Constant-pressure sealing device for polish rod of pumping unit

Abstract

The invention discloses a pumping unit polish rod constant-pressure sealing device, and belongs to the field of oil exploitation, the pumping unit polish rod constant-pressure sealing device comprises a hydraulic push type constant-pressure pre-tightening sealing assembly, a hydraulic connecting pipeline and an adjustable constant hydraulic assembly, and through cooperation of the hydraulic push type constant-pressure pre-tightening sealing assembly, the hydraulic connecting pipeline and the adjustable constant hydraulic assembly, the constant hydraulic pressure can be adjusted. The pre-tightening force of the sealing filler can be accurately controlled and kept stable for a long time, the sealing performance of the sealing filler is automatically supplemented, the use efficiency of the sealing filler is maximized, meanwhile, the labor intensity of operators is relieved, and the operation time of the operators is shortened.

Description

Technical Field

[0001] This invention belongs to the field of oil extraction, specifically relating to a constant pressure sealing device for the polished rod of an oil pumping unit. Background Technology

[0002] In oil extraction technology, pumping unit components are used to extract oil from the formation. The surface pumping unit drives the downhole pump to move up and down through the sucker rod, continuously pumping oil out of the wellhead. This is a commonly used oil extraction method in the current oil extraction industry.

[0003] As the sucker rod moves upward, a certain pressure is generated inside the wellhead. The performance of the sealing components used to seal the polished rod (the uppermost sucker rod) directly affects oil extraction, mainly in the following aspects: First, if the preload of the sealing packing is insufficient, the polished rod will not seal properly, and oil in the well will overflow through the gap between the polished rod and the sealing packing, causing environmental pollution. Second, if the preload of the sealing packing is too large or there is significant uneven wear, the frictional loss of the sealing packing will be large, resulting in an increased frequency of sealing packing replacement. Third, the sealing packing needs to be replaced after a period of use to maintain its sealing performance. Due to the narrow location of the sealing packing, the replacement operation is difficult, time-consuming, and labor-intensive.

[0004] Technicians are continuously improving the polished rod sealing assembly at the wellhead of pumping units. However, two major problems persist: seal failure due to unstable preload and difficulty in removing used packing material during replacement. Therefore, developing a sealing assembly that can maintain a consistent preload for the packing material over a long period and facilitates easy replacement, thereby achieving reliable sealing of the polished rod, efficient use of the packing material, and convenient replacement, and solving the problems existing in current pumping unit wellhead polished rod seals, is a pressing technical challenge in the oil extraction field.

[0005] In existing wellhead polished rod sealing technology for oil pumping units, the replacement, addition, and pre-tightening of the sealing packing are usually done based on personal experience. This cannot achieve precise control of the pre-tightening force. Furthermore, as the polished rod moves back and forth, the sealing packing is quickly worn away, or over time, the elastic expansion of the sealing packing itself may not be sufficient to replenish the seal, leading to seal failure. Through long-term practice, technicians have made some improvements to this component.

[0006] For example, in Chinese patent literature, publication number CN205225150U, publication date May 11, 2016, entitled "A Leak-Proof Pumping Unit Wellhead Packing Box," the wellhead packing box includes a packing cap, a sealing packing box, packing, an annular cover plate, an annular scraper blade, a gland head, and an annular centering washer disc. The packing, also called sealing packing, utilizes a lubrication hole on the side wall of the sealing packing cap that communicates with the upper lubrication chamber. Adding lubricating grease to the upper lubrication chamber reduces frictional loss and mitigates wear on the sealing packing.

[0007] The publication number is CN111594089A, the publication date is August 28, 2020, and the name is Energy-saving Adjustable Packing Box. It mainly solves the problems of time-consuming and labor-intensive removal of sealing packing from existing oilfield sealing packing boxes, and the easy entry of sealing packing debris into the oil pipe causing blockage. This technology can bidirectionally compress the sealing packing, extending its service life to a certain extent. When removing waste sealing packing, no tools are needed, which also reduces the labor intensity of on-site operators to some extent.

[0008] As can be seen from the above, none of the existing technologies can achieve precise control of the pre-tightening force of the sealing packing and maintain a stable pre-tightening force over a long period of time, resulting in sealing failure and increased wear. When replacing the sealing packing, the removal of the waste sealing packing still requires manual operation, which is time-consuming and labor-intensive. Summary of the Invention

[0009] To address the shortcomings of the prior art, this invention provides a constant pressure sealing device for the polished rod of a pumping unit, which can precisely control the preload of the sealing packing and maintain a stable preload for a long time, automatically replenish the sealing performance of the sealing packing, maximize the efficiency of the sealing packing, and reduce the labor intensity and working time of the operators.

[0010] This invention is achieved through the following technical solution: A constant pressure sealing device for the polished rod of a pumping unit, characterized in that it comprises a hydraulically driven constant pressure pre-tightening sealing assembly, a hydraulic connecting pipeline, and an adjustable constant hydraulic assembly; the hydraulically driven constant pressure pre-tightening sealing assembly includes a hydraulic outer cylinder, which is connected to the adjustable constant hydraulic assembly via the hydraulic connecting pipeline; the lower end of the hydraulic outer cylinder is a connecting flange that mates with a wellhead valve flange, the upper end of the hydraulic outer cylinder is a stuffing box for filling with sealing packing, and a packing gland is provided at the top of the hydraulic outer cylinder, the packing gland being threaded and mating with the hydraulic outer cylinder; a hydraulic inner cylinder is installed inside the hydraulic outer cylinder, and the hydraulic inner cylinder is connected to the hydraulic outer cylinder and sealed by a sealing gasket to form an annular cylinder. An annular piston is installed inside the annular cylinder. Sealing rings are provided on both the inner and outer sides of the lower part of the annular piston. A limiting component is provided at the lower end of the hydraulic outer cylinder to limit the downward position of the annular piston. A separating component is provided on the upper inner wall of the annular piston to form two internal through holes of different diameters. The inner wall of the larger diameter internal through hole cooperates with the hydraulic outer cylinder to form a seal, and the outer wall cooperates with the inner wall of the hydraulic outer cylinder to form a seal. The smaller diameter internal through hole is used to pass through the polished rod of the pumping unit. An adjustable constant hydraulic component provides pressure to the cavity between the annular cylinder and the annular piston, and adjusts the pressure of the annular piston acting on the sealing packing in the sealing stuffing box to adjust the preload of the sealing packing.

[0011] Furthermore, the adjustable constant hydraulic component includes a hydraulic cylinder, a piston installed inside the hydraulic cylinder, and a step provided to limit the lower limit of the piston's downward displacement. A cylinder top locking ring is provided at the top of the hydraulic cylinder to limit the upper limit of the piston's upward displacement. A step is provided at the lower end of the piston, so that the piston forms two sections with different diameters. A piston sealing ring is provided at the lower end of the piston. The upper section of the piston passes through the cylinder top locking ring. A weighted bucket is provided at the top of the piston, and a weight is placed inside the weighted bucket. The weight applies pressure to the hydraulic cylinder through the piston. A hydraulic oil pipeline connector is provided on the lower exterior of the hydraulic cylinder, and the hydraulic oil pipeline connector is connected to the hydraulic cylinder through a through hole.

[0012] Furthermore, the hydraulic connection pipeline includes a hydraulic oil pipeline with a convenient connector, an oil cup valve is provided on the hydraulic oil pipeline, and the bottom of the oil cup valve is connected to the hydraulic oil pipeline; an oil cup valve front control valve is provided at the front end of the oil cup valve, an oil cup valve rear control valve is provided at the rear end of the oil cup valve, and a pressure gauge is provided between the oil cup valve front control valve and the oil cup valve rear control valve, and the pressure gauge is connected to the hydraulic oil pipeline through a pressure gauge control valve.

[0013] Furthermore, the oil cup valve consists of a valve body, valve needle, valve stem, valve seat, oil cup, oil cup cover, handwheel, etc. The valve needle and valve stem are designed as an integral unit, with external threads engaging with internal threads of the valve body. The displacement of the valve needle is controlled by rotating the handwheel at the upper end of the valve needle. The bottom of the oil cup has a connecting hole to the upper part of the valve seat. The oil cup is connected to the hydraulic oil pipeline through the connecting hole, and the hydraulic oil in the oil cup can enter and exit the hydraulic oil pipeline. Hydraulic oil can be added to the oil cup by opening the oil cup cover.

[0014] Furthermore, a limit locking ring is installed on the upper part of the hydraulic outer cylinder to limit the upper limit of the displacement of the annular piston.

[0015] Furthermore, the lower end of the hydraulic outer cylinder is a connecting flange that mates with the wellhead valve flange; a convenient interface for hydraulic oil lines is provided on the outside of the hydraulic outer cylinder, and the convenient interface for hydraulic oil lines is connected to the hydraulic outer cylinder through a through hole; a handle insertion hole for inserting a handle is provided on the outside of the packing gland.

[0016] Furthermore, the hydraulic outer cylinder can be machined separately from the connecting flange and then connected as a whole, or the connecting flange can be designed as a threaded connection.

[0017] Furthermore, the weighted barrel is designed to be cylindrical.

[0018] Furthermore, a bracket is provided on the top of the hydraulic cylinder, and a cylindrical bracket cover is provided on the top of the bracket, which is distributed in a ring around the weighted barrel; a base is connected to the bottom of the hydraulic cylinder.

[0019] Furthermore, locks or pins are installed between the bracket and the cylindrical bracket cover for restriction.

[0020] The working principle of this invention is as follows: Install the constant pressure sealing device for the polished rod of the pumping unit at the top of the wellhead assembly. Pass the polished rod through this assembly and connect it to the adjustable constant pressure hydraulic assembly via a hydraulic connection line. Open the front control valve and pressure gauge control valve of the oil cup valve, close the rear control valve of the oil cup valve, open the oil cup valve, add an appropriate amount of hydraulic oil to the oil cup, lift the weight bucket at the top of the piston, and the hydraulic oil in the oil cup is drawn into the cylinder. Close the oil cup valve, open the rear control valve of the oil cup valve, and add a weight to the weight bucket. The hydraulic oil flows through the hydraulic oil line to the annular cylinder in the hydraulic constant pressure pre-tightening sealing assembly. The hydraulic oil pushes the annular piston upward, compressing the sealing packing in the sealing stuffing box. After being compressed, the sealing packing expands radially, affecting the polished rod of the pumping unit located at the center. The system achieves a constant pressure preload on the sealing packing by adjusting the amount of weight. This allows observation of hydraulic oil line pressure changes and determination of the total weight based on the optimal preload required for different sealing packings. When the sealing packing is worn out, the annular piston moves upward, continuing to apply constant pressure to the packing, compressing it and compensating for the reduced sealing performance caused by packing wear. As the annular piston moves upward, the piston at the weight end moves downward, maintaining a constant pressure within the constant pressure sealing assembly. During initial use, repeatedly pumping oil or loosening the union to vent air from the constant pressure sealing assembly can remove air from inside, ensuring more reliable pressure transmission from the hydraulic oil and maximizing the utilization rate of the sealing packing.

[0021] When the hydraulic cylinder piston descends to near the low position, hydraulic oil needs to be replenished. During operation, close the control valve at the rear end of the oil cup valve to maintain the pressure at the wellhead. Open the oil cup cover, add an appropriate amount of hydraulic oil to the oil cup, remove the weight from the weight bucket, open the oil cup needle valve, lift the weight bucket, and the hydraulic oil is replenished into the constant pressure sealing assembly. Close the oil cup valve, put the original weight back into the weight bucket, open the control valve at the rear end of the oil cup valve, and the constant pressure sealing assembly returns to normal working condition.

[0022] When the sealing packing needs to be replaced, stop the pumping unit, close the wellhead polished rod sealing valve, close the front control valve of the oil cup valve, and open the oil cup valve. The hydraulic system pressure at the wellhead end is released, and the hydraulic oil exceeding the atmospheric pressure flows back into the oil cup. Remove the packing gland to open the sealing packing. Close the oil cup valve and slowly open the front control valve of the oil cup valve. The pressure in the annular cylinder at the wellhead end rises, pushing the annular piston upward, which can push out all the sealing packing in the stuffing box without manual cleaning. When adding new packing, close the front control valve of the oil cup valve again, open the oil cup valve, and press the annular piston down to the bottom dead center. The hydraulic oil in the annular cylinder flows back into the oil cup, and new sealing packing can be added into the stuffing box. After the sealing packing is added, tighten the packing cap, close the oil cup valve, and open the front control valve of the oil cup valve. At this time, since the total amount of weight applied in the weighting barrel has not changed, the hydraulic system pressure is the same as before. Restore the pre-tightening of the packing, and the well production can be resumed.

[0023] The beneficial effects of this invention are as follows: When applied to pumped oil wells, this invention enables precise control and long-term maintenance of the pre-tightening force of the sealing packing, automatically replenishing its sealing performance and maximizing its efficiency. This reduces costs and increases efficiency. Furthermore, it eliminates the need for manual adjustment during the packing's lifespan, lowering labor costs. The most time-consuming and labor-intensive task of packing removal in traditional techniques is also transformed from manual labor to hydraulic automatic removal, significantly reducing the workload and time required for operators. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 for Figure 1 Schematic diagram of the structure of the hydraulically driven constant pressure pre-tightening sealing assembly; Figure 3 for Figure 1 Schematic diagram of the adjustable constant pressure hydraulic assembly; Figure 4 for Figure 1 Schematic diagram of the composition and connection of the hydraulic connection pipeline; Figure 5 for Figure 4 Schematic diagram of the oil cup valve structure; Figure 6 for Figure 3 Schematic diagram of the support structure.

[0025] Reference numerals: 1-Hydraulically driven constant pressure pre-tightening sealing assembly; 2-Adjustable constant hydraulic assembly; 3-Hydraulic connection pipeline; 101-Smooth rod of pumping unit; 102-Hydraulic outer cylinder; 103-Hydraulic inner cylinder; 104-Annular piston; 105-Sealing packing; 106-Packaging gland; 107-Sealing gasket; 108-Hydraulic pipeline quick connector; 109-Annular cylinder; 110-Sealing ring; 111-Handle socket; 112-Limiting assembly; 113-Separating assembly; 201-Hydraulic cylinder; 202-Hydraulic oil; 203-Piston; 204-Bracket. 205-Weighted bucket, 206-Cylindrical bracket cover, 207-Base, 208-Hydraulic pipeline connector, 209-Piston sealing ring, 210-Cylinder top locking ring, 211-Weighted object, 212-Limit step, 301-Hydraulic oil pipeline, 302-Oil cup valve front end control valve, 303-Pressure gauge control valve, 304-Pressure gauge, 305-Oil cup valve, 306-Oil cup valve rear end control valve, 51-Valve body, 52-Connecting hole, 53-Oil cup, 54-Hydraulic oil, 55-Oil cup cover, 56-Valve seat, 57-Valve needle, 58-Valve stem, 59-Handwheel. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Example 1 A constant pressure sealing device for a pumping unit's polished rod includes a hydraulically driven constant pressure pre-tightening sealing assembly 1, a hydraulic connection pipeline 3, and an adjustable constant pressure hydraulic assembly 2. The hydraulically driven constant pressure pre-tightening sealing assembly 1 includes a hydraulic outer cylinder 102, which is connected to the adjustable constant pressure hydraulic assembly 2 via the hydraulic connection pipeline 3. The lower end of the hydraulic outer cylinder 102 is a connecting flange that mates with a wellhead valve flange, and the upper end of the hydraulic outer cylinder 102 is a stuffing box for filling with sealing packing 105. A packing gland 106 is provided at the top of the hydraulic outer cylinder 102, which is threaded into the hydraulic outer cylinder 102. A hydraulic inner cylinder 103 is installed inside the hydraulic outer cylinder 102. The hydraulic inner cylinder 103 is connected to the hydraulic outer cylinder 102 and sealed by a sealing gasket 107 to form an annular cylinder 109. An annular piston 104 is installed inside the cylinder 109. The lower part of the annular piston 104 is provided with sealing rings 110 on both the inner and outer sides. The lower end of the hydraulic outer cylinder 102 is provided with a limiting component 112 to limit the downward position of the annular piston 104. The upper inner wall of the annular piston 104 is provided with a separating component 113 to form two inner through holes of different diameters. The inner wall of the annular section of the larger diameter inner through hole cooperates with the hydraulic outer cylinder 102 to form a seal, and the outer wall cooperates with the inner wall of the hydraulic outer cylinder 102 to form a seal. The smaller diameter inner through hole is used to pass through the polished rod 101 of the pumping unit. The adjustable constant hydraulic component 2 provides pressure to the cavity between the annular cylinder 109 and the annular piston 104, and adjusts the pressure of the annular piston 104 acting on the sealing packing 105 in the sealing stuffing box to adjust the preload of the sealing packing 105.

[0028] In implementation, the limiting component 112 and the separating component 113 can be in the form of steps. The lower end of the hydraulic outer cylinder 102 is provided with a step one to limit the downward position of the annular piston 104. The upper inner wall of the annular piston 104 is provided with a step two to form two inner through holes of different diameters in the annular piston 104.

[0029] Example 2 This embodiment further elaborates and supplements the implementation of the present invention based on Embodiment 1.

[0030] In one embodiment of this invention, the adjustable constant hydraulic component 2 includes a hydraulic cylinder 201. A piston 203 is installed inside the hydraulic cylinder 201, and a step is provided to limit the lower limit of the downward displacement of the piston 203. A cylinder top locking ring 210 is provided at the top of the hydraulic cylinder 201 to limit the upper limit of the upward displacement of the piston 203. A step is provided at the lower end of the piston 203, so that the piston 203 forms two sections with different diameters. A piston sealing ring 209 is provided at the lower end of the piston 203. The upper section of the piston 203 passes through the cylinder top locking ring 210. A weighted bucket 205 is provided at the top of the piston 203. A weight 211 is placed inside the weighted bucket 205. The weight 211 applies pressure to the hydraulic cylinder 201 through the piston 203. A hydraulic oil pipeline 301 connector is provided on the lower exterior of the hydraulic cylinder 201. The hydraulic oil pipeline 301 connector is connected to the hydraulic cylinder 201 through a through hole.

[0031] Pressure regulating equipment is a conventional technical means in the prior art. It can be used to regulate pressure with oil pumps or pneumatic pressure. The advantage of the adjustable constant hydraulic group used in this embodiment compared with the prior art is that by adjusting the amount of weight 211, the pressure change of hydraulic oil line 301 can be observed. By referring to the optimal pre-tightening force required by different sealing packings 105, the total amount of weight 211 can be determined, thereby achieving constant pressure pre-tightening of sealing packings 105.

[0032] In another embodiment of this invention, the hydraulic connection pipeline 3 includes a hydraulic oil pipeline 301 with a convenient connector. An oil cup valve 305 is provided on the hydraulic oil pipeline 301, and the bottom of the oil cup valve 305 is connected to the hydraulic oil pipeline 301. An oil cup valve front control valve 302 is provided at the front end of the oil cup valve 305, and an oil cup valve rear control valve 306 is provided at the rear end of the oil cup valve 305. A pressure gauge 304 is provided between the oil cup valve front control valve 302 and the oil cup valve rear control valve 306, and the pressure gauge 304 is connected to the hydraulic oil pipeline 301 through a pressure gauge control valve 303.

[0033] Furthermore, the oil cup valve 305 is composed of a valve body 51, a valve needle 57, a valve stem 58, a valve seat 56, an oil cup 53, an oil cup cover 55, a handwheel 59, etc. The valve needle 57 and the valve stem 58 are designed as an integral part, and the external thread is engaged with the internal thread of the valve body 51. The displacement of the valve needle 57 is controlled by rotating the handwheel 59 at the upper end of the valve needle 57. The bottom of the oil cup 53 is provided with a communication hole 52 at the upper part of the valve seat 56. The oil cup 53 is connected to the hydraulic oil pipeline 301 through the communication hole 52. The connection between the oil cup 53 and the hydraulic oil pipeline 301 is controlled by rotating the handwheel 59 at the upper end of the valve needle 57 to control the displacement of the valve needle 57. The hydraulic oil 202 in the oil cup 53 can enter and exit the hydraulic oil pipeline 301. The hydraulic oil 202 can be added into the oil cup 53 by opening the cup cover.

[0034] When it is necessary to replenish or change the engine oil, it can be done quickly through the oil cup valve 305; when it is necessary to replace the packing, it can quickly depressurize and return the hydraulic oil 202 in the annular hydraulic cylinder 201 through the oil cup valve 305; it can display the real-time pressure through the pressure gauge 304, and can also adjust the system pressure as needed by observing the indication of the pressure gauge 304, so as to provide accurate preload force for the packing.

[0035] In implementation, the constant pressure sealing device for the polished rod of the pumping unit is installed at the top of the pumping unit wellhead assembly. The polished rod 101 of the pumping unit passes through this assembly and is connected to the adjustable constant hydraulic assembly 2 via the hydraulic connection pipeline 3. The front control valve 302 and pressure gauge control valve 303 of the oil cup valve are opened, the rear control valve 306 of the oil cup valve is closed, and the oil cup valve 305 is opened. An appropriate amount of hydraulic oil 202 is added into the oil cup 53. The weight bucket 205 at the top of the piston 203 is lifted, and the hydraulic oil 202 in the oil cup 53 is drawn into the cylinder. The oil cup valve 305 is closed, the rear control valve 306 of the oil cup valve is opened, and a weight 211 is added to the weight bucket 205. The hydraulic oil 202 flows through the hydraulic oil pipeline 301 to the annular cylinder 109 in the hydraulic constant pressure pre-tightening sealing assembly. The hydraulic oil 202 pushes the annular piston 104 upward, compressing the sealing packing 105 in the sealing stuffing box. 5. After being compressed, it expands radially to form a seal on the polished rod 101 of the pumping unit located at the center. By adjusting the amount of the weight 211, the pressure change of the hydraulic oil line 301 can be observed. By referring to the optimal preload required by different sealing packings 105, the total amount of weight 211 can be determined, thereby achieving constant pressure preload on the sealing packings 105. When the sealing packings 105 are worn out, the annular piston 104 moves upward to continue applying constant pressure to the sealing packings 105, compressing the sealing packings 105 and replenishing the reduced sealing performance caused by the wear of the sealing packings 105. When the annular piston 104 moves upward, the piston 203 at the weight end moves downward, and the pressure inside the constant pressure sealing assembly remains constant. When the constant pressure sealing assembly is put into use for the first time, the air inside the constant pressure sealing assembly can be discharged by repeatedly pumping oil or loosening the union to vent air, which can make the pressure transmission of the hydraulic oil 202 more reliable.

[0036] This allows for full utilization of the sealing packing 105, maximizing its utilization rate. During the replacement cycle of the sealing packing 105, manual tightening is unnecessary, reducing on-site management workload.

[0037] When the piston 203 of the hydraulic cylinder 201 descends to near the low position, hydraulic oil 202 needs to be replenished. During operation, close the control valve 306 at the rear end of the oil cup valve to maintain the pressure at the wellhead. Open the oil cup cover 55, add an appropriate amount of hydraulic oil 202 into the oil cup 53, remove the weight 211 from the weight bucket 205, open the needle valve of the oil cup 53, lift the weight bucket 205, and the hydraulic oil 202 is replenished into the constant pressure sealing assembly. Close the oil cup valve 305, put the original weight 211 back into the weight bucket 205, open the control valve 306 at the rear end of the oil cup valve, and the constant pressure sealing assembly returns to normal working condition.

[0038] When the sealing packing 105 needs to be replaced, stop the pumping unit, close the wellhead polished rod sealing valve, close the front control valve 302 of the oil cup valve, open the oil cup valve 305, the hydraulic system pressure at the wellhead end is released, and the hydraulic oil 202 exceeding the atmospheric pressure flows back into the oil cup 53. Remove the packing gland 106, so that the sealing packing 105 is in the open state, close the oil cup valve 305, and slowly open the front control valve 302 of the oil cup valve. The pressure of the annular cylinder 109 at the wellhead end rises, pushing the annular piston 104 upward, which can push out all the sealing packing 105 in the stuffing box without manual cleaning; When adding new packing, close the front control valve 302 of the oil cup valve again, open the oil cup valve 305, and press the annular piston 104 down to the bottom dead center. The hydraulic oil 202 in the annular cylinder 109 flows back into the oil cup 53, and new sealing packing 105 can be added into the stuffing box. After the sealing packing 105 is added, tighten the packing cover, close the oil cup valve 305, and open the front control valve 302 of the oil cup valve. At this time, since the total amount of the weight 211 applied in the weighted bucket 205 has not changed, the hydraulic system pressure is the same as before. Restore the pre-tightening of the sealing packing 105, and the oil well production can be restored.

[0039] Example 3 This embodiment further elaborates and supplements the implementation of the present invention based on Embodiment 1 or Embodiment 2.

[0040] As one embodiment of this invention, a limiting locking ring is provided on the upper part of the hydraulic outer cylinder 102 to limit the upper limit of the displacement of the annular piston 104, so as to prevent the annular piston 104 from dislodging from the annular oil cylinder 109 when changing the packing.

[0041] In another embodiment of this invention, the lower end of the hydraulic outer cylinder 102 is a connecting flange that mates with the wellhead valve flange; a convenient interface for the hydraulic oil pipeline 301 is provided on the outside of the hydraulic outer cylinder 102, and the convenient interface for the hydraulic oil pipeline 301 is connected to the hydraulic outer cylinder 102 through a through hole; a handle insertion hole 111 for inserting a handle is provided on the outside of the packing gland 106; since the packing gland is no longer used as a component for applying pre-tightening force, and the gland is removed in a depressurized state, it is easier to remove the gland. The traditional packing gland handle design is eliminated, and a handle insertion hole 111 is reserved instead. In this way, as an unattended pumping unit wellhead, it can reduce the risk of accidental adjustment by others.

[0042] As another embodiment of this invention, the hydraulic outer cylinder 102 can be machined separately from the connecting flange and then connected as a whole, or the connecting flange can be designed as a threaded connection.

[0043] Furthermore, the hydraulic outer cylinder 102 and the hydraulic inner cylinder 103 are machined as a whole to avoid the leakage of hydraulic oil 202 due to gasket seal failure.

[0044] As another implementation of this embodiment, the weighting bucket 205 is designed as a cylinder, which can be used for various different weights 211. In this way, local materials can be used for counterweighting when used in the field, such as gravel, instead of using standard weights, which can greatly reduce the cost of using the equipment.

[0045] In another embodiment of this invention, a bracket 204 is provided on the top of the hydraulic cylinder 201. The bracket 204 is connected to the upper end of the hydraulic cylinder 201 and is arranged in a ring around the weight tank 205. This facilitates lifting the weight tank 205 when replenishing the hydraulic oil 202, and also ensures that the weight tank 205 can move freely up and down. The top of the bracket 204 is provided with a cylindrical bracket cover 204. The lower edge length of the cylindrical bracket cover 204 is long enough to ensure that it overlaps with the weight tank 205 when the weight tank 205 is at the bottom dead center. This ensures that rainwater will not enter the weight tank 205 and cause changes in the total weight. At the same time, it can also reduce the impact of natural environmental changes (such as sandstorms, storms, etc.) on the weight tank 205. A base 207 is connected to the bottom of the hydraulic cylinder 201.

[0046] As another implementation method of this embodiment, a lock or pin is provided between the bracket 204 and the cylindrical bracket cover 206 for restriction, which can reduce the arbitrariness of unrelated personnel changing the added weight in unattended areas in the wild.

[0047] As another implementation method of this embodiment, the base 207 can also be designed as a bracket 204 or a skirt, etc., so as to adapt to different processing requirements and on-site installation and use environment needs.

Claims

1. A constant pressure sealing device for the polished rod of an oil pumping unit, characterized in that: The system includes a hydraulically driven constant pressure pre-tightening sealing assembly (1), a hydraulic connection pipeline (3), and an adjustable constant hydraulic assembly (2). The hydraulically driven constant pressure pre-tightening sealing assembly (1) includes a hydraulic outer cylinder (102), which is connected to the adjustable constant hydraulic assembly (2) via the hydraulic connection pipeline (3). The lower end of the hydraulic outer cylinder (102) is a connecting flange that mates with the wellhead valve flange, and the upper end of the hydraulic outer cylinder (102) is a stuffing box for filling with sealing packing (105). The top of the hydraulic outer cylinder (102) is provided with a packing gland (106), which is threaded to mate with the hydraulic outer cylinder (102). A hydraulic inner cylinder (103) is installed inside the hydraulic outer cylinder (102). The hydraulic inner cylinder (103) is connected to the hydraulic outer cylinder (102) and sealed by a sealing gasket (107) to form an annular cylinder (109). The annular cylinder (109) contains... An annular piston (104) is installed. Sealing rings (110) are provided on both the inner and outer sides of the lower part of the annular piston (104). A limiting component (112) is provided at the lower end of the hydraulic outer cylinder (102) to limit the downward position of the annular piston (104). A separating component (113) is provided on the upper inner wall of the annular piston (104) to form two inner through holes of different diameters. The inner wall of the annular section of the larger diameter inner through hole cooperates with the hydraulic outer cylinder (102) to form a seal, and the outer wall cooperates with the inner wall of the hydraulic outer cylinder (102) to form a seal. The smaller diameter inner through hole is used to pass through the polished rod (101) of the pumping unit. The adjustable constant hydraulic component (2) provides pressure to the cavity between the annular cylinder (109) and the annular piston (104) to adjust the pressure of the annular piston (104) acting on the sealing packing (105) in the sealing stuffing box to adjust the preload of the sealing packing (105).

2. The constant pressure sealing device for the polished rod of an oil pumping unit as described in claim 1, characterized in that: The adjustable constant hydraulic assembly (2) includes a hydraulic cylinder (201), a piston (203) is installed inside the hydraulic cylinder (201), and a step is provided to limit the lower limit of the downward displacement of the piston (203). A cylinder top locking ring (210) is provided at the top of the hydraulic cylinder (201) to limit the upper limit of the upward displacement of the piston (203). A step is provided at the lower end of the piston (203) so that the piston (203) forms two sections with different diameters. A dense seal is provided at the lower end of the piston (203). The upper section of the piston (203) passes through the cylinder top locking ring (210). The top of the piston (203) is provided with a weighted bucket (205). The weighted bucket (205) contains a weight (211). The weight (211) applies pressure to the hydraulic cylinder (201) through the piston (203). The lower part of the hydraulic cylinder (201) is provided with a hydraulic oil pipeline (301) connector. The hydraulic oil pipeline (301) connector is connected to the hydraulic cylinder (201) through a through hole.

3. A constant pressure sealing device for the polished rod of an oil pumping unit as described in claim 1 or 2, characterized in that: The hydraulic connection pipeline (3) includes a hydraulic oil pipeline (301) with a convenient connector. An oil cup valve (305) is provided on the hydraulic oil pipeline (301), and the bottom of the oil cup valve (305) is connected to the hydraulic oil pipeline (301). An oil cup valve front control valve (302) is provided at the front end of the oil cup valve (305), and an oil cup valve rear control valve (306) is provided at the rear end of the oil cup valve (305). A pressure gauge (304) is provided between the oil cup valve front control valve (302) and the oil cup valve rear control valve (306). The pressure gauge (304) is connected to the hydraulic oil pipeline (301) through a pressure gauge control valve (303).

4. The constant pressure sealing device for the polished rod of a pumping unit as described in claim 3, characterized in that: The oil cup valve (305) consists of a valve body (51), a valve needle (57), a valve stem (58), a valve seat (56), an oil cup (53), an oil cup cover (55), and a handwheel (59). The valve needle (57) and the valve stem (58) are designed as a single unit, with the external thread engaging with the internal thread of the valve body (51). The displacement of the valve needle (57) is controlled by rotating the handwheel (59) at the upper end of the valve needle (57). The bottom of the oil cup (53) is provided with a connecting hole (52) to the upper part of the valve seat (56). The oil cup (53) is connected to the hydraulic oil pipeline (301) through the connecting hole (52). The hydraulic oil (202) in the oil cup (53) can enter and exit the hydraulic oil pipeline (301). The hydraulic oil (202) can be added to the oil cup (53) by opening the cup cover.

5. The constant pressure sealing device for the polished rod of an oil pumping unit as described in claim 3, characterized in that: A limit lock ring is provided on the upper part of the hydraulic outer cylinder (102) to limit the upper limit of the displacement of the annular piston (104).

6. The constant pressure sealing device for the polished rod of an oil pumping unit as described in claim 3, characterized in that: The lower end of the hydraulic outer cylinder (102) is a connecting flange that mates with the wellhead valve flange; a convenient interface for hydraulic oil pipeline (301) is provided on the outside of the hydraulic outer cylinder (102), and the convenient interface for hydraulic oil pipeline (301) is connected to the hydraulic outer cylinder (102) through a through hole; a handle insertion hole (111) for inserting a handle is provided on the outside of the packing gland (106).

7. The constant pressure sealing device for the polished rod of an oil pumping unit as described in claim 3, characterized in that: The hydraulic outer cylinder (102) can be machined separately from the connecting flange and then connected as a whole, or the connecting flange can be designed as a threaded connection.

8. The constant pressure sealing device for the polished rod of an oil pumping unit as described in claim 3, characterized in that: The weighted bucket (205) is designed to be cylindrical.

9. The constant pressure sealing device for the polished rod of an oil pumping unit as described in claim 3, characterized in that: The top of the hydraulic cylinder (201) is provided with a bracket (204), and the top of the bracket (204) is provided with a cylindrical bracket (204) cover, which is distributed in a ring around the weighted barrel (205); the bottom of the hydraulic cylinder (201) is connected to a base (207).

10. The constant pressure sealing device for the polished rod of an oil pumping unit as described in claim 3, characterized in that: Locks or pins are provided between the bracket (204) and the cylindrical bracket cover (206) for restriction.

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