CA1294996C

CA1294996C - Universal expansion joint

Info

Publication number: CA1294996C
Application number: CA000523237A
Authority: CA
Inventors: Stanislaw Lukasiewicz
Original assignee: Individual
Current assignee: Individual
Priority date: 1986-11-18
Filing date: 1986-11-18
Publication date: 1992-01-28
Anticipated expiration: 2009-01-28

Abstract

ABSTRACT OF THE DISCLOSURE
The conventional expansion joint for use in pipelines and other structures includes a bellows sandwiched between two end plates which are used to mount the joint in the pipeline, and rings of T-shaped cross-sectional configuration. Such expansion joints are relatively limited in terms of the pressure and temperature under which they can operate. A simple expansion joint for use under high operating temperatures and pressures includes flexible bellows extending between end plates, with tie rods connecting the end plates exterior to the bellows for limiting the spacing between the end plates. The bellows are defined by a flexible shell in the shape of a cylinder with annular corrugations defined by a plurality of annular projections alternating with annular troughs, and rings in the troughs.
The projections are sufficiently high, the troughs sufficiently deep and the bellows sufficiently flexible that virtually the entire exterior surface of each projection contacts the entire exterior surface of the adjacent projection and the sides of the projections surround the cable when the joint is under maximum pressure.

Description

~f~9~396 This invention relates to an expansion joint, and in particular to an expansion joint for interconnecting pipes of other structures.
Expansion join-~s are used to compensate for thermal expansion of pipelines or other structures subjected to high pressures and temperatures. The joints are used in power plants, chemical and petrochemical plants, pipelines, etc. The joints are more effective than other simple compensation devices such as pipe loops. ~xpansion joints require less space and have pressure drops which are only a fraction of the pressure drops across pipe loops. Moreover, expansion join-ts result in relatively small heat loss, and require lower insulation costs than other devices.
There are presently available different types of expansion joints. Examples of such joints are described in Canadian Patent No. 633,790, which issued to J.D. Minges on January 2, 1962; 633,791, which issued to W.H. Reid on January 2, 1962;
650,450, which issued to H.R. ~hodes on October 16, 1962; 969,576, which issued to Peter C. Wright et al on June 17, 1975 and 1,157,~96 which issued to C. Vinciguerra et al on November 29, 1983.
Another type of expansion joint, and perhaps the most common includes a corrugated cylinder or bellows reinforced by equalizing rings of T-shaped cross section for supporting the corrugations.
Such joints operate at pressures up to 300 psi and allow for longitudina~ travel of up to 0.75 inch per corruyation. A problem common to existing expansion joints is the limitations of pressure and temperatur~ under which such joints can operate.
The object of the present invention is to overcome the above-identified problem by providing a relatively simple expansion S joint, which can be used at high operating temperatures and pressures .
Accordingly, the present invention relates to an expansion joint comprising spaced apart end plate means for mounting the expansion joint in a pipeline or other structure; flexible bellows means extending between said end plate, said bellows means including flexible shell means in the shape of a cylinder with annular corrugations defined by a plurality of annular projections alternating with annular troughs; and ring means in each said trough, whereby when the joint is placed under pressure, the sides of adjacent projections contact each other over a substantial portion of their surfaces.
The invention will now be described in greater detail with reference to the accompanying drawings, which illustrate a preferred embodiment of the invention, and wherein:
Figure 1 is a partly sectioned side elevation view of an expansion joint in accordance with the present invention;
Figure 2 is an end view of one-half of the expansion joint of Fig. l;
Figures 3 to 5 are schematic cross-sectional views of a portion of a bellows used in the expansion joints of Figs. 1 and 2;

~2~96 Figure 6 is a partly sectioned, side elevation view of an expansion joint in accordance with the present invention;
Figure 7 is a partly sectioned, end view of the joint of Fig. 6;
Figures 8 to 10 are schematic cross-sectional views of a portion of a bellows used in the joints of Figs. 6 and 7;
Figure 11 is a cross-sectional view of a ring used in the expansion joint of Figs. 6 to 10; and Figure 12 is a cross-sectional view of an alternative form of ring for use in the joint of Figs. 6 to 10.
With reference to Fig. 1, the preferred embodiment of the expansion joint includes flexible metal bellows 1 sandwiched between a pair of end structures defined by end plates 2, and annular plates 3 of I,-shaped cross section welded to the inner periphery of the pIates 2. Gussets 4 extend between the plates 2 and the plates 3 for reinforcing the structure. The plates 3 are used for mounting the joint in a pipeline (not shown) or other structure. The outer peripheries of the plates 2 are interconnected by longitudinal~y extending tie rods 6, the ends oE which are threaded for receiving nuts 7. The rods 6 and the nuts 7 limit the travelling distance of the expansion joint. The rods 6 also provide protection for the bellows 1 during transporting and installation of the joint. A generally cylindrical outer cover 9 is connected to the inner surface of one plate 3 and extends over the bellows 1 into overlapping relationship with ~ Z~ 6 the other plate 3. An inner cover 10 extends from the outer surface of one plate 3 into overlapping relationship with the other plate 3 to protect the interior of the bellows 1.
The bellows 1 i9 defined by a flexible metal, cylindrical shell folded to define a plurality of corrugations, including alternating outwardly ex-tending, annular corrugations or pro-jections 12 and annular, deep troughs 13. The projections 12 and the troughs 13 are generally U-shaped in cross section. A ring 15 defined by a cable is provided at the bottom of each trough 13.
More specifically each projection 12 is defined by a pair of annular sides 16 and an integral semicircular outer end 17.
The troughs 13 are defined by the adjacent side walls 16 o~
adjacent projections 12, and an inner end 18 integral with such side walls 16 and extending partially around the ring 15.
In the following description of Figs. 6 to 12 of the drawings, whenever possible, the same reference numerals have been used to identify elements which are similar or identical to elements of Figs. 1 to 5.
With reference to Figs. 6 and 7, a second embodiment of the expansion joint includes the flexible bellows 1 sandwiched between annular rings or end plates 2. The L-shaped plates 3 are replaced by sleeves or pipe sections 20, which are welded to the end plates 2. Gussets 4 extend between the plates 2 and the pipe sections 20 for reinforcing the struc~ure. The pipe sections 20 are used ror mounting the joint in a pipeline ~ 2~L~

(not shown) or other structure. The joint also includes the tierods 6 and nuts 7 of the embodiment of the invention of Figs. 1 and 2. A cover 22 on the second embodiment of the invention includes a c~lindrical centre portion and inwardly inclined ends 23. One end of an inner cover 25 is ~elded to one of the pipe sections 20. The inner cover 25 is defined by a short sleeve, which is welded to a pipeline during mounting of the expansion joint.
With reference to Figs. ~ to 11, the bellows 1 of 10- the second embodiment of the invention is similar to the bellows 1 of Figs. 3 to 5. The ring 15 of the first embodiment of the invention is replaced by a ring 26 of drop-shaped cross section.
As shown in Figs. 11 and 12, the rings 26 can either be formed of homogeneous, high strength steel, or alternatively produced using a prestressed steel cable 28 covered with a plastic coating 29, which defines the drop-shape.
During installation, the expansion joint must be stretched tFigs. 3 and 8) in the cold state to an extension equal to the maximum expected compression of the bellows 1 (Figs. 5 and 9) minus the spacing or distance bet~een the corrugations.
If S is the magnitude of the expected total compression a number of required corrugations, n, is calculated from the formula n = d where d denotes the design displacement covered by one corrugation and equal to "1". The initial total stretching o~ the expansion joint (from the neutral position), tFig~ 4), SO' is defined by SO = n(d - e) = S (1 ~ d) ~ 0.625S, where e is the width of the trough (e ~
During operation under high pressures, the thin walls 16 of adjacent projections 12 of the bellows 1 contact each other over a large surface area. This diminishes the maximal bending stress, i.e. spreads such stress over a large area. When the joint reaches its highest operating temperature, the adjacent side walls 16 contact each other over virtually their entire ~rea, and surround the rings 15 or 26 to spread the effects of the pressure over the maximum area. Because high bending stresses due to high pressure are significantly eliminated using the structure described above, the problem of material creep is reduced.
In conventional expansion joints, high bending stresses are the main reason for limitations of working conditions under high pressures.
The configuration of the expansion joint described hereinbefore permits the use of the joint at relatively high operating temperatures and pressures. The performance character-istics of the joint translate into a reduction in size and costof the jointj while ensuring safe operation. Because of the geometry of the currugations or bellows, the expansion joint can compensate for relatively large axial and lateral displacements.
The bellows is normally constructed of multi-layered, thin, elastic corrosion resistant material such as stainless steel, alloys or other non-metallic materials.

Claims

1. An expansion joint comprising spaced apart end plate means for mounting the expansion joint in a pipeline or other structure; flexible bellows means extending between said end plate means, said bellows means including flexible shell means in the shape of a cylinder with annular corrugations defined by a plurality of annular projections alternating with annular troughs;
and ring means in each said trough, whereby when the joint is placed under pressure, the sides of adjacent projections contact each other over a substantial portion of their surfaces.

2. An expansion joint according to claim 1, wherein said projections are sufficiently high, the troughs sufficiently deep and the bellows means sufficiently flexible that virtually the entire exterior surface of each projection contacts the entire exterior surface of the adjacent projection, and said sides surround said ring means when the joint is subjected to high pressure.

3. An expansion joint according to claim 1 or 2 including tie rod means extending between said end plate means exterior to said bellows means for limiting the spacing between said end plate means.

4. An expansion joint according to claim 1 or 2, wherein said ring means is circular in cross section.

5. An expansion joint according to claim 1 or 2 wherein said ring means is drop-shaped in cross section.