Expansion Spool
Wednesday, February 17, 2016
General Principle
A pipeline can be a single or
piggybacked pipeline system, pipe-in pipe or bundled system. Its expansion is
dependent on the temperature, pressure profile, pipeline self weight and
friction forces. The expansion analysis will interface with:
- Tie-in Design;
- Lateral and Upheaval Buckling Assessment;
- Free-span Assessment;
- Crossing Design;
- Bottom Roughness/ Stress Assessment.
The maximum pipeline end
expansion is calculated for the lower bound friction coefficient and the
highest pipeline axial stresses are derived for the higher bound friction
coefficient. The increased axial resistance from backfill along the route
should be also accounted for. The input data for expansion analysis includes:
- Pipeline and Coatings Properties;
- Minimum Contents Weight;
- Temperature Profile & Pressure Profile;
- Geotechnical Data;
- Depth of Burial.
Expansion Analysis
The expansion analysis determines
the maximum pipeline expansion at the two termination points and the maximum
associated axial load in the pipeline. Both results have significant
implications in the design as:
- Axial load will determine if the line may buckle during operation, and hence additional analysis/restraint will be required;
- End expansions dictate the expansion that the tie-in spools (or other) would have to accommodate.
The degree of the expansion by
the pipeline is a function of the operational parameters and the restraint on
the pipeline. The line will expand up to the "anchor point", and past
this point the line does not expand (hence fully restrained). The distance
between the pipeline end and this length is determined based on the operational
parameters and the pipeline restraints. The less the restraint the greater the
anchor length becomes and hence the greater tie-in expansion becomes.
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Source:
Bai, Yong and Bai, Qiang. Subsea
Pipelines And Risers. USA: Elsevier Inc. 2005.
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