PUSH-TOGETHER PIPE ASSEMBLY

Description

Technical Field

This invention relates in general to methods and apparatus for joining pipe ends and in particular to a push-together assembly method for joining pipe ends.

Background Art

There are a number of applications for joining pipe ends in which it would be desirable to join the ends without the necessity of rotating the respective pipes themselves. One example would be in the oil industry, and particularly in the area of offshore production. On a drilling rig, rotation of one pipe end relative to the other is typically accomplished either by use of a hydraulic power tong which requires a specialized crew to operate, or a more basic "rope technique" consisting of pulling on a soft rope from the drilling rig main winch capstan. Final make-up torque is achieved by using a mechanical tong. The maximum amount of rotation achieved in one stroke of such a mechanical tong/cathead chain assembly is approximately one-quarter to one-third of a turn without the necessity of having to reset the assembly by manual reverse rotation. Production pipelines, on the other hand, have often been welded together in the past.

A suitable push-together connection which did not require rotation of the respective pipe ends being joined would have advantages in off shore applications, for example, by providing the ability of being able to make-up and disconnect underwater connections remotely. Also, a push-together connection of this type would be simple to implement and would eliminate costly welding operations which have become almost prohibitive in some situations due to the high hourly cost of offshore operations.

There are other applications where, for example in construction, oil and gas and mining, where a slight rotation of one or both of the pipes being joined may be acceptable. Such a connection system could have application for drive pipe, riser pipe, conduit and casing liners for oil and gas operations, for example.

One way that the oil industry has attempted to address the problem of creating a secure pipe connection, particularly in joining offshore casing and tubing, was by introducing a

specialized generation of thread connectors using modified A.P.I, threads. These threaded connectors are still widely used today, for example, for dimensions below twenty-four inches, despite the general requirement of a minimum of two and one-half turns of rotation for make-up.

A threadless connector for large diameter casings has also been used in the past which was based upon a snap-ring linkage type mechanism. These "snap-ring" type connectors offer fast make-up but offer neither the low weight-to-capacity ratio, nor the integrity or price competitiveness of the threaded connector for a given capacity.

Another type connector featuring radial dogs was introduced to replace flange connections, in a mechanical configuration for drilling riser connections, and in a hydraulic configuration for wellhead connections. Recently, the use of dog type connectors has been extended to offshore platform anchoring pile connections, but its success has been limited by its high cost, due to the large number of parts and the relatively heavy section required in the design and manufacture of such a connector.

Another technique which has been proposed for joining pipe ends, where the pipes themselves cannot be rotated, is the use of the so-called "adhesion joint." This method injects, for example, an acrylic adhesive into the clearance of the joint interval, after which a post-line tube is inserted. It is possible to carry out the construction in a shorter time than the welding method, but the adhesive may not be applied uniformly, resulting in compromised connections. The adhesives may be messy to apply and may not furnish the required strength for some connection applications.

U. S. Patent No.4,487,433, issued December 11 , 1984, to Miller, shows an anti-rotation coupling wherein similarly pitched and profiled, but oppositely threaded ends, are provided for two couplings incorporating an anti-rotation member such as a tongue and groove or a hole and dowel pin. The patent seems to be primarily concerned with keeping the pipes anti-rotational once the connection is assembled, however.

U.S. Patent No. 4,846,508, issued July 11, 1989, to Pallini, Jr. Et al., shows a tubular connector system for joining two pipe ends without the necessity of rotating the pipe

ends. One pipe end is provided with an external thread and a second pipe end includes multiple thread lead entries. A special tubular connector is also provided which includes an internal thread at one end and internal multiple thread lead entries at the other end. The tubular connector is first threaded onto the first pipe. Next, the second pipe is stabbed into the second end of the tubular connector and the tubular connector is then rotated less than a single turn with respect to the second pipe to fully mate the tubular connector and the second pipe. It appears that the connector is screwed all the way in on a first pipe end and is then "backed-off" a slight amount as the second pipe end is screwed in (rotated less than a single turn).

A need exists, therefore, for an improved method and apparatus for joining tubular pipe ends, which method does not require the rotation of one pipe section relative to another, or which requires only slight rotation of one of the pipes.

Disclosure of Invention

The push-together pipe assembly of the invention allows two pipe sections to be joined with only a partial rotation of one of the sections. The pipe assembly includes a first pipe having a first tapered end with an inner extent and an outer extent. The tapered end slopes inwardly from the inner extent to the outer extent thereof to thereby form a respective mouth opening of the first pipe. The first pipe tapered end has a specially contoured engagement surface, the engagement surface being comprised of a plurality of helical spline wedges, each of which is oppositely tapered from an inner extent to an outer extent thereof in width, whereby the helical spline wedges form an alternating series of lands and grooves as viewed from the respective mouth openings.

The second pipe to be connected also has a specially contoured engagement surface on an outer extent thereof, the second pipe engagement surface being sized to be matingly engaged with the first pipe engagement surface, whereby the respective pipe ends may be joined by axial movement of one pipe relative to another. The axial movement of one pipe relative to another causes a slight rotation of one pipe relative to another. Preferably, the rotation of one pipe relative to another is less than one complete turn.

In one version of the invention, the specially contoured surfaces on the first pipe end are on the exterior of the first pipe end, and wherein the second pipe end is a box end. In another version of the invention, the specially contoured surfaces on the first pipe end are on the interior of the first pipe end, and wherein the second pipe end is a pin end. In both versions of the invention, the helical spline wedges are arranged on the specially contoured surface of the pipe along a dominant axis, the dominant axis being longitudinal rather than helical.

In the method of joining two pipe ends of the invention, the first and second pipes are provided with the specially contoured engagement surfaces, as previously described.

The first pipe end is brought into engagement with the second pipe end. A selected one of the first and second pipes is then pushed axially with respect to the other respective pipe, thereby securing the pipe ends together. An assembly force is thus applied to a selected one of the pipes in order to form a connection between the two pipes, and wherein the assembly force causes one of the pipes to rotate less than 360° before the pipes are fully connected.

In one aspect of the invention, the pipes being joined are tubular goods of the type used in construction, oil and gas and mining. The tubular goods can be used to join drive pipe, riser pipe, conduit and casing liners for oil and gas production.

Additional objects, features and advantages will be apparent in the written description which follows.

Brief Description of Drawings

Figure 1 is a perspective view of a coupling used in one version of the tubular connector system of the invention.

Figure 2 is a partly schematic view of the coupling of Figure 1 being used to join two opposing box pipe ends, the pipe ends being shown in partly transparent fashion for ease of illustration.

Figure 3 is an exploded view of another version of the coupling of the invention in which the coupling has the specially contoured surfaces on the interior of the tapered ends thereof for mating with specially contoured exterior surfaces on the pin ends of the two pipes to be joined.

Figure 4 is a simplified schematic illustration of a thread on a tubular body illustrating the definition of a thread versus a spline.

Figure 5 is a view of another versions of the pipe connection system of the invention in which a flush push joint is utilized.

Best Mode for Carrying Out the Invention

Turning to Figure 1 , there is shown one version of a push together coupling of the invention, designated generally as 11. The coupling is used to join two sections of pipe such as the sections represented by the opposing box pipe ends 13, 15 in Figure 2. As shown in Figure 1 , the coupling body has a first tapered end 17 and a second tapered end 19 which are joined together a respective inner extent 21 thereof. Each of the tapered ends 17, 19 slopes inwardly from the inner extent 21 to an outer extent 23, 25 thereof to thereby form a respective mouth opening of the body, such as mouth opening

27.

In the version of the invention illustrated in Figures 1 and 2, each of the first and second tapered end 17, 19 has a specially contoured exterior surface. The exterior surface is made up of a plurality of of "helical spline wedges" such as wedges 29, 31 , 33 illustrated in Figure 1. These specially designed "wedges" are partly in the form of a thread and partly in the form of a spline. Each of the wedges is oppositely tapered from an inner extent 35 to an outer extent 37 thereof, whereby the helical spline wedges form an alternating series of lands 39 and grooves 41 on the exterior surface of the body as viewed from the respective mouth openings 27.

The specially contoured exterior surfaces of the coupling 11 resemble a "spline" in that they form alternating lands and grooves 39, 41. They also resemble a spline in that the

respective wedges 29, 31, 33 are arranged on the exterior surface of the coupling 11 along a dominant axis 43, the dominant axis being longitudinal or axial rather than helical, as in the case of a typical thread. Conversely, however, even though the wedges are aligned predominately along a longitudinal axis 43, as will be explained in greater detail, there is a radial component of movement during makeup of the pipe connection.

As shown in Figure 2, the first and second tapered ends 17, 19 of the coupling 11 are sized or shaped appropriately to be received on mating internal surfaces 45, 47 provided on the respective box ends of the two pipe sections 13, 15 to be joined. As will be appreciated with respect to Figure 2, an assembly force must be applied to the coupling 11 in order to form a connection between the two pipe sections 13, 15. The assembly force causes the coupling 11 to rotate less than 360° before the ends 13, 15 are fully connected. Preferably, the assembly force causes the coupling to rotate less than 90°, and most preferably less than about 45° before the pipe ends are fully connected.

Figure 4 is a simplified representation which further illustrates the combined spline/thread nature of the helical spline wedges of the invention. As has been discussed, the wedge surfaces are acted upon by an assembly force causing the coupling to move primarily along a longitudinal or axial path of travel. With a typical thread form of pipe connection, the dominate axis is normally helical. There are also not as many turns per inch with the special helical spline wedges of the invention as compared to a normal thread form. Figure 4 is intended to be a simplified representation of a thread form of a tubular connection. Thus, with respect to Figure 4, the angle α is approximately 45°. For an angle generally less than almost 45°, more of a push connection is achieved. Where the angle α is greater than about 45°, more of a torque force connection results. In the case of α is equal to 0°, a pure spline connection results.

In order to makeup the connection, a selected coupling end 19 is first inserted approximately halfway into the mating pipe end 15. The coupling is generally free stabbing until about the halfway point, at which resistance is encountered from the wedge lands and grooves making contact. In the preferred design, the lands and grooves contact first before the respective 49, 51 make contact. The second pipe end 13 is then pushed in the direction of the first pipe end as with a hydraulic tool. For the ten start

coupling illustrated in Figure 1 , the coupling rotates approximately 36° radially during makeup before the pipe outer extents 53, 55 make contact. Contact between the pipe ends 53, 55 and engagement with the coupling 11 is achieved without any rotation or torque of the respective pipe ends 13, 15.

Figure 3 shows another version of the connection system of the invention in which the specially contoured surfaces on the coupling 12 and opposing pipe ends 14, 16 are essentially reversed. That is, the helical spline wedge surfaces 18, 20 on the coupling 12 are one the interior of the first and second tapered ends. Similarly, the respective opposing pipe ends to be joined 14, 16 are "pin" ends having specially contoured exterior helical spline wedge surfaces 22, 24. The makeup of the connection is in other respects identical to that previously described.

Figure 5 illustrates another version of a push-together pipe assembly of the invention which is used for joining two pipe sections with only a partial rotation of one of the sections. The pipe assembly shown in Figure 5 is made up of a first pipe 57 having a first tapered end 59 with an inner extent 61 and an outer extent (shown in phantom lines as 63). The tapered end 59 slopes inwardly from the inner extent 61 to the outer extent 63 thereof to thereby form a respective mouth opening of the first pipe. As has been described with respect to Figures 1-2, the first pipe tapered end 59 has a specially contoured engagement surface, the engagement surface being comprised of a plurality of helical spline wedges, each of which is oppositely tapered from an inner extent to an outer extent thereof in width, whereby the helical spline wedges form an alternating series of lands and grooves as viewed from the respective mouth openings.

The push-together pipe assembly of Figure 5 also includes a second pipe 65 having a specially contoured engagement surface on an outer extent thereof, the second pipe engagement surface being sized to be matingly engaged with the first pipe engagement surface, whereby the respective pipe ends may be joined by axial movement of one pipe relative to another. In the version of the invention shown in Figure 5, the second pipe 65 has a "box" end with the specially contoured surfaces being on the interior of the pipe end adjacent the mouth opening. The specially contoured surfaces on the first pipe end are on the exterior thereof so that it constitutes a "pin" end. The axial movement of one

pipe 57 relative to the other 65 causes a slight rotation of one pipe relative to another. The rotation will be relatively slight, amounting to less than 360°, or one complete turn. It will be understood, as has been explained with reference to Figures 1 and 3, that the . positions of the specially contoured surfaces on the pipe ends could be reversed, i.e., so that the first pipe 57 is a box end and the second pipe 65 is a pin end. As has been described with respect to the earlier versions of the invention, the helical spline wedges are arranged on the specially contoured surface of the selected pipe end along a dominant axis, the dominant axis being longitudinal rather than helical.

An invention has been provided with several advantages. The push-together connection of the invention allows two pipe sections to be joined with only a slight rotation of one pipe relative to the other. This can be particularly advantageous in applications such as construction, oil and gas and mining, where a slight rotation of one or both pipes being joined may be acceptable. Such a connection system can be used advantageously for drive pipe, riser pipe, conduit and casing liners for oil and gas production, for example. The connection system is relatively simple in design and economical to manufacture. Previous connections systems requiring welding of the pipe ends required on the order of five hours per connection where as the connection system of the invention can be made up in about five minutes or less. The multiple wedge segments forming the specially contoured surfaces of the coupling assist in holding the opposing pipe ends together to keep them from inadvertently separating. That is, multiple wedge surfaces are present at the connection unlike a regular threaded connection in which the thread runs out at the outer extent of the pipe ends. The additional contact area provides a more secure connection overall.

While the invention has been shown in several of its forms, it is not thus limited but is susceptible to various changes and modifications without departing from the spirit thereof.