JPS60136691A - Rod and pipe - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to rods and pipes, and provides improvements in rods and pipes that have application in oil producing wells, but are not necessarily limited to use in oil producing wells. It's not something you can do. In particular, the invention relates to insulating tubes, methods of forming thick-walled pipes, and paraffin scrapers attached to rods or pipes.

One aspect of the present invention relates to an insulating tube, such as a tube that carries steam downward to heat viscous oil in an oil producing well.

Viscous crude oil is difficult to pump, so it is often necessary to heat it to reduce its viscosity. This is most conveniently accomplished by pumping steam downward into the well. However, the distance is very large, and in a typical silica cement liner, 100% steam at the top of the well becomes 75% to 80% steam at the bottom of the hole.

Attempts have been made to insulate the tubes conveying the steam downwards, but this has been without any success. Insulating materials and/or
The basic principle of a coaxial double tube with an outer annulus filled with an inert gas is known and works well up to a certain point. Because the tubes used to feed down the hole are formed in relatively short lengths, the problem is that there are a large number of tube-to-tube connections. Conventionally,
It has been common practice to weld the inner and outer tubes together at their joints to form a closed annulus containing insulating material. The end is usually extended outward by inflating the inner tube to an outer diameter equal to the outer diameter of the outer tube.
U, were formed by welding them together. The ends of the two wooden tubes are externally threaded and joined together by well-known ratchet connections.

Therefore, at each connection between two adjacent tubes there is a section where the inner tube is not insulated and the internal steam is cooled at many of these points. Attempts have been made to smooth the passage of the tube through which the steam is directed downwards by providing inserts to cover the insulation gaps, but this provides less heat retention.

According to a first aspect of the present invention, the tubes have spaced apart tubes defining an inter-tube space therebetween and spaced apart tubes on the side of each other. a coupling means for coupling first and second insulating tubes, the first and second insulating tubes having first and second coupling portions capable of being coupled to form an inner tube seal and an outer tube seal spaced apart from each other; is provided.

Advantageously, the inner and outer tubes are joined to each other at each end so as to communicate the spaces between adjacent tubes. Alternatively, each tube may have a sealed intertube space.

The intertube space is provided or adapted to serve as a thermal insulation means. The means may create a vacuum within the intertube space. Preferably, the outer tube is correspondingly formed with a barb for engaging the other.

The outer tubes may be engaged with each other by a connection between their overlapping portions, said connection preferably being a connection with a barb. In this case, it is advantageous for G to have an end with a pin and box-shaped connection. Alternatively, the outer tubes may be engaged together by a collar that engages the shoulder of one tube and the neck of the other tube.

Either one of the ends may be provided with an annular channel in its end face, which channel communicates with the intertubular space of the tube by at least one opening. Corresponding ends of adjacent tubes are provided with at least one opening rounded to connect the intertube space to the annular channel to which the ends are connected.

Preferably, each end has a plurality of openings, for example eight openings.

In embodiments in which the tubes are connected to each other by a collar, there is no need to provide a channel as the tubes can be precisely aligned by rotating the shouldered tabs relative to the collar. In this embodiment, each intertube space has at least one opening on each end face.

The openings are aligned by rotating one tube relative to the other.

The tube may be two tubes of different diameters;
Each is friction welded to a preformed connection at each end.

In one embodiment, the preformed connection is a bottle-type connection at one end of the tube and a box-type connection at the other end. In other embodiments, the preformed connection is a pair of engageable ends, one of which is externally threaded and the other cooperates with an internally threaded collar. It has an outer shoulder adapted to

According to a second aspect of the invention, there is provided a thermally insulating fluid transfer tube having first and second duplexes disposed one in the other, the space therebetween being a vacuum. .

Each such pair of tubes is connected with an adjacent pair of tubes to allow fluid to flow within the inner tube and tube m1
It is preferable to communicate the vacuum section along the space.

Advantageously, a vacuum pump is provided at the top of the well to maintain the vacuum down to the depth of the well.

- In an aspect, the invention relates to a method of forming thick wall pipes. A particular but non-limiting application is a method of forming a drill pipe with a thick walled middle section that acts as a wear band.

Such drill pipes are well known and are particularly useful for directional drilling, but may be used for many other applications. Traditionally, it has been difficult to form thick-walled midsections.

Since it acts as a wear pad, the material forming the part is inflexible by its nature. However, a snap-on rubber-coated three-wrap rubber-coated,
Attempts have also been made to form molded rubber coatings in place. All of these? The disadvantage is that there is no or little net resistance.

It has also been proposed to provide a metal sleeve of two semi-circular parts or a slide-on metal sleeve. These need to be fixed in place, and one way to do this is by welding. This can deteriorate the underlying material or cause stress to be concentrated at the end of the sleeve when the pipe bends.

Any of these can make your pipes bad.

Alternatively, such parts can be fixed in place with an adhesive, such as an embossed adhesive which provides very strong adhesion. However, depending on the surface conditions or downhole conditions, the adhesive may not be able to hold the part against the large forces applied to the part. In such a case, the wear pad is twisted loosely against the drill pipe and slides along the pipe from the center of the pipe toward the tool mount at one end of the pipe. In such a position it is almost useless.

Another way to form such a section is to form a pipe with thick walls along the entire extent and to work the pipe in the section between the wear band and the end with thin walls. This method, of course, suffers from the high initial cost of the thick walled tube in addition to the cost of forming the large profile tube into a pipe of the desired wall thickness, flexibility and weight. In order to improve this method, an attempt was made to provide a pipe with a thin wall, expand the middle part of this pipe, and process this expanded part into a desired shape. after that,
A joint is welded to the end. However, this method also has problems with the cost and difficulty of the diameter expansion step and processing cost.

It is an object of one aspect of the present invention to provide a method for forming thick-walled pipes that alleviates the above-mentioned disadvantages.

According to one aspect of the invention, forming a shaped section of a pipe with a relatively thick wall, and forming a shaped section of a pipe with a relatively thin wall;
A method of forming a thick-walled pipe is provided comprising the steps of providing two pipes and welding the two pipes to respective ends of the shaped section.

The preferred method of welding is wear welding, but butt welding or induction welding may also be used.

Preferably, the two pipes are formed by cutting a single pipe, and the single pipe is provided with a connecting member at each end before being cut into two. In another case of providing two separate short pipes, a connecting element is provided on each of the short pipes and the ends without connecting element are welded to the shaped part.

Alternatively, the shaped section may be welded to two pipes, i.e. short pipes, and this step is followed by welding a connecting member to each end of the integral pipe so formed. Another process follows.

According to another aspect of the invention, there is provided an apparatus for using the method of the first aspect of the invention, the apparatus comprising an abrasion welding machine having a hollow spindle received through a pipe.

Another aspect of the invention relates to a paraffin scraper that is attached to a suction rod or other rod or pipe to clean the walls of the output pipe with paraffin or other solid formations.

It is known to provide a paraffin scraper which is attached to the suction rod and which contacts the wall of the output pipe such that contact is effected by the natural movement of the rod away from the center of the pipe; Or at least have many blades protruding from the rod sufficiently close to the wall.

Of course, it is necessary to leave channels between the blades through which the rising oil passes. For ease of manufacture, it has been common to configure the blades parallel to the longitudinal axis of the suction rod. This allows the blade to be shaped without the difficulties caused by undercut surfaces. However, such paraffin scrapers have the disadvantage that the wall portion facing the channel through which the oil flows is not scrubbed during the normal up and down reciprocation of the suction rod.

To overcome this drawback, it is necessary to rotate either each scraper or the entire rod. A Rondo rotating machine was developed, but its use added complexity to the operation that would otherwise be preferable.

The object of the invention is to alleviate the above-mentioned disadvantages and to provide a paraffin scraper which is capable of scraping the entire circumference of the wall of the output pipe by performing a simple vertical repetitive motion.

According to one aspect of the invention, an oil passage for passing oil axially and an axial direction configured such that the entire circumference of the inner surface of the pipe can be scraped by the axial movement of the scraper. The object of the present invention is to provide a paraffin scraper for scraping and smoothing the inner surface of a pipe having a generally cylindrical body with blade means disposed on the outside.

The blade means has a plurality of parallel blades, for example three, separated from each other by a respective plurality of corresponding helically extending channels, each blade enclosing a portion of said periphery. .

Advantageously, one end of one plate occupies the same angular position on the circumference as the other end of the next adjacent blade.

The scraper may be formed of many, preferably two, engageable parts. A claw or fastening means may be provided to join two or more parts. Additionally or alternatively, adhesives may be used to join the parts.

Preferably, the scraper is made of aluminum or a plastic material, such as nylon or sulfurized polyphenylene resin.

Next, embodiments of various aspects of the present invention will be described in detail by way of example with reference to the accompanying drawings.

Referring to the drawings, part 1 of the drawings shows a connection between two insulating tubes. On the left side of Fig. 1, there is a connecting part with surfaces of the same outer diameter and height as shown in Fig. 1, and on the right side of Fig. 1, a thickened pin and a box-shaped connecting part are shown. A connection with 12 is shown. Each tube has a large diameter outer tube 1 and a small diameter inner tube 13,
Both tubes are arranged approximately coaxially and are friction welded at their ends to connection pieces formed in two opposite connections 26, 27 along line 10. Reference numeral 11 indicates a welding protrusion. This protrusion remains on both sides of the weld facing the intertube space, but has been removed from the outer surface of the outer tube and the inner surface of the inner tube.

One end is connected to a connecting part 26 which includes a pin-type connecting part I4. This pin-shaped connection 14 cooperates with a box-shaped connection 15 at the corresponding end of the adjacent tube. The connection has a modified sawtooth thread 4 with a 45° torque shoulder 2 on one end and a 606 metal-to-metal seal on the other end.
connected by. A sealing ring 3 is provided at the midpoint of the modified serrated thread 4. When the connection is completely screwed in, the ends of the inner tubes 13 sealingly abut each other, forming a continuous hole 9 through which steam can pass. The vapor is isolated from external influences by a vacuum created in the space 16 between the tubes.

As can be seen from the figure, the deformed serrated screw 4 is a serrated screw 4.
and the outer wall of the inner tube 13 to leave a space 17 between the tube and the outer wall of the inner tube 13. In this way, substantially the entire surface of the inner tube 13 is covered by the vacuum isolation.

In order to maintain a vacuum throughout the series of tubes, it is necessary to provide communication between the spaces 16 between adjacent tubes. This is achieved by an annular chamfer formed on one end face of the box-shaped connecting portion 15. (However, this can also be formed in a pin-type connection as well.) This channel communicates with the space 16 between the tubes by eight openings 8 in this case. The openings 8 are formed around the channel 7 at equal angular H intervals.

The corresponding pin connection also has a number of openings of equal size, these openings occupying the space between the tubes where the opening 8 of the pin connection becomes smaller when the two tubes are screwed together. 17 to channel 7. As a result, communication between the spaces between the tubes is maintained regardless of the radial arrangement of the tubes. Annular seals 6 are provided on both sides of the channel to prevent loss of vacuum at these locations.

FIG. 4 shows a blanking shoe that closes the lower end of the inter-tube space 16. This shoe 18 has a box-shaped connection with a modified sawtooth thread 4, a 45° torque shoulder 2 and a 60° metal-to-metal seal 5.

Although not shown in the figures, a seal may be provided on the shoulder 5 to prevent communication between the lowermost intertube space 16 and the steam hole 9. A box-shaped connecting portion 19 having a threaded portion for connecting another tube is provided at the lower end of the blanking shoe 18.

FIG. 3 shows a steam injection and vacuum exhaust cap 20 provided at the top of the well. This camp 2O has an opening 8 cooperating with the channel 7 of the uppermost insulating tube.
and a vacuum seal 6. The lower end of the cap is formed as a pin-type connection and is connected to the box-type connection of the uppermost tube. A vacuum inlet part 21 is provided above the point connected to the uppermost tube, and this vacuum inlet part 21 has a threaded part formed inside thereof to be connected to a pipe running to a vacuum pump (not shown). has been done. The uppermost part of the cap is provided with a box-shaped connection 22 for connecting a pipe leading to a steam generator (not shown) or other steam source. The invention has thus been described with reference to the specific embodiments illustrated. In addition, if the mating connections are modified accordingly, for example, instead of referring to the box-type connections, reference can be made to the bottle-type connections.
Consider other types of connections, which are shown in detail in FIGS. 5-7. FIG. 5 shows the connection between two tubes. Each tube has an outer tube 1 and an inner tube 13 between which an annular intertube space 16 is formed, the inner tube 13 forming an aperture 9 for passage of steam.

The tubes are connected to each other by opposing connections with collar connections 23. The collar 23 has a thread on the inside of one end which engages a thread formed on the outside of one end of the tube.

The other end of the collar 23 is provided with an inner shoulder 20 which cooperates with the shoulder on the other side of the outer tube 1 . This allows the tube to rotate relative to the collar until the collar is fully screwed, allowing the angle of the tube to be adjusted.

The spaces 16 between adjacent tubes are interconnected by eight openings 8. However, only one is shown correctly in this example where the tubes are aligned. An annular sealing ring 6 having a rectangular cross section is provided, and a hole 8 is provided on one side of this annular portion. The seal may be glass-filled PTFE, which prevents communication between the vacuum and the vapor within the bore 9 or between the vacuum and the atmosphere outside the tube. The ends of each tube are matched and dimensioned so that there is contact wherever possible between the respective faces of each tube, thereby ensuring the best possible seal.

FIG. 7 shows a modification of the connection between the spaces between the tubes. Here, the passage between the vacuum part and the outer influence part connecting the holes 8 is further curved, whereby a better sealing is achieved.

Using vacuum pumps of known type, a series of tubes embodying the invention can be evacuated to a depth of at least 5,000 feet, and possibly deeper.

Vacuum is a very good form of thermal insulation, so the steam is optimally directed down the hole.

Although the insulating tube is described as being used to channel steam down the hole, it can be used to supply hot or cold fluids as well. Both the inner tube 13 and the outer tube I, in particular the inner tube 13, are prestressed to withstand the surrounding vacuum on the outside and the pressurized steam on the inside at the focal point. Alternatively or additionally, struts may be provided between the inner and outer tubes to increase their strength.

It is also possible to fill the space between the tubes with a porous insulating material in order to provide strength without destroying the thermal insulation obtained by the action of the vacuum.

Consider other embodiments of the invention in which a vacuum is created within the space between each tube and the space is sealed. This can be achieved during manufacturing the insulation tube. In this example, adjacent tubes are shown.

Referring now to the drawings, and in particular to FIG. 8, a drill pipe is shown having two wear bands mounted in the middle. The total length of the drill pipe is 44'7''. The tool mounting box section 31 has a length section 32 that is at least 27". The number of tools (=J bin section 33 has a length section 34 that is at least 21"). Each of the central tool wear pads 35 has a length 36 of at least 34 inches.

As can be seen, the remaining length of the pipe is 34 in total.
'll''. This length is divided into three parts, which may all be the same or different.

These three pipes 52 preformed medium heat tool wear pads 35. The method of assembling the drill pipe from the tool handle sheath 31 and the tool mounting pin part 33 is carried out by friction welding each pipe at each end to one of the sections shaped along the friction weld line 37. There is.

Friction welding is a method in which one of the pipes or shaped sections is gripped by a hydraulically operated chuck and the other component is gripped by a hydraulic clamp. The ends of the components are aligned and moved into tight contact. The clamp holds one component firmly, and the chuck holding the other component is driven by a preset rotational speed morph.

This rotation speed is generally below 500 r,p,m.

Axial pressure is applied and frictional heat is generated at a controlled rate as the metal softens and slowly collapses from the hot joint to form an expanded collar. When the predetermined temperature conditions are set, the rotating spindle is disconnected from the main motor and stopped, and the increased axial pressure forges and hot-treats the joint to form a high-strength solid weld. .

The accuracy and quality of the welded assembly is A, P, 1. Exceeds the requirements specified in the standard. The joint has a fine structure, a narrow heat-affected zone, and excellent chemical properties. This method has low energy consumption and has 100% metal-to-metal joints with the properties of the original metal. No external consumable or protective gas is required, and only a portion of the swollen collar needs to be removed in a low metal consumption process.

The difficulty with friction welding from the perspective of making drill pipes is the length of the pipe. Tool mounting box or number of tools (NJ
It is well known to add pin sections to the ends of long pipes;
In this method, the pipe is fixed and the tool mount is rotated within the chuck. However, if it is desired to weld the central tool pad section in place, it is natural to weld the long pipe to the long pipe already welded to the central tool pad section. Until now, it was thought to be impossible to rotate such a length of pipe with a hydraulic chuck. By making the chuck hollow, it is now possible to carry the extra length of pipe through the chuck to a safe position behind the friction welding machine. As a result, the chuck can control the components being welded at a point near the weld, ensuring alignment accuracy.

If there is sufficient clearance at the rear of the chuck and the chuck has a hollow section of a diameter large enough to accommodate any wear band or tool mount on the pipe, if necessary, this There is almost no limit to the length of pipe that can be handled by the method).

Since the initial price of two short pipes is less than the initial price of one pipe of the same length, there are many short pipes.

By using this method, you can save a lot of money. The wear bar throat may also be formed as a relatively short cornice that is later inserted as a part of the drill knob and machined into the final shape. This also saves cost compared to machining longer pipes with wear pads. Friction welding may also be used to weld two different metals together (thus, if desired, the wear pawl may be formed from different materials suitable for the purpose.

FIG. 9 shows four types of drill pipes with a smooth wear pad in the center. In this case) the eve is conveniently <30'6# in length and the dimensions for the tool mount and wear pad are the same as similar parts of the eve shown in FIG. As can be seen, thick walls can be made with any desired cross-sectional shape. As shown, the elevator shoulder 39 is ideally angled at an angle of 18 degrees. The shoulder 4O for the wear pad is also ideally 1
The bin shoulder 42, however, is angled at an angle 43 of 35°.

Another advantage of this method is that the thick wall section and the corresponding thin wall section of the pipe may be achieved in any of a number of ways. As shown in FIG. 9(a), the pipe expands inward. In FIG. 9(b), the pipe expands outwardly, and in FIG. 9(c), the pipe expands both inwardly and outwardly.

FIG. 9(d) shows a pipe having relatively thick walls throughout.

FIG. 10 illustrates the various types of wear pads that can be achieved with the method of implementing this aspect of the invention.

Figure 10 +81 shows a smooth wear pad;
The one shown in Figure fb1 has a wear pad with a ribbed carbide molding. Figure 10+01 shows a ribbed type wear band and Figure 10(d) shows a spiral type wear band. FIG. 10+81 shows a helical wear pad having a helical carbide molding.

Figure 10+f1 has a central section that is a replaceable soft rib protector.

FIG. 11 shows a developed version of the inwardly expanded drill pipe shown in FIG. 9(a). Fruit shown -
In the example, an inner tube of alloy steel 4 is placed inside the completed drill pipe under water pressure until it is reliably sealed.
4 has been inserted. The annular portion formed between the tube 44 and the inwardly expanded portion of the pipe is provided with a vibration damping layer 45 made of polyurethane material.

This may be added at an intermediate stage of the inner tube insertion process. Such pipes are useful for directional drilling.

A method embodying this aspect of the invention is described with reference to inserting a wear pad into a drill pipe. This may also extend to other pads and space forming devices such as drill pipes, suction rods, etc. Friction welding creates a joint that is equally strong and identical to the metal itself, preventing deformation within the pipe and being able to withstand large forces better.

This method is specifically described with respect to friction welding.

However, it should be understood that butt welding or induction welding may be used with equally good results in some cases.

In another aspect, the invention relates to a paraffin scraper.

Referring to FIGS. 12-15, a paraffin scraper 51 is shown attached to a rod 52.

This scraper consists of a body with three blades 53 separated from each other by three channels 54.

The blade 53 contacts the wall of the output pipe and scrubs it clean with paraffin or other solid formation.

Channel 54 allows oil to flow through the scraper.

The blades and channels extend helically from one end of the scraper to the other, each surrounding a portion of the scraper. As shown more clearly in Figure 12,
The sink point 56 at one end of one blade then occupies the same angular point on the circumference of the body of the scraper as the point 57 at the other end of the adjacent blade. In this way, the blades surround the scraper so that any point on the pipe wall can come into contact with a portion of one blade during normal up and down movement of the suction rod 52.

The paraffin scraper is formed as two injection molded parts such that the two halves can be joined along a line indicated at 58. As can be seen from FIG. 13, the two halves are formed with a dovetail joint so that they can be held together, but this is not strictly necessary. In order to successfully apply the injection molding process, it is necessary that the molded shapes have no undercut edges. Although the dovetail can be formed by using a separate mold piece, the complex shape of the helical channel 54 is not possible with conventional molding processes. By forming the channel 54 with less than a semicircle or an equivalent curvature, and careful consideration of the circumferential position, it has been realized that the scraper can be injection molded in two approximately semicylindrical halves.

It is recommended that the scraper be made of durable plastic material. Nylon or sulfurized polyphenylene resins have been found to be particularly suitable.

Half of the scraper is in contact with the rod, and the other half is glued to the rod so that it can be positioned on the rod. If a dovetail is provided, the second half engages the first half and slides axially along the rod. The two halves are each adhered to each other and to the rod by adhesive. Epoxy resins or vinyl ester resins have proven particularly suitable.

A paraffin scraper embodying this aspect of the invention is also useful for locating a suction member or other rod approximately in the center of a pipe or other hole even in cases where there are no paraffin formations.

Figures 14 and 15 illustrate another embodiment of this aspect of the invention, including a preferred method of attaching the scraper to the rod.

A scraper 101 of the same design as shown in FIGS. 12 and 13 is provided with a central hole 105. Hole 105
are a pair of recesses 11 arranged in the center of the scraper 101.
7.

A nylon insert 118 having a hollow frustoconical shape is disposed in engagement within the bore 115 as shown in FIG. Inserts 118 are provided on either side of hole 115, each insert being formed into two mating halves to fit within hole 115. Each insert 1-118 also has a pair of dovetail projections 119 that fit into corresponding recesses 117.

In use, use a hydraulic ram to insert
One inserter eye 18 is inserted into the hole 101 from each end, biasing the rod 102 into position, the protrusion 119 is biased into the recess 117, and then the insert 118 is inserted into the hole 101. Hole 105 and mouth.

grip the door 102 and fix both to each other.

Of course, preventing the scraper from rotating around the rod, preventing it from moving along the rod, abutting it on the rod, and applying a corresponding pressure against the inner surface of each half is possible. When two halves are joined together by sliding a dovetail joint, it is necessary to provide a certain elasticity to the abutment or scraper.

The scraper is described as having three blades and three channels. Of course, this number can vary if restrictions on undercut edges are followed. Also, it is not necessary to extend the entire length of the scraper because of the blade. In some cases it may be advantageous not to do so. For example, each channel may include a channel 54 separating each blade.
It may be divided into two or more parts with intersecting channels in between. It is also possible to provide a scraper function as part of some other downhole tool, where the scraper blade simply needs to occupy a shorter tool.

[Brief explanation of the drawing]

FIG. 1 is an axial cross-sectional view of a connecting portion between two insulating tubes, FIG. 2 is a radial cross-sectional view showing the connecting portion, and FIG. 3 is a steam injection and FIG. 4 is an axial cross-sectional view of a vacuum evacuation camp; FIG. 4 is an axial cross-sectional view of a blanking tube that closes the lower ends of a series of insulating tubes according to one aspect of the present invention; FIG. 6 is a radial cross-sectional view of the connection shown in FIG. 5; FIG. 7 is a vacuum connection shown in FIG. 5; FIG. FIG. 8 is a partial side cross-sectional view of a drill pipe according to one aspect of the present invention, and FIG. 9 is a modified partial side cross-sectional view of a drill pipe according to one aspect of the present invention. FIG. 10 is a side view of six drill pipes according to one aspect of the invention, each having a different configuration of wear band in the middle; 12 is a side view of a scraper according to an embodiment of the invention placed in position on a rond; FIG. 13 is a plan view of the scraper, and FIG. 14 is a cross-sectional view of the scraper similar to that shown in FIG. 12 showing a preferred fixing configuration.
5 is a cross-sectional view taken along line χ-X' in FIG. 14. 1...Outer tube, 13...Inner tube,
12... Connecting part, 14... Bottle type continuous Usukichi@■, -
15... Box-shaped connection part, 16... Space between tubes, 51... Scraper, 52... Mouth/throat, 53
...Blade, 54...channel. Engraving of the drawings (Contents include: FftI-S FIG9°FlG, 10
, Title of the invention Rod and pipe 3, Relationship with the case of the person making the amendment Patent applicant 4, Agent 107 (2 idiots)

Claims (1)

[Claims] 1. first and second lengths each having inner spaced apart tubes and outer spaced apart tubes defining an intertube space therebetween; Connecting means for connecting two insulating tubes, the connecting means having first and second connecting portions that can be connected to form an inner tube seal and an outer tube seal that are spaced apart from each other. 2. A patent for first and second lengths of insulating tubes, each having an inner and outer duplex, each having an intertube space therebetween, and for connecting said first and second lengths of insulating tubes to each other. An insulating tube structure comprising a connecting means according to claim 1. 3. A thermally insulating fluid transfer tube having first and second tubes disposed within the other, the space between the tubes being evacuated. 4. It has two coaxial tubes whose ends are joined to each other and a means for connecting two adjacent tubes,
An insulating tube in which the ends of each tube are sealed against each other and the ends of each outer tube are adapted to engage each other. 5. A method of forming a thick-walled pipe, the method comprising: providing a shaped section of pipe with a relatively thick wall; providing two lengths of pipe with a relatively thin wall;
The method includes the step of welding the pipe to each end of the shaped section. 6. A friction welding machine for use in the method of claim 5 for friction welding the pipe and the shaped part together, the friction welding machine having a hollow shaft for receiving through a length of pipe. The device comprising: 7. A paraffin scraper for scraping and smoothing the inner surface of a pipe, such that the oil passage for passing oil in the axial direction and the inner surface of the pipe are scraped around the entire circumference of the pipe by the axial movement of the scraper. Said scraper having a generally cylindrical body with axially outwardly disposed blade means configured to.