RU2527562C2 - Fabrication of downhole pump sucker rod - Google Patents

Abstract

FIELD: engines and pumps.

SUBSTANCE: invention relates to machine building and can be used in production of long-sized sucker rods making the component of sucker rod string in oil extraction. Bar is subjected to machining and straightening-finishing. Thread is cut at bar ends while bulge is swaged ahead of said thread. Thrust ring is fitted at the bulge of bar every end and secured thereat. Thread heads are screwed on thread with interference fit. Internal and external thread is made on one thread head. Only internal thread is made on other head. Flats are made at side surfaces of thread heads. Used thrust ring has conical bore. Said thrust ring can be fitted in place at press in cold of hot state.

EFFECT: higher reliability, lower labour input.

6 cl, 4 dwg

Description

The invention relates to the field of engineering, and more particularly to the production of long sucker rods, which are components of a string of sucker rod rods used in oil production.

A known method of manufacturing a sucker rod, "Oil production by deep pumps" G. Rieschmüller. 1988 [1], consisting of a rod body in the form of a rod and threaded heads necessary to connect the rods to the column using couplings. According to the method, the head is made by upsetting the end of the rod, followed by execution on the thread head. Landing is carried out in several stages using a forging tool of a special design, which guarantees the alignment of the rod and the threaded head.

The disadvantages of the method include the fact that over time, due to wear of the forging tool, the alignment of the rod and the head during the manufacture of the rod is violated, which leads to a decrease in the quality of the manufactured rod. Moreover, even slight misalignment of the rod and the threaded head, exacerbated by the presence of a stress concentrator at the point of the diameter difference along the length of the rod that occurs during the formation of the threaded head, leads to a decrease in the reliability of the rod in operation due to the possibility of its failure as a result of fatigue fracture. It should also be noted that the method does not allow to vary the properties of the material of the rod and the threaded head to reinforce weak sections of the rod or sections that are subject to the greatest loads in operation.

In addition, the process of disembarking the threaded head at the end of a long bar is rather complicated, which, combined with the use of several stages of disembarkation, leads to an increase in the labor intensity and energy consumption of the rod manufacturing process.

A known method of manufacturing a pump rod RU No. 2119858 from 1998 [2], according to which for the body and the heads of the rod use billets of steel of different grades, separately carry out the thermal and mechanical processing of the billets, then by friction welding to the ends of the rod representing the rod body weld heads. The technological process for manufacturing a sucker rod is considered to be easily controllable and provides mass production of sucker rods of various quality categories, including those with a smaller amount of misalignment of the rod and the threaded head, and operational reliability. However, a high degree of quality and operational reliability of the rod using this manufacturing method cannot be obtained. First of all, the stress concentrator is preserved, which is now caused not only by the difference in the diameters of the rod and the threaded head, but also by the presence of a welded joint at this point, which, as a rule, is inferior in strength to the base material even with the highest quality of welding. As a result, the rod may break at the place of welding during operation. In addition, the method is not inferior in complexity and energy consumption to the method [1], since it is also multi-operational and requiring special equipment, in particular a friction welding machine, which allows welding long parts with a diameter of 8 to 30 mm with a force of up to 10 tons.

Closest to the claimed method is a method of manufacturing sucker rods RU 2329129 from 2008 [3], including machining the rod, including threading on the bosses obtained by upsetting the ends of the rod, and connecting the rod with threaded heads, where as threaded heads they use union nuts, which are pre-planted on the rod before landing.

However, the risk of a rod body and lugs at its ends occurring during misalignment remains with all the ensuing consequences for the rod quality described above, and this danger is greater the larger the diameter of the lug. It is necessary to note here that the diameter of the bosses of the boss should be sufficient to create a thrust collar for the union nut. As a result, the stress concentrator also remains due to the difference in the diameters of the rod and boss, although, as already noted, the degree of its influence on the quality of the rod is less than in [1]. The labor-intensive operation of landing the lobes is preserved, although, as already noted, it has one stage.

The objective of the invention is to increase reliability and reduce the complexity of manufacturing a pump rod.

The problem is solved by rolling the rods, machining, straightening, polishing and connecting with threaded heads. At each end of the rod 1 (Fig. 3), upsetting is performed in the form of a thickening to fit the thrust ring 2, the thrust ring is fixed and the threaded heads are tightened, and external and internal threads are made on the threaded head 3, and on the other threaded head 4 only internal thread, with flats provided on the outer surface of the threaded heads.

The hole of the thrust ring is tapered. The thrust ring is planted under pressure in a heated or cold state. The dimensions of the holes of the thrust ring are determined from the condition of landing a heated or cold ring on the bar. The length of the threaded part of the heads for connecting to the bar is longer than the corresponding lengths at the ends of the bar, for the convenience of screwing the heads with an interference fit. A threaded head having an internal thread at both ends is made so that the internal thread located in the peripheral part is longer than the length from the end of the nipple to the thrust collar.

An example of the method

A bar stock with a diameter of 100 mm from steel 30XMA is rolled onto a bar with a diameter of 20 mm. After rolling, the rods are tempered, forming the required level of mechanical properties. Then the bars are subjected to preliminary dressing and surface turning on a lathe to a diameter of 19.5 mm. Then follows the dressing-polishing operation by the method of cross-helical rolling. In the process of dressing, polishing, deformation hardening of the surface of the bar occurs, which significantly increases the fatigue strength and reliability of the rod. Rolling is carried out by polished hard alloy rolls, resulting in a bar of 19 mm with a hardened surface with a roughness of not more than R 0.63 and a curvature of not more than 0.3 mm per 1 m of length. Further, the rods are cut into 8000 mm long measured billets (rod body) and at their ends a thickening for the thrust ring is formed and tapered thread is obtained by knurling. Then, threaded heads are screwed onto the bar with an interference fit.

The threaded connection of the heads with the body of the rod is tightened to reduce the influence of the main variable loads on the strength of the threaded connection. In the tensioned state, the variable load is only partially transmitted to the threaded part and the strength of the tensioned joint at variable loads is greater than the unstretched one, which is relevant for variable loads on the rod string. The landing of the ring on the conical upset area of the bar allows to reduce the thickening of the landing. The tension is used to create a certain pressure at the joint of the parts for its tightness, which prevents loosening and wear of the connection.

To confirm this fact, a finite element calculation was performed. The equivalent stress at the discharge groove in front of the thread of the bar with tension and without tension was measured for cases of screwing the threaded head with an interference fit and without. For both cases, stretching occurs with the same effort. The results are shown in Fig.1 and Fig.2, according to which for the case of make-up tightening, the voltage amplitude is reduced, which increases the fatigue strength of the area. Figure 3 shows the structure of the pump rod: 1 - rod with upset, 2 - thrust ring, 3 - threaded head with external and internal thread, 4 - threaded head only with internal thread, 5 - flat. Figure 4 shows the heads of the finished pump rod.

Perhaps by landing in one transition a slight increase in the diameter of the rod under the thrust ring, which is unable to adversely affect the quality of the rod. The shape of the planted section of the bar has a smooth increase in diameter, which prevents the formation of a stress concentrator. For the manufacture of threaded heads, a material having greater strength can be used. The greater strength of the material of the threaded head can be achieved, in particular, due to the different heat treatment of the rods, the threaded head can be made of steel of a different brand, which has greater strength due to alloying.

The technical result of the method is to increase reliability and reduce the complexity of the rod and the entire column of the rods by ensuring the alignment of the rod and the threaded heads, as well as by preventing the occurrence of hubs.

The advantages of this method compared with known technical solutions is to increase reliability and reduce the complexity of manufacturing a pump rod.

Threaded heads and thrust rings are small in size, which allows them to be manufactured on high-performance machines. A large number of parts can be processed in one furnace.

Information sources

1. Heinrich Reschmüller. Oil production by deep sucker rod pumps. Ed. "Scheler-Blackman GMBH", Terlitz, 1988, 150 p.

2. RF patent No. 2119858, IPC V23P 15/00, 1998

3. RF patent №2329129, IPC В23Р 15/00, 2008 (prototype).

Claims (6)

1. A method of manufacturing a sucker rod for a deep pump, including rolling the bar, machining it, straightening-polishing and connecting with threaded heads made with internal thread, characterized in that at each end of the rod a thread is rolled up, before which upsetting is obtained a thickening for thrust rings, and thrust rings are fixed on the aforementioned thickenings of the bar, and the connection of the rod with threaded heads is carried out by screwing them with an interference fit on the threads at the ends of the bar, using threaded olovki with flats on the outer surface, and one of the screw heads operate with an external thread. 2. The method according to claim 1, characterized in that the hole of the thrust ring is conical. 3. The method according to claim 1, characterized in that the fixing of the thrust ring is produced under pressure in a heated or cold state. 4. The method according to claim 1, characterized in that the dimensions of the holes of the thrust ring are set from the condition of ensuring its fastening by landing on the rod a heated or cold thrust ring. 5. The method according to claim 1, characterized in that the length of the threaded portion of the inner surface of the threaded heads exceeds the length of the corresponding end of the threaded rod to allow screwed threaded heads to be tightened. 6. The method according to claim 1, characterized in that the threaded head having only an internal thread is performed with said internal thread at both ends, while the length of the peripheral part with an internal thread exceeds the distance from the end of the rod to the thrust ring.

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