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23 Pages·2009·2.55 MB·English

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n Multi-diameter, bi-directional
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The Alve Pigging Experience
Aidan O’Donoghue
[email protected]
www.pipeline-research.com
Pig Testing at K-Lab, Kårstø
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Dewaxing R&D

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Dual Diameter Pigging
Alve Field Overview
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•10” x 12” Pipeline – 25% increase in diameter;
•12” 5D bends – no bends in 10”;
•Pigging facilities only topside Norne (No launcher/receiver subsea);
•Vertical launch and receipt;
•RFO Philosophy – two scenarios.
Pig Functional Requirements
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• The pigs must be fully bi-directional with high sealing ability in
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e both directions;
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e • Low flow rates were expected, in the region of 300-400 l/min
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m • Good seal efficiency and pig support/centralisation were required
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components along the system. The risk of gas bypassing on
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return to Norne could result in hydrate formation;
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• Ratio between pig flip differential pressure (pressure to flip the
seals forward and cause them to fail) and running differential
pressure to be at least 5:1;
• The drive differential pressure in all pipeline components was
requested to be less than 7 bars;
• Pigs to be fitted with isotope holder for tracking purposes;
• Pig handling to be considered for vertical launch and receipt.
Development Strategy
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n Study Options
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A Select Pig Type Single concept and spares – not

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a a competition!
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A Detailed
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Test /
Optimise
Supply Four
off Pigs for
Alve Project
Pig Selection for Alve
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• “Traditional”, V-slot supports;

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e • Paddle Pig from Pipeline Engineering;
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e • Wheel Pig from FTL Seals Technology;
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• Other technologies.

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Initial Pig Concept
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• Single seal for all diameters;
• Wheels in an axi-symmetrical layout.
Piggability – problem at bend
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Limited interference
between the seals and
the inside of the bends.
There is therefore a risk of
leakage.
Final Base case pig design
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Buckling Modes
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• No buckle;

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• Buckles when forced, but recovers;
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b • Buckles only when forced but does not recover;
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a • Buckles even when not forced to do so.
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