T-piece preformer

Abstract

A T-piece preformer for forming a T-piece in a pipe-in-pipe (PIP) pipeline for a marine environment, the PIP pipeline has at least inner and outer pipes having an annular space thereinbetween, and one or more cables extending along the annular space. The T-piece preformer includes at least: (a) inner and outer longitudinal collars; (b) annular walls between the inner and outer collars; (c) cable apertures through each annular wall; and (d) one or more guide points on the outer collar radially offset from the or each cable apertures, to guidance for a hole into the T-piece performer. The T-piece preformer can be assembled into a PIP pipeline, and requires a final hole during laying. The T-piece preformer has cable apertures through each annular wall, for allowing continuation of cables in the annular space through the PIP pipeline and T-piece preformer, and the T-piece.

Claims

1. A pipe-in-pipe (PIP) pipeline for laying in a marine environment comprising a plurality of PIP sections, each PIP section having at least inner and outer pipes having an annular space thereinbetween, the PIP pipeline having a continuum of the inner and outer pipes of the PIP sections and one or more cables extending along a continuum of the annular space, and further comprising one or more T-piece preformers, each T-piece preformer comprising at least: (a) inner and outer longitundinal collars corresponding in circumference to the circumferences of the inner and outer pipes of the PIP pipeline; (b) one or more annular walls extending between the inner and outer collars; (c) one or more cable apertures through each annular wall; and (d) one or more guide points on the outer collar radially offset from the one or more cable apertures, and able to provide guidance for a hole into the T-piece preformer from outside the outer collar to within the inner collar.

2. A PIP pipeline as claimed in claim 1 having at least three and at most eight cable apertures evenly distributed around the one or more annular walls, and the one or more guide points radially distributed around the outer collar.

3. A PIP pipeline as claimed in claim 1, wherein the or each guide point is recessed into the outer collar.

4. A PIP pipeline as claimed in claim 1, wherein the T-piece preformer is forged.

5. A PIP pipeline as claimed in claim 1, being a reelable bulkhead.

6. A PIP pipeline as claimed in claim 1, wherein the pipe-in-pipe (PIP) pipeline is reelable.

7. A PIP pipeline as claimed in claim 1, wherein the PIP pipeline is configured for the laying in a marine environment with a reeled lay method.

8. A method of laying a PIP pipeline according to claim 1, the method comprising the steps of; (a) providing the PIP pipeline of claim 1 on a marine vessel; and (b) laying the PIP pipeline of step (a) into the marine environment.

9. A method of laying as claimed in claim 8, wherein the laying of step (b) comprises a reeled-lay method.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the present invention will now be described by way of example only and with reference to the accompanying diagrammatic drawings in which:

(2) FIGS. 1a and 1b are prior art cross-sectional part-formed and fully formed PIP pipelines including a conventional T-piece;

(3) FIG. 2 is a part-cut away perspective view of a T-piece preformer according to one embodiment of the present invention;

(4) FIG. 3 is a radial cross-sectional view of a mid-point along the T-piece preformer of FIG. 2;

(5) FIG. 4 is a longitudinal cross-sectional view of the T-piece preformer of FIGS. 2 and 3 between two PIP pipeline sections to form a PIP pipeline according to another embodiment of the present invention;

(6) FIG. 5 is a schematic side view of the reeling of the PIP pipeline of FIG. 4 onto a marine vessel with a lay tower;

(7) FIG. 6 is a schematic side view of the unreeling of the PIP pipeline of FIG. 5 on a marine vessel in a marine environment, and the part-laying of the PIP pipeline in the marine environment;

(8) FIG. 7 is an enlarged longitudinal cross-sectional view of part of FIG. 6 showing the PIP pipeline with a formed T-piece; and

(9) FIG. 8 is a part-cut away perspective view of the formed T-piece in FIG. 7 in isolation.

DESCRIPTION OF PREFERRED EMBODIMENTS

(10) Referring to the drawings, FIGS. 1a and 1b herewith relate to the prior art method of locating a conventional T-piece 4 in an un-reeled pipeline 2 as discussed hereinbefore. The un-reeled pipeline 2 is cut at the point of laying, such as on the lay ramp, to allow the introduction and positioning of a conventional T-piece 4. The inner pipe 6 of the T-piece 4 is then welded via welds 5 to the inner pipe 7 of the pipeline 2 first, and then two outer shells 8 are provided to create the connection and continuation of the outer pipe 10 of the conventional T-piece 4, and the outer pipe 12 of the pipeline 2. The conventional T-piece 4 provides an outstanding injection port 14 for the introduction of methanol (MeOH) or other chemical agents as discussed above. Once the welding is completed as shown in FIG. 1b herewith, the laying of the pipeline 2 can continue.

(11) As mentioned above, the method and operation shown in FIGS. 1a and 1b is not carried out on PIP pipelines having cables extending along the annular space between the inner and outer pipes, as this would also require the cutting and hopeful reconnection of all the cables. Not only have such cables been particularly fitted during installation onshore and may not be readily accessible offshore, but assurance is also required about the integrity of the continuation of the cable functions once cut and reconnected.

(12) Also, the nature and shape of the conventional T-piece 4 means that it cannot be added into the pipeline as part of the assembling process offshore for two reasons. Firstly, the injection port 14 extends beyond the outer circumference of the pipeline 12, which does not allow it to be properly reeled onto a storage reel. Secondly, it is not able to accommodate cables therethrough.

(13) FIGS. 2 and 3 show a T-piece preformer 20 according to one embodiment of the present invention for forming a T-piece in a pipe-in-pipe (PIP) pipeline for laying in a marine environment.

(14) The T-piece preformer 20 comprises an outer longitudinal collar 22 and an inner longitudinal collar 24, corresponding in circumferences to the circumferences of inner and outer pipes of a PIP pipeline or PIP pipeline sections as discussed hereinafter. Between the inner and outer collars 22, 24 extends an annular wall 26. The skilled man is aware that the inner and outer collars 22, 24, and the annular wall 26, may have any suitable relative dimensions, which dimensions are not limited to those shown in FIGS. 2 and 3. However, by way of example only, FIG. 2 shows the outer collar 22 being of a shorter length than the inner collar 24, and the annular wall 26 having a length (or depth) close to but not the same as the length of the outer collar 22.

(15) Extending through the length or depth of the annular wall 26 are six cable apertures 28. The cable apertures 28 are in the form of longitudinal slots, able to accommodate the passage of one or more cables extending along the PIP pipeline as discussed hereinafter.

(16) The T-piece preformer 20 also includes a number of guide points 30 radially distributed around the circumference of the outer collar 22 to mark locations where any transverse drilling required through the T-piece preformer would avoid any cable apertures 28, and therefore any cables passing through the T-piece preformer.

(17) FIG. 2 also shows in dashed form the intended transverse or radial path 36 for a hole from one guide point 30 into the T-piece preformer 20 from outside the outer collar 22 to within the inner collar 24, and hence to within the bore of the inner pipeline of the PIP pipeline.

(18) FIG. 4 shows the T-piece preformer 20 in a longitudinal cross-section, with the inner and outer collars 24, 22 and annular wall 26 thereinbetween. The T-piece preformer 20 is located between two PIP pipeline sections 40. Each PIP section 40 comprises an outer pipe 42 and an inner pipe 44.

(19) In general, the conjunction of a number of such PIP sections 40 forms a PIP pipeline 52 with continuous longitudinal inner and outer pipes having an continuous annular space 46 thereinbetween.

(20) According to one embodiment of the present invention, to form a PIP pipeline with a T-piece preformer in-line therein, the T-piece preformer 20 can be located in line with the free end of one PIP section 40. The inner collar 24 of the T-piece preformer 20 can then be welded to the inner pipe 44 of the PIP section 40 in a manner known in the art, followed by the direct or indirect connection of the outer collar 22 with the outer pipe 42. FIG. 4 shows the addition of half shells 48 between the outer collar 22 and the outer pipe 42 in a manner known in the art. Thereafter, a second PIP section 40 can be located at the other or free end of the T-piece preformer 20 and connected thereto, generally in the same manner, by welding and the use of half shells 48.

(21) It can be seen from FIG. 4 that the circumferences of the inner and outer collars 24, 22, by corresponding with the circumferences of the inner and outer pipes 44, 42 of the PIP sections 40, create an overall PIP pipeline 52 having a continuous outer circumference along the PIP sections and T-piece preformer, and a continuous bore 51 along the inner pipeline in the same manner.

(22) After forming of the PIP pipeline 52 as shown in FIG. 4, one or more cables 50 can now be installed in the PIP pipeline 52 along the annular spaces 46 and through the cable apertures 28 of the T-piece preformer 20. The cable apertures 28 are not shown in FIG. 4 as these are not part of the longitudinal cross-section comprising the guide port 30, which is radially offset therefrom as shown in FIG. 3. FIG. 4 shows two cables 50 in this regard.

(23) Overall, FIG. 4 shows a pipe-in-pipe (PIP) pipeline 52 for laying in a marine environment comprising a plurality of PIP sections 40, each section having at least inner and outer pipes 44, 42 having an annular space 46 thereinbetween, the PIP pipeline 52 having a continuum of the inner and outer pipes of the PIP sections and one or more cables 50 extending along the continuum of the annular spaces 26, and further comprising one the T-piece preformer 20 of FIGS. 2 and 3.

(24) FIG. 4 also shows a method of forming the PIP pipeline 52 having the T-piece preformer 20, which method is usually carried out most conveniently and economically onshore.

(25) It is preferred that the T-piece preformer 20 is forged as a single integral piece, as shown in FIG. 2, whilst still allowing the overall PIP pipeline 52 as shown in FIG. 4 to be reelable, particularly for laying in a marine environment using the reeled lay method as discussed hereinafter.

(26) FIG. 5 shows schematically the reeling of the PIP pipeline 52 of FIG. 4 onto a storage drum or reel 54 on a marine vessel 56, generally still at an on-shore location. The marine vessel 56 includes a lay tower 58 having a number of apparatus 60 extending therefrom, which includes strengtheners, tensioners and one or more clamps as discussed hereinafter.

(27) Following reeling of the PIP pipeline 52 as shown in FIG. 5, the reeled PIP pipeline is transported to a marine environment, usually the relevant part of the sea or ocean into which the PIP pipeline 52 is to be laid. At the relevant location, the PIP pipeline 52 is then unreeled from the reel 54 for laying in the marine environment, by its passage towards the top of the lay tower 58 and through the apparatus 60, followed by passage through a moonpool 62 in the marine vessel 56 and entry into the marine environment 62 in a manner known in the art.

(28) At least one, generally at least two or more of the apparatus 60 include clamps or clamping means or other clamping devices, able to hold a portion of the PIP pipeline 52 static, as it passes through the lay tower 58 prior to entry into the marine environment 62. The nature and design of the clamps are known in the art. The holding of a pipeline immediately prior to its entry into the marine environment for action on the pipeline is known in the art, is not discussed in further detail herewith.

(29) FIG. 7 particularly shows the holding of the portion of the unreeled PIP pipeline 52 which comprises the T-piece preformer 20 between two apparatus 60, just prior to the entry of that portion of the PIP pipeline 52 into the marine environment 62. After holding said portion of the unreeled PIP pipeline 52, a hole 66 can be drilled (by a simple representative drill piece 64) from the most suitable or appropriate of the guide points 30 in the T-piece 20 from outside the outer collar 22 to within the inner collar 24.

(30) After or during forming the hole 66, there can also be provided, generally machined, a recess or rebate 32 extending around the position of the guide point 30, and an upstanding fluid entry port 34, such that a hose or the like can in use be directly connected onto the fluid injection port 34 for the supply of a fluid directly through the fluid injection port 34 and hole 66, and into the bore 51 within the inner pipeline of the PIP pipeline 52.

(31) Following the creation of the hole 66, there is formed the T-piece 68 in the PIP pipeline 52 now ready for subsequent use as described above. The final form of the T-piece 68 is shown in isolation and in more detail in FIG. 8.

(32) Following the creation of the hole 66 and the forming of the T-piece 68, the pipeline 52 can continue to be laid in the marine environment 62 as shown in FIG. 6.

(33) The present invention provides a T-piece preformer which can be assembled into a PIP pipeline onshore, and only requires the provision of a final hole during laying. Moreover, the T-piece preformer has one or more cable apertures through the or each annular wall, particularly adapted for allowing the continuation of cables in the annular space through the PIP pipeline, and so through the subsequently formed T-piece.

(34) In particular, such cables have not been cut after their installation into the PIP pipeline, and the forming of the hole in the T-piece preformer, to form the T-piece, can be a simple operation that can easily be carried out on the marine vessel, based on the guide point(s) provided. This is possible by the creation of a suitable T-piece preformer having the required cable apertures and a radially offset guide point, and which can be easily machined on the lay ramps.

(35) Various modifications and variations to the described embodiments of the invention will be apparent to those skilled in the art without departing from the scope of the invention as defined herein. Although the invention has been described in connection with specific preferred embodiments it should be understood that the invention as defined herein should not be unduly limited to such specific embodiments.