Introduction

This invention relates to forming bends in steel pipelines .

Background of the Invention

The creation of bends in steel pipelines is

traditionally accomplished by the use of a separate bend installed into the pipeline. The bend is either procured as an off the shelf butt weld fitting, or a mitre cut bend fabricated into the steel pipe. Another option is an induction bend formed into the pipe by special equipment.

All bends of the type described above require predetermined angles to be known prior to the installation of the pipeline to ensure the correct alignment of the pipes is maintained. This means that in almost all cases bend angles need to be measured and therefore

predetermined prior to manufacture .

Although the ball and socket jointing of steel pipes does provide some flexibility to achieve a change in pipeline alignment the angle change is only minor, about 3°, and does little to substantially change the alignment of the pipes.

This invention is an attempt to solve the problem of predetermined bend angles therefore giving the installer the flexibility to create the angles required during the installation process.

It is these issues that have brought about the present invention. Summary of the Invention

According to one aspect of the present invention there is provided a method of forming a bend in a metal pipeline, the method comprising cutting the ends of two pipes at a predetermined angle, forming a ball in one cut end and a socket in the other cut end, joining the ends of the pipe to locate the ball within the socket, axially rotating one pipe relative to the other until the axes of the pipes are inclined to one another at a selected angle, and welding the ends of the pipes to one another.

According to a still further aspect of the present invention there is provided a pipe bend comprising two lengths of metal pipe, each length having a longitudinal axis, one end of each length being cut at an angle to the longitudinal axis, one length having a socket formed adjacent to the cut and the other length having a ball formed adjacent to the cut whereby, the ball of one length and the socket of another length can be fitted together and one length can be axially rotated relative to the other to define a bend in the pipe.

Preferably the cut angle is between 70° and 85° to the longitudinal axis.

Description of the Drawings

An embodiment of the present invention will now be described by way of example only with reference to the accompanying drawings in which:

Figure 1 is a side elevation of two pipes with ends cut to a specific angle (α) ,

Figure 2 is a side elevational view showing the cut pipe ends after being formed in a ball and socket press,

Figure 3 is a side elevational view showing the two ends in abutting contact with the longitudinal axes of the ends aligned, and

Figure 4 is a side elevational view showing the inclination of the respective pipe ends after one pipe has been axially rotated relative to the other.

Description of the Preferred Embodiment

A method of forming a bend in a steel pipeline is illustrated in Figures 1 to 4. Two pieces 11, 12 of cylindrical pipe are cut to specific lengths. As a first step (Figure 1), one end 13, 14 of each piece of pipe 11, 12 is cut at a specific angle X to the longitudinal axis of the pipe. The angle a is selected to give the required maximum bend when the two pipes are joined. To provide a maximum bend angle of 22.5° each pipe should ideally be cut at an angle a of 78.75°. However, it is understood that the angle a can preferably vary between 70 and 85° and even lower angles are possible. It is also envisaged that bend angles up to 30° are possible.

Once the ends of the pipes have been cut to the desired angles a suitable forming and pressing machine (not shown) is placed against the end 13 of the first pipe 11 to form a ball 15 in the end of the pipe and a pressing machine is placed against the end 14 of the other pipe 12 to form a socket 20, see Figure 2. This ball 15 and socket 20 technology is well known in the art and it is understood that the machines that form the balls and sockets are placed in a direct contact parallel to the cut end of the pipe and not perpendicular to the longitudinal axis of the pipe. Once the appropriate ball 15 and socket 20 ends are provided in each pipe 11, 12, the two pipes are placed in abutting contact with the ball 15 of one pipe 12 fitting within the socket 20 of the other pipe 12. The pipes are fitted together to ensure a uniform minimum entry or overlap of the formed ends. A calibrated angular scale

(not shown) is placed on the periphery of each cut end of the pipes. The scale is calibrated between 0° and 22.5°. The scales are positioned so that when 0° of pipe 11 is lined up with 0° of the other (12) the axes of the pipes are aligned, see Figure 3, and when 22.5° of one pipe is lined up with 22.5° of the other pipe the angle between the longitudinal axes or bend angle β is 22.5° as shown in Figure 4.

By axially rotating one pipe 11 relative to the other 12 the longitudinal axis of one pipe is placed at an angle to the longitudinal axis of the other and this angle can be selected from 180° (Figure 3) to the maximum angle shown in Figure 4, which is in effect twice the cut angle a, i.e. the included angle between the longitudinal axis of the two joining pipes of Figure 4 is 2 a or 157.5° or a bend angle (β) of 22.5°. Once the desired angle is selected the pipes can then be welded together using conventional welding technigues externally or both externally and internally. A threaded test hole can be provided in the socket 20 to enable an air test of the joint after assembly to verify the joint seal during pipeline construction. A grub screw can then be inserted into the hole and a seal weld is placed on top.

In this manner the pipes are assembled on site by first laying the first pipe by rotating the pipe so that the scale indicates the desired bend angle. The second pipe is then rotated to the same bend angle and attached to the first pipe. The pipes are only welded together once the desired angle of bend has been produced. The ball and socket arrangement also provides a small degree of variability as is conventional in that type of jointing technique .

To produce bend angles greater than 22.5° an

intermediate pipe section is introduced. The intermediate pipe section has opposite ends cut at the predetermined angle with a socket formed in one end and a ball formed in the other end in the same manner as described above. The intermediate section is then connected between the two pipes to increase the bend angle between the pipes. In a situation where a 90° bend is required three intermediate pipe sections are joined end to end and then are secured between the pipes to ultimately define a maximum bend angle of 90°. Alternatively if the bend angle (P)is 30° then two intermedial pipe sections are joined between the pipes to produce angle of 90°.

In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.