GB1592455A

GB1592455A - Methods of installing an outer pipe on an existing pipeline

Info

Publication number: GB1592455A
Application number: GB3504076A
Authority: GB
Original assignee: Press W & Son Ltd
Current assignee: Press W & Son Ltd
Priority date: 1977-11-18
Filing date: 1977-11-18
Publication date: 1981-07-08

Description

(54) IMPROVEMENTS IN OR RELATING TO METHODS OF INSTALLING AN OUTER PIPE ON AN EXISTING PIPELINE (71) We, WILLIAM PRESS AND SON LIMITED, a British Company, of 22 Queen Anne's Gate, London, SWIH 9AH., do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement: This invention relates to methods for installing an outer pipe on an existing pipeline.

The invention provides a method of installing an outer pipe on an existing pipeline comprising the steps of, providing two semi-circular section steel pipe pieces, mounting spacers for an outer pipe on the existing pipeline to space the outer pipe from the pipeline, then bringing together the two semi-circular pipe pieces around the existing pipeline with the longitudinal edges of one pipe piece abutting the longitudinal edges of the other pipe piece and with one pair of said abutting edges above the existing pipeline without imposing the weight of the pipe pieces on the existing pipeline, clamping said two pipe pieces together, supporting the outer pipe from below without imposing the weight of the pipe pieces on the existing pipeline so that the pipe can be rotated around the existing pipe and can be moved along the existing pipe, then welding said one pair of abutting pipe edges together, then rotating the pipe to bring the other pair of edges to a position above the existing pipeline, then welding said other pair of pipe edges together and locating the outer pipe in the required longitudinal position along the existing pipeline.

A plurality of said outer pipes may be installed on the existing pipeline one after the other and welded together end-to-end.

The two semi-circular section pipe pieces may be formed by cutting a pipe at diametrically spaced locations around the pipe.

The following is a description of a specific embodiment of the invention, reference being made to the accompanying drawings in which: Figure 1 is an elevation view of one of a pair of pipe carriers; Figure 2 is a perspective view showing the components of the pipe carrier of Figure 1 exploded apart; Figure 3 is an exploded perspective view of a jig for supporting a pipe; Figure 4 is an end elevation view of the jig of Figure 3 on an enlarged scale; Figure 5 is a plan view of the jig of Figure 3 on the same scale as Figure 4; Figures 6-14 show various stages in the assembly of an outer pipe formed in two semi-circular section pipe pieces on an existing pipeline using the pipe carrier and pipe support; and Figure 15 shows one side of a modified form of the pipe carrier of Figures 1 and 2 on an enlarged scale.

There are a considerable number of pipelines for gas, oil and other fluids laid in the ground and many such pipelines have been in existence for a considerable number of years. Many pipelines are laid across open countyside and it is the practice when new roadways are laid over such pipelines, or the ground loading over such pipelines is increased for any other reason, to install a reinforcing outer pipe over the existing pipeline to assist in carrying the additional load imposed on the pipeline. To install an outer pipeline, it is necessary to excavate the ground around the existing pipeline to expose the pipeline and this is usually done in limited sections at a time. A steel outer pipe is cut at diametrically spaced locations into two semi-circular section pieces. Annular spacers are mounted on the existing pipeline and the two pipe pieces are assembled around the existing pipeline on the spacers and are welded together. Further lengths of outer pipe are then assembled on the existing pipeline in a similar manner welded together end-to-end until a sufficient length of the existing pipeline has been covered by the new outer pipe to provide the required reinforcement to the existing pipeline. Sealing rings may be mounted between the ends of the new outer pipe and the existing pipeline and the space between the existing pipeline and new outer pipe may be purged with nitrogen or completely filled with a hard setting non-corrosive grout.

There now follows a description of a method for carrying out the above operation in accordance with the present invention and a description of apparatus for use in the method, and reference will be made firstly to Figures 1 and 2 of the accompanying drawings. As indicated above, a new outer pipe is first cut into two semi-circular section portions. A support assembly which will now be described is intended to lift the two pipe pieces and lower them into position around the existing pipeline and bring the two pipe pieces together ready for reattachment. The support assembly comprises a pair of carriers for supporting the split pipe at the two ends thereof one of which carriers is indicated generally at 10 in Figures 1 and 2. The carrier comprises two jaw members 11, 12 and the two jaw mem- bers carry semi-circular pipe support elements 13, 14 which are of similar radius to that of the pipe to be supported. Each of the pipe support elements has a semi-cylindrical part 1 5 reinforced by a radially outwardly extending flange 16. The part 15 of each pipe support element carries five screw thread operated clamps 17 spaced apart around the element for attaching an end of a pipe half to the support element as shown in Figure 9. The clamps 17 are preferably of the Lindapter" type.

As best seen in Figure 2 of the drawings, the jaws 11 comprise a pair of spaced parallel plates 20 and the jaws 12 comprise a pair of spaced parallel plates 21. The plates 21 are connected at their upper ends by a sleeve 22. The plates 20 of the jaws 11 engage either side of the plates 21 and the pin 18 is inserted through aligned holes in the plates and the sleeve 22 and is held in place by a castellated nut 23 screwed onto the end of the pin and held in place by a locking pin 24. The plates 21 of the jaw 12 are extended away from the jaw 20 to form a side arm 25. A single acting hydraulic ram 26 is connected between the jaws to open the jaws and to allow the jaws to close, the cylinder of the ram being connected by a bolt 27 to the end of the arm 25 remote from the jaw 12 and the piston rod of the ram being connected to the jaw 20, by a bolt 28. The ram is connected by a conduit 29 to a pump for hydraulic fluid indicated at 29a on Figure 10.

As can be seen in Figures 10 and 12. two carriers as illustrated in Figures 1 and 2 of the drawings are provided, the carriers being suspended jaws downwards on wire strops 30 passed around the sleeves 22 from the ends of a balanced beam 30a having an integral eye (not shown) at the centre thereof to receive the hook 31 of a hoist.

The method of use of the support assembly will be described as part of the operation of installing an outer pipe on an existing pipeline as a whole later in the description.

Reference is now made to Figures 3 to 5 of the accompanying drawings which illustrate a jig for supporting a pipe from below indicated generally at 35. The jig comprises two trestles 36 connected by cross bracing 37 and 38 to form a rigid structure. Each trestle 36 has two legs 39 and at the lower end of each leg 39 there is a screw jack 40 for raising and lowering the trestles. A base frame 41 is mounted on the trestles on which two parallel slideways 42, 43 are mounted. The slideway 42 supports two slides 44 on which roller housings 45 are mounted supporting rollers 46 for rotation about upwardly extending divergent axes so that the rollers present upwardly facing surfaces to receive and cradle between them a pipe. A lead screw 47 is mounted at the ends of the slideway 42 in upstanding plates 48 and passes through screw threaded hubs 49 in the roller housings 45. The lead screw 47 has oppositely handed threaded portions for engaging in the respective hubs 49 and two locking collars 50 are located on the lead screw on either side of one of plates 48 to lock the lead screw against rotation. Rotation of the lead screw in one direction separates the rollers 46 and rotation in the opposite direction brings the rollers together for a purpose described below.

The second slideway 43 carries two slides 50a on which wheel housings 51 are mounted in which upstanding wheels 52 are supported for rotation about spaced parallel axes. The wheel housings 51 are adjusted along the slide by a lead screw arranged in an identical manner to that for the roller housings 45 and like parts have been allotted the same reference numerals. Thus by rotation of the lead screw 47 passing through the housings 51 the separation of the wheels 52 can be varied.

In use a pipe is located with the axis of the pipe extending parallel to the axes of the roller wheels 52. The weight of the pipe can be taken on the wheels 52 or the rollers 46 and can be transferred from the wheels to the rollers by separating the wheels and bringing the rollers together and equally from the rollers to the wheels by separating the rollers and bringing the wheels together. The pipe is supported by two such support structures spaced apart along the length of the pipe and when the pipe is supported on the wheels of the two structures, it can be rotated about its own axis and when it is supported on the rollers of the two support structures. it can be moved longitudinally.

There now follows a description of the method of installing an outer pipe on an existing pipeline. Figures 6 and 7 of the drawings show an existing pipeline indicated at 55 which has been exposed by excavation and shuttering 56 supported by bracing 57 is located along either side of the trench to permit workers to enter the trench. Two jigs 35 are located beneath the section of the pipeline to be covered with an outer pipe and are spaced apart along the length of the pipe with the axes of the wheels 52 of the support structures extending parallel to the existing pipeline as can be seen in Figure 6.

Insulating spacer rings 58 are bolted around the existing pipeline at locations spaced along the pipeline.

A steel outer pipe of the required diameter and length is then cut by welding torches at diametrically spaced locations to form the pipe into two halves. As shown in Figure 8 of the drawings, the two halves 60, 61 are then re-assembled and secured together with temporary annular straps 62. The support assembly is then brought into operation and the carriers 10 are lowered into alignment with the ends of the pipe and the pipe is arranged so that one of the joints between the pipe is located at the top and one at the bottom of the pipe. The two jaws of each carrier are then secured to the two respective pipe halves by the clamps on the jaws and the pipe is then raised by means of the hoist as illustrated in Figure 9 and is brought to a position adjacent the trench. The temporary straps 62 are then removed. The hydraulic pump 29a is operated to deliver hydraulic fluid to the rams 26 to separate the jaws 11, 12 of each carrier and thereby separate the pipe halves as illustrated in Figure 10. The assembly is then lowered over the existing pipeline as illustrated in Figures 11 and 12 and eventually the fluid pressure to the rams 26 is slowly released to allow the jaws to come together under the weight of the pipe halves and the pipe halves to embrace the existing pipeline as shown in Figure 13. The temporary straps 62 are then re-applied to the pipe halves to clamp the pipe halves together. The support structures below the pipeline are then adjusted to take the weight of the outer pipe on the wheels 52 leaving the rollers 46 out of engagement with the pipe. The carriers 10 are then disconnected from the pipe and withdrawn by the hoist. The upper joints between the pipe half is then welded together as illustrated in Figure 14, the temporary clamps being moved to permit the complete length of the pipe to be welded and then the pipe is rotated on the wheels 52 to bring the welded joint to the bottom of the pipe and the other joint to the top for welding. When the joint has been completely welded, the temporary clamps are removed. The rollers 46 can then be brought in to take the weight of the pipe and the wheels 52 moved out so that the lon gitudinal position of the outer pipe can be adjusted along the pipeline as required.

A succession of outer pipes is assembled on the pipeline in this way the pipes being welded together end-to-end until sufficient of the existing pipelines has been covered by outer pipes. The ends of the outer pipe are then sealed to existing pipe using annular sealing rings and the space enclosed between the outer pipe and the existing pipeline may then be purged with an atmosphere such a nitrogen. Normally only a part of the complete length of pipeline to be protected will be exposed at any one time and as an outer pipe is applied to the pipeline, the excavated trench will be filled in as a further length of the pipeline is exposed further along the pipeline.

To enable the pipe carrier illustrated in Figures 1 and 2 of the drawings to carry smaller diameter pipes, the clamps 17 are removed from the parts 15 of the support elements and arcuate inserts 70 are secured in the support elements to the semicylindrical parts 15 by bolts 71 as illustrated in Figure 15 (which shows one side only of the pipe carrier). Two inserts are provided in each support element. The clamps 17 are then mounted on the inner peripheries of the support elements to receive and support a pipe. Various sets of inserts may be provided each set having a differing radial depth so that the pipe carrier can be used for lifting pipes of various diameters.

A device for locating a pair of semicircular pipe pieces around an existing pipeline, as hereinbefore described with reference to Figures 1, 2 and 15, and a jig for supporting a pipe, as hereinbefore described with reference to Figures 3 to 5, form the subjects of our U.K. Patent Specifications Nos. 1 592 456 (7944252) and 1 592 457 (7944253'), respectively, both of which are divided herefrom, and attention is directed to the claims thereof.

WHAT WE CLAIM IS: 1. A method of installing an outer pipe on an existing pipeline comprising the steps of, providing two semi-circular section steel pipe pieces, mounting spacers for an outer pipe on the existing pipeline to space the outer pipe from the pipeline, then bringing together the two semi-circular pipe pieces around the existing pipeline with the longitudinal edges of one pipe piece abutting the longitudinal edges of the other pipe piece and with one pair of said abutting edges above the existing pipeline without imposing the weight of the pipe pieces on the existing pipeline, clamping said two pipe pieces together, supporting the outer pipe from below without imposing the weight of the pipe pieces on the existing pipeline so that the pipe can be rotated around the existing pipeline and can be moved along the existing pipeline, then welding said one

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. at 55 which has been exposed by excavation and shuttering 56 supported by bracing 57 is located along either side of the trench to permit workers to enter the trench. Two jigs 35 are located beneath the section of the pipeline to be covered with an outer pipe and are spaced apart along the length of the pipe with the axes of the wheels 52 of the support structures extending parallel to the existing pipeline as can be seen in Figure 6. Insulating spacer rings 58 are bolted around the existing pipeline at locations spaced along the pipeline. A steel outer pipe of the required diameter and length is then cut by welding torches at diametrically spaced locations to form the pipe into two halves. As shown in Figure 8 of the drawings, the two halves 60, 61 are then re-assembled and secured together with temporary annular straps 62. The support assembly is then brought into operation and the carriers 10 are lowered into alignment with the ends of the pipe and the pipe is arranged so that one of the joints between the pipe is located at the top and one at the bottom of the pipe. The two jaws of each carrier are then secured to the two respective pipe halves by the clamps on the jaws and the pipe is then raised by means of the hoist as illustrated in Figure 9 and is brought to a position adjacent the trench. The temporary straps 62 are then removed. The hydraulic pump 29a is operated to deliver hydraulic fluid to the rams 26 to separate the jaws 11, 12 of each carrier and thereby separate the pipe halves as illustrated in Figure 10. The assembly is then lowered over the existing pipeline as illustrated in Figures 11 and 12 and eventually the fluid pressure to the rams 26 is slowly released to allow the jaws to come together under the weight of the pipe halves and the pipe halves to embrace the existing pipeline as shown in Figure 13. The temporary straps 62 are then re-applied to the pipe halves to clamp the pipe halves together. The support structures below the pipeline are then adjusted to take the weight of the outer pipe on the wheels 52 leaving the rollers 46 out of engagement with the pipe. The carriers 10 are then disconnected from the pipe and withdrawn by the hoist. The upper joints between the pipe half is then welded together as illustrated in Figure 14, the temporary clamps being moved to permit the complete length of the pipe to be welded and then the pipe is rotated on the wheels 52 to bring the welded joint to the bottom of the pipe and the other joint to the top for welding. When the joint has been completely welded, the temporary clamps are removed. The rollers 46 can then be brought in to take the weight of the pipe and the wheels 52 moved out so that the lon gitudinal position of the outer pipe can be adjusted along the pipeline as required. A succession of outer pipes is assembled on the pipeline in this way the pipes being welded together end-to-end until sufficient of the existing pipelines has been covered by outer pipes. The ends of the outer pipe are then sealed to existing pipe using annular sealing rings and the space enclosed between the outer pipe and the existing pipeline may then be purged with an atmosphere such a nitrogen. Normally only a part of the complete length of pipeline to be protected will be exposed at any one time and as an outer pipe is applied to the pipeline, the excavated trench will be filled in as a further length of the pipeline is exposed further along the pipeline. To enable the pipe carrier illustrated in Figures 1 and 2 of the drawings to carry smaller diameter pipes, the clamps 17 are removed from the parts 15 of the support elements and arcuate inserts 70 are secured in the support elements to the semicylindrical parts 15 by bolts 71 as illustrated in Figure 15 (which shows one side only of the pipe carrier). Two inserts are provided in each support element. The clamps 17 are then mounted on the inner peripheries of the support elements to receive and support a pipe. Various sets of inserts may be provided each set having a differing radial depth so that the pipe carrier can be used for lifting pipes of various diameters. A device for locating a pair of semicircular pipe pieces around an existing pipeline, as hereinbefore described with reference to Figures 1, 2 and 15, and a jig for supporting a pipe, as hereinbefore described with reference to Figures 3 to 5, form the subjects of our U.K. Patent Specifications Nos. 1 592 456 (7944252) and 1 592 457 (7944253'), respectively, both of which are divided herefrom, and attention is directed to the claims thereof. WHAT WE CLAIM IS:

1. A method of installing an outer pipe on an existing pipeline comprising the steps of, providing two semi-circular section steel pipe pieces, mounting spacers for an outer pipe on the existing pipeline to space the outer pipe from the pipeline, then bringing together the two semi-circular pipe pieces around the existing pipeline with the longitudinal edges of one pipe piece abutting the longitudinal edges of the other pipe piece and with one pair of said abutting edges above the existing pipeline without imposing the weight of the pipe pieces on the existing pipeline, clamping said two pipe pieces together, supporting the outer pipe from below without imposing the weight of the pipe pieces on the existing pipeline so that the pipe can be rotated around the existing pipeline and can be moved along the existing pipeline, then welding said one

pair of abutting pipe edges together, then rotating the pipe to bring the other pair of edges to a position above the existing pipeline, then welding said other pair of pipe edges together and locating the outer pipe in the required longitudinal position along the existing pipeline.

2. A method as claimed in claim 1 wherein a plurality of said outer pipes are installed on the existing pipeline one after the other and are welded together end to end.

3. A method as claimed in claim 1 or claim 2 wherein the two semi-circular section pipe pieces are formed by cutting a pipe at diametrically spaced locations around the pipe.

4. A method of installing an outer pipe on an existing pipeline substantially as described hereinbefore.