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The Alexander L. Kielland accident- 30 years later

“What did we learn - and applyand

What should we not forget?”

Torgeir MoanCeSOS, NTNU

e

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Outline Alexander Kielland on the Ekofisk field in March 1980 The Investigation The Causes of the accident

- Technical and Physical Causes-Consequences- Human and Organizational factors

Lessons learnt and their implications- whether they are implemented or not- how they are implemented

The Future - also, in view of other experiences

Concluding remarks

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Alexander Kielland on the Ekofisk field in March 1980

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There had been:- (No Blow-out)

- No overload due tomooring forces

- No SABOTAGE

The investigation Hypotheses

e.g. based on mapping of risks in the ”Safety Offshore Program” Evidence

- record of wave, wind conditions- design, fabrication and operation logs- load, response, fatigue, ultimate strength reanalysis- hearing of designers, fabricators,

classification societies, NMD/NPD

- the failed structure

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Technical-physicalpoint of view- Capsizing or total loss of

structural integrity commonly develops in a sequence of events

Human andorganizational point of view- All decisions and actions

made – or not made duringthe life cycle are the responsibility of individuals and organizations(and regulators)

Criticalevent

Fault tree

Event tree

- Fatalities- Environmental damage

- Property damage

Important with a dual view on accidents

Mangement and Oversight andRisk Tree (MORT)- nuclear, aerospace experiences

6The Alexander Kielland Accident (1980)

Technical-physical Causes-consequences

fatigue/ fracture in brace D-6

rupture/collapse in the other 5 bracesloss of column D

listingflooding

capsizing

evacuationescape

Fatigue failure

BraceD-6

Plate ofthe brace

Hydro-phonesupport

-123 fatalities-total loss of platform

7 The Alexander L. Kielland accident in 1980Technical causes &consequences

• fatigue failure of one brace- initiated by a

grossfabrication defect

• ultimate progressivefailure of braces

• progressive flooding

• inadequate evacuation (e.g. lifeboats) and rescue operation

Human and organizational factors

• fabrication defect due to - bad welding- inadequate inspection

• no fatigue design check carried out

• codes did not require structuralrobustness (damage - tolerance)

• damage stability rules did not cover loss of a column

• failure to shut doors, ventilatorsetc. contributed to the rapid flooding and capsizing

• evacuation not planned for an accident of this kind

• lack of life boats, survival suits• long mobilizing time for rescue

vessels/helicopters

Plate ofthe brace

Hydro-phonesupport

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Lessons learnt & their implications

- the experiences

depending on: - the background/perspective of viewing the ALK accident(in 1980 vs today)

- the experienced accident;and its probability and consequences (i.e. risk)

- ALARP principle of risk acceptance

- whether the experiencesshould be implemented or not ?

- if implemented, how ?

Tendency to overreact on a single accident

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System-related accidents on the Norwegian North Sea; i.e. duringthe pioneer period of 1966-1980: - Ekofisk Alpha, - Deep Sea Driller, - Helicopter accidents, - Ekofisk Bravo, - Alexander L. Kielland

Offshore accident experiences in Norway up to the Alexander Kielland accident

+123

+123 = 215

Fatalities

Environmental damage due to oil releases

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The five causes of the accident

Hydrophone supportPlate of

the brace

Hydro-phonesupport

• fatigue failure and fractureof one brace- initiated by a gross fabrication defect …..

• progressive ultimatefailure of bracesand loss of column

• progressive flooding of the deck and capsizing

Knowledge

Use of knowledge-common practice-attitudes

Acceptance limits• inadequate

evacuation/escapeand rescue operations

• safety management: HOF

11The Fatigue Failure: Analyses and Design

Truss work with tubular jointsSteel plated structure

A 24 m long crack

- Knowledge about-Response, -Resistance (Effect of initial defects)

- Fatigue design check- inspection, attitude, uncertainties

/∆= ≤ =∑ ic d

ic

nD 1 FDFN

Crack behaviour Fatigue failure:- visible crack - through thickness crack- member failure Fracture

12The Fatigue Failure & Fracture: HOF Experiences& Practices before the ALK accident

- 1840- 50

- 1847- 70

- 1895

- 1948

- 1953

- 1950’s

- 1960’s

- 1963

- 1969-73

- 1979

- 1980

First fatigue failures - of vehicle and machine shafts -documented in journals

Wöhler’s scientific investigations………………………………..

Kipling’s description of propeller shaft fatigue failure in ”Bread upon the waters”

Nevil Shute’s description in ”No Highway” of airplane loss due to fatigue………………………………..

Comet airplanes loss due to fatigue

Fatigue failures of welded bridges and ship structures –and R & D

Textbooks on fatigue of welded structures

Paris-Erdogan’s law ( fracture mechanics)

Offshore Rules with fatigue requirements

Ranger I jack-up failure in the Gulf of Mexico

The Alexander L. Kielland accident in the North Sea

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The Fatigue Failure: Fracture mechanics analysis

BraceD-6

E

D

(Moan, ISOPE, 2006)

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Fracture of brace D-6 and progressive failure of 5 braces: Structural robustness (ALS) - Fatigue failure vs final fracture of a member

- Failure of one brace causing ultimate failure of 5 remaining braces and loss of column

Alexander Kielland, 1980

- Failure of a single member was critical

”Missing” brace; also on the other side

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Ranger I, 1979

Structural robustness: HOF (practices)

2001

• General statements

16Robustness in stability

• existing damage stability criteriaconsidered 1 – 2 compartment damage (flooding) – 400 – 800 t(typically due to ship collisiondamage)

• loss of column D implied a netloss of buoyancy of 2000 t

Survival would require buoyancy of the deck

• failure to shut doors, ventilatorsetc. contributed to the rapid flooding and capsizing

NMD: large scale damage condition

Damage stability requirements for floating platforms have existed since the first rules for floating (drilling) platforms

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System Robustness: ALS Criteria

-Including moooring systems due to a very high failure rate of individual lines(also for DP systems)

- Requires tools for demonstrating robustness

- Judgement in practical implementation

(NPD, 1984)

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In general: PSA’s Management Regulations

Prevent the occurrence of accidental events

Protect against accidental events or reducetheir consequences- Provide measures to detect control and mitigate hazards at an early time to avoid escalation.

- Tolerate at least one failure or operational error without resulting in a major hazard or damage o structure

Practical problem in Implementation for:- Complex

systems where components are not easily defined

Robust organisation

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Escape & Evacuation procedure & system• Accident scenarios

− “Marine events” (listing, …)

− Fire or explosion(Effect of heat and smoke)

• Issues in platform design − escape ways

− evacuation means:coverage and quality (lifeboats, survival suits,

−equipment for safety and life – saving−annual training sessions

• Implications:- distance between hazardous areas and accomodation- location of lifeboats etc- protection of escape ways and evacuation means

Routes from hazardous areas to a lifeboat stations, or sheltered area etc

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Escape & Evacuation procedure & system Emergency preparedness for the area

Rescue helicopter stationed along the coast

Stand-by vessel in the field

Annual training sessions

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Safety Management

• Risk analyses (QRA, …..)

Unacceptable region

ALARP region

Broadly acceptable region

Negligible Risk

New installations

Critical eventFault tree Event tree

1978 - Early offshore risk analyses 1979 - Safety Offshore Program 1981 - NPD Guidelines for

Quantitative Risk Analysis 1984 - NPD’s Accidental Collapse

Limit State (ALS)- Studies in UK, US

1991 - NPD Regulations for risk analysis

1992 - HSE Safety case, UK (ALARP principle)

Total assessment of hazards that can cause failure- from Prescriptive to Goal-based to Prescriptive Approach

Conceptual – detailed design stages Human and organizatonal factors Education, training

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Safety Management: Risk reduction actions

Causes

• Calculated risk during design

• Errors and omissions

• Unknown phenomena

Action

• Increase safety margins of safety factors(ULS, FLS)

• Individual and organizational knowledge, skills and attitudes

• Safety culture• Quality control• Robust design

(ALS)• Research & development

Phase

• Design

• Design• Fabrication• Operation

• Design

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Safety Management: HOF Adequate design, fabr. and

operational basis

Competence of those who - make regulations(critera, methods, acceptance level etc)

- do the workin design, fabrication and operation(training..) software

Quality Assurance and Control of - the design process and - the structure (inspection..)

- QA/QC of novel concepts requires - robust control, i.e. independent reviews- possibly R&D

- Event Control of accidental events

ALK-no fatigue design check-inadequate inspection

Hydrophone holder was not a focus area(”non-structural”)

Recent examples of novel problems:- Ringing- Flexible riser ”corrosion” fatigue- Tether springing- Vortex induced motion

ULS:RC/γR > γDDC + γLLC + γEEC

FLS:D=Σni/Ni ≤allowable D

24What has been done to avoid catastrophic accidents of the ALK type ?

• fatigue failure - fabrication defects, fatigue, corrosion/wear, inspection,

• ultimate progressive failure of braces- initiating event (explosion/fire, ship

collision..) • progressive flooding - ballast error,

• inadequate evacuation (e.g. lifeboats) and rescue operation

ACTION taken:

Improved and new design criteria The main issue is:

- practice the criteria- QA/QC in fabrication, design

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Fatalities in Norwegian offshore activities

ALK: 123

26 The Futurein view of the past activities on the Norwegian Continental Shelfand elsewhere

Pioneer period of 1966-1980 with different accidents:- Ekofisk Alpha, Deep Sea Driller, helicopter accidents,

Ekofisk Bravo, Alexander L. Kielland

Safety management in large field development projects: 1980-90- NPD guidelines for conceptual safety assessment

( -Piper Alpha accident in UK)

Cost-effective field development and operation: 1990-2000- NORSOK; NPD regulations for risk analysis;

HSE ”Safety Case” (ALARP)- new concepts, FPSO- Sleipner A accident

Minimum installations and extended operation: 2000-

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The main issue Focus on Safety Management

– tranfer the lessonscombined with new experiences

- Sleipner GBS, 1991 - international experiencesneed to be considered

- blowouts, fires/explosions!

- indicators monitoring gas leaks etc and other ”near accidents”

Safety culture, attitudes, Based on experiences,Robustness in hardware, humanware..

28Future challenges – new technolgies

Ageing systems – in generalDegradation due to fatigue or corrosion

etc.- there is time to follow up- if not properly managed, may imply structural, pipe, machinery failures -e.g. with more frequent gas leaks

LNG technology development Complex and compact process facility

(fire/explosion hazards) Cargo transfer in open seas Sloshing of LNG in partly filled tanks Operation of vessels close to facilities

may cause collision hazard

Arctic operations Cold climate, darkness, ice loading

Financial downtimesmay implyservice life extension

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Increased focus on safety of marine operations

Challenges:- hydrodynamic modelling

of motions- automatic control- reliability and safety

(human factors)- simulator training

of the crew!

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Concluding remarks• Accidents like ALK can be avoided by implementing the knowledge

and practicing established safety principles (the barriers: design, inspection and repair criteria are available)

• The lesson that still need to be remembered is that human factors play a decisive role in safety and that proper safety culture and management are required in the involved organisations

• Focus on ageing due to fatigue, corrosion and wear, also with respect to process, equipment etc

• The fire and explosion (especially associated with blowouts) and marine hazards need to be managed since errors/faults may easily happen during operations. Quality assurance is a challenge.