PUSH TOGETHER TUBULAR CONNECTION SYSTEM

Description

Technical Field

This invention relates in general to methods and apparatus for joining pipe ends and in particular to methods and apparatus for joining pipe ends without the necessity of rotating the pipe.

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 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 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.

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.

In addition to the oil industry, numerous other applications exist for joining tubular pipe ends. For example, tubular pipe connections are used in a variety of civil engineering applications, including their utilization in providing structural support in the construction field. One such use of tubular pipes can be found in the building of underground tunnels. More specifically, tubular pipes provide support to large underground tunnels that are typically used as roadways or other transportation means. The large scale construction of underground tunnels for transportation applications is presently underway in Europe, Japan and elsewhere.

In a typical procedure to construct an underground tunnel, a large pipe, or possibly several large pipes, is laid by a boring machine and forms the main tunnel. Next, a boring machine proceeds to lay relatively smaller curved pipes surrounding the main tunnel to provide additional structural support These small curved pipes are commonly constructed as 10 foot sections having, for example, a 32 inch outer diameter. It is then necessary to connect these individual sections to provide a single, lengthier curved pipe adjacent to the underground structure. The process is repeated, placing these connected pipe sections parallel to one another for the duration of the desired length along the main tunnel, creating in effect a "whalebone" configuration surrounding the main tunnel. The voids in and around the pipes will be subsequently filled with concrete. In an application such as an underground roadway that reaches upwards to 12 miles, somewhere on the order of 80,000 connections would be needed to couple the individual

pipe sections together to provide enough support to adequately enlarge the surrounding area of the main pipe.

Various techniques have been provided at the present time for connecting these individual curved tunnel pipe sections where the pipe sections themselves cannot be rotated. As with the offshore oil industry, one technique presently used in many situations, is to join two or more of these pipe sections together by welding, either by hand welding or semi-automatic welding processes. Welding is a time consuming activity, at best. Also, there is the possibility of defects in the welds and poor workability of the resulting materials due to heating of the metal. In low temperatures, countermeasures such as the preheating are necessary. In general, a welding process can take somewhere from 2 to 5 hours to weld one connection for a tunnel pipe section, depending on the size or complexity of the connection. With this in mind, time constraints virtually eliminate the practicality of welding each coupling in large projects consisting of thousands of pipe sections of the type under consideration.

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. _r 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

multiplθ 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). Even this slight amount of rotation would not be acceptable in many of the applications discussed above, however.

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.

Disclosure of Invention The present invention effectively provides an apparatus and method to connect tubular pipe sections without the necessity of rotating the pipe sections themselves, which thereby overcomes various of the problems discussed with respect to the prior art, as will become apparent to those skilled in the art from the detailed description which follows.

The connector system of the invention includes a push-together coupling for joining two pipe sections without the necessity of rotating the pipe sections. The coupling includes a coupling body having a first tapered end and a second tapered end joined together at a respective inner extent thereof, each of the tapered ends sloping inwardly from the inner extent to an outer extent thereof to thereby form a respective mouth opening of the body.

In one version of the connector system of the invention, each of the first and second tapered ends of the coupling body has a specially contoured exterior surface, the exterior surface being comprised of a plurality of helical spline wedges. Each of the helical spline wedges is oppositely tapered in width from an inner extent to an outer extent thereof, whereby the helical spline wedges form an alternating series of lands and grooves on the exterior surface of the body as viewed from the respective mouth openings. The first and second tapered ends of the coupling body are sized to be received on mating surfaces

provided on respective ends of the two pipe sections to be joined to engage the respective pipe ends by axial movement of one pipe relative to another.

The helical spline wedges are arranged on the exterior surface of the coupling along a dominant axis, the dominant axis being longitudinal or axial rather than helical. An assembly force is applied to the coupling and respective pipe ends. The assembly force causes the coupling to rotate less than 360° before the pipes are fully connected. The pipes which are being joined together may be arranged to form a relatively straight line when assembled, as in a typical oil and gas pipeline or offshore pipeline or riser. Alternatively, the pipe sections may be arranged along a curved axis when assembled, as in the case of an underground tunnel support structure. The exterior surfaces of the coupling may also be specially treated, as by roughening, so that the connection assembles with a required degree of force, but resists disassembly due to the action of the specially treated surfaces engaging mating surfaces of the connection.

In another version of the connector system of the invention, the specially contoured surfaces on the coupling and on the respective ends of the two pipe sections to be joined are essentially reversed. That is, the coupling has the specially contoured surfaces on the interior surfaces of the first and second tapered ends. Likewise, the pipe ends to be joined are "pin" ends having mating specially contoured exterior surfaces.

The push-together coupling previously described can be used as a part of a tubular connector system for joining two pipe ends where a first pipe end is provided having a box end or pin end as described and a second pipe end is provided similarly having a box end or pin end as described. The first and second tapered ends of the coupling are shaped to mate with the specially machined surfaces provided on the opposing pipe ends, respectively, to engage the respective pipe ends by axial movement of one pipe relative to another.

In the method of assembling a pipe connection of the invention, a first and second pipe ends to be joined are provided as previously described. The first end of the coupling is threadedly engaged with the first pipe end until the coupling is supported on the first pipe end. The pipe end of the second pipe is then engaged with the second end of the

coupling and the second pipe is pushed axially with respect to the coupling and the first pipe, whereby the coupling rotates relative to the respective pipe ends and secures the pipe ends together.

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 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 simplified view of an underground transportation tunnel using a whalebone superstructure for reinforcement, the superstructure being comprised of tubular pipe segments joined end to end in an semi-arcuate arrangement.

Best Mode for Carrying Out the Invention

Turning to Figure 1 , there is shown 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.

!n 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 axiaJ 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 is a simplified illustration of a tunnel system including tunnel segments 57, 59 of poured concrete. The tunnel segment 59 has a supporting super structure comprised of a "whalebone" arrangement of tubular pipe segments 61, 63. In the example illustrated in Figure 5, each pipe segment 61 , 63 is approximately ten feet long and has an OD of approximately 32 inches. The pipe segments are joined end to end, as previously described, in order to make each "whalebone" section. The pipe interiors and

surrounding void is then typically filled with concrete. The improved push-together coupling of the invention can be used to quickly and efficiently assemble the tunnel segments described.

An invention has been provided with several advantages. The push-together connection of the invention allows two pipe sections to be joined without the necessity of rotating the pipe sections. This can be particularly advantageous in applications such as surface line pipe connections, undersea pipe systems and tunnel super structure supports. The coupling 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 only one of its forms, it is not thus limited but is susceptible to various changes and modifications without departing from the spirit thereof.