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Transcript of Www.pipelineengineering.com PIPELINE ENGINEERING Multi-Diameter Pigging – Factors affecting the...
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PIPELINE ENGINEERING
Multi-Diameter Pigging – Factors affecting the design and selection of pigging tools for multi-diameter lines
Karl Dawson
PPSA Aberdeen
19th November 2008
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Agenda
• Why Multi-Diameter Lines?• Definitions• Pig Selection• Pig Design• Provision of data for pig design• Prototype Development and Validation Testing• Case Study• Summary• Presentation End
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Definitions
Industry Accepted Definitions:
• Dual-diameter – Operates in 2 distinct diameters
• Multi-diameter – Operates in two or more diameters and may operate in a range diameters or sizes in between
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Why Multi-Diameter Lines?
Multi-Diameter lines are installed due to:• Cost
– Procurement– Installation– Associated features
• Standardisation – deepwater– Valves– Connectors
• Weight • Space• Necessity
– Tie-in– Control Pressure losses
Subsea Pigging Loop
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Pig Selection
Purpose of Pigging Operation:
• Dewatering• Cleaning – debris removal• Gauging• Batching• Inspection• Camera• Apply internal treatment Wax Removal
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Pig Design
• Internal Diameters– Range of sizes
• Bend Radii– 5D, 3D or 1.5D
• Feature definition and configuration– Valve
• Gate• Full bore ball• Check
• Lengths of run• Transitions• Location of features
– In relation to one another and specified diameters
Factors Affecting Pig Design:
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Pig Design Continued
Factors Continued:
• Flow and Pressure Conditions• Medium• Expected Debris or Internal Line Condition• Pig Trap
– Dimensions– Configuration
• Interaction of Pig Characteristics to Negotiate Features
Build up of Deposits
Dual Diameter with Unbarred Tee
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Provision of Data
Interaction of line and pig features
Influencing factors:• Interaction• Variation • Combination
All available data is of use in the process of design: ‘Every Little Helps’
Stick to the facts – never assume
Wye and Bend Combination
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Prototype Development and Validation Testing
Why Test?
• Prove design• Prove Functionality• Gather Data• Experience the unpredictable
The overall objective to maximise tool effectiveness and to minimise risk Test Rig Example
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Case Study 600m Water Depth: 8” x 10” Flooding, Cleaning and Dewatering Tool
Operational Requirements:• 8” Launcher and pipe work ID = 190.5 mm• Connector ID = 179.8 mm• 5D bend ID = 190.5 mm• Tapered transition = 1 in 6• 10” Line ID = 241.3 mm• Buckle arrestor = 236.5 mm• Length fixed at 400 mm due to laydown head• To be back loaded in to laydown head ID = 190.5 mm• Bi-directional capability
Functional Requirements:• Remove construction debris• Flood line for hydrotest• Dewater line
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Pig Design:
• Mandrel Body
• Segmented Supports active in all diameters
• Diameter specific seals for each line section
• Symmetrical disc packs
• Transmitter housing
Initial Design
Case Study 600m Water Depth: 8” x 10” Flooding, Cleaning and Dewatering Tool
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Test Rig Design:
Case Study 600m Water Depth: 8” x 10” Flooding, Cleaning and Dewatering Tool
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Final Proven Design
Modifications made following trials:
• Extra discs fitted and radial grooves added to improve support in larger diameter
• Support flexibility improved in tapered transitions through reconfiguring the disc pack
• Quantity of sealing discs reduced to prevent discs clashing and loss of positive seal
Pig has successfully been run in field operations
Case Study 600m Water Depth: 8” x 10” Flooding, Cleaning and Dewatering Tool
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Conclusions
• Involvement in the FEED stage is invaluable for both parties
• Free flow of information is key to an effective and suitable design solution
• Changes are ok, but the impact must be assessed
• Testing of the intended design is essential at reducing the risk involved in field operations
• With modern design capabilities and functional testing, multi-diameter pigging need not be a subject to be avoided, instead with careful consideration even the most arduous of diametrical variations may prove piggable