Apparatus and method for introducing into and removing from a pipe a device which is advanced and retracted by a cable

Abstract: Apparatus for introducing into and removing from a pipe (5) a device (25) which is advanced and retracted by a cable (11), the apparatus comprising an insertion tube (1) having an end for mounting above a hole (23) bored in the pipe wall, an auxiliary tube (2) attached to the wall of the insertion tube (1) and having an end opening into the bore of the insertion tube and a rod (6) with an end (27) which is insertable through the auxiliary tube (2) into the pipe bore by way of the opening in the auxiliary tube, the rod end (27) having means (28) to engage the cable (11) as it is retracting the device (25) to hold the cable (11) away from the sides of the hole (23) until the device (25) is aligned within the hole (23), the auxiliary tube (2) being arranged so that its axis is, in use, in line with the hole (23) in the pipe wall (4).

Description: The present invention relates to apparatus and method for introducing into and removing from a pipe a device which is advanced and retracted by a cable. Such devices as closed circuit television cameras and sprayers are introduced into gas and other utility pipes respectively to inspect the walls of the pipes and spray them with a protective coating. The devices are attached to cables which are used to advance or push the devices along and retract or pull the devices from the pipes as well as carrying picture information in the case of TV cameras or sealants in the case of the sprayer devices. The devices gain access internally to the pipe by way of a hole bored in the wall of the pipe. In the case of a gas pipe, both the hole boring and the introduction and removal of the device are done in such a way that gas does not escape from the pipe. To this end a plate valve is first fitted to the pipe wall and the hole is bored with a drill via a gland mounted on the valve so that when the valve is opened and drilling takes place, the gland forms a seal with the body of the drill to prevent the escape of gas. The valve is then closed and the drill and gland removed. Next the cable is threaded into a device/cable insertion tube well known in the art and through which, in use, the device is inserted into the pipe and into which, after use, the device is retracted. The cable forms a gas tight seal with an annular plug located at a far end of the tube. In preparation for insertion into the pipe, the cable is attached to the device and the cable is pulled back to pull the device into the tube which is clear of the plate valve. The near end of the tube is now mounted in a gas tight manner on the plate valve. The tube therefore enables insertion into and removal from the pipe to be performed with no escape of gas. Now the plate valve is opened to permit the device to be pushed by the cable through the hole in the pipe wall into and along the pipe bore to carry out the inspection or spray coating as the case may be. After the particular task has been performed the cable is then pulled back through the plug to pull the device back along the pipe, through the hole, past the open plate valve and thence into the insertion tube when the tube can be removed from the plate valve which is closed. Unfortunately a problem occurs with the conventional equipment as described above in that on retraction the device gets caught on the wall of the pipe surrounding the hole and sometimes cannot be pulled through the hole. US -A- 5025670 shows a configuration with two angled tubes for a camera, the tube selected being dependent on the direction of travel required. A guide bar assists with handling the cable. The present invention is concerned with providing an improved arrangement. According to the invention there is provided apparatus for introducing into and removing from a pipe a device which is advanced and retracted by a cable, the apparatus comprising an insertion tube having an end for mounting above a hole bored in the pipe wall, a second tube attached to the wall of the insertion tube and a rod with an end which is insertable through the second tube into the pipe bore, the rod end having means to engage the cable as it is retracting the device to hold the cable away from the sides of the hole, characterised in that the insertion tube is vertically mounted, and the second tube is an auxiliary tube mounted entirely on the wall of the insertion tube to provide access to the pipe via the insertion tube, the axis of the auxiliary tube being in line, in use, with the hole in the pipe wall. Other preferred embodiments are specified in dependent claims 2-5. An embodiment of the invention will now be particularly described with reference to the drawings in which:- Figure 1 is a side view of an insertion and auxiliary tube in position mounted on the wall of a gas main, Figure 2 shows the position as the device is being retracted and the cable is being held away from the walls of the hole by the rod, and Figure 3 shows a close-up view of the end of the rod engaging the cable during retraction of the cable. Referring to Figures 1 and 2 the apparatus comprises a known-type so-called insertion tube 1, an auxiliary tube 2 attached by welding to the wall of the insertion tube 1, a known-type plate valve 3 for mounting on the wall 4 of the pipe 5 and a rod 6 (Figure 2) for insertion into the auxiliary tube 2. The insertion tube 1 is of conventional design and as it has already been described in some detail in the introduction will not be described in great detail here. The tube 1 is used to enable devices such as close circuit television cameras, pipe wall spray devices and inflatable stopper bags to be introduced into gas pipes in particular in such a way that gas does not escape into the atmosphere during such operations. The tube 1 is flanged at either of its ends 7 and 8 for connection to corresponding flanges of the plate valve 3 in the case of end 7 and of a cable sealing plug assembly 9 in the case of end 8. The assembly 9 houses an annular rubber plug 10 which has a central aperture (not shown) through which, in use, the cable 11 can pass as shown in Figure 2. The aperture is small enough to form a gas tight seal with the cable 11, the plug 10 itself being located in a housing 12 in the assembly 9 with which housing 12 the plug 10 also forms a gas tight seal. The auxiliary tube 2 which is of smaller external and internal diameter than the insertion tube 1, extends outwardly at an acute angle from the axis of the insertion tube 1 and is welded to the external wall of the insertion tube 1. The auxiliary tube 2 opens at its lowermost end 13 connected to insertion tube 1 into the bore of the insertion tube 1 as shown in Figure 2. Mounted at the other uppermost end 14 of the auxiliary tube 2 is a rod sealing plug assembly 15. The assembly 15 comprises an annular rubber plug 16 similar to plug 10, plug 16 also having a central aperture (not shown) through which, in use, the rod 6 can pass as shown in Figure 2, the aperture in the plug 16 being small enough to form a gas tight seal with the rod 6. The plug 16 is retained in a housing 17 in the assembly 15 with which housing 17 the plug 16 also forms a gas tight seal. The plate valve 3 is mounted on the wall 3 of a gas pipe or main 5 by means of a pair of pipe straps 21 and 22 as conventional. In the situation shown in Figures 2 and 3, a hole 23 has already been drilled in the pipe wall 4, the plate 24 in the valve 3 opened and the device in this case a motor driven wheeled inspection camera 25 has been inserted into the pipe bore 26 via the insertion tube 1. In Figure 2 the camera 25 is being retracted by the cable 11 and it is now desired to lift the camera 25 through the hole 23 and thence through the plate valve 3 and into the insertion tube 1. It will be seen from Figure 2 that the axis of the auxiliary tube 2 is arranged so that it is, in use, in line with the hole 23 in the pipe wall 4. This enables the end 27 of the rod 6 to be pushed through the auxiliary tube 2 into the pipe bore 26 by way of the hole 23 and engage the cable 11 as shown in Figures 2 and 3. The end 27 of the rod 6 has means in the form of U-shaped clip 28 shown inverted for holding and retaining the cable 11 so that the rod 6 can, in use, hold the cable 11 away from the sides of the hole 23 until on further retraction the camera 25 is pulled up into alignment with the hole 23 but spaced from the walls 29 thereof. Thereafter the rod 6 is removed from the auxiliary tube 2, the camera 25 can be pulled up into the insertion tube 1 and the plate 24 in the plate valve 3 closed.

Claims: Apparatus for introducing into and removing from a pipe a device (25) which is advanced and retracted by a cable (11), the apparatus comprising an insertion tube (1) having an end for mounting above a hole (23) bored in the pipe wall, a second tube (2) attached to the wall of the insertion tube and a rod (6) with an end which is insertable through the second tube into the pipe bore, the rod end having means (28) to engage the cable as it is retracting the device to hold the cable away from the sides of the hole, characterised in that the insertion tube (1) is vertically mounted; and the second tube (2) is an auxiliary tube mounted entirely on the wall of the insertion tube to provide access to the pipe via the insertion tube, the axis of the auxiliary tube being in line, in use, with the hole in the pipe wall. Apparatus as claimed in claim 1, wherein the auxiliary tube and the insertion tube are configured to gain access to the pipe bore via common closure means (3). Apparatus as claimed in claim 2, wherein the common closure means comprises a plate valve (3) mounted in use above the hole, the insertion tube being mounted apon the plate valve. Apparatus as claimed in claim 1, 2 or 3 wherein a first fluid tight seal (15) is provided in the auxiliary tube to effect sealing between the rod and the auxiliary tube, and a second fluid tight seal (10) is provided in the insertion tube to effect sealing between the cable and the insertion tube. Apparatus as claimed in any one of claims 1 to 3, wherein the insertion tube comprises a first elongate portion (1) terminating at respective ends in first and second flanges (7,8), a second flanged portion being attached to the first portion and having a plate valve (3) therein, the auxiliary tube (2) being attached to the first portion of the insertion tube. A method for introducing and removing a device from a pipe using the apparatus of claim 1, the method comprising introducing the device vertically through the insertion tube into the pipe bore, moving the device along the pipe bore to a desired position, withdrawing the device from the pipe bore and utilising the guide rod to hold the cable away from the sides of the hole.

Inventors: COTTON MICHAEL, HORAN KEVIN MICHAEL, COTTON, MICHAEL, HORAN, KEVIN MICHAEL
Applicants: BRITISH GAS PLC, BG PLC
Application year: 1996
Main classification: F16L55
IPC codes: F16L55, G02B6, B08B9