CN101021147A - Sucker rod connection with improved fatigue resistance - Google Patents

Abstract

Sucker rod connections are provided, preferably for rods with 5/8'' to 1 1/8'' diameter, with improved fatigue resistance, formed by applying diametrical interferenc e to prevent disengagement, reducing axial interference between the pin shoulder of a mal e member and the box shoulder of a female member. The connection may comprise a tapered threaded connection and trapezoidal threads, where contact among threads is flank-to- flank, load and stab, the crest of the thread being a little larger than the root of the thread. Each rod may have from about 4 to 10 threads per inch, preferably about 6 and 10 threads per inch (25.4 mm), the thread flank angle ranges from about 2.degree. to 10.degree., preferably about 3.degree. with a line perpendicular to the connection axis, and the connection taper is from about 1/15 to 1/30 relative to diameters of the connection. The flank-to-flank contact improves fatigue performance and the width and angle of the threads are determined considerin g a very low plastic thread deformation. Furthermore, the tensile stresses and plastic deformations that appear upon loading the rod connection are reduced and their distribution is more homogeneous than in the case of a cylindrical connection with no diametrical interference, where release engagement depends solely on axial interference.

Description

Pumping rod connecting device with improved antifatigue

Technical field

Embodiments of the invention relate to a kind of pumping rod connecting device, more particularly, relate to a kind of pumping rod connecting device with improved antifatigue and preparation method thereof.

Background technology

The bar that sucker rod is normally made by steel or other materials is to be used for forming the mechanical component between surface and downhole (downhole) element of being positioned at of insert pump.Sucker rod is grown up about 25 to 30 feet (about 7 to 9 meters) usually, has threaded so that the downhole element easily advances and withdraws from the end of stock.Sucker rod can be connected with a screw thread box or other are threaded the connecting thread pin.Usually the diameter of sucker rod be 5/8 " (5/8 inch), 3/4 ", 7/8 ", 1 " and 1-1/8 ".

Diameter is 22.22 millimeters (1/8 inches), grade D, and the bar of API-11B produces the failure problems especially severe.Most of faults of pole occur in the last connecting portion (screw thread) of threaded.In the prior art, for example diameter is 22.22 millimeters (1/8 inches), grade D, and the bar of API-11B, the screw thread of bar is columniform, the diameter of pin screw thread is slightly more small than the diameter of described box.As Figure 1A and shown in Figure 3, when linking together, have only the load side (load flanks) of pin to contact with box.Therefore in other words,, be necessary when they contacts because there is not radial interference (interference), introduce between the shoulder of the shoulder of box and pin, connecting high be out of shape in case anti-avulsion from.This distortion produces bigger axial tension and produce compression in box in pin.Because assembling, the pulling force in the pin is added to the external tension (fatigue) of circulation again, and is displaying when bar is pumped in well.As a result, thus this tension force often surpasses the screw thread place that power that steel can bear in the end connects ruptures shank.

Summary of the invention

For solving the problem of bar fatigue, some embodiments of the present invention relate to the connection of sucker rod, and target is to strengthen because the tired fault-resistant ability that causes.

One embodiment of the present of invention relate to a kind of linkage of sucker rod, the end that preferably includes the rod that is connected the screw thread box has the pin of screw thread, wherein improve antifatigue by using radial interference, it prevents to break away from and reduces substantially with the axial interference in the design formerly.More particularly, the embodiment of the invention relates to a kind of linkage, and it comprises tapered thread connection, trapezoidal thread and side being threaded to side, load and clinching.Further embodiment comprises the shoulder near the rear end screw thread of pin, and its surface is perpendicular to the axle of pin.Described box can have another shoulder that close screw thread begins, and its surface is perpendicular to the axis of described box.In the time will assembling, two surfaces are in contact with one another with accurate control radial interference.

In one embodiment, the connection of a taper or taper thread, trapezoidal thread, side are combined side screw thread contact, load and clinching.Preferably, described linkage per inch approximately comprises 4 to 10 screw threads, it is characterized in that, the angle of the flank of each screw thread roughly becomes 2 to spend to the scope of 10 degree with respect to the vertical line that connects axis, preferably, is approximately 3 degree.The tapering that is threaded is roughly from 1/15 to 1/30 of the diameter of described connection.

End in assembling also can comprise shoulder, and is similar but inequality with preceding case.Like this, the minimizing that can obtain axial interference by the mode of radial interference prevents to break away from.The reason that can obtain this radial interference is that the trapezoidal entity part of a screw thread enters the part of the trapezoidal sky of another screw thread, obtains the wedge shape effect.In other words, the top of screw thread is greater than the root of screw thread.

As mentioned below, tired parameter D is calculated by following formula:

$\stackrel{\&OverBar;}{{\mathrm{\&sigma;}}_m}=\frac{{\mathrm{<figure-callout\; id="1"\; label="S\; m"\; filenames="A20071000084400151.png"\; state="\{\{state\}\}">S</figure-callout>}}_m+S_{m2}+S_{m3}}{3}$

${\mathrm{\&sigma;}}_a=\frac{[{(S_{a1}-S_{a2})}^2+{(S_{a2}-S_{a3})}^2+{(S_{a3}-S_{a1})}^2{]}^{1/2}}{\sqrt{2}}$

$D=\frac{\frac{T}{3}-\stackrel{\&OverBar;}{{\mathrm{\&sigma;}}_m}}{{\mathrm{\&sigma;}}_a}$

Wherein:

S _Ai: the alternating component of main stress bar

S _Mi: the average weight of main stress bar

T: minimum tensile strength

Maximum value and minimum value according to duty cycle are calculated alternating component and average weight.

Preferably, coefficient D is higher than or equals 1 to guarantee extremely long fatigue life.

In the research formerly, (API recommends to carry out 11BR according to the API-11BR standard, " Recommended Practice for Care and Handling of Sucker Rods ", in October, 1989, this whole introducing for your guidance), after the shoulder contact, the circumferential displacement of the external diameter of the shoulder of pin be 7.14 millimeters (9/32 "); Such shift value means 0.14mm (the axial interference of .0055 ").(external diameter of the shoulder of 1.626 "), girth are 129.75 millimeters (5.108 ") for 41.3 millimeters of pins; Therefore screw thread axial distance (thread lead) is 2.54 millimeters, and (.100 "), the circumferential displacement of 7.14 millimeters (.281 ") produces the axial interference of 0.14 millimeter (.0055 ").

Therefore, the purpose of some embodiment described herein provides to be had radial interference the sucker rod of (diametricalinterference) connects, and it can reduce axial interference.

Another purpose of some embodiment described herein is to connect by tapered thread described connection is provided, and has trapezoidal thread, side to side, load and clinching and the contact between them.

Another purpose of some embodiment described herein is to reduce axial interference by radial interference.

Another purpose of some embodiment described herein is by the side side, load and clinching and the contact between them to be improved anti-fatigue ability.

The other purpose of some embodiment described herein is the width of thread and the angle that low thread distortion and design correspondingly are provided.

The other purpose of some embodiment described herein is to reduce tensile stress and distortion when connecting when loading, and reduces plastic strain, and is more even compared with the distribution of those tension force of cylindrical thread connected mode and distortion like this.

Description of drawings

Fig. 1 shows the taper connection according to one embodiment of the present invention.

Figure 1A is presented at cylindricality traditional between sucker rod and the screw thread box and connects.

Figure 1B shows the taper connection of using trapezoidal thread according to one embodiment of the present invention.

Fig. 1 C shows the pitch line position with respect to trapezoidal thread among Figure 1B, makes that the cavity side of this screw thread is identical with solid side.

Fig. 2 A and 2B show the improved Goodman chart of D grade pumping rod, and the both is used to detect the maximum stress of fatigue limit, minimum stress and the permission of stress.Three load cycles from-1.8 to 7.2kg/mm ²(2.56 to 10.2ksi (KSI)), 1.8 to 20.7kg/mm ²(2.56 to 29.4ksi) and 13.5 to 27kg/mm ²(19.2 ksi are to 38.4ksi).Here the 3rd load cycle of Shi Yonging is meant in three load cycle and connects pointed that.

Fig. 3 is presented at each main stress bar of the yield stress that connects with respect to tradition in the assembling process.

Fig. 4 A is presented at the plasticity tension force in the assembling process, and Fig. 4 B is presented at the plasticity tension force under the 3rd load cycle maximum load that is used for traditional cylinder connection.For two kinds of situations, plasticity tension force is at (A) with (C).

Fig. 5 is presented at the chart that five zoness of different are used for the fatigue ratio D of traditional rod connection.

Fig. 6 is presented in the assembling process and is used for cylinder in tension force and is connected on the screw thread contact force corresponding to maximum fatigue and cyclic.

Fig. 7 is presented in the connection of embodiment of the present invention under the 0.20mm radial interference, in assembling process corresponding to three right angle main stress bares of yield stress; Wherein the main stress bar for numerical value i equals 1,2 or 3.Relative main stress bar N ° of i=main stress bar i/ yield stress.(also with reference to Figure 11)

Fig. 8 A shows the plasticity tension force under the 0.20mm radial interference in being connected of an embodiment of the invention with 8B, in assembling process and under maximum load, shows plasticity tension force (A).

Fig. 9 shows the chart of fatigue ratio D in the connection of one embodiment of the present invention, under five kinds of zoness of different and 0.20mm radial interference, has shown zone C.

Figure 10 is presented in the connection of one embodiment of the present invention, and under the 0.20mm radial interference, the chart of contact force on the screw thread in assembling process and in the assembling process of maximum load, has the top line of the expression axial force limit (5000kg).

Figure 11 is presented in the connection of one embodiment of the present invention, under the 0.10mm radial interference, in assembling process with respect to three main stress bares of yield stress.

Figure 12 A and 12B are presented at the plasticity tension force in being connected of one embodiment of the present invention, the 0.10mm radial interference and have shown in the maximum load of plasticity tension force (A).

Figure 13 shows the fatigue ratio D chart of one embodiment of the present invention, the plasticity tension force (C) shown in having under five zones of different 0.10mm radial interference.

Figure 14 is presented at the chart of contact force on the screw thread of connection of one embodiment of the present invention, under the 0.10mm interference, in assembling process and have in the assembling process of maximum load, has the top line of the expression axial force limit (5000kg).

The specific embodiment

The present invention is about sucker rod, illustrates hereinafter especially for the embodiment of the connection of this sucker rod.

As shown in Figure 1, being threaded between sucker rod and screw thread box comprises box thread end 20 according to one embodiment of present invention, and perhaps box and male thread end 40 are perhaps sold, and both are corresponding mutually, usually, and cone-shaped inner surface 22,42.Preferably, cone-shaped inner surface 22,42nd, about 1/15 to 1/30 of the diameter of pin or box.These cone-shaped inner surfaces 22,42 comprise screw thread.Shown in Figure 1B, screw thread 100 have internal diameter wherein the external surface of each screw thread and pin or box engage and external diameter wherein each screw thread arrive its top.Like this, each screw thread has the groove 102 that is adjacent.

Box thread end 20 and male thread end 40 are adjacent to shoulder 30 when coupling together fully, as shown in Figure 1.

The connection that the present invention proposes, what be connected with radial interference is that tapered thread connects, the axial shrink value that does not need original known thread to connect is so high.Analyzed two axial shrink values (0.10 and 0.05 millimeter),, adopted less value on the basis of obtaining a result according to the limited component models that is used to connect.

The character of D grade material is existing in API 11B to be determined.According to von Mises stress criterion and isotropic hardening, desirable material is elastoplast, have the polyteny hardened material of relevant plasticity.Steel are embodiment, and this material has the linear deformation in its elastic limit.Along with the generation of permanent deformation, plastic deformation occurs on the elastic limit.

The cardinal principle situation of five embodiment of following form display analysis.Comprise that from one tapered thread connects, trapezoidal thread and side are to the side, (for example contacting of load and clinching, the contacts side surfaces of shown screw thread 100 among Figure 1B), but the effect of difference choice variable, for example in the axial interference of shoulder, radial interference, the width and the flank angle of screw thread are all analyzed.

In the embodiment of each above-mentioned five analysis,, thereby and both diameters are subtracted each other the measured place radial interference by the pitch diameter of thread of measuring pin, the pitch diameter of thread of box.Like this, the pitch diameter of thread on the meaning pin of radial interference is bigger than the pitch diameter of thread of box.

But the groove of screw thread also may interference.In other words, the outside diameter of thread of pin can be bigger than the screw thread interior diameter of box.

More than each width of thread of five embodiment measure at the threaded line place of each screw thread 100, shown in the label Y of Fig. 1 C.Measure flank angle γ (gamma) in lateral side wire with between, shown in Figure 1B perpendicular to the line of connecting axle.

Following table shows different situations.

	The axial screw thread of per inch (screw thread/25.4 millimeter)	Angle of the flank (load and clinching)	Axially interference	Radial interference
					Embodiment
1	8	7°	0.10mm	0.20mm
					Embodiment 2	8	7°	0.05mm	0.20mm
Embodiment 3	8	7°	0.05mm	0.05mm
					Embodiment 4	6	3°	0.05mm	0.20mm
Embodiment
	5	6	3°	0.05mm	0.10mm

Yield stress: 59.77kg/mm2=85 KSI (initial stress of D grade yield stress or plastic strain)

Five embodiment interpretations of result

The icon that should be noted that Fig. 6 shows the power on the screw thread be applied to pin, and No. 1 pitch of thread from shoulder farthest.

Embodiment 1

Design more undesirable both ways: (the plastic screw thread) of structure and fatigue (bigger negative value coefficient).In the high more place of major principal stress, coefficient D shows poor more performance.Such stress is the result of axial interference.

Embodiment 2

We improve stress distribution in the reduction of axially interference at hypothesis, and therefore, fatigue ratio D is confirmed.But, the problem of screw thread plasticizing or screw thread fatigue is still arranged.

Embodiment 3

From structure and tired related angle, though the result that present embodiment obtained is pretty good, radial interference is considered very little, because it is near producer's the grade of tolerance, and 0.05 millimeter of general every part (perpart).Like this, 0.05 millimeter radial interference means, in practical operation, this radial interference is can be the same with 0.10 millimeter big or can be the same little with 0.00 millimeter.

Embodiment 4

With tired relevant, the result who is obtained is pretty good from structure.Remember linkage producer's tolerance, analyze repeatedly that this numeral is considered to the radial interference value of nominal with 0.20 millimeter radial interference.

Embodiment 5

Analyzed a less radial interference value in the present embodiment.Obtained result is good concerning two radial interference values.Scope of determining and producer's tolerance are consistent.

Fig. 1 (A and B) and Fig. 2 (A and B) are existing hereinbefore to be described.Fig. 3 to 14 shows the comparative result of two designs, and clear proof taper connection is for the advantage of cylindrical connection.As in the used description of Fig. 3 to 14, " equipment " or " assembling " moment of torsion is the needed moment of torsion of axial interference of obtaining specified quantitative, is applied to after the shoulder 30 and contacts, as shown in Figure 1.Numeral shown and tightening the process intermediate principal stress, equal plastic strain and the final power on the pin screw thread and calculate the fatigue ratio that is considered to crucial in some zone.Remember the relation of producer's tolerance value, test need be considered two radial interference when carrying out, and one lower (0.10 millimeter) in higher one (0.20 millimeter) and the Embodiment B all produces similar effect in the embodiment A.Fig. 3,7 and 11 show the disappearance along with the high stress areas between the last screw thread that is connected at shoulder with pin, the main stress bar value is also reducing.Because reduce axial interference, thereby improve the fatigue performance that connects.

About plastic strain, it is unimportant that Fig. 8 A, 8B, 12A, 12B are presented in the taper connection plasticity.For 0.20 millimeter radial interference in Fig. 8 A and 8B, have only plastic strain, for 0.10 millimeter radial interference among Figure 12 A and the 12B, almost there is not plasticity.Among Fig. 4, the plasticity of seeing in cylindrical connection is more remarkable, and the last threaded portion that influence is connected with pin also is the most incidental place of fatigue.

It is better that fatigue ratio D shows in taper connection, and (referring to Fig. 5,9 and 13), this coefficient must be than 1 great fatigue lives to guarantee to connect greatly,

At last, be understandable that the power on pin screw thread of final force rate in cylindrical connection that (Figure 10 and 14) is added on the pin screw thread in taper connection is littler owing to less axial interference.

Though foregoing description shows, describes and points out the novel feature that the present invention is the most basic, but be understandable that, technical field those skilled in the art still can use different omission of the present invention, variation alternative, the details form to utilize the present invention in the scope that does not break away from the present invention's enlightenment.Therefore, the scope of the present invention's enlightenment should be not limited to aforementioned discussion, and should be limited by attached claim.

Claims (20)

1. a pumping rod connecting device comprises 5/8 inch to 11/8 inch of API scope, comprising:

The taper male element comprise several trapezoidal threads and

The female element of taper also comprises several trapezoidal threads, and wherein said male element can be housed in described female element to be threaded;

Wherein, the screw thread of male element and the screw thread of female element be the side to contacts side surfaces, therefore each screw thread has two sides, prevents the disengaging between public and female element and fully reduces axial interference setting up radial interference between described public affairs and the female element.

2. linkage according to claim 1 is characterized in that, described male element has shoulder and its surface longitudinal axis perpendicular to described male element, and described shoulder is positioned at the screw tip near described screw thread augmenting portion.

3. linkage according to claim 2 is characterized in that, described female element has shoulder in its front, perpendicular to the longitudinal axis of described female element.

4. linkage according to claim 3 is characterized in that, when the assembling linkage, described two shoulders contact also is provided at accurate radial interference between described male element and the female element screw thread.

5. linkage according to claim 1 is characterized in that, each described male element and female element comprise 4 to 10 screw threads on per inch.

6. linkage according to claim 1 is characterized in that, each described male element and female element comprise 6 to 10 screw threads on per inch.

7. linkage according to claim 1 is characterized in that the screw thread of described male element and female element all has angle of the flank, and load and clinching are with respect to have about 2 to 10 degree perpendicular to the vertical line that connects axis.

8. linkage according to claim 1 is characterized in that the screw thread of described male element and female element all has angle of the flank, and load and clinching are with respect to have about 3 degree perpendicular to the vertical line that connects axis.

9. linkage according to claim 1 is characterized in that, the tapering of described male element and female element with respect to male element and female element diameter separately in 1/15 to 1/30 scope.

10. pumping rod connecting device comprises:

Pin with screw tip part of taper; With

Box with screwed hole of taper, the end portion of wherein said pin is fixed by radial interference;

Wherein, the screw thread of described pin and box is trapezoidal, and the screw thread of described pin is that the side contacts side, load and clinching with the screw thread of described box, and the wedge shape effect is provided.

11. linkage according to claim 10 is characterized in that, approximately comprises 4 to 10 screw threads on described each pin and the box per inch.

12. linkage according to claim 10 is characterized in that, approximately comprises 6 screw threads on described each pin and the box per inch.

13. linkage according to claim 10 is characterized in that, the screw thread of described pin and box all has angle of the flank and has the angle of about 2 to 10 degree with respect to the vertical line that is connected axis.

14. linkage according to claim 10 is characterized in that, the screw thread of described pin and box all has clinching side and load flanks, has the angle of about 3 degree with respect to the vertical line of pin and box axis.

15. linkage according to claim 10 is characterized in that, the tapering of the perforate of described pin end portion and box with respect to separately diameter in 1/15 to 1/30 scope.

16. the pumping rod connecting device with axial interference of improved antifatigue and minimizing comprises:

The pin that comprises several trapezoidal threads with tapered distal end part; With

Box with screwed hole of taper, the end portion of wherein said pin is fixed by radial interference;

Wherein the screw thread of (i) described pin and the screw thread of box are that the side contacts load and clinching to the side; (ii) comprise about four to ten screw threads on each described pin and the box per inch; The screw thread of (iii) described pin and box has angle of the flank, and load and clinching have the angle of about 2 to 10 degree respectively with respect to the vertical line perpendicular to pin and box axis; The tapering of the perforate of (iv) described pin and box with respect to the diameter of end portion and perforate in 1/15 to 1/30 amplitude range; (v) surperficial shoulder is positioned on the pin and is positioned at the axis of the front of described box perpendicular to described box perpendicular to described pin axis and near rear end screw thread and another surperficial shoulder.

17. linkage according to claim 16 is characterized in that, comprises six screw threads on each described pin and the box per inch.

18. linkage according to claim 16 is characterized in that, the screw thread of described pin and box has angle of the flank, and load and clinching have the angle of about 3 degree with respect to the vertical line of linkage axis.

19. a method that connects sucker rod comprises:

Provide and have the sucker rod that has the tapered thread end portion;

Provide and have the box that has the tapered thread perforate;

To have the perforate that the tapered thread end portion is screwed into described box, and it is characterized in that, the screw tip part radially is connected with described threaded hole.

20. the method for connection sucker rod according to claim 19 is characterized in that, the end portion of described screw thread comprises trapezoidal thread.

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