OTC 21844

Developments in Managing Flexible Risers and Pipelines, A Suppliers Perspective C. S. Dahl, B. Andersen and M. Groenne, NKT Flexibles I/S

Copyright 2011, Offshore Technology Conference

This paper was prepared for presentation at the Offshore Technology Conference held in Houston, Texas, USA, 25 May 2011. This paper was selected for presentation by an OTC program committee following review of information contained in an abstract submitted by the author(s). Contents of the paper have not been reviewed by the Offshore Technology Conference and are subject to correction by the author(s). The material does not necessarily reflect any position of the Offshore Technology Conference, its officers, or members. Electronic reproduction, distribution, or storage of any part of this paper without the written consent of the Offshore Technology Conference is prohibited. Permission to reproduce in print is restricted to an abstract of not more than 300 words; illustrations may not be copied. The abstract must contain conspicuous acknowledgment of OTC copyright.

Abstract With the increasing use of flexible pipe technology - driven by the move to deeper, more marginal and more challenging conditions - the need for systematic management of the flexible pipes is becoming more apparent. In particular, the full implementation of Riser Integrity Management (RIM) plays a vital role to ensure an efficient and safe operation. This paper will discuss issues regarding Riser Integrity Management raised by operators and addressed to NKT Flexibles (NKTF) as the supplier. The discussion will include measurements and tests of flexible pipes, assessment and repair of possible damages, as well as assessment of change of regime e.g. change of location/ bore contents/ pressure/ temperature/ souring. Riser condition monitoring and inspection form an important part of integrity management together with processing and analyses of the monitored data. The present paper identifies and discusses available and emerging options for condition monitoring and for engineering assessments and remedial actions, and discusses the recently developed technology of embedded optical fiber monitoring for quantifying the integrity of the flexible risers during their service life. Introduction Early Flexible Pipe Development The development and use of flexible riser and pipeline technology for offshore oil and gas production is relatively young, however, flexible pipelines were applied for other purposes, before the introduction to the offshore industry.

The concept of a flexible armored marine pipeline was first introduced and applied at a significant scale in the World War II project codenamed PLUTO (PipeLine Under The Ocean) for transporting fuel under the British Channel from the United Kingdom to Normandy, France. The design was based on high voltage marine power cable technology. The first commercial marine pipeline was installed between two Danish islands in 1964, also based on marine power cable technology. The step on to high pressure pipelines, reinforced against collapse, for the offshore industry was taken in 1972, applying technologies developed by IFP, France.

Early Experiences Initially, flexible pipelines have been considered maintenance free and not in need for regular inspection. Since their first introduction, a vast number of improvements have been introduced to the design and manufacturing of the pipes, end-terminations and accessories. The use so far has been essential to the development of the offshore industry, and of the floating production systems in particular. At the same time the manufacturers and operators have faced a number of challenges mainly relating to materials,

2 OTC 21844

malfunctioning of annulus ventilation systems, unfavourable handling during installation or operation, externally inflicted damages, and to operational conditions outside the original design envelope of the products. These challenges have, in a number of cases, led to damages causing the flexible pipe to deteriorate rapidly resulting in a need for early replacement. Riser Integrity Management As a logical result of the experiences from the early flexible risers and pipelines, the industry is taking steps to implement regular inspection and maintenance programs for their portfolio of flexibles. In 2008 Det Norske Veritas issued guidelines for recommended practice of Riser Integrity Management [DNV 2008]. Here DNV defines Riser Integrity Management (RIM) as a continuous process of knowledge and experience management applied throughout the lifecycle of riser systems. RIM programs are to include various aspects such as:

Early stage planning Definition of safe operational limits Riser monitoring Condition monitoring Processing and analysis of monitored data Risk based inspection Coherent inspection/maintenance/repair planning Emergency response planning Periodic demonstration of technical and operational integrity

Adding to this, special attention is needed in cases where radical changes are made to the riser system such as:

Change of operational conditions Change of service Decommissioning

Flexible Pipe Design Pipe Structure Flexible pipes, as discussed here, are unbonded structures consisting of helically wound metallic armour wires or strips combined with concentric layers of polymers, textiles, fabric tapes, lubricants and optional insulation.

Figure 1: Typical cross section of flexible pipe End-Fitting Each layer of the flexible pipe is mechanically terminated inside the end-fitting in such a way that fluid seals are maintained under the specified design and operational conditions. The end-fitting design secures an anchoring of the armour layers and sealing capacity of the polymer liner materials as well as the main steel members of the flexible pipe.

OTC 21844 3

Fgure 2: Typical cross section of end-fitting

ed Design the cost-and-performance optimized design using the most cost effective materials ns for fulfilling the requirements. The minimum materials dimensions also serve to

oading and the added buoyancy requirements from the configuration.

s a pipe supplier NKTF delivers services to operators along with the pipe systems in order to handle issues during erators cover a large variety of issues and concerns, which can be addressed by the design

original design information.

Figure 3: Types of queries received from operators, Frequency (%)

his distribution shows a broad range of issues which all contribute to the operators Asset Management of Risers and lowlines of which the RIM form a significant part.

OptimizCharacteristic for the flexible pipes is nd the minimum acceptable dimensioa

minimize the topsides l

This in turn means that regularly there is only little play in terms of acceptability of deviations from the original design & operational conditions.

Queries from Operators, Issues Raised Aoperation. The queries from op

ong with the engineering staff al The relative frequency of the various issues being in the operators focus may be illustrated by the types of tasks requested/undertaken, as illustrated in Figure 3, below.

TF

4 OTC 21844

Engineering analysis The engineering analyses requested by the operators are mostly reanalysis based on recorded or expected change of operating conditions for the flexible.

Focus is on short-term and long-term effects of operation outside the original design envelope - typically focusing on:

or lower)

ects,..)

ation test results and updated analysis methods are applied together with ns to achieve a best understanding of the consequences of the change of

ath of the pipe.

visual inspection of the pipe, combined with annulus vacuum and volume testing, pressure testing, check of vent valves and also inspection of any ancillary components stored on the site.

istic solutions and time and use at the operators decision gates and the onwards ITT process.

cialists are deployed to perform temporary repai r to perform complete permanent repairs e.g. by cutting, re-termination and perhaps inserting a repair

d ed in a suitable place, and here the supplier is a natural partner for the operator, as handling and storage of these

large and heavy items require that special equipment and site conditions are in place.

pact testing or midscale testing for

perature sealing characteristics.

n rer would be related to assisting the operator during the installation

by onboard mon oring of the operation combined with standby duty for repair of possible damages to the outer sheath or

e in-service phase, as may be seen in Figure 3, above.

th specifications/assumptions during design includes e.g.:

bore contents (souring) temperature (higher fatigue (larger external forces/excursion/..)

er sand contents) erosion of carcass (high impact resistance (dropped obj

In the reanalysis, a combination of materials qualificavailable operating history and predicted conditioconditions.

Offshore Tests The offshore tests are mainly made up by annulus vacuum and volume tests conducted routinely to confirm the integrity of the outer she

Requalification of Spares Several operators have spare risers or jumpers stored as a back-up for crucial components in their production set-up. The requalification often includes

FEED Studies With some operators, the use of Front End Engineering Design Studies by key suppliers during the inception phase for projects is becoming standard. Such FEEDs may provide at the earliest project state the best realcost estimates for

Damage Assessment and Repair Whenever a damage is discovered/suspected a careful assessment is required to determine the necessary actions on a short term and for medium and long term. Dependent of the conditions, manufacturer spe

rs ojumper.

Spare parts, Storage During operation needs for spares such as anodes, gaskets etc. may arise. Also at times there are pipes and parts which neeto be stor

Laboratory Tests Laboratory tests may be testing of polymer coupons which have been deployed on process piping right next to the flexiblepipe, thus showing the polymer degradation over time. Other tests are related to e.g. imverification of l

ow tem

Replacement Replacement of pipes may in some cases be needed due to excessive damage or wear of the pipeline. During the installatioof a replacement pipe, the involvement of the manufactu

itother components during the installation. Also commissioning tests such as annulus testing may be involved.

Data for change of service Change of service conditions accounts for about half of the requests received at NKTF for assistance during th

Changes of service compared wi

Change of operating temperature Change of pressure

OTC 21844 5

Change of chemical composition (e.g. souring)

while at other times, the operators are experiencing unexpected

Whenever a reassessment of the pipe is requested, NKTF will ask for the operational history of the riser/flowline. During the

esign. At these times, carefully maintained records and data prove t e very valuable to the operator.

way.

he single most frequent damage & problem area on flexible pipelines is perforation of the outer sheath. The consequence is may lead to accelerated corrosion of the armour wiring which in turn may

f the inner liner and leakage of the bore contents to the sea/air.

of

of the outer sheath. he damages may be handled differently, depending on their severity, e.g.:

lifetime reassessed.

ple

ve testing of flexible riser systems is establish the present condition and to predict the possible degradation of the risers thus preventing loss of containment. However, the composite structure of flexible pipes, involving multiple layers of metallic and polymeric materials, imposes heavy demands on the capability of the inspection

e ability to inspect critical locations such as beneath bending stiffeners, in sag-bend areas and end

onitoring of temperature, pressure and by bore fluid testing Monitoring using in-line mounted test coupons

r annulus

es include: nitoring of stresses in tensile armour

Adding of additional production strings to flow, thus changing bore content Relocation of pipe for other use.

Sometimes the requests for assistance are issued up front, production conditions which have sometimes developed over some time.

reassessments it is of paramount importance to be able to replace assumed conservative design assumptions with actual records, thus facilitating an optimized reanalysis compared to the time of d

o b

Frequently the experience is that an incomplete set of records makes this reassessment of fitness for purpose difficult thereby limiting/shortening operational use of the flexible.

Preparedness for remedial actions Damages should not happen, but should be prepared for any

Tsea water intrusion into the annulus, whichultimately lead to failure by wire breakage followed by the burst o

In case a rupture to the outer sheath is detected and the hole is sealed off, the corrosion process may be halted by the lackfree oxygen. Naturally a significant part of the RIM is therefore focusing on monitoring, inspection and repair (where needed) T

Minor - repair at next opportunity Deeper scratch or more serious problem - manufacturer to be consulted, repair initiated, records kept,

condition/remaining Major - immediate need for assessment/action

Preparedness could include: outer sheath repair clamp on store, outer sheath repair kit parts such as outer sheath sampiece, canusa, etc. spare risers/jumpers.

Inspection techniques The objective of in-service non-destructi

techniques. Furthermore, thfittings is a major challenge. Presently, a number of technologies exist or are under development, ref. e.g. [MCS Kenny 2010]. Conventional inspection techniques include:

Visual inspection by diver/ROV M Gas sampling of riser annulus Vacuum & volume testing of rise Internal gauging Hydrostatic testing Radiography Eddy current

Newer inspection techniqu

Fibre optic mo

6 OTC 21844

On-line di-electrical sensing of test coupons X-ray/gamma-ray tomography

nnulus flooding detection

ely used technique to assess the integrity of a riser system, including ancillary , tethers, manifolds, buoyancy modules, bend stiffeners). Typically, this is carried out

spection, but can also be performed internally in the pipe bore using pig-mounted cameras. operational intervention and possibly flushing and cleaning of the riser prior to the inspection.

ly

e mpling at the separators and consequently, these data may not be

lly representative for the fluid composition in the riser bore.

s

have been established, e.g. as part of the factory acceptance testing and/or after installation of the riser.

d ed for the

armour) is low.

r owever, development work is progressing and several new techniques exist which will be

escribed briefly in the following.

Fibre Optic Monitoring - Use of fibre optic fibres embedded in tensile armours to monitor temperature and strains in the

Di-electric sensing - Remote sampling technique to provide in-line sampling of polymer ageing/degradation of polymeric

-ray / gamma-ray Tomography - Recent technique to directly inspect each layer (polymer and steel) for defects, e.g. to

ltrasonic inspection - An ROV-based inspection of outer tensile wires and annulus flooding detection. hnique which should have greater depth of penetration of the pipe

etallic layers.

Ultrasonic wire inspection and a Magnetic flux leakage wire inspection Laser leak detection Accoustic motions monitoring

Conventional techniques Visual inspection is the most wid

equipment (e.g. mid-water archesas an external visual inHowever, this requires The visual inspections are useful when verifying the overall integrity of a riser system, but they can not accuratedetermine the remaining service life in the system.

The pressure and temperature are normally measured on the topside facilities based on an excursion limit. Thus, no regular recording/logging is normally performed with the intent to use the data as part of an integrity assessment. Thbore fluid composition is typically monitored via safu

The use of test coupons to assess the ageing of polymeric inner liner materials is not a widely used technique for the flexible risers. When undertaken, it is normally via the topside facility which may not represent the most critical bore environment.

Annulus gas sampling and annulus vacuum testing are seeing increased use but are not yet commonly used techniquewithin the industry. When using vacuum testing for assessing the annulus volume it is important that baseline measurements

Radiographic examination may be performed in special cases where detailed inspection of e.g. an end fitting or localisepipe anomaly is required. To avoid operational intervention the double wall shot technique is normally adoptpipe.

Eddy current techniques have been employed to inspect the armour layers in the flexible pipes. However, the technique is not widely used and the reliability of detecting wire breakage beyond the first metallic layers (i.e. carcass and outer tensile

The conventional inspection techniques cannot fully inspect all the layers of a flexible pipe. Also, the equipment is limited in its ability to inspect along the full length of a riser including critical locations like the bend stiffener/restrictoareas and end fittings. Hd

Newer techniques Techniques currently under development & implementation for flexible risers include:

armour wires.

test coupons placed in the pipe bore rather than test coupon removal. Xinspect a full end fitting/cross section of the pipe. U

Magnetic Flux - An alternative to eddy current tecm

OTC 21844 7

aser leak detection - Visual detection of leaks in outer sheath by illuminating emerging annulus inhibitor. monitoring - Various techniques for monitoring the condition of appurtenance, based on measured

ads and offsets.

The existing and developing inspection techniques and their application are outlined in Table 1, below.

L

Motions and loadlo

8 OTC 21844

Table 1: Summary of inspection techniques and their possible application (non-complete)

Detection/Test Method

Ann

ulus

Flo

odin

g

Bre

ach

of O

uter

She

ath

Ann

ulus

Cor

rosi

ve G

asse

s

Ven

ting

Val

ve F

unct

ion

End

Fitt

ing

Sea

ling

Pol

ymer

Ove

rhea

ting

Pol

ymer

Deg

rada

tion

Tens

ile W

ire F

atig

ue

Tens

ile W

ire B

reak

age

Ben

ding

Stif

fene

r Fun

ctio

n

Teth

erin

g/A

ncho

ring

Inte

grity

Sys

tem

Inte

grity

Flow

ass

uran

ce

Wax

ing

Visual/video inspection by (by diver/ROV)

X

X

X X

Annulus Vacuum and Volume Testing (pneumatic evacuation & pressurization)

X X

X X

Venting Volume Monitoring (pressure build-up, on-line analysis)

X

X

Vent Gas Monitoring (sampling chromatography, online analysis)

X

Polymer Coupon Testing (coupon sampling and laboratory testing)

X

Annulus Temperature Monitoring (fibre optic)

X

X

Strain Monitoring (fibre optic, strain gauge)

X

X

Monitoring of Bending Stiffener Tip Position/Curvature (accoustic)

X

Survey of armour wires and water in annulus (ultrasonic)

X

X

Survey of armour wires in annulus (magnetic flux)

X

Laser leak detection survey (optical)

X

I-tube camera survey (video)

X

X

Tether load monitoring (load cell)

X

Vibration monitoring

X

Accessories motions monitoring(Bend stiffener, buoyancy elements, MWA)

X

OTC 21844 9

Embedded Monitoring As outlined above, the condition of flexible pipes should be regularly monitored in order to ensure safe operation of the asset at its optimum level for the maximum period of time. New advances in optical technology and riser manufacturing techniques enable a new suite of embedded real-time monitoring systems providing a continuous picture of a risers condition during operation. Equipped with data management and visualization software, the underlying technologies and measurements will be directly accessible to the end user. This improves decision making by allowing structural and temperature issues to be detected at the earliest possible stage and remediated in the most efficient manner.

Reliable embedded monitoring systems will allow operators to continuously monitor the condition of risers, enabling condition dependent maintenance. The combined use of point sensors and fully distributed sensors throughout the risers allow various events to be continuously monitored. This includes breach of outer sheath, condensate build up in the annulus, polymer layer temperature, operational temperature along the entire length of the pipe, tensile wire fatigue and tensile wire break detection.

Within the last couple of years a number of techniques have been developed for monitoring flexible pipelines [Carneval et al. 2006; Marinho et al. 2008; Pipa et al. 2010; Weppenaar et al. 2008]. Most of these techniques were developed for monitoring the integrity of the outer sheath or the integrity of the tensile armor wires. One of the most promising technologies for real-time monitoring is embedding optical fibers in flexible risers. Optical fibers have shown to have very good properties especially for sensing temperature and strain in the longitudinal direction along the length of the fiber. This technology has been utilized for many years in other industries, and is supported by an extensive range of established equipment and procedures from the optical telecommunications industry. Embedding the optical fiber has the advantages that there are no protrusions on the outside of the pipe and it is not affected by changes in pipe diameter, for example at bend limiters, so that optical fibers can be used to monitor anywhere along the pipe. A technique has been developed to epoxy the optical fibers in grooves in the tensile armor wires, which are then incorporated into the flexible pipe [Andersen 2001] as shown in Figure 4.

Figure 4: Optical fibers are embedded in grooves in the tensile armor wires (foreground)

Embedding the optical fibers inside the tensile armor wires has the advantage that the fibers are well protected throughout the pipe manufacturing processes, installation, and during operation of the pipe. The use of epoxy ensures changes of strain in the tensile armor wire are transferred to the optical fiber for an accurate measurement. The embedded optical fibers can also be used to measure other parameters in the pipe, in particular temperature.

Temperature Monitoring Temperature monitoring of the annulus region of a flexible pipe (the section between the inner and outer sheath) can yield important information about the operational condition of the pipe system. The temperature monitoring system is based on optical fiber sensors embedded in the annulus of the flexible riser. The temperature is monitored continuously along the entire length of the instrumented pipe, and log coherent data of temperature, time and position.

In operation, temperature monitoring can assist with process control in case of a temporary shut-in of the flow in the bore. For certain production materials hydrate plugs can be formed if the temperature drops below a certain point. These plugs are very difficult to dissolve once formed in the pipe. With a temperature monitoring system in place in the flexible pipe information can be obtained for deciding when to either turn the flow back on or to back flush with a dissolvent fluid.

Another operational application is to monitor the flexible pipeline for hot spots in sections with added insulation on the pipe. This could be in the region of the pipe immediately under the floating vessel where a bending stiffener is mounted over top of the riser for over bend protection. This bending stiffener is a large polymer construction, which will add significant extra

10 OTC 21844

insulation locally. If a well is running at a high temperature these hot spots may reach temperatures which can increase the susceptibility to aging for some of the polymer materials.

Temperature monitoring can also be used for detection of breach of the outer sheath of flexible pipes. An outer sheath breach will affect the pipe integrity and can shorten pipe lifetime due to ingress of seawater. Outer sheath breaches can be caused in various ways during the pipe lifetime:

During pipe installation due to mishandling Due to interference with e.g. anchors and mooring lines Due to dropped objects from platform or support vessel Due to wear in operation, for example in guide tubes (e.g. bellmouth) Due to abrasion at the riser touchdown area on the seabed

Seawater flooding of the riser annulus will aggravate corrosion leading to weakened fatigue life of the tensile armor wires. Therefore, it is important to detect and repair any breaches of the outer sheath as soon as possible. Repairing a breach will stop the replenishment with fresh (aerated) seawater to the annulus and thereby limit the corrosion. Since corrosion is severely aggravated by the supply of fresh seawater, it is important to be able to detect a second breach or a faulty repair clamp on an already flooded riser. With an embedded fiber optic temperature monitoring system, an outer sheath breach can be detected from wet annulus conditions just as well as dry. This differs from a vent gas monitoring system [Weppenaar et al. 2008], which will only be able to detect a breach on a riser with a dry annulus. Once the annulus is flooded the gas detection system looses its ability to detect further breaches.

Detection of an outer sheath breach with a temperature monitoring system is based on the temperature difference which is typically present between the bore and the ambient sea water. The thermal design of a flexible pipe line is such that the main temperature drop will be across the two polymer layers (inner liner and outer sheath). Temperature profiles of the outer wall of a typical flexible pipeline are shown for four different temperature differences between bore and ambient in Figure 5. If a breach appears in the outer sheath the temperature will be dragged down towards the ambient temperature locally at the position of the breach.

Figure 5: Temperature profile across the section of a typical flexible pipe structure for four different temperature differences.

20

25

30

35

40

45

50

55

60

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

Tempe

rature

ontheinside

ofthelayer[C]

Layerno.

Strain Monitoring The integrity of the flexible pipe in the longitudinal direction is maintained by the two layers of tensile armor wires wound helically around the pipe in opposite directions. The tensile armor wires are highly strained as they carry all the weight of the pipe. The strain in the tensile wires is continuously cycled by the motions of the surface vessel due to wind, waves and sea current, which can lead to metal fatigue and eventually wire break. It is therefore of great interest to monitor the strain in the tensile armor wires of the flexible riser.

Embedding strain sensing optical fibers directly into the tensile armor wires enables an accurate measurement of the strain in the wires. However, for practical reasons the number of strain sensing points has to be limited to a reasonable number, which

T=31C

T=22C

T=12C

T=2C

OuterSheathB

ore

Sea

PositionofSensorFiber

OTC 21844 11

means that the sensing points have to be positioned to cover the most significant areas of interest. From the detailed system design (that includes the installation on the seabed, the floating vessel and the flexible riser) it is known that in most cases the length of riser that will experience the largest strain is in the area of the top end fitting and in the area immediately below the floating vessel as shown in Figure 6. The areas of interest to be covered by the strain monitoring system are marked with horizontal black lines on the pipe.

What is also shown in Figure 6 is that the access to the riser at the top section is very limited. The riser will typically be hanging through an I-tube from the hang-off point down through the vessel, and there will typically be a bending stiffener structure mounted over top of the riser immediately below the vessel to limit the bending of the pipe at that position. It will therefore be very difficult to mount external measurement equipment on to the riser in this area, but an embedded system can be used to make measurements in this location.

The strain data collected from the optical fibers can be used for continuously monitoring the remaining fatigue life capacity of the tensile amour wires. For fatigue monitoring the strain is continuously monitored in a number of wires on the circumference. This will yield information on the number of load cycles the wires are going through and the amplitude of the strain levels. By applying a method called Rainflow counting the fatigue damage to the wires can be derived. The flexible riser is designed in order to withstand a certain level of fatigue damage over the lifetime based on a design envelope of data on wind, waves, sea current etc. With the actual strain measurement and Rainflow counting the remaining fatigue damage capacity can be continuously monitored. In some years the installation will experience more storms and severe weather conditions than others, which can then be accounted for in the data. At the end of the designed riser lifetime, it will then be possible to evaluate if the riser has fatigue damage capacity for extended operation.

Figure 6: The highest strain levels will in most cases be in the area close to the top end fitting or immediately below the floating vessel.

12 OTC 21844

Summary & Conclusions When planning for success with flexible risers and flowlines in the future one should learn from the experience and information gathered over the last decades. Based hereon it is recommended that a life cycle approach to the flexible should be adopted by the operators all the way from the project conceptual phase and throughout the service life of the flexible.

It is quite likely that the flexible during its intended service life will encounter unexpected conditions such as being exposed to other bore conditions, forces and service conditions than designed for and being exposed to external damage, etc. As a basis for acting in at the right time and in the optimum way to these challenges, the information and preparedness must be in place beforehand. Therefore close monitoring of the operational conditions and of the integrity of the flexible is of paramount importance.

The inspection and monitoring systems available or under development offer a range of possibilities. Of these methods the continuous monitoring e.g. from instrumentation embedded into the flexible pipes themselves combined with monitoring of bore parameters and annulus parameters, such as contents and flow through the venting system bear obvious advantages from a simplicity and durability and cost point of view leading to early warnings and condition based inspections inspection.

In addition, a general preparedness for challenges should be in place, including engineering preparedness in-house and with the manufacturer and preparedness for remedial actions including repair parts and equipment, and for critical items even pre-produced spare sections.

When this set-up is in place the operator will have the best chances of discovering challenges/problems at an early stage where consequences may be minimized in terms of physical, environmental and financial risk.

References

[Andersen et al. 2001] Andersen, M., Berg, A., and Saevik, S., Development of an Optical Monitoring System for Flexible Risers, Offshore Technology Conference, OTC Paper No. 13201, Houston, May 2001.

[Carneval et al. 2006] Carneval, R.O., Marinho, M.G., and Santos, J.M. 2006. Flexible Line Inspection, Proc., 9th

European Conference on Nondestructive Testing, Berlin, Germany 106. [DNV 2008] DNV 2008: Recommended Practice DNV RP-F206: 2008 Riser Integrity Management, Det

Norske Veritas. [Marinho et al. 2006] Marinho, M.G., Camerini, C., and Morikawa, S. 2008. New Techniques for Integrity Management

of Flexible Riser End Fitting Connection, Proc., ASME 27th International Conference on Offshore Mechanics and Arctic Engineering (OMAE 2008), Estoril, Portugal, OMAE2008-57941.

[MCS Kenny 2010] MCS Kenny 2010; Reference No. 2-4-5-013/SR01 Rev.01, State of the Art Report on Flexible Pipe Integrity May 2010.

[Pipa et al. 2010] Pipa, D., Morikawa, S., Pires, G., Camerini, C., and Santos, J.M. 2010. Flexible Riser monitoring

Using Hybrid Magnetic/Optical Strain Gage Techniques through RLS Adaptive Filtering. EURASIP Journal on Advances in Signal Processing 2010: Article ID 176203.

[Weppenar et al. 2008] Weppenaar, N. and Kristiansen, M. 2008. Present and Future Possibilities Within Optical

Condition Monitoring of Flexible Risers. Proc., Offshore Technology Conference 2008 (OTC 08), Houston, Texas, USA, 19427.

AbstractOffshore TestsInspection techniquesConventional techniquesNewer techniques

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