GB2082708A

GB2082708A - Process for tapping a pipe conveying a fluid

Info

Publication number: GB2082708A
Application number: GB8125492A
Authority: GB
Original assignee: Compagnie Francaise des Petroles SA
Current assignee: Total Compagnie Francaise des Petroles SA
Priority date: 1980-08-22
Filing date: 1981-08-20
Publication date: 1982-03-10
Also published as: NO153018C; GB2082708B; NO153018B; NO812836L; IT8123592A0; FR2488972B1; IT1169271B; FR2488972A1

Abstract

The invention relates to a process for tapping a fluid carrying pipe, particularly but not exclusively a submerged pipe. According to the process one or two banking devices 8, 9 are introduced into the pipe through one or two coupling pieces 6, 7 installed on the section 12 of the pipe 1 to be replaced. The blanking devices 8, 9 are displaced in the pipe in directions away from the section, and brought into operation. The section is then cut at 10 and 11 between the banking devices 8, 9 and the respective coupling pieces 6, 7. <IMAGE>

Description

SPECIFICATION Process for tapping a pipe conveying a fluid The invention relates to a process for tapping a pipe conveying a fluid, in particular a pipe conveying a petroleum product. It applies more especially, but not exclusively, to an immersed gas pipe.

It has already been proposed to isolate a portion of pipe in which, for example, a damaged section has to be replaced, by introducing therein, through its ends, two blanking devices which are then placed at the ends of the portion to be isolated. In this way, it is possible to replace a pipe section by a new section whilst at the same time finally obtaining a pipe which has the same configuration as a newly installed pipe.

However, the two ends of such a pipe are not always accessible and it is sometimes desirable to be able to carry out this isolation by introducing blanking devices directly from the outside into the pipe in the tapping region.

For this purpose, it has been proposed to use T-shaped pieces possessing one arm which is welded to the pipe and another arm which forms a tube fitted with a connecting flange, on which one side of an intermediate valve referred to as a "sandwich valve" is mounted, the other side of which valve can be connected to the casing of a drilling, branching or blanking machine, so that it is possible to drill the pipe on one side, in the tapping region, and introduce therein, at the drilled location, a branching device or a blanking device.

This procedure makes it possible firstly to install a by-pass for a section to be replaced, then to isolate this section and finally to replace it, after which the by-pass can be removed. It is thus possible to carry out the tapping operation whilst at the same time leaving the pipe under pressure ("hot tapping"), and hence without interrupting the production, but, after the tapping operation, T-pieces with the associated intermediate valves, which are weak points, remain on the pipe.

Moreover, this technique, which is used on land, cannot at the present time be used under water, in particular because it is impossible to weld the said T-pieces to the pipe under water, due to the fluid pressures prevailing in the pipe.

The invention proposes to obtain a pipe which, after a tapping operation, has the same configuration, without a weak point, as a newly laid pipe, by tapping, from the outside, only that region in which a replacement is to be carried out, and, in the case of an immersed pipe, by filling with water only that zone in which the tapping operation is carried out.

According to the invention there is provided a process for tapping a pipe for conveying a fluid, for the purpose of replacing a pipe section therein, comprising installing at least one coupling piece on the pipe, the coupling piece having one arm fixed in a leaktight manner to the pipe in the tapping region and another arm forming a tube provided with connecting means to which the casing of a machine is connectable with the interposition of an intermediate valve, connecting the casing of a drilling machine, by which the pipe is drilled on one side, and then the casing of a machine for introducing a blanking device, by which a controllable blanking device is introduced into the pipe, to the connecting means, moving the blanking device in the pipe in a direction away from the pipe section to be replaced, bringing the blanking device into action, and then cutting the pipe section to be replaced at a location between the blanking device and the coupling piece through which it is introduced.

Before the coupling piece is installed, the pressure in the pipe can be reduced sufficiently for the seal between the coupling piece and the pipe to be obtained simply by screwing. It should be recalled in this respect that the coupling piece is separated from the pipe by cutting the section to be replaced. This tapping process can be termed "cold tapping".

If a section must be replaced simply in order to modify an installation, or if it is only slightly damaged and its internal cross-section has not been substantially narrowed, it may be possible to install only one coupling piece on the pipe, on the pipe section to be replaced, and successively to introduce two blanking devices through the coupling piece, which blanking devices are moved in the pipe in directions away from the pipe section to be replaced, respectively on one side and on the other side of this coupling piece, along the pipe, so that they enclose the pipe section to be replaced, which section carries the coupling piece.

If one of the ends of the pipe is accessible, it is possible to use the invention only on that side of the section to be replaced which is further from this end of the pipe, and to introduce a blanking device from this end of the pipe on the other side of the section, in the way which is already known.

It is also possible, in particular if the pipe is very greatly damaged, to install two coupling pieces towards the ends of the section to be replaced, and to introduce a blanking device through each of these coupling pieces, each of which blanking devices is moved in a direction away from the section to be replaced, on the side of the coupling piece which was used to introduce the blanking device in question, each of the two cuts in the pipe section to be replaced being made between a respective blanking device and the coupling piece which was used to introduce it.

The blanking device may consist of a mechanical device or totally or partially of a chemical substance with a modifiable form, such as, for example, a hardenable gel. In the latter case, removal of the blanking device can be effected, if appropriate, by degradation of the chemical substance.

A deflection system may be introduced into the pipe, at the same time as the blanking device, the deflection system acting to direct the blanking device in the direction in which it moves away from the coupling piece through which it is introduced. The deflection system may comprise, in particular, a system which directs a fluid for pushing the blanking device, or of a ramp which directs a self-propeiiing carriage forming part of the blanking device.

The blanking device may be joined to the outside of the pipe, through the coupling piece, by an umbilical cable which ensures the transmission of energy, commands and/or return information. A source of energy, such as a battery, and systems of transmitting and receiving acoustic signals can alternatively or additionally be installed on the blanking device.

Energy is transmitted in hydraulic form and/or in electrical form.

The blanking device preferably comprises an inflatable sealing device which at least ensures the ieak-tightness thereof. The blanking device may be held in position either by the same device as the sealing device, which is possible in the case of an inflatable device, or by another device, in particular an inflatable device or a controlled mechanical device, for example of the type consisting of jaws operated by a jack.

The blanking device preferably comprises locking means, for example of the type consisting of a non-return clack valve, which ensure that the same state is maintained after breakage or removal of the umbilical cable.

An embodiment of the invention will now be given without implying a limitation, reference being made to the attached drawings in which: Figure 1 shows, in a longitudinal view with a partial section, a pipe on which two blanking devices have been installed; Figure 2 shows the same pipe and also a new pipe section, before the operation for welding this section to the pipe; Figure 3 shows the side view of a coupling piece; Figure 4 is a diagrammatic view of the inside of a pipe at right-angles to a coupling piece, at the moment when a blanking device is descending into the pipe; and Figure 5 shows a diagrammatic side view of a blanking device.

In Figure 1, a pipe 1 provided with a concrete covering 2 has a defect in a region 3. After this defect has been located, the pipe 1 is stripped of concrete in two zones 4 and 5, in each of which a leak-tight T-shaped coupling piece 6, 7 is installed, through each of which a blanking device 8, 9 is introduced into the pipe, each blanking device being moved away from the region 3.

When these blanking devices have been brought into action and maintained in this state, the central portion of pipe is then filled with water, or brought to the same pressure as the hydrostatic pressure, and the pipe is cut at the locations indicated by the broken lines 10 and 1 which define a section 12. The cuts are made between the coupling pieces and their respective blanking devices.

It is then possible to remove the pipe section 12, position a new pipe section 13, shown in Figure 2, and join this section 13 to the pipe 1 by welding operations which are carried out, after removal of the water present in the cut ends of the pipe, in leak-tight chambers represented by broken lines 14 and 15. It then only remains to drive out the blanking devices 8 and 9 by increasing the fluid pressure, from one or other end of the pipe 1 , to a pressure level greater than.

that which the blanking devices can withstand, in order to have again a pipe which is similar to a newly laid pipe as regards the resistance to internal and external pressure and leaktightness.

In Figure 3, there is shown a T-shaped coupling piece, such as the piece 6, which comprises a lower half-shell 16 joined to an upper half-shell 17 by bolted flanges 1 8, 1 9, together forming one of the arms of the T, whilst a tube 20 surmounted by a flange 21 forms the other arm of the T. An intermediate valve 22 is mounted on the flange 21, for example by bolting, and can be opened or closed by displacing a slide transversely to the axis of the tube 20, by means of an operating device 23. A casing 24, containing a machine for carrying out an operation on the pipe, is fixed to the valve 22, for example by bolting.

In this case, it is envisaged that a casing 24 of a milling machine, which makes it possible to drill on one side of the pipe 1 is first mounted on valve 22, and then a casing 24 of a machine for introducing a blanking device, such as 8, through the hole drilled by the milling machine, is then mounted on valve 22.

The machine for introducing a blanking device comprises means for lowering, into the pipe 1, a deflector 25, shown in Figure 4, and also a blanking device such as 8.

Figure 4 shows a carrying cable 26 and an umbilical cable 27, but it is possible to use a single electrical-carrying cable to ensure both the handling of the blanking device and its connections for supplying energy, receiving commands and sending return information.

Figure 5 shows a blanking device on a larger scale. This blanking device comprises a sealing device 28 which comprises, for example, an inflatable device, and a carriage 29 which carries this device 28 and is fitted with traction and/or guiding wheels 30 and with jaws 31 which are intended to be applied against the internal surface of the pipe 1 to hold the carriage 29 in position.

These jaws 31 are controlled by jacks located in arms 32. The wheels 30 can be mounted on jacks located in arms 33, in order to reduce the bulk during the descent of the blanking device. Those wheels 30 which are driving wheels are driven by.

a motor or several motors located in the carriage.

These motors are electric or hydraulic.

In the case of the example shown, the carriage 29 is self-propelling and it receives its driving energy via the umbilical cable 27. It would also be possible for the carriage 29 only to have a guiding function in the pipe 1; in that case, its displacement could be ensured by a fluid under pressure, introduced into the pipe 1 through the coupling piece 6, it being possible for the sealing device 28, slightly inflated, to ensure a certain leaktightness during this displacement, and the deflector 25 then no longer being a simple guide ramp but a blanking shutter also ensuring a certain leaktightness.

The blanking device also possesses holding devices, such as non-return clack valves or various locking means (not shown), which enable it to remain in position and in the sealing position during the breakage of the umbilical cable 27 which is necessitated by the cutting of the pipe between 10 and 11.

Of course, numerous modifications can be applied to the embodiments which have now been described without going outside the scope of the invention.

Claims

1. A process for tapping a pipe for conveying a fluid, for the purpose of replacing a pipe section therein, comprising installing at least one coupling piece on the pipe, the coupling piece having one arm fixed in a leaktight manner to the pipe in the tapping region and another arm forming a tube provided with connecting means to which the casing of a machine is connectable with the interposition of an intermediate valve, connecting the casing of a drilling machine, by which the pipe is drilled on one side, and then the casing of a machine for introducing a blanking device, by which a controllable blanking device is introduced into the pipe, to the connecting means, moving the blanking device in the pipe in a direction away from the pipe section to be replaced, bringing the blanking device into action, and then cutting the pipe section to be replaced at location between the blanking device and the coupling piece through which it is introduced.

2. A tapping process according to claim 1, wherein two blanking devices are introduced into the pipe successively through one coupling piece located on the pipe section to be replaced, and are moved in the pipe in directions away from the pipe section to be replaced, respectively on one side and on the other side of the coupling piece, so that they enclose the pipe section to be replaced.

3. A process according to claim 1, wherein two coupling pieces are installed on the pipe towards the ends of the pipe section to be replaced, and one blanking device is introduced through each of the coupling pieces, each blanking device being moved in the pipe in a direction away from the section to be replaced, to one side of the respective coupling piece through which the respective blanking device was introduced, and the two cuts of the pipe section to be replaced are made between a respective blanking device and the coupling piece through which the blanking device was introduced.

4. A process according to any one of the preceding claims, wherein a guide ramp is introduced into the pipe for directing the blanking device in the direction in which it moves away from the coupling piece through which it is introduced into the pipe.

5. A process according to any one of claims 1 to 3, wherein a shutter for blanking the pipe is introduced into the pipe, the blanking device being moved away from the coupling piece through which the blanking device is introduced, by the thrust of a fluid which enters the pipe through the coupling piece and which is displaced in the pipe in a direction away from the shutter.

6. A process according to any one of claims 1 to 4, wherein the or each blanking device comprises displacement means and is moved away from the respective coupling piece through which it is introduced, by operation of the displacement means.

7. A process according to any one of the preceding claims, wherein an umbilical cable is attached to the or each blanking device, which cable passes through the coupling piece through which the blanking device is introduced, and at least provides for the transmission of energy, commands or return information between the outside of the pipe and the blanking device.

8. A process according to claim 7, wherein locking means are attached to the or each blanking device for maintaining the blanking device in the same state after breakage of the umbilical cable.

9. A process according to any one of claims 1 to 6, wherein the or each blanking device is provided with a source of energy.

10. A process according to any one of the preceding claims, wherein the or each blanking device is fitted with acoustic signalling means.

11. A process according to any one of the preceding claims, wherein the arm of the or each coupling piece which is fixed to the pipe is fixed thereto by screwing.

12. A process according to any one of the preceding claims, wherein the or each blanking device at least partially comprises a chemical substance with a modifiable form.

13. A process according to claim 12, wherein the or each blanking device at least partially comprises a hardenable gel.

14. A process for tapping a pipe for conveying a fluid for replacing a pipe section therein substantially as herein described with reference to the accompanying drawings.