GB2191842A

GB2191842A - Concentric pipe joint

Info

Publication number: GB2191842A
Application number: GB08713765A
Authority: GB
Inventors: Eraldo Raffaeli; Alberto Anselmi; Roberto Bruschi
Original assignee: SnamProgetti SpA
Current assignee: SnamProgetti SpA
Priority date: 1986-06-20
Filing date: 1987-06-12
Publication date: 1987-12-23
Also published as: SE8702466D0; CN87104323A; SU1560066A3; NO872550D0; IT1204399B; CN1010120B; NO872550L; SE8702466L; IT8620864A0; GB8713765D0; JPS631887A

Abstract

A joint for supporting and connecting the ends of two concentric pipes 1,2 comprises a screw fitting 8,9. One half 8 of the latter is formed on either an inner cylindrical ring 7 or an extension of the inner pipe 2, (Figs. 4,5 not shown) whilst the other half 9 of the screw is formed on an outer cylindrical ring 10. The rings 7,10 are butt-welded onto the ends of the pipes 1,2. The ring 10 is radiused, by means of an intermediate frusto- conical ring 11, to a further cylindrical ring 12 provided on its inner surface with the thread 9. <IMAGE>

Description

SPECIFICATION Improved joint for the connection of the ends of two concentric pipes The present invention relates to a new joint which allows an efficient and rapid connection of the ends of two concentric pipes to be performed even, and above all, if they have a small diameter. It is hence particularly useful in the construction of heat-insulated double-pipe pipelines having an inner diameter of 10 inches or less.

In particular, the present invention is substantially an improvement of British patent application No. 85.10636 filed on April 26, 1985.

In the above said patent application, the construction is disclosed of heat-insulated pipelines, which are obtained by butt-welding to each other prefabricated double-pipe lengths, denominated "bars", each of them consisting of two concentric pipes collected with each other at their ends by cylindrical joints having a longitudinal generatrix section which is substantially shaped as a horizontal "Y' '-shaped fork, wherein an outer ring to be welded, in correspondence of an end thereof, to the larger-diameter pipe of the bar, is radiused, in correspondence of its other end, through an intermediate cone-frustum-shaped ring, to an underlying inner cylindrical ring to be welded onto the corresponding end of the inner pipe of the same bar.

Such a solution allowed not only the on-thespot welding times of the different bars to be contained within the same limits as necessary for the conventional pipelines, but it also allowed pipelines free from discontinuities and perfectly fulfilling the requirements of a higher degree of heat insulation to be constructed. In fact, the special "Y' '-shape of the joint creates, between the two adjacent bars which are butt-welded to each other, a chamber po- sitioned outside the pipeline and hence easily accessible for applying to it, after the welding of the same bars, a packing of heat-insulating material, that allows a perfect and continuous heat insulation to be achieved throughout the pipeline.

But, in as much as such a process provides the butt-welding of the ends of the outer ring and of the inner ring of the "Y"-shaped joint respectively to the larger-diameter pipe and to the inner pipe of the bar, it is clear that it can only be applied if carrying out the said inner welding is possible and hence only if the diameter of the inner pipe has such a value as to allow the coupling and welding equipment to be introduced into it.

It derives from the above that, in case of heat-insulated pipelines constituted by two concentric, small-diameter pipes, the inner pipe of which has a diameter of 10 inches or less, said "Y"-shaped joint cannot be used, in that the welding of the small inner pipe of the pipeline to the inner ring of the "Y"-shaped joint becomes complex and extremely burdensome, if not even impossible, and hence all of the advantages deriving from the application of such a joint are lost.

Purpose of the present invention is precisely to obviate the above-said drawback, and hence to supply an improved cylindrical joint, always having a longitudinal generatrix section which is substantially shaped as a horizontal "Y"-shaped fork, which allows a simple and fast connection of the ends of the two concentric pipes of a heat-insulated pipeline, even, and above all, if it has a small inner diameter.

Such a purpose is substantially achieved by adopting a joint made of two pieces to be coupled with each other by screwing.

More specifically, the cylindrical joint for connecting the ends of two concentric pipes, having a longitudinal generatrix section which is substantially shaped as a horizontal "Y"shaped fork, is characterized according to the present invention in that it is constituted by two distinct parts to be coupled with each other by screwing, one part of which is constituted by a first inner cylindrical ring to be butt-welded onto the end of the inner pipe of.

said concentric pipes, said first inner pipe being provided on its outer surface with a threading suitable to cooperate with a mating threading provided on the inner surface of a second cylindrical ring of said second part of the joint, which second ring is radiused, through an intermediate cone-frustum-shaped ring, to a third outer cylindrical ring of said second part of the joint, which must be buttwelded onto the corresponding end of the outer pipe of said two concentric pipes.

In such a way, in fact, after the said first parts of two connecti#on joints being buttwelded onto the ends of the inner pipe of the two concentric pipes, and after said pipes being coaxially slid inside each other and after to the first parts of the joints the other parts of the same joints being screwed, the outer rings of these latter parts can be easily butt-welded onto the corresponding ends of the outer pipe of the two concentric pipes.

On the other hand, this screwing system yields the further advantage that the pipes can be pre-tensioned, during their assembling step, by a simple further screwing, in as much as the threadings on the two ends of the pipes are provided opposite to each other, so that decreasing the stresses during the operation is possible.

Then, according to a variant of the invention, said part of the joint which is constituted by a first inner cylindrical ring to be buttwelded onto the end of the inner pipe of said two concentric pipes, said first inner ring being provided on its outer surface with a threading, is abolished, and its functions are performed by the end portion of the same inner pipe, which on its outer surface is provided, to that purpose, with the threading for being coupled with the second joint part.

The invention is now better explained by referring to the hereto attached drawings, which illustrate a preferred form of practical embodiment, supplied to purely exemplifying but not limitative purposes, in that technical or structural variants can be always supplied at any time, without leaving the scope of the present invention.

In the drawings: Figure 1 shows a partial longitudinal sectional view of a pipeline contructed with bars adopting the joint according to the invention; Figure 2 shows an enlarged-scale cutaway of a partial perspective view of the pipeline, made according to A-A path of Fig. 2; Figure 3 shows a partial longitudinal sectional view of the joint of Fig. 2; Figure 4 shows a cutaway of a partial perspective view of the pipeline constructed by using a variant of the joint, it too according to the invention; Figure 5 shows a partial longitudinal sectional view of the joint of Fig. 4.

Referring to the Figures, with 1, the prefabricated pipe lengths or bars are respectively indicated, which must be butt-fastened to each other, by the weld 13, for constructing a heat-insulated pipeline, and of which in Fig. 1 only three lengths, respectively 11, 12 and 13, are visible.

Each length or bar 1, is constituted by two concentric pipes 2, and 31, the inner one 2 of which is of the diameter provided for the pipeline to be constructed. Said concentric pipes 2, and 3 are then connected with each other at their ends by two identical cylindrical joints 4j, which are butt-fastened onto said pipes by means of the welds 5j and 6i.

Said special joints 4, have, according to the invention, a longitudinal generatrix section which is substantially shaped as a horizontal "Y"-shaped fork, and consist of two distinct pieces (see specifically Figs. 2 and 3) which can be coupled with each other by screwing, of which one piece of the joint is constituted by an inner cylindrical ring 7, to be butt-fastened, by said weld 5j, onto the end of the inner pipe 2, of the bars 1,.

Said ring 7, is provided on its outer surface with a threading 8, (see specifically Fig. 3), suitable to cooperate with a mating threading 9, provided on the other piece constituting the joint 4,.

This second piece of the joint 4, is then constituted by an outer cylindrical ring 10j to be butt-fastened, by means of said weld 6j, onto the end of the outer pipe 3 of the.bars 1,, which ring is radiused, in correspondence of its other end, by means of a cone-frustumshaped ring lli, to a further cylindrical ring 12,, on the inner surface of which the said threading 9j is provided.

According to a variant of the invention, joints 4 (see specifically Figs. 4 and 5) are instead adopted, which are different from the above-disclosed joint 4 substantially only in that the inner threaded cylindrical ring 7 is eliminated, and its functions are performed by the same inner pipe 2, of the bar, which is provided, to that purpose, on the outer surface of its end portion, with said coupling threading 8i.

Claims

1. Cylindrical joint for connecting the ends of two concentric pipes, which has a longitudinal generatrix section substantially shaped as a horizontal "Y"-shaped fork, characterized according to the present invention in that it is constituted by two distinct parts to be coupled with each other by screwing, one part of which is constituted by a first inner cylindrical ring to be butt-welded onto the end of the inner pipe of said two concentric pipes, said first inner pipe being provided on its outer surface with a threading suitable to cooperate with a mating threading provided on the inner surface of a second cylindrical ring of said second part of the joint, which second ring is radiused, through an intermediate cone-frustum-shaped ring, to a third outer cylindrical ring of said second part of the joint, which must be butt-welded onto the corresponding end of the outer pipe of said two concentric pipes.

2. Cylindrical joint according to claim 1, characterized in that it is constituted by only said second part, the threading of which cooperates with a mating threading provided on the same outer surface of the end of said inner pipe of said two concentric pipes.

3. Improved joint for connecting the ends of two concentric pipes, particularly useful in the construction of heat-insulated pipelines of small diameter, as substantially herein disclosed and illustrated.