PIPELINE SYSTEMS

Abstract: A cable entry or exit pipe (30) is formed on a fluid transportation pipeline (10) whilst in normal operation full of and transporting a fluid under a positive pressure, by a method which comprises the steps: (a) producing two semi-cylindrical shells (14,16), one (14) of which carries an oblique branch pipe (30) and has an aperture (34) aligned with the bore of the branch pipe (30); (b) securing in a fluid tight manner around the pipeline (10) the two shells (14,16) so as to form a reinforcing collar (12) carrying an oblique branch pipe (30) lying at an acute angle suitable for the entry into and exit from the pipeline (10) of a cable (68); (c) securing in a fluid tight manner to the free end of the branch pipe (30) an isolating valve (62); (d) securing in a fluid tight manner to the free side of the isolating valve (62) a fluid tight drilling apparatus (70) equipped with a drill bit; (e) opening the valve (62) and introducing the drill bit through the opened valve (62) into the branch pipe (30); (f) rotating and progressively advancing the drill bit into contact with and through the wall (38) of the pipeline section (10); (g) withdrawing the drill bit and closing the valve (62); and (h) removing the drilling apparatus (70). Preferably, a liner (40) inserted into the branch pipe (30) between steps (g) and (h) serves as a cable guide.

Description: This invention relates to fluid transportation pipeline systems for transporting bulk liquids or gases over substantial distances, and to a means for and a method of modifying such a pipeline system whilst it is in normal operation, whereby to effect a permanent change in such a system. In our concurrently filed, co-pending patent application No. 88 305 148.4 there is disclosed the concept of, and a method of, deploying within (instead of alongside) a fluid transportation pipeline for transporting bulk liquids or gases an electrical or other cable or line for transmitting data, control or other signals which need to be transmitted from one location on a pipeline system to another such location. In the case of a new pipeline, suitable branch pipes for the entry and exit of such a cable or line can be readily provided, by design, from the outset, that is during the construction of the pipes from which the system will eventually be assembled on site. However, there is also a need to provide such branch pipes permanently on existing pipelines, even whilst they are in normal operation, full of a liquid or gas flowing under a high positive pressure. Formation of branch pipes on existing pipelines carrying fluid under pressure is generally known, though usually for the purpose of tapping off fluid from the pipeline. US-A-997,464, which is considered to be the closest prior art, discloses a method of forming a branch pipe at an acute angle to a pipeline by attaching a clamp piece to the pipeline and inserting a cutting means through a valve attached to the clamp piece. When the wall of the pipeline is breached by the cutter the latter is withdrawn and the valve controls the flow of fluid from the pipeline through the clamp piece. US-A-3,703,909 discloses a similar method of cutting a hole in a pipeline wall using a cutter advanced through the branch pipe. Again this branch pipe is suitable only for tapping off fluid from the pipeline. US-A-4,649,94 8 discloses the formation of a so-called "Wye" device which is provided with a curved guide directional shoe for insertion of a leak detector apparatus into the pipeline. However, the leak detector apparatus is carried at one end of the cable by which it is deployed into the pipeline and it is withdrawn from the pipeline by withdrawing the cable back through the guide shoe. It is to be noted that it would be impractical to attempt to locate, capture and withdraw the free end of a cable inserted from another branch pipe upstream of the desired exit branch pipe using the form of curved guide shoe shown, especially since the branch pipe is at right angles to the pipeline immediately adjacent the pipeline wall. Moreover, attempting to insert or withdrawn a cable via the acute angled branch pipe of US-A-997,464 or US-A-3,703,909 would only cause damage to the cable by virtue of the sharp jagged edges of the hole breached in the pipeline wall by the cutting means. Therefore, according to one aspect of the present invention there is provided a method of forming a cable entry or exit pipe on a fluid transportation pipeline whilst in normal operation full of fluid under a positive pressure, which method comprises the following steps:- a) forming a branch pipe at an acute angle on said pipeline in known manner, the angle being suitable for the entry into or exit from the pipeline of a cable, said branch pipe having isolating valve means through which drilling means can be inserted and subsequently withdrawn; (b) inserting drilling means into said branch pipe via said valve means, drilling the wall of the pipeline to form an oblique aperture where the branch pipe is secured and subsequently withdrawing said drilling means; c) adapting said drilling means to carry a branch pipe liner, introducing into said branch pipe via said isolating valve means, utilising said drilling means, the branch pipe liner for secure lodgement in the branch pipe to serve as a cable guide tube, the liner having a free end protruding through said aperture shaped and smoothed so as to minimise damage to an electrical or other cable or line being fed into or withdrawn from the pipeline through the branch pipe. In order to connect the bore of the branch pipe with the bore of the pipeline, the present invention preferably provides in the branch pipe guide and support surfaces through which a rotating drill may be introduced for the purpose of drilling an oblique or skewed aperture through the wall of the pipeline section, the guide and support surfaces providing both guidance and sideways support for the drill during the course of drilling the pipeline aperture. Preferably, the cable guide is supported in the branch pipe by at least one of the said guide and support surfaces. Other features of the present invention will become apparent from reading of the description that follows hereafter, and of the claims appended at the end of that description. One straight pipeline section having secured thereon a branch pipe, and a method of providing that branch pipe, all according to the present invention, will now be described by way of example and with reference to the accompanying diagrammatic drawings. In those drawings: Figure 1 shows a side view, partly in vertical diametral section, of a part of an existing pipeline which has been newly fitted with a cable exit branch pipe in accordance with the present invention, and indicates other apparatus which is used in the deployment of a cable in that pipeline; Figure 2 shows, to a large scale and in a vertical diametral section, part of the pipeline shown in Figure 1, together with the associated branch pipe and a branch pipe liner; and Figure 3 shows an end view of the pipeline shown in the Figure 1 and its associated branch pipe. Referring now to the drawings, a straight section of a steel pipeline 10 carries externally thereon a cylindrical steel collar 12 comprising upper and lower half-shells 14, 16 which have been welded together along opposed longitudinal margins 18, 20 over enclosed backing strips 22, 24, and which have been welded to the pipeline 10 at their respective circumferential margins 26, 28. The upper half-shell 14 has welded thereto an oblique branch pipe 30 which is inclined to the pipeline on an angle of approximately thirty degrees. The branch pipe carries a circular flange 32 at its upper, free end, and communicates at the lower end with an aperture 34 formed in the upper half-shell 14, and with an aligned aperture 36 drilled in the pipeline wall 38. The branch pipe has secured therein a cable guiding sleeve or liner 40. That liner defines a longitudinal cylindrical bore 42 which communicates at its lower end with the bore 44 of the pipeline 10. The lower end of the liner constitutes an obliquely shaped nozzle 46 which projects only a short way into the pipeline bore 44, and which has smoothly rounded surfaces 48 over, or against, which an electric or other cable may pass, or lie, without suffering damage. The liner is supported in position in the branch pipe by a screw-threaded upper portion 50 which is engaged in a screw-threaded throat 52 of the branch pipe 30, and is secured against rotation by a locking screw 54 which locates in a longitudinal keyway 56 formed in the upper end of the liner. The longitudinal bore 42 of the liner opens out at its upper end from a circular into a square cross section, for the purpose of receiving therein a driving tool (not shown) of square transverse cross section. Arcuate gouges 58 are formed in that upper part of the liner bore, for the purpose of receiving temporarily sping-biased location balls (not shown) provided on the said driving tool. The liner is guided and supported near its lower end by a cylindrical support surface 60 formed within the branch pipe 30. To the branch pipe flange 32 is secured an isolating valve unit 62, by bolts 64, and to the free side of that valve unit is bolted a fluid sealing means 66. An electrical or other cable 68 is enclosed within the pipeline bore, being there submerged in the fluid being transported in the pipeline (from left to right in the Figure 1) at a high positive pressure of the order of 1440 pounds per square inch (approximately 99.6 bar) or more, and a flow rate of the order of two metres per second. The cable exits from the pipeline via the nozzle 46 and longitudinal bore 42 of the liner 40, the isolating valve unit 62, and the fluid sealing means 66. The cable enters the pipeline at an upstream location (not shown) through a Similar assembly of branch pipe (secured in like manner to the pipeline), branch pipe liner, isolating valve unit, and fluid sealing means, but in this case the assembly is inclined to the pipeline from the opposite direction, i.e. at an acute angle relative to the part of the pipeline that lies upstream of the branch pipe. To make possible the deployment of that cable in the existing pipeline 10, and whilst it is in normal operation transporting bulk liquid under a high positive pressure, a branch pipe 12, 30 is first secured externally on the pipeline at each of the selected upstream and downstream locations. This is achieved by assembling around the pipeline at each such location the two half-shells 14, 16 which constitute a said collar 12 with attached branch pipe 30. After inserting the said backing strips 22, 24 between the pipeline and the respective pairs of opposed longitudinal margins 18, 20 of those half-shells, the longitudinal edges of the half-shells are welded together. Thereafter, the collar so formed has its two ends welded to the pipeline along circumferential paths 26, 28. In each case, the welds so made are fluid-tight welds. The isolating valve unit 62 is then bolted to the branch pipe flange 32, and to the free side of that valve unit is bolted, in a fluid tight manner, a fluid tight drilling machine 70 having a drill bit in position. That drilling machine is indicated in Figure 1 by chain-dotted lines. With the isolating valve in the open condition, the drill bit is advanced into the bore of the branch pipe 30, through the cylindrical support surface 60 and into contact with the outer surface of the pipeline 10. With the drill bit rotating, it is advanced still further so as to cut an oblique aperture 36 in the pipeline wall. The drill bit is then retracted into the drilling machine, the valve is shut, and the drill bit is replaced by a said driving tool carrying on its square free end a branch pipe liner 40. The liner is located axially on the driving tool by spring-loaded balls which engage in the arcuate gouges 58 formed in the liner bore. The isolating valve 62 is opened, and the liner 40 advanced into the branch pipe so as to bring the screw-threaded portion 50 thereof into engagement with the screw-threaded throat 52 of the branch pipe bore, whereupon the liner is rotated to screw it firmly into its working position in the branch pipe, with the nozzle thereof projecting a short way into the pipeline bore 44. The driving tool is then withdrawn from the end of the liner (against the resistance offered by the spring-loaded balls), and from the isolating valve unit, whereupon the isolating valve is closed, and the drilling machine removed. The fluid sealing means 66 is then secured to the isolating valve unit in place of the drilling machine, and a cable 68 is deployed in the pipeline in the manner described in the afore-mentioned co-pending patent application, to which the reader's attention is hereby directed for further information concerning the method of deployment of the cable. The screw-threaded engagement of the liner in its socket 52 enables the subsequent removal of the liner from the branch pipe at any time, in the event, for example, that it is necessary to seal the branch pipe temporarily by means of a screw-threaded sealing plug (inserted in place of the liner) as a preliminary to removing the slide valve for replacement or repair. In such a case, the cable would be removed from the pipeline first so as to enable the slide valve to be closed temporarily as a preliminary to the withdrawal of the liner. If desired, the screw-threaded portion 50 of the liner 40 may be shortened, so as to permit the use in association with such a shortened liner of a screwed annular retention plug. Such a modified construction would permit the temporary sealing of the branch pipe without the need to remove the liner itself, since the temporary screwed sealing plug could be inserted in place of the annular retention plug alone. Alternatively and more advantageously, the liner 40 may be shortened by omitting the screw-threaded portion 50, and be provided instead with a radial flange for effecting axial location of the liner in the branch pipe, and an axial keyway for effecting rotational location in the branch pipe. In that case, the liner would be secured against axial movement by an annular retention plug screwed into the screw-threaded throat 52 of the branch pipe. Such an arrangement has the two advantages: (a) that the liner 40 once inserted need never be removed, and (b) that it ensures correct and easy positioning of the obliquely-shaped nozzle end 46 of the liner relative to the bore 44 of the pipeline into which it protrudes. For a pipeline having a nominal bore of approximately 8 inches (203mm) diameter, the branch pipe has had an internal diameter of approximately 2 inches (51mm). The branch pipes, the method of securing them to a pipeline, described above make it possible to deploy a cable or other line in an existing pipeline whilst it is in normal operation transporting fluid under a high operating pressure, and with the minimum of difficulty. Whereas the branch pipe has been described as being inclined at angle of approximately thirty degrees to the pipeline, any other angle of inclination may be selected instead, provided that it will ensure for a cable to be deployed in the pipeline a smooth passage into/out of the pipeline, and at the same time not present any insuperable difficulties in constructing and securing the branch pipe and drilling the aperture in the pipeline wall. Whereas, it is preferred to provide around the pipeline section 10 the reinforcing collar 12 (14, 16) for carrying the branch pipe 30, that collar may be omitted and the branch pipe secured directly to the pipeline section. If desired, additional guide and support surfaces may be provided for supporting and guiding the drill bit and the liner 40.

Claims: A method of forming a cable entry or exit pipe (30) on a fluid transportation pipeline (10) whilst in normal operation full of fluid under positive pressure, which method comprises the following steps:- a) forming a branch pipe (30) at an acute angle on said pipeline in known manner, the angle being suitable for the entry into or exit from the pipeline (10) of a cable (68), said branch pipe (30) having isolating valve means (62) through which drilling means can be inserted and subsequently withdrawn; (b) inserting drilling means into said branch pipe via said valve means (62), drilling the wall of the pipeline (10) to form an oblique aperture (36) where the branch pipe (30) is secured and subsequently withdrawing said drilling means; and is characterised by the step: c) adapting said drilling means to carry a branch pipe liner (40), introducing into said branch pipe (30) via said isolating valve means, utilising said drilling means, the branch pipe liner for secure lodgement in the branch pipe to serve as a cable guide tube, the liner having a free end (46,48) protruding through said aperture shaped and smoothed so as to minimise damage to an electrical or other cable or line being fed into or withdrawn from the pipeline through the branch pipe. A method according to claim 1, wherein the branch pipe (30) incorporates at least one guide and support surface (60) for guiding and supporting the drilling means as it is rotated and progressively advanced into contact with and through the wall (38) of the pipeline section (10). A method according to claim 1 or 2, wherein said branch pipe (30), is disposed at an angle of substantially thirty degrees to the pipeline section (10). A method according to any preceding claim, wherein the isolating valve (62) comprises a slide valve. A method according to any preceding claim, wherein the pipeline (10) has a nominal bore (44) of approximately 203mm, and the branch pipe (30) has an internal diameter of approximately 51mm. A cable entry or exit branch pipe (30) formed on a fluid transportation pipeline (10) at an acute angle thereto into which branch pipe drilling means are insertable, the wall of the pipeline (10) being drilled to form an oblique aperture (36); characterised in that said branch pipe (30) has secured therein a branch pipe liner (40) having a free end (46,48) projecting into the pipeline (10) and being shaped and smoothed to minimise damage to a cable (68) being fed into or withdrawn from the pipeline (10) through the branch pipe (30).

Inventors: DE LA SALLE, BRIAN EDWARD
Applicants: NORTHERN TELECOM LIMITED
Application year: 1988
Main classification: F16L41
IPC codes: H02G1, G02B6, F16L55, F16L41