Feat flexible pipe

  • View
    1.619

  • Download
    1

Embed Size (px)

DESCRIPTION

BEST PRACTICES for FLEXIBLE PIPE INTEGRITYBlog : http://rismandukhan.wordpress.com

Text of Feat flexible pipe

  • 1. BEST PRACTICESforFLEXIBLE PIPEINTEGRITYE VOLVE 1 PAM BOSCHEE l OIL & GAS FACILITIES EDITOR 2 3 4 5

2. perators...BASED ON THE PROJECT DATABASE, KEY FLEXIBLE PIPE STATISTICS ARE AS FOLLOWS:are increasingly recognizing the need for a systematicassessment and management of flexible pipe integrity,but the identification of critical criteria and the means tobest achieve valid and efficient inspection and monitoring(I&M) continues to evolve. Emerging technologies inI&M and operators expanding implementation of risk-based management are leading the way toward achieving58 %of installed flexible pipes are risers.a comprehensive integrity management approach forflexible pipeline and riser systems worldwide.Flexible pipes are being installed and operatedof all flexible pipes have design 76 %in more marginal and challenging offshore conditions,adding to the complexity of acquiring complete and valid pressures of lessdata for the determination of their integrity. Especiallythan 5,000 psiimportant is the accurate assessment of the remaining(345 bar).life of a flexible riser so operators can avoid costlypremature change outs. of all flexible pipesTo further develop the definition of best practicesin flexible pipe integrity assurance, the SureFlex Joint 90 %are less than 10-in. in diameter.Industry Project (JIP) presented key findings from itsextensive 20-month-long survey work, including flexiblepipe use worldwide, statistics on design limits, damage,and failure incidences. Conducted under the auspices ofthe Oil and Gas UK, a trade association for the United < 50,000Pressure by internal diameter (pID)Kingdom upstream oil and gas industry, the State of psi-in. of the majority ofthe Art Report on Flexible Pipe Integrity and Guidance flexible pipes.Note on Monitoring Methods and Integrity Assurance forUnbonded Flexible Pipes (2010) revisited the state of of flexible pipe hasflexible pipe since the first survey in 2001 to 2002. The been designed for ascope of work was international in its content and had thesupport of international companies outside of the UK.70 %temperature of less than 176FOBrien et al. (2011) reported the outcomes of (80C).the JIPs data gathering from flexible pipe operatorsworldwide, manufacturers, and specialists in the field.From the time of the first survey, MCS Kenny compiledof operating flexible risers are in a wateran in-house database of flexible pipe use, damage, andfailure incidents. A comprehensive literature review was 70 %depth of less than 3,281 ftalso performed. The resultant database covered 1,900flexible risers and 1,400 static flexible flowlines; 130 (1000 m).production facilities worldwide; and 315 individualdamage and failure incidents from around the world.16 Oil and Gas Facilities February 2012 3. 2,000 1,800 1,600 1,400 1,200Water Depth, m 1,000 800 600 400 200 0 0 2 4 6 8101214 16 18 Internal Diameter, in.Fig. 1Water depth vs. internal diameter for flexible pipe in operation worldwide. 20,000P*ID=30,000 18,000 P*ID=50,000 16,000 P*ID=70,000P*ID=80,000 14,000 Pressure, psi 12,000 10,0008,0006,0004,0002,000 0 0 2 4 6 8 10 12 1416 18 20 Internal Diameter, in.Fig. 2 Design pressure vs. internal diameter for operating flexible pipe. The deepest water depth in which a flexible riser isannulus between the internal barrier sheath and the externalinstalled is about 6,234 ft (1900 m) with a flexible pipesheath of the flexible pipe.internal diameter (ID) of about 7.5 in. as shown in Fig. 1.Patrick OBrien, group director of strategic business andAlthough flexible risers with ID of more than 16 in. havemarketing at Wood Group Kenny, said, We might attributebeen installed offshore, these are in water depths not this increase to people not being fully aware of the real extentexceeding 1,312 ft (400 m). Fig. 2 shows the largest pIDof external sheath damage in 2001, as they were likely notvalue in operation, 80,000 psi-in. for a 12-in. flexible pipe. testing for it. However, when the issue was raised in the firstThe majority of flexible pipe in use has a pID value of lessreport, more operators by good practice would regularly testthan 50,000 psi-in.the annuli of their flexible risers, and we began to see a higher incidence of the damage. In 2001, external sheath damage was identified whenFlexible Pipe Failure/Damage Mechanismsmeasurement of annulus pressure through a vent valve atThe most recent survey found that external sheath damage the riser vessel connection revealed that the annulus did notremains the most common failure, showing an increase since hold its pressure, indicating that the sheath may have been2001 (Fig. 3). The external sheath is an external polymerbreached, most likely by a small crack or a pinhole in thebarrier applied to the flexible pipe to resist mechanicalexternal sheath farther down the riser. In these cases, grossdamage and seawater corrosion of the tensile and pressurestructural damage of the armor wires within the annulus wasarmor wires of the flexible pipe. Its presence creates annot found to have occurred. February 2012 Oil and Gas Facilities 17 4. 40%35%2002 UKCS and Norway onlyOthers: Smooth bore collapses % of Failure/Damage Incidents30% 2010 Worldwide Pigging Damage Upheaval Buckling25%Excess Torsion Excess Tension Sheath cracking20% Armour wire failure15%10%5%0%red th th d ak in g on es enure rhe loo enagsioea ea iluLeali ti agailOtsa erbckrro e/FFaShShom ng dcFaliB lo Co Ov age ssalAnal B irit t iOv vic ern ern rcaax m dFtemDeDa WInt IntCa Enys ry ath ed ut la tSlloAg he cilnPuAnlS Ve naterExFig. 3 Flexible pipe failure/damage mechanisms. their focus on how they connect and install their flexible risers to the floating production facility so as to avoid this failure mode in the future, he added.Two failure/damage mechanisms showing significant decreases in incidence since 2001 were related to the internal sheathaged internal sheaths and polyvinylidene fluoride (PVDF) internal sheath pullout failures (Fig. 3). The oil and gas industry has studied the causes of aged internal sheaths, largely affected by high water content and elevated bore temperatures on polyamide 11 (PA11), a high-performance polymer material that allows for higher operating pressures than does high-density polyethylene (HDPE). As a result, operators gained a better understanding of the properties of PA11 and how to monitor, control, andFig. 4 General armor wire corrosion.predict its life cycle.PVDF internal sheath pullout failures have dropped withOne finding related to external sheath damage hasthe introduction of new end fitting designs developed by theonly emerged since the original study, OBrien said. Thereflexible pipe manufacturers.is a subset of external sheath damage where general andextensive armor wire corrosion (Fig. 4) occurs due to grossexternal sheath damage along a region of the riser withinEarly Planning for Integrity Managementthe splash zone and where the riser may also be shielded OBrien noted that the survey results point to the need forby vessel structures. The shielding effect of the vessel operators to consider their flexible pipe integrity managementstructures can prevent proper operation of the risers strategies at the earliest stages possible. From the minutecorrosion protection system, while the splash zone causesyou think about designing a flexible riser or flexible pipeline,intermittent wetting effects that provide a supply of oxygen,even at concept, front-end engineering design, and intowhich encourages a highly corrosive environment. Hiddenoperations, the guidance note recommendations proposelocations at the riser top section close to end fittings, forwhat should be done at those stages to consider integrity,example at J-tubes, are susceptible to this type of external he said.sheath breach and subsequent armor corrosion. Operators One of the challenges in developing an early I&Mwere generally not aware of its incidence or prevalence in the strategy is the lack of coordinated efforts between projectfirst study, but there have been significant instances of it inteams charged with the design and the operations personnel.the last number of years, he said. Operators have increased How do you get a change in behavior at the project stage?18 Oil and Gas Facilities February 2012 5. exposing armor wires to the same conditions. However, thereis significant evidence for that not being the case.PA-11 External Sheath5 Operators have made decisions to change out risersCarbon Steel Tensile Armors4 because their integrity prediction methods indicated that theCarbon Steel Pressure Armor 3riser was approaching its predicted fatigue life. Regarding PA-11 Pressure Sheath2 the selection of appropriate I&M methods, OBrien said,1InterlockedPart of the problem is that there is no single magic piece Stainless Steel Carcassof technology out there that is able to properly inspectflexible pipe. It is a bit like detective work, selecting a rangeof alternative inspection and monitoring techniques, whichwhen utilized together help you to establish the currentintegrity of your flexible pipe.In a recent case, following the decommissioningFig. 5 Flexible pipe layers of dissected riser. Source: OTC 22398.of a 10-year-old flexible riser with a flooded annulus,the dissection, inspection, and laboratory analysis ofcomponents showed that the condition of the armor wireSample 1Sample 2remained comparable to the as-manufactured conditions(Charlesworth et al. 2011). End FittingBend Stiffener Subsea I-Tube Flexible PipeFatigue Performance of a Flooded AnnulusCharlesworth et al. described the dissection process andFig. 6 Locations of flexible pipe dissection. Source: OTC 22398.condition of a flexible, high-pressure gas riser following itsdecommissioning from the West of Shetland (WoS) region.BP managed riser integrity using a risk-based approachProject teams are focused on design, aiming for controlledon its WoS flexible risers installed in the