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Lear ning the lessons of deepwater assetintegrity11/01/2010

Past and recent events point to need for careful assessment of m aterials perfor mance and corrosion protection

 

Dr . Binder Singh

Wood Group Integrity Managem ent

Dr. Paul Jukes

MCS Kenny

Bob Wittkower 

JP Kenny Inc.

Ben Poblete

Cameron

On the July 6, 1988, the world’s worst offshore oil industry disaster occurred on the Piper Alpha platform in the UK sector of the North Sea. The loss of life was staggering: 167 dead, with 62 survivors, and dozens badly injured. Much has beenwritten and debated on the incident. The goal here is to examine a new angle on the subject matter, in the context of Inherently Safe Design, and the allied second tier items of interest. These are the corrosion-related items that havebeen accepted as pertinent over the years, but often erroneously perceived with less priority.

This is largely because the s ubject matter is considered too specialis tic, or complex and often requiring costly subjectmatter expertise. As a result, corrosion integrity is sometimes dangerously taken off the agenda by non-subject-appreciative project or even industry leaders. As part of this process, it is necessary to examine the role of corrosion

mechanism s in the root cause analyses of mos t significant failures, and virtually all loss-of-performance issues.

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Piper Alpha before Accident. (Courtesy Wood Group)

The Piper Alpha accident was a monumental event. It is, perhaps, in terms of impact a top-five engineering disaster onthe global scale, considered to be in the same league as Chernobyl, Challenger, Three Mile Island, Flixborough, etc. Interms of cost, it was also very expensive (estimated at more than $3.4 billion). And in many ways it is historicallycomparable to other 

high-impact human events, in that people (certainly in the British Isles and the North Sea community) often remember where they were on the day. In that way, Piper Alpha seems to have uniqueness about it, which may be due to the factthat it was offshore and involved a heavily manned producing platform. With the benefit of hindsight, we can concludethat the disas ter was de facto man m ade, in that the original platform had m any major design changes made to convertit into a gathering and distribution hub.

Though not a deliberate act in any way, many human and engineering errors were seen to hideous ly come into play.Many studies have looked at that aspect, including the Cullen Report which was published in 1990. This was the

culmination of a thorough two-year inquiry involving many interviews with survivors, families, and subject-matter expertsof the day. The Cullen report has tended to be the mainstay reference source for all new offshore design andoperational guidelines the world over. Some regions have used the findings rigorously whereas others have used themless in depth. Overall, the report led to the effective dissolution of the prescriptive regulations sanctioned up to that point,and replaced them with the evolution of the goal-setting integrity regulations in the UK and with derivatives thereof.

On the plus side, the m ajor outcome of the dis aster has been far better, safer, and more efficient engineering practicesfor the oil industry. And this, in turn, has reinforced the need for Inherently Safe Designs and procedures. These havebeen realized by better, more focused research, better applied knowledge management, and a greater sense of publicand indus try responsibility by the new generation of engineers and scientists.

Many more offshore, subsea and integrity-related projects and courses have evolved worldwide, largely at contractresearch or post-graduate level, much to the advantage and betterment of the industry. This has been promulgated bythe recognition that the design of the ass et – structure, pipeline, and pressure plant – can no l onger be based onprojected revenues alone. Yes, the ultimate decision m aker or breaker can and often is the commercial s ensibility, but agreater sense of responsibility to the public, and the environment, has fallen into place. This is largely Regulatory-driven,but one can still discern a good dos e of professionalism , merit and worthiness in the arena.

Root causes

Regarding the accident there was, perhaps, no s ingle root cause event that was to blam e. Rather, it was a confluence of many critical factors that were almos t the “perfect storm.” This is often described as the jigsaw or “Swiss cheese” effect,whereupon critical events occurring at a certain juncture in time; and as a consequence the failure sequence fell intoplace, with tragic results. In reality, integrity management (IM) is far more complex than basic maintenance (a commonmisnomer). The parameters affecting IM are non-linear, and have their greatest impact during IM pre-planning, post-planning, action and reaction, etc. They usually involve the alignment of bad sequences, events or circumstances. Theyare invariably all time-dependent and thus multi-dimensional in nature. This has traditionally made IM a difficult subjectto grasp, especially since it transcends both CAPEX and OPEX cost centers.

The Piper Alpha explosion.

The Piper Alpha platform was commissioned in 1976, but was modified to act as a major gas processing and gatheringstation. This m eant it was handling large amounts of high-pressure gas, with a dispersed plant layout, makinginspection, maintenance and repair difficult. The rapid technology advances of the day, coupled with powerfulcommercial pressures, clearly had a lot to do with the event. Regarding the best way forward, it is important to identify allintegrity-related threats, some of which may be discerned as at a secondary level, albeit with the potential to give similar disas trous results if not taken fully into account. The majority of these are m aterials performance and corrosion related.

 

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The latter is an important point, and necessitates the examination of second tier issues , which usually arise withinlower profile design parameters. Examples include press ure (leak) containment, corrosion analysis, erosion, wear andtear, inspection, monitoring, pigging, and maintenance. Thus, it is not hard to see that once the Piper Alpha wasconverted to its hub status, it became more important to continue producing. As a result, the inspection, maintenanceand corrosion control aspects became less important.

 After the disaster it became apparent that the Piper suffered serious corrosion problem s, particularly regarding thecondensate pumping systems, which were in fact later determined to be at the heart of the problem on that fateful day.Essentially, the condensate pum ps were under much delayed repair and maintenance schedules. On the fateful day,the work was underway but incomplete. Thus, the supervisor prepared a permit to work (ptw) for the work to becontinued by the next shift. The pump was temporarily blanked off, and the paperwork was submitted. Unfortunately, theptw got mislaid and the next shift erroneously switched on the pump. Since the backup was offline, the blind flangefailed and a m ass ive leak of gas under high pressure was released. A detonation was inevitable. When it happened,the fire fighting systems failed, other platforms continued to feed into the hub, and the disas ter as we know it unfolded.

 After the accident, due to the media frenzy of the day, the causes were various ly reported over the first year as: metalfatigue, poor maintenance, inadequate operating procedures, bad work practices, human error, etc. The full report is apublic document, and much educational material, videos/DVDs etc. are readily available for the interested reader. TheCullen report and other studies have highlighted many reasons for the disas ter, the mos t damning of which were:

Poor plant design (including rapid modifications and changes )Breakdown of the permit to work system (probably not fully tested under all scenarios)Bad maintenance managementInadequate safety auditing, and training proceduresPoor communications (all levels)Poor emergency management (including with regard to action of surrounding platforms).

The Cullen report made over 106 recommendations, which included in s ummary:

The transfer of government res pons ibili ty for offshore health and s afety to the Heal th and Safety Executive (HSE)

was generally well received.The establishment of a Safety Case regime (entailing independent verification).Overall review of legislation, definition of best practices, and better use of loss prevention studies.Better work force involvement (crucial but sensitive).Verification and intervention when necessary.Permit-to-work systems (ideally fail safe and tamper proof).Systematic approach to safety, responsibility of everyone (senior management and down the line).Emergency response and incident reporting (effectively by training and changes in attitude and culture).

It has to be said that most of the activities listed above still fall in the grey area of judgment, and in that case bestpractices must therefore be interpreted and appli ed through the identification of safety critical systems and components,proactive risk analysis, risk reduction, and therefore risk management. There are many other important derivations fromthe Cullen report, but without unnecessarily going outside the scope of this article, it is quite clear that management of change (MOC) is and will continue to be the best tool available in the ever-improving area of knowledge management.

Industry changes

The many ensuing industry changes identified since the disaster have, in fact, taken many years to come to fruition.Overall, most offshore regions – in particular the North Sea, GoM, and Australia – have embraced the new culture of 

safety. To be sure, there is sometimes a dangerous disconnect between theory and the actual practice of implementation. The rest of the world

has responded in a slower m anner, but with positive results, especially the SE Asia regions and offshore India.

The very heartening implementation of best practices (by choice, not necessarily regulation) has given greater confidence for the new, challenging deepwater explorations and subsea tie backs in the GoM and the new frontier Arcticregions. The most notable changes are interpreted as follows:

Changes to offshore asset design, requirements for design review, more latitude for concept creativity, better rationale for engineering conservatism and pragmatic s afety.New goal-setting legislation; i.e. the Safety Case, and better use of subject matter experts (SMEs).The goal setting idea replaces the prescriptive method. This has proved to be a s tep change in offshore safetyand engineering performance.

For the GoM, it has been s tated that the regulations conferred by the governing (now former) MMS are “fit for purpose.”

This suggests the designs are suitable at construction, but the gradual drift of this m eaning has evolved to “life-cyclefitness for purpose” and this appears to be adopted and embraced by the more recent generation of engineers (typically5-10 years

experience) as they enter the fray. The subtle debate now ongoing is at the material selection stage. There are twoschools of thought, namely the distinction being m ade of whether to select carbon s teel and then carefully manage theoperational corrosion; or to select the corrosion resi stant alloy option with minimal corrosion management. The contraryarguments are usually cost-center based, with strong opinions tested for CAPEX and OPEX scenarios. In other words,do we pick materials for immediate fitness for service at fabrication (“just build it”) or fitness for materials life cycleperformance? The answer is now emerging as a requirement for both, and to that effect the materials engineeringspecialist is having an ever-more assertive role to play within the large multidiscipline teams usually engaged on highcapital projects.

Implementation

The implementation of the Cullen report recommendations has, it is believed, shown through various studies thatreportable incidents that impact safety issues in the UK sector have been significantly reduced by some 75% – a major achievement. This clearly means the industry is on the right track, but there are still problems and iss ues. It is arguedthat more attention should and m ust be made to the secondary tier items such as root cause corrosion mechanisms ,

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advanced

monitoring and ins pection techniques, etc. This as pect is bes t illustrated by an adaption of the “Swiss cheese” effect. Itis to this effect that this article is targeted, with the intent that by paying more focused attention to these parameters andfindings, the integrity management dis cipline will be more substantively improved.

The Cullen report also identified two areas of under-emphasis that may be appropriately reasoned, firstly the industrytendency to avoid the acceptance of external consultants’ advice if the recommendations are not supported by moreexperienced personnel, often even if the consul tation seems logical and s afety sensible. The case of the central riser argument for the Piper Alpha is cited; here evidently the dangerous proximity of the risers to the control and radio roomareas was, in fact, identified, but no action taken (design change, relocation, blast walling, etc). Nowadays, virtually allnew designs insis t on the risers being as far away as possible from the accommodations.

The “Swiss cheese” analogy as applied to materials engineering.

The second point of obs ervation is the concept of addressing root cause effects. The Piper Alpha condensate pumpproblems that initiated the whole tragic sequence of events were plagued with corrosion problems, the attendance towhich was seemingl y consistently delayed as lower priority. Apparently some platform corrosion iss ues were left for over four years. If corrosion managem ent as a recognized discipline had been in place, rather than an ad hoc to-doitem, then again (with the benefit of hindsight), the tragedy could have been avoided. That, unfortunately, is how thelearning and knowledge managem ent process works. And it has to be said that companies today often have veryvaluable lessons-learned m eetings after major projects are concluded. There is a strong case, and new initiatives,underway for such formal lesson learning on an ongoing basis .

The use of m odern-day corrosion risk ass essment techniques are under development and application. It is hoped thatultimately these will be implemented by the weight of motivation, though in reality some degree of mandatory regulationmay be ultimately required. In almost all m ajor comparable disas ter cases, the commonality has been the confluence of many variables coming into a tragic alignment, sometimes referred as the jigsaw or “Swiss cheese” effect. The authorsof this article contend that in almost all cases, the loss of materials performance as stimulated by corrosion is the rootcause effect. A close examination of the modes of failure reveals the uncanny role of corrosion dissolution at either themacro or micro level (whether it be by alloy, embrittlement, crevice corrosion, mixed metal galvanic, etc) the outcome isthe same: s evere loss of material properties and/or load carrying capabilities.

The resolution of the corrosion as pect will, therefore, in virtually all cases eliminate the closure of the jigsaw effect,thereby preventing the failure. On a positive note, the concepts of knowledge management, advanced inspectiontechniques, implementation of MOC, and the m ore newly defined roles and responsibilities for pertinent decisionmakers, etc., have all been very instrumental in making this industry safer and better equipped to tackle the challengesfaced ahead. It is s trongly argued that one new recomm endation that would be ins trumental in helping improve thisaspect an order of magnitude would be the “mandatory” requirement for each asset to subm it a clear annual corrosionintegrity statement on the facility, and pertinent (safety critical parts) thereof. The burden for doing this is not high, but theresults would be extremely positive.

Conclusion

The Piper Alpha review has been a work in progress, with many derived findings, conclusions and specifically KPI-based recomm endations, most of which are capable of being tailored to new and existing projects. The mos t valuableobservation is the need for continued life cycle vigilance, most likely through diligent but limited regulatory control, sincethe North Sea experience has shown that “over regulation” can im pose major financial burdens often to the detriment of the project, and sometimes to the creativity of solutions.

It is important for the future deepwater offshore comm unity to look more closely at new des igns and new solutions fromboth a materials fabrication and the materials performance basis , especially for safety critical elements s uch as SCRs,and press ure containment plant, and potential leak sources at interfaces. Companies must continually re-educate s taff so that less ons learned (and near miss es) are not forgotten, and be prepared to look at alternative approaches todesign/operational issues even if they emanate from unconventional s ources.

Better cooperation between the CAPEX and OPEX cost centers is vital if full advantage of lessons learned from Piper  Alpha and other disas ters are to be realized. In reality, this may take the form of an extended CAPEX comm itment.History has shown that major step change progress is usually made after major disasters and often through non-

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conventional means. The new s olution sets, and developments vis-a- vis inherently safer designs will come from acloser liaison between industry and academia, as exemplified by the JIPs already in place. The powerful role of academia – whether through JIPs or s elf driven changes in university curricula – will be ins trumental in the paradigmshift required and perhaps expected.

Acknowledgment

Based on a paper presented at the Deep Offshore Technology International Conference, held at the George R. BrownConvention Center in Houston, Texas, February 2-4, 2010; and on a paper presented at the Offshore TechnologyConference, “Offshore Integrity Management 20 years on—Overview of Lessons Learnt Post Piper Alpha (Paper # OTC-20051-PP).

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