neil henry, abb consulting, january 2013 european oil ... · pdf fileeuropean oil storage...
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© ABB Group January 22, 2013 | Slide 1
European Oil Storage Conference Managing and Maintaining Tank Integrity
Neil Henry, ABB Consulting, January 2013
Maintaining tank integrity- overview
Life extension and maintenance:
managing the assets
Concerns about ageing storage tanks
What causes storage tanks to deteriorate?
- how this influences integrity
- specific and proven case studies
Types of storage tank and materials of construction
Practical advice on how can integrity be managed
© ABB Group January 22, 2013 | Slide 2
© ABB Group January 22, 2013 | Slide 3
Introduction
Tanks are in all shapes and sizes
Most are of carbon steel (some stainless steel)
Certain duties are pressurised (eg liquified gas)
Can be very large inventory of hazardous fluid
Service life can be very long (over 70 years)
May have very limited inspection
Large numbers manufactured of non-metallic
materials
An ageing forgotten asset?
© ABB Group January 22, 2013 | Slide 4
Ageing tanks – “a riveting subject”
© ABB Group January 22, 2013 | Slide 5
Why is there a concern?
COMAH Competent Authority Priority area for UK (Seveso directive)
“…50% of European major hazard losses of containment are primarily due to ageing plant mechanisms”
(Ageing Plant Operational Delivery Guide June 2010)
“30% of “potential major accident” incidents associated with ageing of one type or another
(HSE Research Report 823)
ABB experience - there is often limited knowledge of condition of storage tanks (and other COMAH equipment) to assess if deterioration is a problem.
(ABB contributed to the HSE Research Report 509)
There is a need to understand the potential for deterioration and the stage of life that the item is at.
© ABB Group January 22, 2013 | Slide 6
Ageing Plant – Not us?
The quotes below are typical examples from organisations and individuals
that are not recognising or not acting on the signs of ageing
There haven’t been any problems up to now, so the equipment is
safe, isn’t it?
We don’t have any drawings for this vessel; and we don’t know what
the material is.
It’s only been in service for two years so it can’t be ageing.
The integrity of our equipment is separate from our safety
management.
Our equipment does not contain defects.
We maintain and inspect only equipment to meet the PED (UK
Pressure Systems Safety Regulations) and usually stock tanks are
not pressure vessels.
Ref: HSE RR 509 – Plant Ageing – Management of equipment containing hazardous fluids or pressure
© ABB Group January 22, 2013 | Slide 7
Current Performance on Ageing Plant
Ref: IChemE Loss Prevention Bulletin 224, April 2012 - Management of Ageing Plant, S Pointer HSE
© ABB Group January 22, 2013 | Slide 8
Management of “Life”
For ageing and vulnerable items do we recognise the potential for defects?
Identify potential failure scenarios based on condition eg. base leak, hole in shell.
Contingency plan for leaks / defects – to manage safety:
Transfer of inventory
Temporary repair
Continue operation and manage leak / defect
Shutdown
Condition assessment
Materials and deterioration modes
Operating conditions
Recognition of “change”
Plan for business requirements
Funding
Resources / contracts
Planned outage
© ABB Group January 22, 2013 | Slide 9
Why does equipment fail? Investigation Data.
© ABB Group January 22, 2013 | Slide 10
Failure patterns of 40 years ago
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What affects asset life?
Design
Construction
Operation
Maintenance
Inspection
Modifications
Suppliers
Asset Life Factors Across the Life Cycle
•Life-limiting factors assumed at design stage
•Design quality
•Quality of original fabrication & installation
•Operating within design limits
Knowledge of equipment condition e.g.
•Inspection of static equipment
•Condition Monitoring of rotating equipment
•Maintaining equipment in ‘fit for service’ condition
•Quality of spare parts and repairs
•Change of equipment or operating procedure that
negates original design assumptions
•Obsolescence of equipment
© ABB Group January 22, 2013 | Slide 12
Is integrity managed?
Application of an RBI process (typically API 571)
Describes 60 plus deterioration mechanisms
(refinery bias)
Is a ‘guide to deterioration’ (recommends
specialist assistance)
Significant resource / time commitment
Not always considered for storage
© ABB Group January 22, 2013 | Slide 13
Fuel storage problems
Corrosion of tank shell is usually localised
Tank base particularly vulnerable:
External deterioration (Kerosene)
Internal corrosion / microbiological action
Corrosion of roof occurs (diesel & fuel oil duties)
Hydrogen sulphide (H2S)
Water vapour
Floating roof location most vulnerable (petrol storage)
© ABB Group January 22, 2013 | Slide 14
Fixed roof tanks - Tank uplift
Although low pressure, there are significant loads from the pressure
on the roof
If force up > weight of roof + shell, tank needs hold down
LIQUID
WELD
TEARS
Small pressure LARGE area
TYPICALLY
1/4" THICK
1/4" THICK
© ABB Group January 22, 2013 | Slide 15
Frangible roof design
Tanks are weakest at the shell-to-base weld
Light seal weld in roof designed to protect against
catastrophic failure at base from overpressure
See EEMUA 180 for guidance on design specification
Ensure relief devices are correctly sized and maintained
© ABB Group January 22, 2013 | Slide 16
Floating roof problems
Vulnerable to poor water drainage
Pontoons can corrode and sink
Seals deteriorate (fire potential)
Corrosion to walkway causing it to seize
Corrosion to roof support leg housings
Rim Seal
Sunken roof
Poor water
drainage
© ABB Group January 22, 2013 | Slide 17
External corrosion - Shell, roof and base
External corrosion / pitting to shell and roof – paint system breakdown
Corrosion / pitting to under-side of base plate
Seal lost at base-plate edge – corrosion up to 1m in from edge
Corrosion also seen randomly across the base
Severe corrosion to tank roof
Foliage growing at base-plate edge
© ABB Group January 22, 2013 | Slide 18
Corrosion Under Insulation (CUI)
Water enters damaged cladding at top and runs down tank walls
Accelerated corrosion occurs at hold-up points eg. Stiffening rings and base
© ABB Group January 22, 2013 | Slide 19
Internal corrosion - Shell, roof and base
Internal corrosion / pitting to shell at product / vapour interface
Corrosion / pitting to base - sludge
Internal corrosion to roof space, including structure members - condensation
Corrosion behind roof seals
Lining deterioration
Under deposit corrosion
Corrosion behind roof seal
Extensive corrosion to tank bottom
© ABB Group January 22, 2013 | Slide 20
External Corrosion
Design Temp : 100 Deg
Baseplate Nominal Thickness : 10.0mm
Depth of Corrosion Up to 8.0mm
© ABB Group January 22, 2013 | Slide 21
Damage Found on Inspection
Severe metal loss due to water pooling under tank base
© ABB Group January 22, 2013 | Slide 22
Do inspection schemes include all damage mechanisms?
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Leaks from manways and branches
Use the correct gasket and fastener
specification
Only capable and experienced
personnel to make these joints
Consider ‘Critical Joint’ management
system. ie. joint assembly witnessed
and logged
© ABB Group January 22, 2013 | Slide 24
316 Stainless Steel on “Warm” Sulphuric Acid
Internal view – “as new”; all damage originated from outside
Mechanism - chloride stress corrosion cracking (SCC)
© ABB Group January 22, 2013 | Slide 25
Failure Examples : Lack of weld fusion
Tank in service for over 20 years, without failure
Mechanism - flexing of weld with lack of root fusion
(Note – most storage tanks have limited construction testing)
© ABB Group January 22, 2013 | Slide 26
Bottom Plate Rotation – Low Cycle Fatigue
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Tank failure example (background information)
Storage tank on liquid sulphur duty
Operating temperature = 120ºC
Operating pressure = a few mmHg or inches water gauge
The tank was insulated and heated by steam coils, 300mm
above the base of the tank.
The tank looked to be in good condition before the incident.
Inspection reports did not highlight any problems
Considered a none corrosive service (internal)
Temperature above “serious concern” range, for corrosion
under insulation (CUI)
© ABB Group January 22, 2013 | Slide 28
Extent of spillage
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Defect at base of tank
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Explanation of failure
Insulation
Corrosion band
Broken guttering allowed water behind insulation
Water
accumulation
here
The base of the tank had filled with
inert material insulating the lowest
section
© ABB Group January 22, 2013 | Slide 31
Inspection frequencies
Codes are not
Prescriptive. Only
guidance given
Example:- Table from
EEMUA 159
Other factors to consider,
listed in API 653:-
- nature of product
- corrosion rates
- operational regime
- prevention systems
© ABB Group January 22, 2013 | Slide 32
Non-metallic tanks
Non-metallic equipment offers cost effective long term service for many
process duties
Knowledge and experience are essential for assessment to maximise
service life
Ensure good design, fabrication and construction
Review operating regimes
Apply maintenance care, inspection and condition monitoring that are
appropriate to the duty, equipment type and age
Aim to have confidence in integrity of equipment for long term service
e.g. 10, 20 or 30 years, or more
Details guidance in HSE document PM75 (GRP), PM 86
(Thermoplastics)
© ABB Group January 22, 2013 | Slide 33
Typical results of Ageing Plant Study
ALS Category
7% 1%11%
73%
8%
A
B
C
D
E
Items need to be replaced
within next 20 years Items need major repairs
within next 20 years
Items need minor repairs
within next 20 years
Items can continue to be operated
for the next 20 years
Items need further
evaluation
© ABB Group January 22, 2013 | Slide 34
Summary
Know and understand you assets and their ageing status
Identify and manage deterioration mechanisms and look to
minimise or eliminate as many as possible / practical
Have in place a sound integrity management system
Allocate responsibility for assets within your organisation
Use an experienced and capable inspection organisation
Use the standards and guidelines available (100 years experience)
Carry out regular visual checks with own staff
Act on any defects identified to prevent further damage
Ageing assets can be managed safely and effectively
providing the methodology is understood and applied.
© ABB Group January 22, 2013 | Slide 35
The conclusions & benefits
Identification of problems allows solutions to be found,
providing for:
Safe operations, for future service
Confidence in asset condition
Prevention or reduction of deterioration / failure
Improves management of total operating cost
Optimised life of equipment life
Regulatory compliance and improved corporate
reputation
Technical justification for continued service and
replacement planning (all critical equipment)
Makes safe, financial sense
© ABB Group January 22, 2013 | Slide 36
Information Sources
www.hse.gov.uk/comah/ca-guides.
(“Ageing plant delivery guide” contains eight links to relevant info).
HSE Doc SPC/Tech/Gen/35. Integrity of storage tanks
HSE RR 760. Mechanical Integrity of Storage tanks
HSE RR 509. Ageing Plant
HSE RR 823. Plant Ageing Study
HSE RR616. Fitness for Service Review
EEMUA Guide 159. Maintenance and Inspection of Storage
Tanks
www.chemical.org.uk/non_metallic_storage_tanks.
HSE PM 75 & PM 86. Non-metallic storage tanks
Corrosion of above ground storage tanks containing fuels
(NACE; Materials Performance, March 2012).
© ABB Group January 22, 2013 | Slide 37