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PIPELINE FREESPAN

ASSESSMENT

I. OBJECTIVESObjectives of this study are as follow:

To re-assess the criticality ofanomalous free spans with regardsto the seabed characteristic and realcase pipeline operation whilstmaintaining the integrity of pipelinethroughout its useful remaining life.

To provide recommendation forfreespans rectification worksincludes number of rectification work and approved method

To provide inspection and monitoring requirements, controlling parameters forfuture use of underwater inspection project.

II. REFERENCESThe following document shall refer in performing freespan assessment study:II.1. Det Norske Veritas, DNV RP-F105 Free Spanning Pipelines, Feb 2006.II.2. Det Norske Veritas, DNV-OS-F101 Submarine pipeline systems. 2007II.3. Det Norske Veritas. DNV-RPF109 On-bottom stability design of submarine

pipelines.` 2010.II.4. Muhlbauer, W. Kent, Pipeline Risk Management Manual Third Edition, Elsevier.

2004

III. SCOPE OF WORKIII.1. To perform freespans assessment as per fatigue life assessment and ultimate limit

strength for the following freespans as per methodology provided in Article IV.III.2. To perform reassessment of freespans based on interacting multiple single spans

as per historical finding from as laid inspection and baseline inspection providedby company. This work items shall includes:

- Review of pipeline inspection reports- Performing freespans interacting analysis based on DNV RP-F105- Assess acceptance criteria by comparing survey result versus

allowable static span lengths- Review historical freespans from as laid survey, baseline inspection

and future governing cases.III.3. To assess the criticality of unsupported tube turns as found from the latest

underwater inspection.III.4. To provide solid and sound engineering recommendation for the pipeline

freespans rectification includes but not limited to number of rectification work,specification of rectification (e.g. grout bag, mattress, rock damping, etc), andacceptance criteria.

III.5. To provide final report as deliverable of study that shall include originalcalculation sheet, FEA model (if required), and calculation report.

III.6.

To bare all cost arise due the use of proprietary or third party modeling softwarerequired to perform analysis required for this study.

IV. METHODOLOGY

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The Pipeline Freespan Assessment will be based on DNV RP-F105 (Fig-1)

Fig 1 Pipeline Freespan Assessment Methodology

Level 1 Interacting multiple single span analysis,Level 2 Fatigue analysis of anomalous freespans,Level 3 ULS analysis .

V. DATA INPUTSV.1.

The following are data inputs available as required for the assessment offreespans:a. Design allowable span lengths (VIV) static for each pipelinesb. Survey records (as laid and baseline)c. Freespan length and heightd. Seabed soil property datae. Pipeline operating data (design, actual)f. Environmental data (seawater temperature, current and wave occurrence

table, fatigue wave data)g. Pipeline construction data (wall thickness, welding type, corrosion allowance,

corrosion protection coating, concrete coating.h. Raw inspection data available to fit with FEA modeling software

i.

ROV inspection video of all Freespan findings.