HAZ29 122 Failure of Above-ground Storage Tanks (AST)

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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

▪ Thornton Tomasetti provides

engineering design,

investigation and analysis

services to clients worldwide on

projects of every size and level

of complexity.

Failure of Above-ground Storage Tanks (AST)

Companies Involved

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Forensics

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▪ The Energy Institute (EI) is the

chartered professional membership

body bringing global energy

expertise together.

▪ We gather and share essential

knowledge about energy, provide

the skills that are helping us all use

it more wisely, and develop the good

practice needed to keep it safe and

secure

20,000 members | 200 companies | 120 countries

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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