neil henry, abb consulting, january 2013 european oil ... · pdf fileeuropean oil storage...

© 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



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?


Ageing tanks – “a riveting subject”


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.


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


Current Performance on Ageing Plant

Ref: IChemE Loss Prevention Bulletin 224, April 2012 - Management of Ageing Plant, S Pointer HSE


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


Why does equipment fail? Investigation Data.


Failure patterns of 40 years ago


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


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


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)


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


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


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


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


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


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


External Corrosion

Design Temp : 100 Deg

Baseplate Nominal Thickness : 10.0mm

Depth of Corrosion Up to 8.0mm


Damage Found on Inspection

Severe metal loss due to water pooling under tank base


Do inspection schemes include all damage mechanisms?


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


316 Stainless Steel on “Warm” Sulphuric Acid

Internal view – “as new”; all damage originated from outside

Mechanism - chloride stress corrosion cracking (SCC)


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)


Bottom Plate Rotation – Low Cycle Fatigue


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)


Extent of spillage


Defect at base of tank


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


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


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)


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


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.


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


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).

neil henry, abb consulting, january 2013 european oil ... · pdf fileeuropean oil storage...

Documents