CN1443290A - Pipe integral threaded joint - Google Patents

Abstract

Pipe integral threaded joint formed by a male element (1) and a female element (2) respectively placed on the external surface and on the internal surface of two truncated cone-shaped parts of the threading (6, 7, 8, 9) having the same conicity value and being radially spaced, both being respectively divided by annular shoulders (5, 5') which are parallel and orthogonal with respect to the pipe axis. They are provided two sealing surfaces (12, 12', 13, 13'), one of them being cone-shaped and the other being spherical. After the screwing of the two elements (1, 2) said two annular shoulders (5, 5') are in contact. Each male (1) and female (2) element comprises, respectively along its external and internal surface, a circumference cavity (14, 15) placed between a part of the threading and the annular shoulder (5, 5') in order to allow the expansion of the lubricating fat.

Description

Pipe integral threaded joint

technical field

This invention relates to integrally threaded joints for pipes of reduced diameter size, particularly for pipes used in the gas or oil field production industry. The pipes can be used as conduits for pumping gas or oil and casings for wells.

Background technique

The natural gas or oil extraction industry employs pipes having fixed lengths whose ends must be connected to each other in order to reach the enormous depths where hydrocarbon deposits are typically located.

In common drilling techniques, wells, which may have a depth of several thousand meters, are drilled from the surface of the earth or sea in order to reach oil or gas fields. During drilling, the full length of the well is sheathed with metal pipe. The pipe sections with a length of approximately 10 meters are connected to one another by means of threaded joints. These tubes thus constitute a pipeline having the same diameter throughout its length except for the fittings, which generally have an outer diameter at least 1 inch (25.4 mm) greater than the outer diameter of the pipeline.

In order to form an enclosure for the entire depth of the well, several pipelines are used, the smaller the diameter of the pipeline due to the mechanical resistance and the geological characteristics of the site, the greater the depth of the pipeline in order to form a "sleeve" structure. Thus, the deeper the well, the greater its diameter at the surface, since the bottom hole diameter varies according to the pressure and flow rate of the fluid being drawn. Due to the aforementioned adverse consequences, the drilling costs are high, and these well casings require a large amount of material and are therefore expensive. Smaller well diameters also mean shorter drilling and wrapping times. Therefore, it is critical to minimize the diameter of the well and the diameter of the casing for the same amount of fluid being extracted.

Once the drilling is complete, another pipeline is inserted into the cased well, which pumps the oil or gas out of the subterranean field. This line, depending on the overall depth of the well, can be several thousand meters long and is thus also formed by connecting pipes having a length of about 10 meters by means of the aforementioned joints. Usually the second type of tubing is also of the same diameter over its entire length except for the fittings which are generally also of larger outer diameter as in the previous case.

In both of the foregoing cases, the pipes are connected by means of a threaded joint, which may be integral, in which case the pipe has a male thread at one end and a female thread at the other end, or it may be a pipe joint (coupling) form, in which case the pipe has a male thread at both ends and is connected on both sides by means of a female threaded union. Typically, setting a fitting increases the outside diameter of the line at the joint; the larger the outside diameter of the fitting, the larger the basic dimension of the line or bore compared to the tube.

After the oil companies demanded that the cost of oil and gas mines be kept as low as possible, efforts were made to reduce the diameter of the well and thus the diameter of the pipe.

In order to reduce the outer diameter of the pipeline, thereby reducing drilling costs and the amount of material required, threaded joints with reduced diameter sizes are used, which can be divided into three different types according to the required performance and the maximum size allowed . The first, often referred to as "Semi-flush", is a fitting with an outside diameter not exceeding 6% of the pipe's outside diameter. The second type, commonly referred to as "near-flush", is an integral fitting with an outside diameter 2-3% larger than the outside diameter of the pipe. The last type is called "flush" and is an integral joint with an outer diameter corresponding to the outer diameter of the pipe.

The choice of different types of joints depends on the load of the pipeline, the internal and/or external acting pressure, the length of the pipeline and the maximum diameter size allowed in relation to the diameter of the well.

If the joint diameter is reduced, then new technical solutions must be found to compensate for the low structural resistance. In fact, in the parts close to the joints, the efficiency must be less than in the pipeline, due to the presence of structural elements such as threads, seals and shoulders in the thickness of the pipe wall, which will cause damage in critical parts of the male or female components. reduced part.

Minimizing the causes of pipe breaks is critical, as once a pipe breaks after it has been laid in the ground, it is almost impossible to replace the cracked joint, which can have very serious economic consequences and possibly environmental concerns, especially if oil or gas fields Contains harmful ingredients.

Therefore, a great deal of work has been done in the past to improve joints to achieve optimum levels of efficacy, balancing different, sometimes conflicting needs, such as minimum size, maximum structural resistance, and fluid output and/or input maximum tightness. In practice, the pipe is subjected to several forces, namely compression, tension, deflection and pressure by the external fluid and/or the fluid circulating inside the pipe.

Fittings must also have optimum resistance to threading and seizure.

Structural and sealing problems are often exacerbated by fluid temperature, fluid corrosiveness, or environmental conditions in mining areas.

In the past, several schemes have been proposed to satisfy the above conditions.

International Patent Application WO-A-93/18329 relates to a reduced diameter fitting with a central shoulder. Said shoulders are provided on both the male and the female part with a protrusion and a cavity parallel to the tube axis with corresponding surfaces in order to seal off the two joint elements. Two sealing surfaces are provided on the shoulder protrusion. The shoulder divides two radially offset threaded sections, which are conical, or conical and cylindrical.

Such joints are effective, but have a particularly complex structure, making production costly.

European patent application EP-A-767335 relates to a joint of reduced diameter size, provided with a central shoulder, and two metal seals arranged on the male and female ends. This shoulder divides two radially offset, conical and cylindrical threaded sections.

The structure of this joint is simpler than the previous one, but it is still relatively complicated due to the conical and cylindrical threads. In addition, the two seals at the ends of the fitting seal their interior, thereby pressurizing the grease of the threaded connection, which may have an adverse effect on the tightness of the fitting.

Contents of the invention

A first object of the present invention is to overcome the above-mentioned disadvantages of the prior art fittings by means of a novel "near-buried" fitting which, although having the same dimensions as the prior art fittings, does not suffer from the aforementioned problems.

A specific object of the present invention is to provide an integral joint with reduced diameter dimensions and reduced production costs, yet guaranteeing high resistance and working tightness.

Another object of the invention is to provide an embodiment of the above-mentioned joint which simplifies its installation.

The above object is achieved by an integral pipe joint. This integral pipe joint according to claim 1 comprises a pipe integral threaded joint comprising a male member and a female member, said male member being on its outer surface There are two radially spaced, frusto-conical threaded portions separated by a first annular shoulder lying in a plane perpendicular to the axis of the tube, the female member being on its inner surface There are two radially spaced, frusto-conical threaded portions separated by a second annular shoulder lying in a plane perpendicular to the axis of the pipe, the male and female members being Each of them is provided with two sealing surfaces, which are respectively located on the opposite axial ends of the corresponding threaded parts, which can be threaded oppositely to each other one inside the other, so that the two Contact is formed between two annular shoulders, characterized in that the respective two threaded portions of each male and female member have the same conicity value, the first of the respective two sealing surfaces of the male and female members One has a conical shape and the second has a spherical shape.

Thanks to this embodiment, this joint allows easy installation of the pipeline, reducing the risk of damage to the joint, yet guaranteeing an optimum resistance of the pipeline at the joint.

Preferred embodiments of the invention are specified in the claims.

Description of drawings

The features and advantages of the present invention can be further understood by reading the detailed description of non-limiting preferred embodiments of integral joints with reference to the following figures.

Fig. 1 is a sectional view along the axial plane of the joint according to the present invention, with two components in disassembled position among the figures;

Figure 2 shows the joint of Figure 1 with its two components in assembled position;

Figure 3 shows an enlarged view of the details of the threaded connection of the joint in Figure 1;

Figure 4 shows a sectional view along the axial plane of another embodiment of the joint according to the present invention, with the two components in a disassembled position;

Figure 5 shows the joint of Figure 4 with its two components in assembled position.

Detailed ways

Referring now to the above figures, the joint according to the invention comprises two members or tubes, namely a male member 1 and a female member 2 . The joint is made up of an inner 20 in which fluids such as natural gas or oil or other similar fluids or liquids flow under pressure, and an outer 30 which may be filled with different fluids or liquids, usually also filled with pressed. The outer diameter 3 of the pipe 2 with the largest diameter of dimension D' in the joint area is slightly larger than the outer diameter 4 of the dimension D" in the central area of the pipe 2 away from the joint. The above two pipes with different outer diameters 3 and 4 Regions are connected in a gradual way. Dimension D' is greater than dimension D" by a value equal to or less than 3%.

The female part 2 of the fitting has an internal thread divided into two parts, namely steps 8 and 9, with a conical generatrix at an angle to the pipe axis. Said two parts 8 and 9 are radially offset, and the thread can be complete over its entire length, or it can also have a part that is not complete. Said embodiment is represented in FIGS. 1 and 2 .

In another embodiment of the invention shown in Figures 4 and 5, the threaded portions 7 and 8 may each have an end with an incomplete thread.

The two portions 8 and 9 have the same degree of conicity with a value between 6.25 and 12.5%. This range has proven to be optimal, on the one hand because lower values make the thread too long and difficult to connect, and on the other hand because higher values reduce the number of teeth and thus make the thread insufficient in load-bearing capacity.

In the area of connection between the threaded part and the inner surface of the pipe, away from the joint, the female member is provided with an area 12" with a conical surface relative to the axis of the pipe. The conicity of this surface is between 12.5% and 25% so that Good sealing of the corresponding contact surface with the male member is ensured, thereby shortening the sliding time during the threading step.

This range has proven to be optimal with respect to thread conicity, reducing the negative effects of traction loads. In the connection area between the two threaded parts 8, 9, the female member is provided with a shoulder 5" lying substantially in a vertical plane relative to the axis of the joint, the area of which is not less than 25% of the cross-sectional area of the pipe.

Between the shoulder 5″ and the beginning of the threaded portion 8 is provided a cavity 15 which extends along the entire inner circumference of the female member 2. This cavity can be used as an expansion cavity for the grease lubricating the joint, said The grease is present in the two threaded parts 8, 9 and is carried by the pushing action generated by the sliding of the members 1 and 2 during the threaded connection. The solution limits the excessive Grease pressure, thereby reducing stress on joints.

An annular surface 13'' is provided at the end of the female member 2, and this spherical surface is in contact with the conical area 13' facing it after screwed with the male member, ensuring the tightness of the joint to external pressure.

The tooth profile of the thread is of the "hook" type, with a load flank 10 and an entry flank 11 with a negative angle α between 0° and -10°, the entry flank 11 The flanks have a positive beta angle with a value between 10° and 30°. These ranges of values have the distinct advantage of still ensuring that the joint can be easily installed. The load flank with a negative angle can effectively connect the two members of the joint, reducing the possibility of joint disengagement due to too high traction load. An entry flank with a positive, moderate angle enables the threaded connection to work effectively with the ability to withstand compressive loads.

In the area of the outer surface close to the threaded portion of the female member, the male member 1 is provided with a thread placed in a perfect reciprocating manner, which thread has a portion shaped in a strictly analogous manner with respect to the above-mentioned threaded portion of the female member.

The member 1 is provided with two threaded portions 6, 7 separated by a shoulder 5' and a circumferential cavity 14 between the shoulder 5' The provision of the two grease expansion cavities 14 and 15 makes it possible to limit the increase in grease pressure after screwing of the joint, thereby avoiding excessive pressure on the joint and improving the function of the joint.

The connection area between the outer surface of the component 1 and the threaded portion 7 has a conical surface 13' with a conicity between 12.5 and 25%. This surface exerts pressure on surface 13" after the joint has been threaded, and the dimensions and tolerances are chosen such that the metal-to-metal contact ensures a seal against the ingress of liquid or fluid under pressure outside the joint.

Similarly, at the end of the male member 1 there is a spherical surface 12' which exerts pressure on the conical surface 12' of the female member after screwing with said female member. In addition, in this second region, the metal-to-metal contact between the two members creates a pressure which ensures the necessary tightness against the pressure of the fluid inside the tube. According to the invention, the choice of arranging metal seals with spherical and conical surfaces in two regions of the joint end makes the joint less sensitive to pressure loads, which has proven to be optimal for thin tubes. In fact, considering the thinness of the ends provided with the sealing surfaces 12' and 13', the internal and external pressures of the tube acting on said ends tend to cause bending of the ends. Thus, the spherical sealing surface is able to maintain optimum contact, unlike the case of frusto-conical seals where contact cannot be maintained over the entire sealing portion due to the rotation caused by the bending of the ends.

The thread shape of the male member 1 is the same as that of the aforementioned female member 2 . The thread preferably has a complete shape.

In another embodiment of the invention shown in Figures 4 and 5, the ends of one or both of the two threaded parts 6, 7 of the male member, for example the region 6' close to the shoulder 5', may have a band Threads with complete shape. The corresponding part 8 of the female member on the side of the shoulder 5" facing the area 6" has a complete thread. The region 8' on the axially opposite end of the threaded portion 8 to the region 6', i.e. the region close to the sealing surface 12", also has a thread with an incomplete shape. However, this region can also be provided with a complete thread.

The same kind of processing can also be carried out on the threaded parts 7 and 9, wherein part 7 is provided with a complete thread on the side of the shoulder 5' and part 9 is provided with an incomplete thread on the side of the shoulder 5". As an addition to this embodiment or Alternatively, the part 7 can also be provided with a region 7' with an incomplete thread on the side of the sealing surface 13', and the part 9 can be provided with a complete thread on the side of the sealing surface 13".

As can be seen from the foregoing description, according to the advantages of the joint of the present invention, its diameter is smaller than the diameter of the "semi-embedded" joint of the prior art, but slightly larger than the diameter of the "reasonable" joint, and can be Guaranteed optimal performance and productivity.

Claims (11)

1. pipe integral threaded joint, it comprises a male element (1) and a female element (2), described male element is provided with on its outer surface that two spaced radials come, the helical thread portion (6 of frustoconical, 7), described two helical thread portions (6,7) be positioned at separately perpendicular to first annular shoulder (5 ') on the plane of tube axis, described female element surface within it is provided with that two spaced radials come, the helical thread portion (8 of frustoconical, 9), described two helical thread portions by one be positioned at perpendicular to second annular shoulder on the plane of tube axis (5 ") are separately; each in described male element (1) and the female element (2) be provided with two sealing surfaces (12 '; 13 '; 12 ", 13 "); they lay respectively on the axial end portion opposite with respective threaded part (6; 7; 8; 9); corresponding two helical thread portions (6,7,8,9) can one in another, reciprocally be threaded, so that described two annular shoulders (form contact between 5 ', 5 "), it is characterized in that: each male element (1) and female element (2) two helical thread portions (6; 7; 8,9) separately have identical conicity value, separately two sealing surfaces of described male element and female element (12 '; 13 '; 12 ", first in 13 ") has coniform shape, second has spherical form.

2. joint as claimed in claim 1, it is characterized in that: at least one in described male element (1) and the female element (2) is at one of described two helical thread portions and corresponding annular shoulder (5 ', 5 " comprise a circumference cavity (14; 15)); the expansion that described cavity (14,15) is suitable for admitting the joint lubricant grease along its whole surface.

3. joint as claimed in claim 2, it is characterized in that: each in described male element (1) and the female element (2) comprise along its whole surface, be arranged on one of described two helical thread portions and respective annular shoulder (5 ', 5 " the described cavity (14,15)).

4. joint as claimed in claim 3 is characterized in that: (one of D ") is equal to or less than 3% value to described female element (2) greater than the size of same female element (2) external diameter (4) in the size of the external diameter (3) of joint (D ').

5. joint as claimed in claim 4 is characterized in that: two helical thread portions (6,7,8,9) of described male element (1) and female element (2) respectively have the identical conicity value between 6.25 and 12.5%.

6. joint as claimed in claim 5 is characterized in that: (13 ', 12 ") have a conicity value between 12.5% and 25% to the corresponding sealing surfaces of described male element (1) and female element (2).

7. joint as claimed in claim 6 is characterized in that: the shape of thread has the load flank and the flank that enters that is just having (β) angle that have negative (α) angle.

8. joint as claimed in claim 8 is characterized in that: described member (α) angle has the value between 0 and 10 °, and described just (β) angle has the value between 10 and 30 °.

9. joint as claimed in claim 8 is characterized in that: corresponding two helical thread portions (6,7,8,9) of each in described male element (1) and the female element (2) are provided with complete screw thread for its total length.

10. joint as claimed in claim 8 is characterized in that: at least one in described two helical thread portions (6,7,8,9) of at least one in described male element (1) and the female element (2) is provided with first end (6 ', 7 ') of incomplete screw thread.

11. joint as claimed in claim 10, it is characterized in that: described at least one another respective threaded part in described male element (1) and the female element (2) also be provided with one be arranged on the described first end axial opposed end, second area (8 ', 9 '), this zone has incomplete screw thread.

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