GB2113745A

GB2113745A - A pump rod for a pump string

Info

Publication number: GB2113745A
Application number: GB08255978A
Authority: GB
Inventors: Helmut Benteler
Original assignee: Benteler Deustchland GmbH
Current assignee: Benteler Deustchland GmbH
Priority date: 1982-01-23
Filing date: 1982-12-17
Publication date: 1983-08-10
Also published as: JPS58127893A; FR2520435A1

Abstract

A pump rod (3) for a pump string comprises a central stem portion (2) which may be either of solid or tubular construction having welded to each end a screw-threaded end portion (4) separated from the central stem portion by a flat region (13). Each flat region (13) may comprise either part of the stem portion (2) or part of the associated end portion (4). Preferably the end portion (4) is friction welded to the central portion (2). <IMAGE>

Description

SPECIFICATION A pump rod for a pump string This invention relates to a pump rod which finds particular application in the oil industry. In the oil industry, such pump or "sucker" rods connected in a string are used to connect a pump provided at the bottom of an oil well shaft to activating means on the surface so that, where the oil flow is insufficient to raise the oil to the surface, the oil can be pumped to the surface.

Previously, pump rods, which comprise a relatively long central portion and screw-threaded end portions separated from the central stem portion by flat regions, have been produced as complete units from a blank. This necessitates a number of consecutive operations, including repeated heat treatment and machining operations. The rough forms of the screwthreaded end portions are first formed on the pre-rolled semi-product on forging machines in a number of operations. Forging is followed by heat treatment of the entire rod, the nature of the heat treatment depending on the quality required of the pump rod which of course depends on the intended use. As a result of the heat treatment, the pump rod subsequently has to be straightened and this is usually done by stretching. Finally, the external screw-threads are formed in each end portion by machining and rolling.

Pump or "sucker" rods produced in this way consist basically of a relatively long central stem portion made of solid material and externally screw-threaded portions adjoining each end thereof and separated from the stem portion by flat regions produced by forging. Two pump rods are coupled by means of an internally screwthreaded sleeve into which the pump rod screwthreaded end portions can be screwed.

It is an object of the present invention to provide a pump rod for which production costs are greatly reduced in comparison with previous such aump rods by a considerable reduction of production outlay.

According to the present invention, there is provided a pump rod for a pump string, the pump rod comprising a central stem portion and a screw-threaded end portion separated from the stem portion by a flat region, in which pump rod the stem portion and the screw-threaded end portions are interconnected by welding and the flat region forms part of either the stem portion or the screw-threaded end portion.

The present invention also provides a pump string formed by connecting together such pump rods.

In a preferred embodiment, the central stem portion has a screw-threaded end portion of each end, each screw-threaded end portion being connected to the central stem by a flat region, the stem portion and the screw-threaded end portions being interconnected by welding and each flat region forming part of either the stem portion or the associated screw-threaded end portion.

Preferably, the screw-thread of the or each enc portion is formed on the external surface of the end portion. Alternatively, the screw-thread of the or each end portion may be formed on an internal surface. Thus, there is no need for connecting sleeves. For example, the two ends of a first pump rod can both be provided with an external screwthread and the two ends of a second pump rod both with an internal screw-thread, the first and second pump rods then being assembled alternately in sequence to form a pump string.

In a further preferred arrangement, the screwthread of one end portion formed on an external surface of the one end portion and the screwthread of the other end portion is formed on an internal surface of the other end portion. In this way consecutive pump rods can be directly connected together without any additional screwthreaded sleeves. Of course, screw-threaded sleeves may be used to connect two pump rods together so as to be resistant to tension and compression or alternatively, instead of screwthreaded sleeves, couplings having screwthreaded plugs may be used if the screw-threaded end portions of the pump rods to be connected are provided with internal screw-threads.

Advantageously, the stem portion and the or each screw-threaded end portion are interconnected by friction welding and usually the or each end portion is provided with a welding collar. Friction welding enables stem portions of different diameters and/or strengths to be perfectly joined to precisely the screw-threaded proportions required. The connection is made by rotating one of the two parts to be connected while the second part exerts axial pressure on the first part. In these conditions mechanical energy is converted into frictional heat until the welding temperature is reached. The axial pressure is raised at that instant and movement of the rotating part stopped so that the two end faces rubbing on one another are welded together.

Desirably, the stem portion is solid.

Alternatively, the stem portion may be tubular. If the stem portion is tubular, for example, the buckling and bending strength are improved as compared with a solid material given the same tension loading. The use of tubular stem portions also has a favourable effect on assembly and transportation of the pump rods since the weight to be handled can be greatly reduced.

If a tubular stem portion is used, for example, of an outside diameter substantially the same as the diameter of the welding collar, it is advantageous for the flat region to be formed on the stem. In order to reduce machining costs, this can be done by pressing at the same time as the friction welding operation. In such a case the screwthreaded end portions can be made simply as turned parts on a lathe thus saving material and costs.

In a preferred embodiment, where a tubular stem portion has cross-sectional dimensions, for example a diameter smaller than that of the welding collar, the stem end to be connected to the welding collar is widened so that it is of enlarged cross-sectional dimensions relative to the remainder of the tubular stem portion. The widening operation is carried out to obtain substantially identical welding conditions. The flat regions can be formed at the same time as the widening operation and here again the screwthreaded end portions may simply be parts turned on a lathe.

Advantageously, where a tubular stem portion is of large cross-sectional dimensions, for example diameter, than the welding collar, the cross sectionai dimensions of the end of the stem portion to be connected to the welding collar are reduced. The reducing or narrowing operation is again intended to provide substantially identical welding conditions, particularly in the case of the friction welding operation. The flat regions can be produced at the same time as the cross-sectional dimension reduction and the screw-threaded end portions are again simply turned on a lathe.

Conveniently, the screw-thread of the or each end is a conical screw-thread obviating any need for separate screw-thread abutments. Hereagain constructions are possible with and without screw-threaded sleeves or couplings.

For a better understanding of the present invention and to show how the same may be put into effect, reference will now be made to the accompanying drawings, wherein: FIGURE 1 is an elevational view of part of a pump rod embodying the invention; FIGURES 2 to 6 are part-sectional elevational views each showing part of a pump rod embodying the invention; and FIGURES 7 to 10 are part-sectional elevational views showing the manner in which various of the pump or "sucker" rods shown in Figures 1 to 6 are connected to form a string.

Referring now to the drawings, Figure 1 shows a part 1 of a central stem portion 2 of a pump or "sucker" rod 3. The central stem portion is formed of solid material and each end thereof is connected by friction welding to a screw-threaded end portion 4 (only one of which is shown) by friction welding at a joint 5. A bead 6 is formed during the friction welding. The end portion 4 shown in Figure 1 is formed with a cylindrical external screw-thread 7 having an entry bevel 8 to facilitate introduction of the external screw-thread 7 into a corresponding screw-thread. A thread run-out 10 is provided between a collar 9 which acts as an abutment and the external screwthread 7.

The collar 9 and a welding collar 11 are connected by a longitudinal portion 12 of rectangular cross-section which is provided with flat regions 1 3. Each screw-threaded end portion 4 is a turned component produced on an automatic lathe.

Figure 2 shows the screw-threaded end portion 4 of Figure 1 connected to a tubular stem 2a by frictional welding. The outside diameter a of the tubular stem 2a is substantially the same as the outside diameter b of the collar 1 The welding bead 6 shown in Figure 1 has been removed in this embodiment.

Figure 3 shows that a tubular stem 2b, the wall thickness c of which is much thinner than the tubular stem 2a in Figure 2, can be connected by friction welding in the same screw-threaded end portion 4 when the outside diameter d of the stem 2b is substantially unchanged. A tubular stem 2b of this kind can, for example, be used for relatively low loading. Other weight savings can also be obtained in this way.

In the embodiment shown in Figure 4, the screw-threaded end portion 14 comprises only the cylindrical external screw-thread 7 with the entry bevel 8, the run-out 10 and the abutment collar 9.

In this embodiment, the abutment collar 9 also acts as the welding collar and the screw-threaded end portion 14 can thus be simply turned on a lathe.

In the arrangement shown in Figure 4, flat regions 1 5 are integral with a tubular central stem 2c. The flat regions 1 5 may be pressed directly during the joining by frictional welding of the stem 2c to a screw-threaded end portion 14. The outside diameter e of the tubular stem 2c is substantially the same as the outside diameter fof the collar 9.

Figure 5 shows the connection between the screw-threaded end portion 1 4 of Figure 4 and a tubular stem 2d the diameterg of which is smaller than the diameter fof the collar 9. To obtain substantially identical welding conditions, an end 1 6 of the stem 2d is widened out to form a pot as shown in Figure 5. The flat regions 1 5 which are situated between widened end the portion 1 6 and the remainder of the tubular stem 2d can be produced at the same time as the end 16 is widened.

Figure 6 shows the connection of a tubular stem 2e to the screw-threaded end portion shown in Figures 4 and 5. The outside diameter h of the tubular stem 2e is larger than the outside diameter fof the welding collar 9. In order to provide identical welding conditions in this case too, the diameter of an end 17 of the tubular stem 2e must be reduced. The flat regions 1 5 are produced at the same time as the reduction of the diameter of the end 1 7 and the corresponding dimension of the flat regions is also reduced.

Figure 7 is a diagram illustrating the manner in which two pump rods 3 are connected together.

The pump rods 3 may be similar to that shown in Figure 1. As shown in Figure 7, the pump rods are connected using a screw-threaded sleeve 1 8 having an internal screw-thread 1 9. The pump rods shown in Figures 2 to 6 can also be connected in this way.

If, instead of the screw-threaded portions 4 and 14 shown in Figures 1 to 6 which have external screw-threads 7, a screw-threaded end portion 20 having an internal screw-thread 21 is provided on the ends of the pump rods 3, two such pump rods can be connected by a coupling 22 as shown in Figure 8. The coupling 22 comprises two screwthreaded plugs 23 which can be screwed into the internal screw-threads 21 of the pump rods 3.

Figure 9 shows two pump rods 3 connected together without the use of a connecting sleeve 18 or a coupling 22. In this case, an external screw-thread 7 on one pump rod engages directly an internal screw-thread 21 on another pump rod 3. Of course, such an arrangement requires pump rods each having an external screw-thread 7 on one end portion and an internal screw-thread 21 in the other end portion, or a number of pump rods 3 having external screw-threads 7 on each end portion and a number of pump rods 3 having internal screw-threads 21 in each end portion so that first pump rods 3 having external screwthread 7 on each end portion and second pump rods 3 having internal screw-thread 21 in each end portion can be connected together to form a pump string comprising alternate first and second pump rods.

Figure 10 also shows an arrangement wherein two pump rods are directly connected. However, in this arrangement the screw-threaded end portions 24 and 25 to be connected have, respectively, a conical external screw-thread 26 and a conical internal screw-thread 27. This construction eliminates the need for the screwthread abutment collar 9 shown in Figures 1 to 6, only a welding collar 28 being needed.

In a pump rod in accordance with the invention, the central stem portion and the screw-threaded end portions, which are much shorter than the stem portions, are initially separate components.

Consequently the production process no longer requires the handling of complete pump rods; instead the stem portions and the screw-threaded end portions can be machined separately according to requirements. As a result, when the screw-threaded end portions are produced it is no longer necessary to handle stem portions of lengths of up to 9 m and more. On the contrary, the screw-threaded end portions can be designed from the outset as turned parts produced on an automatic lathe. It is only in the final phase that the screw-threaded end portions and the stem portions are interconnected. Another advantage of the initially separate production of the screwthreaded end portions and the stem portion is that the latter no longer have to match the screwthreaded end portions exactly. Stem portions of quite different constructions can be combined with any screw-threaded portions and welded together to form a pump rod. The time and material expenditure is thus guided into more specific production paths thus greatly increasing the cost-effectiveness of pump rod manufacture.

Claims

1. A pump rod for a pump string, the pump rod comprising a central stem portion and a screwthreaded end portion separated from the stem portion by a flat region, in which pump rod the stem portion and the screw-threaded end portion are interconnected by welding and the flat region forms part of either the stem portion or the screwthreaded end portion.

2. A pump rod according to claim 1 , the central stem portion has a screw-threaded end portion at each end, each screw-threaded end portion being connected to the central stem by a flat region, the stem portion and the screw-threaded end portions being interconnected by welding and each flat region forming part of either the stem portion or the associated screw-threaded end portion.

3. A pump rod according to claim 1 or 2, wherein the screw-thread of the or each end portion is formed on the external surface of the end portion.

4. A pump rod according to claim 1 or 2, wherein the screw-thread of the or each end portion is formed on an internal surface of the end portion.

5. A pump rod according to claim 2, wherein the screw-thread of one end portion is formed on an external surface of one end portion and the screw-thread of the other end portion is formed on an external surface of the other end portion.

6. A pump rod according to any preceding claim, wherein the stem portion and the or each screw-threaded end portion are interconnected by friction welding.

7. A pump rod according to claim 6, wherein the or each end portion is provided with a welding collar.

8. A pump rod according to any preceding claim, where the stem portion is solid.

9. A pump rod according to any preceding claim, wherein the stem portion is tubular.

10. A pump rod according to claim 9, wherein a or each end of the tubular stem portion is of enlarged cross-sectional dimensions relative to the remainder of the stem portion and is welded to a welding collar formed on the or the associated screw-threaded end portion.

11. A pump rod according to claim 9, wherein a or each end of the stem portion is of reduced cross-sectional dimensions relative to the remainder of the stem portion and is welded to a welding collar formed on the or the associated screw-threaded end portion.

12. A pump rod according to any preceding claim, wherein the screw-thread of the or each end is a conical screw-thread.

13. A pump rod substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

14. A pump string whenever produced by connecting pump rods in accordance with any one of claims 1 toll.

1 5. Any novel feature or combination of features described herein.