WO1981001184A1

WO1981001184A1 - Axial compensators for pipe lines

Info

Publication number: WO1981001184A1
Application number: PCT/GB1980/000165
Authority: WO
Inventors: R Leif; P Leif
Original assignee: United Gas Industries Ltd
Priority date: 1979-10-17
Filing date: 1980-10-15
Publication date: 1981-04-30
Also published as: SE7908587L; EP0047242A1; SE438022B

Abstract

An expansion element for insulating an axial compensator (10) comprises a pair of skid pipes (1, 2) attached in spaced relationship (11, 12) around pipe ends (13, 14) of the compensator. Each skid pipe (1, 2) is slidable in an end of a guide pipe (5) which over a substantial part of its length is surrounded by a protective pipe (8). All the spaces (9, 11, 12) between the skid pipes (1, 2) and pipe ends (13, 14) and between the protective pipe (8) and the guide pipe (5) are filled with heat insulation material. Due to the ability of the skid pipes (1, 2) to slide in the guide pipe (5), the expansion element follows changes in length of the compensator (10) in response to temperature variations. The expansion element is fitted to the axial compensator (10) before the two are mounted in a pipe line.

Description

Axial Compensators For Pipe Lines.

This invention relates to axial compensators for pipe lines and insulation therefor.

It is known to mount axial compensators in pipe lines, in order to take up variations in length caused by temperature variations. When the axial compensator is mounted in a pipe line in a culvert the pipe is frequently surrounded by an insulating and protective covering. The axial compensator should then also be provided with a protective, and insulating casing which is variable in length to accommodate the variations of the compensator. The mounting of this covering on site involves much work and time, especially in culvert installations with restricted space.

The invention provides a prefabricated insulated expansion element combined with an axial compensator having pipe ends directed in opposite directions and intended to be mounted in a culvert, characterized in that the expansion element comprises a pair of skid pipes, each arranged surrounding a pipe end and spaced therefrom, the spaces being filled with a flexible heat insulation material, the said skid pipes each being slidable in a common guide pipe, which surrounds the axial compensator and is spaced therefrom, each end of the guide pipe having a seal sliding on the skid pipe so that the said skid pipes are movable relative to the guide pipe, a protective pipe secured around the guide pipe and spaced therefrom, the space being filled with a heat insulation material. The prefabricated expansion elerrent is assembled on the axial compensator before they are mounted together in the pipe line, so avoiding the site work referred to above.

The invention is illustrated by two embodiments by way of example shown in the accompanying drawings, in which:-

Figure 1 is a longitudinal section of an expansion element and a side view (partly cut away) of an axial compensator in the expansion element, Figure 2 is a longitudinal section through the right-hand portion of the expansion element of a modified design, and Figure 3 is a side view of the expansion element and of a prestressing means engaging therewith.

The expansion element shown in Figure 1 comprises a pair of skid pipes

(1) and (2) having a central axis in common and arranged in spaced apart relationship. The remote ends of the skid pipes each have an end wall (3) and (4). Their ends facing each other are open and project into a guide pipe (5) which has sealing rings (6) and (7) and scraping edges (5') and (5") located around the respective skid pipe (1, 2) and sliding thereon. About the guide pipe (5) and radially spaced therefrom, a protective pipe (8) is attached rigidly to the guide pipe, so that a closed intermediate space (9) is formed around the guide pipe over a substantial part of its length. The items (1 - 5) and (8) preferably are made of a stable plastics material. The guide pipe (5) extends round an axial compensator (10) spaced therefrom, and the skid pipes (1, 2) each surround a pipe end (13, 14) in spaced relationship thereto leaving spaces (11, 12) communicating wit the space inside the guide pipe. The pipe ends extend through central openings (15) and (16) in end walls (3, 4) of the skid pipes. The diameter of the said openings is equal to the outer diameter of the pipe ends (13, 14). Flexible seals (17) and (18) are attached adjacent the outside of the openings (15, 16) and about the pipe ends.

The axial compensator (10) preferably is of the type described in U.K. Patent No. 1,531,792, which as appears from Figure 1 comprises two pipe connecting pieces (13' , 14') which are axially movable relative each other, their remote ends being connected to the pipe ends (13, 14). The ends of said connecting pieces facing toward each other are connected by means of a bellows (19), the ends of which are sealingly attached to the connecting pieces (13' , 14'). The bellows (19) and the adjacent ends of the connecting pieces are surrounded by a guide sleeve (20) which is spaced from the guide pipe (5) to leave the space continuous with spaces (11, 12). The axial compensator (10) is provided with a stroke limiter (21), which prevents undesired change in length of the bellows (19), as described in U.K. Patent No. 1,531,792. The intermediate spaces (11, 12) and the communicating space at least up to the guide sleeve (20), are filled with flexible or compressible heat insulation material, for example mineral wool, and the intermediate space (9) also is filled with heat insulation material, which need not be flexible or compressible. For temporary co-operation with the expansion element, a prestressing means is provided, which according to Figure 3 consists of two pipe clamp (22, 23) detachably attached on the pipe ends (13, 14). Two rods (24, 25) are attached to extend between the pipe clamps (22, 23). One end of each rod is welded to the pipe clamp (22) while the other end is threaded and extends through a hole in the second pipe clamp (23) and supports a pair of lock nuts (26). The distance apart of the rods exceeds slightly the outer diameter of the protective pipe (8), and the length of the rods is slightly greater than the distance between the outer ends of the skid pipes (1, 2) so that they are located outside the expansion element as shown in Figure 3.

When the axial compensator (10) is to be mounted in the expansion element, the axial compensator (10) first is prestressed in known manner, which state is maintained by means of a fixture or the like engaging with the pipe ends (13, 14) so that the axial compensator is held prestressed, and extended. Its total length will then decrease when the axial compensator is subjected to compressing pressure due to an increase in temperature of the conduit in which it is situated. Thereafter the expansion element is secured around the axial compensator. The prestressing means (22 - 26) is attached to the pipe ends (13, 14) to replace the fixture, which is then removed, the prestressing means maintaining the pipe ends (13, 14) in their positions set relative to each other.

The prestressing means (22 - 26) can alternatively be replaced by four pipe clamps (28 - 31 ) as indicated by dash-dotted lines in Figure 3. Two of the clamps (28, 29) are attached to the pipe ends (13, 14) and rest against the ends of the skid pipes (1, 2) while the other two of the clamps (30, 31) are attached to the skid pipes (1, 2) and rest against the ends of the guide pipe (5) , whereby the pipe ends (13, 14) are held prestressed by the guide pipe and skid ^'pipes instead of by the aforesaid rods (24, 25).

The prefabricated expansion element, thus, .is provided with the prestressing means when the element is delivered to the place of installation. The expansion element thereafter is mounted, with the prestressing means remaining thereon, in a culvert, the pipe ends (13, 14) are connected by welding to the opposed pipe ends of a conduit in the culvert, whereafter the prestressing means is removed and the skid pipes (1, 2) are connected to the protective pipe of the culvert^ preferably by means of a plastic sleeve (27) as indicated by dash-dotted lines in Figure 1, with insulation material inside the plastic sleeve. By prefabricating the expansion element of the special design, the advantage is gained that it can be mounted directly as one unit in a prefabricated culvert with a conduit. No additional insulation need be provided around the expansion element, only around the connection between the ends of the axial compensator and the conduit in the culvert covered by the plastic sleeve (27). The flexible insulation within the skid pipes (1, 2) and guide pipe (5) permit movement of the skid pipes relative to the guide pipe, and said seals (6, 7) prevent water or other particle from penetrating into the structure. The expansion element is easy to manufacture and can be adapted for any type of axial compensator for pipe lines merely by changing the dimension.

Figure 2 shows a modification, in which the ends of the guide pipe (5), of which only one end is shown, are provided with an additional seal (32) and scraping edge (33) thereon in order to improve the resistance to the penetration of water or other particles into the skid pipes. The central portion of the guide pipe in this case is formed by a sheet metal pipe secured by welding, as shown in Figure 2.

The invention must not be regarded restricted only to the embodiment described and shown in the drawing, because the invention can be modified within its scope. The guide pipe, for example, and the walls of the protective pipe connected thereto, may have another longitudinal section shape.

Claims

CLAIMS;

1. A prefabricated insulated expansion element combined with an axial conpensator (10) having pipe ends ( 13, 14) directed in opposite directions and intended to be mounted in a culvert, characterized in that the expansion element comprises a pair of skid pipes (1, 2), each arranged surrounding a pipe end (13, 14) and spaced therefrom, the spaces (11, 12) being filled with a flexible heat insulation material, the said skid pipes (1, 2) each being slidable in a common guide pipe (5), which surrounds the axial compensator and is spaced therefrom, each end of the guide pipe having a seal (6, 7) sliding on the skid pipe so that said skid pipes are movable relative to the guide pipe (5), a protective pipe (3) secured around the guide pipe and .spaced therefrom, the space (9) being filled with a heat insulation material.

2. An expansion element as defined in claim 1 , characterized in that both ends of the guide pipe (5) are provided with an additional seal (32) sliding on the skid pipe (1, 2).

3. An expansion element as defined in claim 1 or 2, characterized in that it carries a detachable prestressing means (22 - 26), which comprises two pipe clamps (22, 23) detachably attached each on one of the pipe ends (13, 14)and interconnected by two rods (24, 25), which are each attached at one end to one pipe clamp (22), the other end, v/hich is threaded, extending through the other pipe clamp (23) and carrying lock nuts (26) adjacent said clamp, so that the axial compensator can be held prestressed while in the expansion element.

4. An expansion element as defined in claim 1 or 2, characterized in that it carries a detachable prestressing means, which comprises two pipe clamps (28, 29) attached to the pipe ends (13, 14) and abutting the outer ends of the skid pipes (1, 2), and two pipe clamps (30 , 31) attached to the skid pipes (1, 2) and abutting the ends of the guide pipe (5), so that the skid pipes and the guide pipe serve as a part of the prestressing means to hold the axial compensator prestressed while in the expansion element.

5. An expansion element as claimed in any of claims 1 to 4 further characterized by each said seal (6, 7, 32) being associated with a scraping edge (5', 5", 33) of the guide pipe which slides oh the skid pipe.

6. An expansion element as claimed in any of claims 1 to 5, further characterized by said protective pipe (3) being rigidly secured to the guide pipe (5) with no provision for relative movement, the space (9) therebetween being filled with a heat insulation material which need not be flexible.

7. An expansion element as claimed in any of claims 1 to 6, further characterized by the space between the guide pipe (5) and the axial compensator being continuous with the spaces (11, 12) between the skid pipes and the pipe ends and being filled with the same flexible heat insulation material.