Pipe in Pipe (PIP) is installation of a second pipeline around the product pipeline from the seawater surrounding it and creates a dry chamber around the pipeline that can be engineered to accommodate a range of advanced insulation techniques.
Figure above illustrates Pipe in Pipe technology for offshore pipeline.
Pipe-in-Pipe Offshore Construction
1. Fixed
- suitable for majority of lay vessels
- field joint uses bulkheads or swaged connectors, no movement between flowline and carrier pipe
- permits vacuum in annulus
- heat loss from flowline to carrier pipe through metal connectors
2. Sliding
- S-lay & J-lay
- uses a butt weld on carrier pipe and allows the flowline to move freely
- flowline may or may not have alignment spacers
- thermal insulation may be on the outside if flow-through-annulus active heating is used
3. Restrained
- polymer bulkheads to hold insulation material in place
- these bulkheads transfer the load during installation and provide concentric alignment
Flow Assurance
Insulation Capabilities
Pipe-in-Pipe Overview
Deepwater Pipe-in-Pipe
Active Heating Pipe-in-Pipe
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