Patent Application
20090184515
This invention relates generally to flexible expansion joints and, more particularly, to a method and apparatus for limiting the axial extension and compression thereof.
Expansion joints are commonly installed in piping systems such as those used in the chemical processing industry, and in the air conditioning, heating, plumbing, refrigerating and ventilating fields. The purposes of such a joint are to provide flexibility for accommodating expansion and contraction due to pressure and temperature variations, and for damping vibrations to thereby reduce noise. In the absence of such an expansion joint in a piping or ducting system, the vibrations and the pressure and thermal changes can produce stress on the system at fixed points such as at vessels and rotating equipment, as well as in the piping or ductwork system itself.
Typically, an expansion joint includes a fluid conducting flexible body member secured between a pair of spaced flanges, with the combination then being interposed within a length of pipe or duct. The flexible body member may be in the form of a metal bellows, a Teflon bellows or an elastomeric spherical arch.
Recognizing that under certain conditions, the assembly can be expanded or contracted beyond the allowable limits of safe operation, provision has been made to axially restrain such motion. This has customarily been accomplished by a pair of limit rods that are axially mounted on opposite sides of the joint and connected at their opposite ends to the flanges or to gusset plates attached to and extending radially outwardly from the coupling flanges. Overextension was prevented by fasteners attached to the limit rods on the axially outer sides of the flanges. Compression of the unit was limited by fasteners located on the axially inner sides of the flanges or by way of a pipe sleeve disposed over each of the tie rods.
Because of the rigidity of the tie rods, and the relative inflexibility of the combination during installation within a system, some expansion joints are now being assembled without tie rods but with a flexible link, such as a cable, interconnecting the spaced flanges. One such arrangement is shown in U.S. Pat. No. 5,273,321. While such an arrangement provides for limited expansion of the joint, it does not prevent the joint from being compressed beyond the allowable limits. Further the need to secure the cables to the flanges complicates the process.
What is needed is an expansion joint that is flexible for installation purposes but which is limited in its axial movement in operational conditions of both expansion and contraction.
Briefly, in accordance with one aspect of the invention, a cable is secured between two gussets by simply extending the cable through one opening in each gusset and then back through another opening therein, with the ends being secured together by a single crimping device.
In accordance with another aspect of the invention, compression of the assembly is limited by a sleeve which is disposed over one strand of the cable, with the other strand being outside of the sleeve to facilitate the crimping process.
In the drawings as hereinafter described, a preferred embodiment is depicted; however, various other modifications and alternate constructions can be made thereto without departing from the true spirit and scope of the invention.
A typical fluid flow pumping and piping arrangement is shown in
In addition to the movement as caused by vibrations as discussed hereinabove, thermal and pressure differences will tend to cause the piping system to expand or contract. That is, as the temperature and/or pressure of the fluid being pumped through the system rises, the piping system will tend to expand, and as they are lowered, the piping system will contract. To accommodate that expansion and contraction, a pair of expansion joints 23 and 24 are installed within the piping system, on either side of the pump 11. The structure of the expansion joints 23 and 24 is set forth in more detail in
Fluidly interconnected between sections of pipe 12 is a fluid conducting flexible body member 26 with appropriate end fittings to match the adjoining pipe fittings. The particular member as shown is a so called bellows design which is formed as a thin walled tubing to form a corrugated cylinder with a plurality of convolutions as shown. Such a member is commonly made from metal (e.g. stainless steel) or Teflon, for example.
The present invention is also applicable to other types of expansion joints. For example, one type of flexible joint commonly used with plastic piping systems is not bellows shaped as shown but rather is formed of a molded spherical flowing arch that is made from an elastomeric material. Although different in structure, these expansion joints also require some type of structure to limit the expansion and contraction of the joint.
The flexible body member 26 is disposed between and connected to a pair of axially spaced flanges 27 and 28 with the interconnection between the flexible body member 26 and the flanges 28 being such that, as the body member 26 expands or contracts, the flanges 27 and 28 are accordingly caused to move toward or away from each other.
Disposed near the radially outer edges of the flanges 27 and 28 are a pair of radially, circumferentially spaced axially disposed tie rod pins 29 and 31 and their associated nuts 32 and 33. The tie rods pins 29 and 31 pass through holes formed in the respective flanges 27 and 28 and the respective nuts 32 and 33 are so positioned on the respective pins 29 and 31, such that clearance spaces 34 and 36 allow for some axial (i.e. outward) movement of the flange 28 but limit the extent to which this can occur. This distance can be selectively adjusted to meet the requirements of the particular expansion joint and application.
In order to limit the movement of the flanges 27 and 28 toward each other, and therefore limit the compression of the expansion joint, a pair of nuts, similar to the nuts 32 and 33, can be selectively placed on the inner sides of the respective flanges 27 and 28. Another approach is to place a pair of sleeves 37 and 38 over the respective tie rods pins 29 and 31 as shown, with the lengths of the sleeves 37 and 38 being generally shorter than the distance between the two flanges 27 and 28. In this way, the flanges 27 and 28 are free to move inwardly, toward each other, to thereby allow for contraction of the body member 26 but this movement is limited when the inner surfaces of the flanges 27 and 28 begin to impinge on the ends of the sleeves 37 and 38.
A variation of the
Use of tie rod pins 29 and 31 as discussed hereinabove is problematic in some situations. For example, since the tie rod pins are installed on the assembly at the factory and shipped to the site for installation, even though the pins 29 and 31 and their associated nuts 32 and 33 are not adjusted to their final position, the assembly is very rigid in nature and presents difficulties in the process of aligning the expansion joint and securing it in its installed position between two pipe sections. Further, there is often very little space in which to work such that final adjustments and the selective positioning of the nuts 32 and 33 can be difficult.
Referring now to
Near the radially outer end of the gusset 42 is a pair of spaced holes 47 and 48. Similarly, near the radially outer end of the gusset 43 is a pair of spaced holes 49 and 51. These holes are used for attachment purposes.
Rather than the use of tie rod pins, the gussets 42 and 43 are interconnected by a cable 52 having two strands 53 and 54. The first strand 53 passes into holes 48 and 51, wraps around the outer surfaces of the respective gussets 42 and 43, and then comes back through holes 47 and 49. The second strand 54 results from the two ends being fastened together by one or more fastening devices 56 such as a crimping device. The result is a double stranded cable which is easy to install either at the factory or on the installation site and which functions to limit the axial separation of the two flanges 39 and 41, and thus the expansion of the expansion joint.
As will be understood, the
While the present invention has been particularly shown and described with reference to preferred and modified embodiments as illustrated by the drawings, it will be understood by one skilled in the art that various changes in detail may be made thereto without departing from the spirit and scope of the invention as defined by the claims.
