Page 337 - Pipelines and Risers

310 Chapter I7

17.3.3 J-nbe Pull-In
General Principle
This method requires the flowline to have the capacity to easily move axially over a relatively
large distance. This limits the option to pulling the flowline directly from the pipelay vessel.

The method of J-tube pull-in is to connect the flowline to a wire and, by pulling the wire, to
pull the flowline through a riser (J-Tube) up to the topsides of the platform. This method
requires the J-tube to be of a reasonably large diameter compared to the flowline.

This method is discussed in further detail by Ellinas (1986).

Installation CapabilitiedConstraints
The principal advantage of this system is that the flowline is tied in directly to the jacket
topsides, so avoiding subsea tie-in work. However, the main disadvantages are:

- Normally used for small diameter lines; the forces involved with large diameter lines
become too high;
- The line is directly tied into the jacket, with no system to accommodate the pipeline
expansion. Large deflections and/or axial forces will be fed into the J-tube during
operation.

This method is very popular for small diameter flowlines, when the pipelay starts at the
jacket.
17.3.4 Connect and Lay Away

General Principle
This method is very similar to the J-tube pull-in method with the exception that the tie-in is
performed subsea. This method is usually applied in diverless operations, where a mechanical
connecting system will be utilized to perform the connection.

Two examples of diverless pull-in and connection tools, McEVOY and FMC, are presented in
Figures 17.2 and 17.3 respectively. There are also diverless connection systems for bundled
lines, two such systems, VETCO and CAMERON are presented in Figures 17.4 and 17.5
respectively. Please see Phillips (1989) for a more detailed description of these Connection
systems.

Installation Capabilities/Constraints
This system is mainly used at subsea manifoldslwellheads, where the water depth prohibits
the use of divers. This is the only system developed for performing diverless connection of
pipelines.

The principal advantage is that this system can be adapted to perform diverless connections.