Pipe-in-pipe pipelines

A pipe-in-pipe (PIP) pipeline assembly comprising:

• (a) a first PIP pipeline length comprising at least a metal inner pipe, an outer pipe, and an annular space thereinbetween, the inner metal pipe of the first PIP pipeline length having an internal diameter;
• (b) a first PIP bulkhead, having
• a first end connected to an end of the first PIP pipeline length and comprising at least a metal inner pipe with a first internal diameter, an outer pipe, and an annular space thereinbetween, and
• a second end comprising an outer pipe with a second internal diameter,
• wherein the second internal diameter of the second end of the first PIP bulkhead is greater than the first internal diameter of the first end of the first PIP bulkhead;
• (c) a second PIP pipeline length, the second PIP pipeline length comprising a metal inner pipe, an outer pipe, and an annular space thereinbetween, the inner metal pipe having an internal diameter;
• (d) a second PIP bulkhead having a first end connected to an end of the second PIP pipeline length and comprising at least a metal inner pipe with a first internal diameter, an outer pipe, and an annular space thereinbetween, and a second end comprising an outer pipe with a second internal diameter, and is joined to the second end of the first PIP bulkhead,
• wherein the second internal diameter of the second PIP bulkhead is greater than the first internal diameter of the first end of the second PIP bulkhead;
• and
• (c) a sleeve at least partly located within the outer pipe of the second end of the first PIP bulkhead, and having a sleeve internal diameter being the same or similar to the internal diameter of the metal inner pipe of the first PIP pipeline length, and having two circumferential shoulders and a recess between the shoulders, at least one shoulder being within the second end of the first PIP bulkhead, and at least one shoulder being beyond the end of the second end of the first PIP bulkhead.

A method of connecting first and second PIP pipeline lengths to form a pipe-in-pipe (PIP) pipeline for laying in a marine environment comprising:

• (a) providing the first and second PIP pipeline lengths, each comprising at least metal inner and outer pipes and an annular space thereinbetween, the inner metal pipe having an internal diameter, and each being attached to a PIP bulkhead having a first end comprising at least metal inner and outer pipes and an annular space thereinbetween and connected to an end of a respective PIP pipeline, and having a second end comprising an outer pipe able to be joined to a second end of a second PIP bulkhead, an internal diameter of the second end being greater than an internal diameter of the first end of the PIP bulkhead;
• (b) connecting the second ends of the outer pipes of the PIP bulkheads;
• (c) providing a sleeve having a sleeve internal diameter being the same or similar to the internal diameter of the metal inner pipe of the first PIP pipeline length, and having two circumferential shoulders and a recess between the shoulders, at least one shoulder being within the second end of the first PIP bulkhead, and at least one shoulder being beyond the end of the second end of the first PIP bulkhead;
• and
• (d) locating the sleeve in the outer pipes of the second ends of the PIP bulkheads prior to step (b), such that one sleeve shoulder is within the second end of the first PIP bulkhead, and the at least one sleeve shoulder is within the end of the second end of the second PIP bulkhead to form an annular space between the sleeve, the two shoulders of the sleeve, and the second ends of the first and second PIP bulkheads.