KR20000022181A - Method of welding pipe - Google Patents

Abstract

PURPOSE: A method of welding pipe is provide to weld sections of pipe together to form a long, continuous pipeline by an apparatus and system whereby the initial or root welding pass made from outside the pipe and that has no internal protrusion of the welding puddle. CONSTITUTION: A welding bug is mounted on a guide track going around the circumference of the pipe and continuously moved along the track. An initial welding pass is applied to the adjacent ends of a first and second pipe from outside the first and second pipe without use of internal line-up clamps with back-up shoes and using a welding wire to form a puddle between the ends of the pipe. During the initial pass, the speed of the welding bug can be varied without regard to the angular position of a welding head and without stopping the bug while the bug is continuously moving about the track on the pipe to maintain the end of the welding wire at a desired position with respect to the welding puddle.

Description

Pipe welding method

One important system for transporting materials such as oil, gas and water is to use pipelines. These pipelines are usually buried underground in the United States and many other countries, and in fact cross cross. Digging the ground with a ditch digger along the route of the defined pipeline forms the pipeline.

Approximately 30 to 60 feet of pipe section is carried to the area where the pipeline is buried. Ends of adjacent pipe joints are connected by welding. Such welding should be so precise that it does not allow even small needle holes. In order to improve the precision of welding, the ends of the pipes should usually be inclined. These pipes are interlocked so that the two pipe sections are aligned as best as possible. Inside the pipe at the weld seam, the welding material should form a smoother surface near the inside of the pipe. In some cases, the welds on the inside of the pipe should have a very small degree of protrusion. Protruding slightly may cause various problems when moving the device from inside the pipe down to detect any defects that may occur within the pipeline. In addition, a pipeline plug is introduced into the pipeline that separates the material present in the pipeline from the others. It can often be seen that gasoline is transported through pipelines. A plug is installed to separate the two materials, and then crude oil is fed through these pipes. At this time, a constant separation of the two materials should be maintained.

In order to prevent the welded molten welding material from protruding inside the pipe, it is more common today to form a first or root pass of the weld inside the pipe. To this end, highly sophisticated and expensive machines are on the market. The cost of renting such a sophisticated device for machining pipes with a three-inch diameter can be as much as $ 1200 per weld, or about $ 2 million a month's rent. This is a very time consuming and expensive welding process. Thus, it can be seen that a less expensive method of welding the pipe sections together is needed.

In recent pipeline welding, welding bugs such as semi-automatic welding machines are often used. Around the outer periphery of the pipe a track fixed at the point where the welding bug is needed to rotate around the pipe cooperates with the welding bug. The bug has a drive motor which drives the bug around the track with the help of a roller. The roller keeps the welding bug along the track even when the welding bug is almost upside down. Specific fastening means are provided to fix the bugs on the track. Means are also provided for receiving pipes of different sizes. The welding bug has an oscillator that vibrates the welding tip across the welding puddle.

The bug also has a wire feeder, which actually includes a motor that drives the wire through a welding head that welds the two pipe sections together.

In operation, the drive motor drives the bug around the track at a predetermined constant speed ratio. When the bug moves from the 12 o'clock position at the top of the pipe to the approximately 9 o'clock position at the middle, the speed is constant. However, in order to balance the downward movement of the welding bug in the 6 o'clock direction, the moving speed must be increased in consideration of the gravity pulling the puddle at high speed. For this purpose, the bug drive motor is stopped at present. The operator adjusts the speed of the drive motor so that the speed of the drive motor is increased, and then starts the drive motor to continue the welding process. The movement of the bug is always interrupted with every speed change.

Stopping the drive motor results in a loss of welding completion time. Other related issues such as maintaining the continuity of the beads should also be considered. However, in spite of these problems, most of the above-mentioned processes are widely used because they are superior to the conventional processes.

It is therefore an object of the present invention to provide an apparatus and system in which the initial or root pass of the weld can be formed outside the pipe and without the internal protrusion of the weld puddle.

The present invention relates to the field of mutual welding of pipe sections to form a long continuous pipeline, and more particularly to a system for performing welding by machine.

1 is a schematic diagram of the main components of the invention,

2 shows a welding bug mounted to a track showing a pipe section to be welded to another section;

3 is a front view of the welding bug of FIG.

4 is a rear view of the welding bug of FIG.

5 is a partial left side view of the welding bug of FIG. 4, FIG.

6 shows a clamping means for detachably fastening the guide roller and the traveling drive roller to the guide track, FIG.

FIG. 7 is a view similar to FIG. 6 except that the clamp is in a released position;

8 and 9 are views showing the shaking of the welding head at the time of coupling,

10 is a bottom view of a welding bug,

11 is a view showing a connection between a potentiometer for driving a drive wire feeder and a potentiometer for a drive motor, in order to adjust the drive wire feeder according to a change in the traveling speed of the welding bug;

12 is a schematic diagram of a system for controlling the speed of a drive motor on a welding bug.

13 shows pulses in the control system of FIG.

The present invention is a method and apparatus for welding an end of a first pipe section to an end of a second pipe section by use of an improved welding bug. The welding bug is provided with a wire feeder, means for driving the wire feeder and driving means for driving the bug around a track on the outer periphery of the pipe. Control means are provided for changing the speed of the bug while the bug is continuously driven around the track. In pipe welding, the pipe is in the horizontal position, ie the axis of the pipe is usually in the horizontal direction. The initial welding pass or root pass is applied adjacent the ends of the first and second pipes from the outside of the first and second pipes. This process does not require the use of line-up clamps with back-up shoes.

Usually two bugs are used, one surrounding half of the track and the other roughly the other half. The bug moves from the 12 o'clock position to the 9 o'clock position in the almost horizontal direction to the nearly vertical direction. During this time the speed of the bug should be changed to keep the electrode with the welding wire in front of the weld puddle. The other bug moves from 12 o'clock to 3 o'clock and moves to 6 o'clock. Two bugs move or rotate at the same time. However, since one of the bugs starts slightly earlier than the other, stops slightly earlier and is removed from the adjacent area, the welding at the point where the weld passes from two bugs meet is continuous. The root pass uses a surface tension transfer (STT) power source. This is new to this combination. By using such a system where bugs and welding wire speeds are appropriate, each edge of the inclined surface is burned only slightly. By the surface tension of the welding mode, the edges are mixed together, so that the knots on each sloped side leave only a small flat weld inside the pipe. Thus, it is no longer necessary to move the initial or root path from inside the pipe or to use equipment inside the pipe. Prior to the present invention, when welding pipes together by means of a system comprising a welding bug, the root pass or initial pass was always made from the inside of the pipe or involved the placement of equipment such as clamps, backup shoes, etc. inside the pipe. However, the present invention eliminates the need for such equipment.

In addition, means are provided for varying the speed of the wire feeder such that a predetermined amount of wire is fed into the welding puddle. In another embodiment, the wire feeder drive speed is controlled by the speed change of the buggy drive motor such that the desired wire feed rate is achieved and thus changed.

In operation, the welding operator continues to observe the welding puddle in relation to the electrode or the end of the welding wire supplied. The operator hopes to keep the ends of the welding wire right in front of the puddle. Thus, the operator changes the speed of the bug to maintain the proper position of the weld head. This is done while the bugs and welding work are in progress without having to be interrupted. During the actual movement of the welding bug, the wire feed drive can be changed to supply a certain amount of welding wire to the electrode. In addition, control may be made such that if necessary, the speed of the wire feeder changes in accordance with the speed of the welding bug.

Referring first to FIG. 1 of the schematic diagram showing the main components of a welding system using an improved welding bug, a first pipe joint 10 and a second pipe joint 12 to be welded together are shown. Is shown. A guide track 14 is disposed and fixed outside of the welded pipe near the position where the pipe ends are to be welded. The welding bug 16 moves on this guide track. Usually consists of two welding bugs, but only one is shown. As the bug moves on the guide track, the positioning or guide bearing or roller 20 keeps the welding bug on the track 14. The welding bug has a drive motor 18 which drives a knured moving roller 21 around the track 14. The speed of this drive motor is controlled by potentiometer controller 22.

A welding head 30 is supported from the welding bug 16 to support a welding wire 28 that passes through the welding head 30 and extends as a welding rod 29. Since the track 14 is disposed on the pipe 12, the end of the welding wire 28 is properly disposed relative to the ends of the pipes 10, 12. A carbon dioxide solenoid valve 32 is supported from the welding bug 16 to provide carbon dioxide or other predetermined gas to be propelled around the end of the welding wire tip 29 at the lower end of the welding head 30.

In operation of the apparatus of FIG. 1, the carbon dioxide solenoid is first opened so that all other gases are blown out from around the electrode 29 before the electrode is powered. Power for the welding head 30 is provided via a conduit 84 from the surface tension transmission power source 31, which is described below as a novel type of power source for automatic welding systems using welding bugs. do. Now start this STT power source.

Next, the wire supply motor 24 and the welding bug drive motor 18 are simultaneously started. As a result, the welding bug 16 begins to move along the track 14. The operator observes the work, in particular the welding puddle. The speed of the welding bug should be such that the wire tip 29 is accurately maintained in front of the puddle. As the welding bug moves around the pipe, gravity changes the movement of the puddle. The operator must compensate for this change in the movement of the puddle by operating the potentiometer controller 22 which changes the drive speed during the welding process. If the wire supply motor does not supply the wire fast enough, the control of the potentiometer controller 26 for the wire drive speed may be increased, or may be reduced if the wire is supplied fast. This control is also made while the welding bug 16 moves along the track 14 (actually the speed of the welding bug moving along the track will never change during welding).

Instead of controlling the drive speed of the drive motor 18 irrespective of the speed of the wire supply motor 24, the speed of the drive motor and the speed of the wire feed motor may be correlated. An apparatus for allowing this is shown in FIG. In this device the operator of the welding bug rotates the handle 38 to adjust the speed of movement of the welding bug. This change is a common potentiometer setting change method that controls the speed of the motor. In this case, a drive chain or a belt 40 is connected between the shaft for the potentiometer for the drive wire supply 26 or the rotor 34 and the potentiometer rotor 36 for the drive motor 28. Thus, as the wheel 38 rotates, the drive chain 40 drives the rotor 34 to adjust the potentiometer for the drive wire feeder 26. Thus, when the speed of the welding bug is changed, the speed of the drive wire feeder can be changed accordingly.

The pipeline tractor 42 has a generator that deducts power to the surface tension transfer (STT) power source 32. In principle, the STT power source is a power source with the ability to discharge and change the electrode current to, for example, about 750 microseconds. The STT power source is marketed by The Lincoln Electric Company, Cleveland, 44117-1199, Ohio.

Next, referring to FIG. 2, which shows an improved welding bug 16 mounted over a track 14 surrounding a pipe 44, the track 14 may be a conventional track that guides a welding bug around a pipe. have. The basic component of the welding bug 16 includes a welding tip or a welding rod 31 formed in the welding head 30, which is a gas cone 50 that sends welding gas, typically carbon dioxide, around the welding rod 31. It is provided. Conduit 84 connects the STT power source 31 to the welding head 30. The welding wire, which is a welding rod wound on a wire reel 58, passes through two shields 60, 62 and a wire feeder 64 therebetween. The wire feeder is conventional and includes a tension adjusting unit 65. This wire feeder 64 is used to drive the wire at a predetermined speed through the welding head 30. A carbon dioxide supply hose 82 is connected to the welding head 30 in a conventional manner. Since the oscillation motor 66 is provided for driving the oscillation mechanism 68 connected through the connecting portion 70 to vibrate the welding head 30, the electrode moves back and forth across the opening between the ends of the pipe to be welded. do. The connection 70 can be used to adjust the position of the welding head 30. The handle 85 is used to adjust the height of the weld head.

Referring now to FIG. 3, which shows an enlarged view of the welding bug 16, an oscillator adjusting mechanism 74 is shown which adjusts the height of the vibration curve, ie, the width of the vibration. May be the same as used).

Next, referring to FIG. 8 showing that the generator tip is in the first position and FIG. 9 showing the welding tip in the second position, the welding tip 52 is supported by the welding head 30. This oscillation system is used in conventional welding bugs and is shown here only to facilitate understanding of the entire system.

3 also shows an adjustment knob 85 for adjusting the height of the welding head against the welding bug and taking into account the height associated with the pipe being welded.

It is essential to provide inert gas to the weld head, in particular carbon dioxide. As shown in FIG. 4, this gas is provided from a gas source hose 78 connected to a solenoid valve 80 with an outlet hose 82 connected to the weld head. Gas is provided through this when the solenoid is opened. Power conduit 84 from STT power source 32 provides an operating current for weld head 30.

Variable swivel adjustment 86 provides a means for adjusting the angle of the welding head as needed.

Next, with regard to the drive motor 18 and the traveling and driving roller 20 staying on the track 14 or moving along the track, the traveling and driving rollers may be conventional and are referred to herein as entirely new combinations. It is shown to complete. Referring now to FIGS. 6, 7 and 10, FIG. 10 is a bottom view of the welding bug 16, showing a block of housings 88A, 88B, 88C, 88D for rollers. Side rollers 90 are shown in blocks 88A and 88C, and jagged wheels 92A and 92B are shown in blocks 88B and 88D that are driven by drive motors 18. . The side rollers keep the welding bugs snug on the track. The jagged roller moves the welding bug along the track. 6 and 7 show a clamping lever for clamping the roller in place. FIG. 7 shows the clamping mechanism released so that the roller can be properly disposed. The roller should fit snugly against the track band. Thus, a spring and adjustment nut 104 are provided.

As shown in FIG. 5, the support bearings 141, 143 on the top surface of the track 14 and the bearings 145, 147 on the bottom surface of the track 14 are brought into contact with the track 14 to bring the welding bug 16 into contact. Keep it.

Also shown in FIG. 10 of the bottom view of the weld head 30 is an oscillator drive motor 66 and an oscillator adjuster 74.

The wire guide mechanism is an improvement of the conventional wire drive system on the conventional welding bug. In the case of the conventional welding bug, the bug had to be stopped before the speed of the wire supply motor or drive motor for the bug was changed. In the present invention, it has been improved to change the drive speed of the wire without interrupting the movement of the welding bug. The drive mechanism for driving the welding bug around the track 14 is an improvement on the driving mechanism of the conventional welding bug, and can change the speed of the drive motor without interrupting the welding process.

Control means for controlling the speed of the bug driving motor and the speed of the wire driving motor will now be described with reference to FIGS. 12 and 13.

Referring to Fig. 12, one control means in schematic form for use in speed control of the drive motor 18 is shown (the system shown may also be used for speed control of the wire feed motor 24). This control means comprises a pulse width oscillator 120 with a power input 122. The reference voltage 124 of the pulse width oscillator 120 is typically 2 and 1 / 2V. The power circuit 132 is connected to the motor 18. The speed of the motor 18 changes with the action of the voltage of the current on the line 132. The output of the motor is provided through variable resistor 128 and line 134 which return to oscillator 120. A feedback line 130 is provided from line 134 to oscillator 120. It has a resistor 126 and provides fine feedback to the oscillator 120. The resistor 128 may be changed to change the speed of the motor 18 (by moving the handle on the potentiometer 22). As the resistance of resistor 128 changes, the output voltage changes on line 132. The voltage on this line 130 is then compared with the oscillator reference voltage 124. The width of pulses 140 and 142 shown in FIG. 13 is changed until the fine feedback on line 130 is equal to the reference voltage. This then controls the speed of the motor 18. Those skilled in the art can easily implement such a speed control system from the above schematic and description. Other means of providing such motor speed control may be used.

4 and 5 show potentiometer welding bug movement speed control knob 26A and wire drive speed control knob 26A mounted on control box 27. These handles can be used in cooperation with the control of FIG. 2 to adjust either or both the speed of the bug drive motor or the wire feed motor. The control conduits 147 and 149 connect the control box 27 to the drive motor 18 and the wire supply motor 24, respectively.

The operation by the basic components of the present invention described above will be briefly described. In operation, the ends of the pipe sections 10, 12 are arranged adjacent to each other, as shown in FIG. 1. The track 14 is connected around the pipe section 12. The STT power source 31 is connected to the pipeline tractor generator 33 to provide power for the welding operation. The track 14 is also set such that the welding tip 29 is properly positioned with respect to the gap between the five sections 10, 12. In general, the height and vibration of the welding head 30 is adjusted.

The carbon dioxide solenoid 80 is then excited to open the carbon dioxide source so that carbon dioxide can be delivered to the welding head 30. After the wire tip 29 is in place, the drive motor 18 and the wire feed motor 24 are basically started simultaneously.

The initial or root pass of the welding process is on the outside of the pipe in the position shown in FIG. 1. The use of surface tension transfer (STT) power source 31 is the most essential. The STT power source does not operate in either the constant current (CC) or constant voltage (CV) mode. Rather, it is a high frequency (wideband), current controlled machine based on instantaneous arc requirements where the power to the arc is not "average DC voltage". It is a power source with the ability to discharge and change the electrode current in microseconds.

As the welding bug 16 advances around the track 14 by the drive motor, the operator closely observes the welding puddle to keep the welding tip 29 just in front of the puddle. When the welding bug 16 moves downward, the welding puddle tries to move faster by gravity. Thus, the welder simply rotates the handle 22A as shown in FIG. 4 to adjust the required speed. Further, the operator can adjust the speed of the wire supply motor 24 by adjusting the handle 26A as shown in FIG. This is done without stopping either the drive motor 18 or the wire supply motor 24. The other side of the pipe also has another welding head (not shown) as shown in FIG. The second worker operates the welding bug in exactly the same manner as described above. Since one of the bugs starts slightly earlier than the other, there is no gap at the top of where the welding bead begins, and one of the bugs stops ahead of the other so that one bug can continue the welding bead until it continues from the bottom. have. All of these processes take place outside the pipe. Due to this novel system described herein there is no protrusion into the dripping pipe. There is no root path inside. This excludes a very expensive procedure. After the root pass is formed, additional welding passes may be made using conventional welding techniques as needed.

Although the present invention has been described to some extent, it will be apparent that various changes in details of the construction may be made without departing from the spirit and scope of this specification. The present invention is not limited to the examples herein, for example, but only by the appended claims or their equivalents, including the full scope of equivalents to which each element is assigned.

Claims (14)

A method of welding an end of a second pipe to an end of a first pipe using a welding bug with a welding wire feeder and means for driving the bug along a track on the outer periphery of the pipe. Continuously moving bugs along the track, Instead of using an internal line-up clamp with a back-up shoe, a puddle is formed between the ends of the pipe with a welding wire so that the first and second pipes from the outside of the first and second pipes are formed. 2 applying an initial welding pass to the adjacent end of the pipe, Initially without stopping the welding bug and without considering the angular position of the welding head while the welding bug continuously moves around the track on the pipe to keep the end of the welding wire in the desired position relative to the welding puddle. Changing the speed of the welding bug during the pass Pipe welding method, characterized in that. The method of claim 1, wherein an additional pass is applied after the initial pass. The method of claim 1, wherein the initial pass is made using a surface tension transfer power source of the initial weld pass. 4. The method of claim 3, wherein the power source has the ability to release and change the electrode current on the order of microseconds. 2. The method of claim 1, comprising changing the speed of the bug in response to observation of the weld puddle as the welding bug moves around the outer periphery such that the welding wire is directly in front of the puddle. 5. The method of claim 4, wherein the rate of release of the wire by the welding wire feeder correlates with the speed of the means for driving the bug around the track. An apparatus for welding one end of a first pipe to a first end of a second pipe, Welding tractor, A power generator disposed on and driven by the tractor, A surface tension transfer (STT) power source connected to the power generator, A welding bug with a wire feeder, means for guiding the bug around the weld head and the outer periphery of the pipe, Connecting means for connecting the welding head of the bug to the STT power source, Manual speed control means independent of the angular position of the welding bug, for automatically changing the speed of the welding bug as the welding bug moves around the track on the pipe. Pipe welding device, characterized in that. 8. A pipe welding apparatus according to claim 7, comprising means for automatically changing the speed of the wire fed from the wire feeder. 8. A pipe welding device according to claim 7, comprising means for changing the rate at which wire is fed from a wire feeder as a correlation of the speed of the welding bug. A method of welding an end of a second pipe to an end of a first pipe using a welding bug with a welding wire feeder for supplying a welding wire and means for driving the bug along a track on the outer periphery of the pipe. Arranging the ends of the first and second pipes in close proximity to each other with an unobstructed clearance between them; Continuously moving bugs along the track, Applying an initial welding pass to the adjacent ends of the first and second pipes from outside the first and second pipes, Changing the speed of the welding bug without stopping the welding bug while the welding bug continuously moves around the track on the pipe to maintain the desired position of the welding puddle and welding wire; Using power from a surface tension transmission power source when applying an initial welding pass; Pipe welding method, characterized in that. The method of claim 10, wherein an additional pass is applied after the initial pass. A method of welding a second pipe to an end of a first pipe using a welding bug with a welding wire feeder and means for driving the bug along a track on the outer periphery of the pipe. Connecting a welding bug to the STT power source, Continuously moving bugs along the track, Applying an initial welding pass to the adjacent ends of the first and second pipes from outside the first and second pipes, Observing the end of the welding wire in relation to the welding puddle; Changing the speed of the welding bug without stopping the welding bug while the welding bug is continuously moving around a track on the pipe to maintain the end of the welding wire just before the welding puddle; Pipe welding method, characterized in that. A method of welding a second pipe to an end of a first pipe using a welding bug with a welding wire feeder and means for driving the bug along a track on the outer periphery of the pipe. Continuously moving bugs along the track, Applying an initial welding pass from the outside of the first and second pipes to the adjacent ends of the first and second pipes using a welding wire to form a puddle between the ends of the pipes, Changing the speed of the welding bug without stopping the welding bug while the welding bug is continuously moving around the track on the pipe to maintain the desired welding puddle; Varying the speed of the wire released on the welding wire feeder as a correlation of the speed of the means for driving the bug around the track; Pipe welding method, characterized in that. An apparatus for welding one end of a first pipe to a first end of a second pipe, With welding tractor, A power generator disposed on and driven by the tractor, A surface tension transfer (STT) power source connected to the power generator, A welding bug with a wire feeder, means for guiding the bug around the weld head and the outer periphery of the pipe, Connecting means for connecting the welding head of the bug to the STT power source, Control means for automatically changing the speed of the welding bug when the welding bug moves around a track on the pipe, Means for varying the rate at which the wire is fed from the wire feeder as a correlation of the speed of the welding bug. Pipe welding device, characterized in that.