMECA gives
frequencies
Consequence: • Failure of secondary containment
• Volume of spilled fluid overtopping
secondary containment
For “Risk” calculation need
additional steps: • P (ignition)
• Thermal Radiation Contours
• P (occupancy)
Failure of Above-ground Storage Tanks (AST)
What are ASTs – how do they fail?
2013 - Ranger Uranium Mine,
Northern Territory, Australia• 1 ML sludge (mud/water/uranium ore/acid)
2011 - Lake Placid, Florida, USA• 300,000 gallon water tank
• “The force from the water was so great,
investigators say it tore through a concrete
block wall, forcing the building to collapse
on top of the two workers inside”
Failure of Above-ground Storage Tanks (AST)
What are ASTs – how do they fail?
2008 - Allied Terminals
Chesapeake, Virginia, US• Spilled 2 million USgal liquid fertiliser
• Injured 4 people.
• US Chemical Safety Board determined
cause as faulty welding.
2006 - LA Gas, Salt Lake City, Utah, US• 13,000 USgal of hydrochloric acid.
• Tank topple due to strong winds
Failure of Above-ground Storage Tanks (AST)
What are ASTs – how do they fail?
2004 - BR Petrochemicals, Vathuruthy, India• One killed, 2 injured
• 1.5 ML of water spilled during a pressure test
2004 -Chevron-Texaco, North Pass,
Mississippi, US• 423 tonnes crude oil spill,
• Collapse due to hurricane Ivan
Failure of Above-ground Storage Tanks (AST)
Boston Molasses Disaster – 100 years ago.
15th January 1919
The North End neighbourhood of Boston, US
• A large molasses storage tank burst
• A wave of molasses rushed through the streets at
an estimated 35 mph (56 km/h),
• Killed 21 ; injured 150.
Failure of Above-ground Storage Tanks (AST)
Existing Analysis by Computational Fluid Dynamics (CFD) Modelling
“Develop failure mode analysis
assessment tool for above ground
storage tanks”
Phase 2-4: • Method for assessing
consequences of AST collapse
Data & Experience
• Computational Fluid Dynamics (CFD) analysis
• Volume overtopping secondary containment (bund)
• Structural loads
• Development of wave return / retaining bund profiles
• Design of bunds and retaining structures
Failure of Above-ground Storage Tanks (AST)
Existing Analysis by CFD Modelling
Failure of Above-ground Storage Tanks (AST)
Existing Structural Analysis
Raw pressure-time
history manipulated
into wall/stem forces
for design
Hand calculations used
to estimate foundation
sizes & limit movement
FEA to check
displacements & extract
member/ connection
forces and moments
Failure of Above-ground Storage Tanks (AST)
Methodology Logic
Developing the new
methodologyExcel based tool
Methodology
Logic
Failure of Above-ground Storage Tanks (AST)
Methodology Logic
Developing the new
methodologyExcel based tool
Define AST &
properties
Failure of Above-ground Storage Tanks (AST)
Methodology Logic
Developing the new
methodologyExcel based tool Define failure
Mode 6:
Failure of
main pipe
Mode 7:
Tank Shell Scoring
Mode 1:
Rocketing ShellMode 4:
Rapid failure
/ unzipping
Mode 2:
Shell / bottom
failure
Mode 3:
Bottom failure
Mode 5:
Medium Shell
Failure
Failure of Above-ground Storage Tanks (AST)
Hydrodynamic Calculations
Developing the new
methodologyExcel based tool
Hydrodynamic
Loading Calc
Mode 1:
Rocketing
Shell
Mode 4:
Rapid failure
/ unzipping
Mode 2:
Shell /
bottom failure
Mode 3:
Bottom
failure
Mode 6:
Failure of
main pipe
Mode 7:
Tank Shell
Scoring
Mode 5:
Medium
Shell Failure
Discharge
through Orifice
Sluice
Discharge
Self-similar
Slumping
Load on
Bund wall
Failure of Above-ground Storage Tanks (AST)
Structural Loading vs. Structural Resistance
Developing the new
methodologyExcel based tool
Hydrodynamic
Calculations
Structural
Resistance
Foundation:• Overturning
• Sliding
• Bearing Pressure
Bund Wall:• Moment
• Shear
Compare with …
Failure of Above-ground Storage Tanks (AST)
Structural Resistance & Overtopping
Developing the new
methodologyExcel based tool
Structural FoS
Structural Resistance
Hydrodynamic Load
Failure of Above-ground Storage Tanks (AST)
Methodology Example
Developing the new
methodologyExcel based tool
Example: Shell /
Bottom Failure
Failure of Above-ground Storage Tanks (AST)
Methodology Example
Developing the new
methodologyExcel based tool
Data Input
Sheet
Failure of Above-ground Storage Tanks (AST)
Methodology Example
Developing the new
methodologyExcel based tool
Example: Shell /
Bottom Failure
Failure of Above-ground Storage Tanks (AST)
Methodology Example
Developing the new
methodologyExcel based tool
Example: Rapid Shell
Failure / Unzipping
Failure of Above-ground Storage Tanks (AST)
Methodology Example
Developing the new
methodologyExcel based tool
Example: Rapid Shell
Failure / Unzipping
Failure of Above-ground Storage Tanks (AST)
Methodology Example
Developing the new
methodologyExcel based tool
Example: Medium
Shell Failure
Failure of Above-ground Storage Tanks (AST)
Methodology Example
Developing the new
methodologyExcel based tool
Example: Medium
Shell Failure
Failure of Above-ground Storage Tanks (AST)
Verification & Validation
Developing the new
methodology
Excel based toolVerification &
Validation
Verification:
• “do the calculations do
what I expect them to do”
• “is the maths correct”
Validation
• “does the code / method /
maths produce results that
represent the real world”
• QA (ISO 9001)
• Consistency Checks
• 3rd Party Testing
• “Cross-code” validation
with data from CFD model
• CFD model previously
validated using HSE R333
Failure of Above-ground Storage Tanks (AST)
Verification & Validation
Developing the new
methodology
Excel based toolVerification &
Validation
Case No. Force [kN/m of bund]
(Source Term)
Force [kN/m of bund]
(CFD)
Ratio
Force (Source Term) /
Force (CFD)
1 0.11 0.04 2.75
2 275 130 2.11
3 828 221 3.74
Case No. Force
[kN/m of bund]
(Source Term)
Force
[kN/m of bund]
(CFD)
Ratio
Force (Source Term) /
Force (CFD)
4 6.6 5.6 1.18
5 3.2 2.4 1.33
6 4.3 4.5 0.96
Catastrophic Tank
Collapse(Mode 1 & 4)
Shell / Bottom
Failure(Mode 2 & 3)
Failure of Above-ground Storage Tanks (AST)
Conclusions
▪ A new failure mode analysis assessment tool for above ground storage tanks
▪ Excel based tool incorporates a range of failure modes:
• catastrophic collapse; failure of tank shell; failure of bottom connection
▪ Provides rapid assessment of existing AST or new sites
▪ Provides data for Risk Analysis
▪ Indicative results – to inform design and indicate if more detailed analysis is
required
▪ Methodology to be published by Energy Institute later in 2019
w w w. T h o r n t o n To m a s e t t i . c o m
w w w. M M I E n g i n e e r i n g . c o m
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