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Flexible Riser MonitoringPSA Flexible Pipe Conference12th December 2007

Johan Kristian Bø

2Title of presentation in Header and Footer

I. Flexible Riser Condition Control

II. Monitoring ProgramStatoilHydro / Technip / Force Technology

III. Use of a Monitoring Program – A Case Study

Contents


I. Flexible RiserCondition Control


Flexible Riser Condition Control

• The target is:

• To inspect Flexible Risers to document remaining service life• Practically this would mean to monitor the condition of each layer to

predict remaining service life.


Direct Flexible Riser Condition Control

• Condition control of Flexible risers is inherently difficult• The flexible risers is a multi-layer design• Both thermoplastic and steel layers have critical functions in the build-up• In addition, the termination of layers in the end-fitting is critical

• Direct monitoring methods are limited,and do not cover condition of all layers



• Examples of available direct monitoring methods are:• Visual inspection (external and close to end-fitting internal)• Pressure sheath coupons• Gauge pigging• Monitoring of pressure sheath position (typically PVDF crimping)• X-ray (inspection of position / condition of internal steel layers)

• In addition earlier attempts have typically focused on Eddie Current• Idea is to check for cracking in steel layers in annulus• No method has been developed that can see all layers

(typically some information of pressure armours has been achievable).• Tomography – Interesting but not practical


II. Riser Monitoring


Riser Monitoring - Report

• Idea is to predict Flexible Riser condition by indirect measurements

• The basic idea of the Riser Monitoring program is

• Data on key parameters are routinely recorded and kept by operators

• Systemising the data in a database make it accessibility, and helps readability– Also ensures quality of data through critical review– “Unnatural” data can be reviewed and discounted if errors are found

• Final report ensures that the data:– Has been reviewed by a competent person– Necessary actions are taken


Riser Monitoring

• Principle is:

• Riser History is recorded• i.e. temperature, pressure and composition of contents

• Systemise all available information in a database• Database is transmitted to Operator for his later use• Data is transmitted annually

• Data is reviewed against original or updated design basis• Review is done by competent person• Review considers latest design principles, including worldwide operational experience• Any outstanding issues is reviewed by relevant expert• A full report is made

• A list of recommendations for further work is included• Could typically be “engineering” that was not industry practise at time of design


Riser Monitoring - Data

• Typical Recorded Data that could be recorded is

• Pressure• Temperature• Bore fluid composition including chemicals• Gas Vent history data• Test Data• Material samples• Motion Data / Curvatures etc.• Special events

• Reports from special events can be included in database• Such reports are often not included in DFO as they are not always directly relevant• Reports have great value in assessing riser status and documentation


Riser Monitoring - Database


Riser Monitoring - Report

• Report review would typically review the following

• Events over and above design values

• Actual operational pressure vs. original service life analysis

• Measured annulus condition vs. assumption in service life analysis

• Operational temperature vs. service life analysis (PA)

• Number of temperature and Pressure cycles (PVDF pressure sheaths)

• Material sample inspection from coupons

• Any anomalies seen in inspections etc.


Riser Monitoring – Link to Riser Inspection

• In addition to recorded data, review of current inspection programs can be made, and additional recommendations or requirements included

• Based on operational experiences worldwide

• Based on development of technology

• Based on issued identified during data review


III. Use of a Monitoring ProgramA Case Study


Use of a Riser Monitoring Program

• Focus is normally on “Condition Monitoring”• This is the basic intent of the program

• In addition the program can be used to assist when reacting to special events• Updated data can be obtained quickly, to ensure that review is realistic• Added value is quick reaction, allowing operation of risers and delayed change-out

• What data that may be useful in a given set of circumstances is difficult to predict


Use of Database - A Case Study

• A potential problem was discovered related to welding of armour wires during manufacturing

• Weld parameters were incorrect, resulting in martensite in weld

• Wire was more susceptible to HIC and SSC

• It could not be excluded that this problem was applicable to risers in operation


Use of Database - A Case Study

• Based on information in Database the following actions were taken• Riser annulus test records were reviewed to ensure that risers were dry• Gas composition was reviewed to find maximum H2S content

– Annulus composition was checked against already existing test data– Conclusion was that the risers could operate based on current operational data

• The initial checks allowed continued operation whilethe issue was investigated• Material testing over a period of months documented that the risers could also sustain

original design conditions• Specific location of potentially defect welds identified• Fatigue at these locations checked• Need for remedial measures established

• Without use of knowledge from database, the extent of remedial measures would measures would have been much greater

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