One way of considering the life ofan oil or gas platform is to com-pare it to a human body. Asevery one of us knows, the older we getthe more problems we have. Once wehave been affected by the early child-hood diseases, such as mumps andmeasles, we normally have a relativelyhealthy life during our teens, twentiesand thirties. Things start to slide in ourforties and fifties and, by our sixties, themajority of us have had some kind ofhealth problems. Cancer is normallypredominant, with breast cancer beingthe biggest natural killer of womenand prostate cancer being the biggestnatural killer of men. Other cancerssuch as lung and skin cancer are usuallyself-inflicted and, to a great extent, canbe prevented by not smoking or havingprolonged exposure to the sun.

Oil platforms follow a similar pattern.After the initial minor commissioningand start-up problems the majority ofplatforms have a relatively trouble-freelife until they are retired from service

and decommissioned. However, withmany now having exceeded their designlife, we are seeing the results of old ageand the increasing number of problemsthat go with extended use. Just like thesituation with the human body, manyof these problems can be preventedwith increased inspection and mainte-nance regimes. (See Figure 1.)

Steel cancerCorrosion is basically the cancer of steeland the old expression Rust neversleeps holds very true. Steel is actuallythermodynamically unstable withrespect to its oxides and rusting is theprimary way for steel to lose the energythat was added in transforming ironore into a steel ingot. Under normalonshore circumstances, steel which hasbeen given a generous paint coatingand is inspected and repainted regu-larly would be expected to remain insound structural condition for manytens of years.

O R T H S E A N platform maintenance

2 PETROLEUM REVIEW JULY 2006

Prevention is betterthan cureThe majority of platforms

in the North Sea were

designed for an operating

life of 25 years. Several of

these are now

approaching 40 years old

and many more are being

considered for a further

extension of life by up to

20 years. Dr Peter Millar*,

Lloyds Register EMEA,

explains how many of the

problems from which such

ageing platforms suffer

can be prevented with

increased inspection and

maintenance regimes.

Figure 1: Lack of inspection and maintenance on a flange and bolts

Offshore, things are not so simple.The ocean is one of the harshest envi-ronments on the planet. Not only is seawater and salt spray highly corrosive,wave motion and wind will also impartfatigue loading, which combines togive corrosion fatigue. Corrosionfatigue is considered synergistic. Thiscan be thought of as 2 + 2 = 5, whichmeans that the combination of corro-sion and fatigue acting together isworse than the effects of them bothacting separately.

Delayed diagnosisMany human diseases remain undiag-nosed and hidden for years and onlybecome noticeable when they start toaffect other organs or bodily systems.The same is true for offshore platforms.Take, for example, corrosion underinsulation (CUI). CUI is insidious andfairly difficult to detect. An inspectionregime requires the removal and rein-statement of the insulation and, inmany cases, scaffolding is needed togain access to the area. For this reasonCUI has tended to only become notice-able once the piping has perforated.Figure 2 shows a typical example.

Given adequate time, money andresources, inspection regimes can bedeveloped to ensure not only the pre-sent integrity of offshore structures andfacilities but also guarantee theirextended working lives. However, inlocations like the North Sea, unknownssuch as the weather and fog can inter-vene to sabotage even the best inspec-tion plans.

Another point that is often over-looked also correlates with the medical

model, and that is frequency of inspec-tion. In our youth and midlife we tendto have very infrequent visits to thedoctor; however, in later years, theseincrease significantly as our bodies suc-cumb to the ravages of time and, inmany cases, neglect. The same is truefor offshore installations. The inspec-tion frequency profile for a platformcannot remain static; it has to be aliving, dynamic thing that changes asthe asset ages. No one would arguethat the inspection and maintenanceschedules for a three-year-old platformare the same as for a 30-year-old one yet, at times, it is easy to forget thatsimple fact. (See Figure 3.)

Targetted inspectionAs an independent inspection authority,the Lloyds Register group is instru-mental in providing integrity services tomany operators worldwide. Part of thatjob involves providing solutions toongoing integrity problems.

With the relatively recent increase inoil prices and the intention of manyoperators to extend the working life of anumber of platforms, the Lloyds Registergroup has started to focus on the prob-lems associated with ageing assets. In thehuman body, old age targets certainareas. Arteries, hearts and lungs are ofprimary concern. Muscles, tendons andskin can largely be ignored. On ageingplatforms, it is the hydrocarbon lines thatshould receive the lions share of theinspection resources. Produced waterand drains may show as much degrada-tion, but the impact of failure on theenvironment, platform integrity and,more importantly, peoples lives, will bemuch less. Given limited inspection bud-gets and resources for older assets, thefocus has to be not just inspection andmaintenance, but targetted, prioritisedand smart inspection and maintenance.

Ultimately, old platforms are like oldpeople. The amount of care and lookingafter they need depends on how theyhave been looked after all their lives.The old saying applies to both Prevention is better than cure.

*Dr Peter McClean Millar is involvedwith Lloyds Register EMEA integrityservices in the North Sea. He has adegree in Metallurgy, a Masters inOffshore Engineering, an MBA and aPhD in Corrosion Fatigue. He is also aDoctor of Chiropractic.

3PETROLEUM REVIEW JULY 2006

Figure 3: Degradation of platform gratings

Figure 2: Typical corrosion under insulation