A hydraulically-acting valve seat puller and a method of using the same

Abstract

The invention discloses a hydraulically-acting valve seat puller and a method for using the same, and relates to the technical field of fracturing pumps, and solves the technical problems of abnormal matching between a drawing rod and a drawing head, thread fracture and bonding. The invention comprises a valve seat body, a drawing head and a drawing rod, one end of the drawing rod is connected to the inner thread of the drawing head, a barb is formed at the lower end of the drawing head, and the upper surface of the barb matches with the lower surface of the valve seat body. The invention comprises a limit block and a locking ring, the limit block is located at the upper end of the drawing head, the limit block is connected to the upper end of the drawing head by screws, the locking ring is located at the outer wall of the drawing head, the inner wall of the locking ring contacts and matches with the outer wall of the drawing head, an inner step is provided on the lower end face of the limit block, the inner step is formed from the geometric center of the limit block toward the radial outward direction, and the inner step presses the upper end of the drawing head; it is used for good matching between the drawing rod and the drawing head, and the invention improves the operation efficiency of the equipment and has the advantages of good operation of the equipment.

Description

Technical Field

[0001] The present invention relates to the field of fracturing pumps, and in particular to a hydraulically-acting valve seat puller structure, which is used for a new valve seat puller and can achieve good matching between a drawing screw rod and a drawing head, and prevent abnormal matching of threads after being stressed during operation, resulting in damage or sticking of the threads. Background Art

[0002] The valve seat body is a key part of the fracturing pump valve box assembly. It is assembled in the valve seat body hole of the valve box body. After the seat is firmly seated, it reaches a tight fit to ensure sealing. After working for a period of time, the working surface of the valve seat will be damaged to a certain extent. If the valve seat body needs to be maintained and replaced, a special valve seat puller is needed to pull out the valve seat body.

[0003] The general valve seat puller consists of the following main components:

[0004] 1. Pulling cylinder: inject liquid into the hydraulic pump to form high pressure, let the cylinder piston drive the drawing screw rod upward, and provide the pulling force F1 to pull the valve seat;

[0005] 2. Drawing screw rod: connected to the drawing head at the lower end and the drawing nut at the upper end. Its function is to open the drawing hook and drive the drawing hook block to pull out the valve seat body upward;

[0006] 3. Pulling head: connected to the drawing screw rod, and after the drawing screw rod is screwed in, the pulling head opens and hooks the lower end surface of the valve seat body. Driven by the drawing screw rod, the valve seat body is hooked upward to realize the function of pulling out the valve seat body;

[0007] 4. Drawing nut: located on the piston of the drawing cylinder, it is threadedly connected to the drawing screw rod and can drive the drawing screw rod upward.

[0008] To this end, it is necessary to design a new type of valve seat puller that can achieve good fit between the pulling screw rod and the pulling hook block, and prevent abnormal fit of the thread after being stressed during work, resulting in thread damage or sticking, to ensure that the puller can work effectively even when pulling out a valve seat with a very tight interference fit, and the new valve seat puller also has good durability to ensure the safety and reliability of the construction operation.

[0009] An innovative improvement is made to the conventional clamp structure valve seat pulling method. The new locking ring structure valve seat pulling method uses a locking ring with excellent strength and rigidity instead of a clamp to lock the pulling hook block, which can ensure that the thread (female buckle) of the pulling head and the thread (male buckle) of the pull rod are always in a normal matching state, thereby effectively avoiding the breakage of the thread tooth root or the adhesion of the thread tooth surface, making the valve seat pulling and extraction operation more reliable and safe, effectively improving the efficiency of equipment maintenance operations, and ensuring the smooth operation of on-site equipment. Summary of the invention

[0010] The purpose of the present invention is to provide a hydraulically-acting valve seat puller to solve the problems of abnormal fit of the threads after the threads are stressed, resulting in thread damage or sticking, as well as fracture of the thread roots of the drawing rod and the pulling head or adhesion of the thread tooth surfaces.

[0011] In order to achieve the above-mentioned purpose, the present invention specifically adopts the following technical solutions:

[0012] A hydraulically-acting valve seat puller comprises a valve seat body, a pulling head and a pulling wire rod, the outer wall of the valve seat body is provided with an O-ring groove, the valve seat body is conical, the O-ring groove is located at the center of the outer wall of the valve seat body, an O-ring is installed in the O-ring groove, one end of the pulling wire rod is connected with the inner thread of the pulling head, the lower end of the pulling head is formed with a barb, the upper surface of the barb cooperates with the lower surface of the valve seat body, the valve seat puller acted by hydraulic pressure also comprises a limit block and a locking ring, the limit block is located at the upper end of the drawing head, the limit block is connected to the upper end of the drawing head by screws, the locking ring is located on the outer wall of the drawing head, the inner wall of the locking ring contacts and cooperates with the outer wall of the drawing head, the lower end surface of the limit block is provided with an inner step, the inner step is formed by the geometric center of the limit block toward the radial outward direction, and the inner step presses the upper end of the drawing head.

[0013] The inner diameter of the locking ring is in the range of φ50-100 mm, the outer diameter is in the range of φ65-120 mm, the height is in the range of 20-50 mm, and the material of the locking ring is any one of 40CrNiMo, 45CrNiMoV or 30CrMnSiNi2A.

[0014] Among them, through holes are opened through the inner and outer walls of the locking ring, and the number of the through holes is 4. The through holes are arranged in a circular array and evenly distributed about the longitudinal axis of the locking ring.

[0015] Among them, the limit block is crescent-shaped and has a through hole. The screw passes through the through hole from the upper end of the limit block and the threaded hole on the upper end of the drawing head to thread the limit block and the drawing head. The number of the through holes is 3 and they are evenly distributed along the crescent-shaped arc direction of the limit block.

[0016] Among them, the number of the drawing heads is 2, the drawing head has an inner circumferential wall, the inner circumferential wall has a thread, the two inner circumferential walls are butt-jointed, and after the inner circumferential walls are butt-jointed, an opening is formed from the upper end to the lower end of the drawing head, and the angle between the lower end and the upper end of the two open inner circumferential walls is 20°. The external thread range of the drawing screw rod is M36×4-M56×5.5, and the internal thread range on the inner circumferential wall of the drawing head is Tr36×6-Tr60×9.

[0017] Among them, the upper end of the valve seat puller acted by hydraulic pressure has a pulling nut which is threadedly connected to the other end of the pulling wire rod. The outer circumferential wall of the pulling nut is provided with a notch, and the outer circumferential wall is also drilled with threaded holes. The number of the notches and the threaded holes is 4, and the notches and the threaded holes are arranged in a ring array on the pulling nut. The notches and the threaded holes are cross-arranged and the angle between them is 45°.

[0018] The locking ring and the drawing head are matched with each other in a basic hole clearance fit, and the matching relationship between the two is:

[0019] The beneficial effects of the present invention are as follows:

[0020] 1. In the limit block and locking ring described in the present invention, the limit block is located at the upper end of the drawing head, the limit block is connected to the upper end of the drawing head by screws, the locking ring is located on the outer wall of the drawing head, the inner wall of the locking ring contacts and cooperates with the outer wall of the drawing head, the lower end face of the limit block is provided with an inner step, the inner step is formed by the geometric center of the limit block toward the radial outward direction, the inner step presses the upper end of the drawing head, the limit block and the locking ring together ensure that the drawing head can work normally, that is, the drawing screw rod can be accurately screwed into the upper end of the drawing head, the drawing head can be opened, and the thread (female buckle) of the hanging drawing head and the thread (male buckle) of the drawing rod screw rod can always be in a normal matching state, thereby effectively avoiding the fracture of the thread root or the adhesion of the thread tooth surface, making the valve seat body drawing and extraction operation more reliable and safe, effectively improving the equipment maintenance efficiency, and ensuring the good operation of the on-site equipment.

[0021] 2. The inner diameter range of the locking ring of the present invention is φ50-100mm, the outer diameter range is φ65-120mm, and the height range is 20-50mm. The material of the locking ring is any one of 40CrNiMo, 45CrNiMoV or 30CrMnSiNi2A. The locking ring has excellent structural strength and rigidity, which can ensure that the thread matching between the drawing screw rod and the drawing head is always in a normal state, prevent abnormal conditions such as slipping and sticking, and improve the safety and reliability of the operation.

[0022] 3. The inner and outer walls of the locking ring of the present invention are penetrated with through holes, the number of which is 4, and the through holes are arranged in a circular array about the longitudinal axis of the locking ring and are evenly distributed, which can reduce the weight of the locking ring and avoid cumbersome assembly of the locking ring.

[0023] 4. The limit block of the present invention is crescent-shaped and has a through hole. The screw passes through the through hole and the threaded hole on the upper end of the limit block from the upper end of the limit block to thread the limit block and the drawing head. The through holes are 3 and evenly distributed along the crescent-shaped arc direction of the limit block. The drawing rod can be accurately screwed into the upper end of the drawing head, effectively limiting the drawing screw from being eccentric when it approaches the upper end of the drawing head, so that the drawing screw can be accurately inserted into the upper end of the drawing head. The limit block can be fastened to the upper end of the pulling head to ensure the reliable operation of the valve seat puller.

[0024] 5. The number of the pulling heads described in the present invention is 2, and the pulling heads have an inner circumferential wall. The two inner circumferential walls are butt-jointed, and an opening is formed from the upper end to the lower end of the pulling head after the inner circumferential walls are butt-jointed. The angle between the lower end and the upper end of the two inner circumferential walls in the opening shape is 20°. The upper end of the pulling head is radially opened, and the lower end of the pulling head is radially opened at the same time, so that the matching area between the upper surface of the barb on the pulling head and the lower surface of the valve seat body is increased.

[0025] 6. The upper end of the valve seat puller acted by hydraulic pressure of the present invention has a pulling nut which is threadedly connected to the other end of the pulling wire rod. The outer circumferential wall of the pulling nut is provided with a notch, and the outer circumferential wall is also drilled with threaded holes. The number of the notches and the threaded holes is 4. The notches and the threaded holes are arranged in a circular array on the pulling nut. The notches and the threaded holes are cross-arranged with an angle of 45°, which facilitates the removal of the pulling nut from the pulling wire rod. The notch is matched with the threaded hole by a special tool or the screw is matched with the notch to rotate and remove it.

[0026] 7. The locking ring and the drawing head of the present invention are matched with each other in a basic hole clearance fit, and the matching relationship between the two is: Ensure that the locking ring and the outer wall of the pulling head are reliably engaged. When the pulling head is radially opened, the locking ring is locked and limits the radial opening of the pulling head. At the same time, a gap is left between the locking ring and the pulling head to facilitate the tightness adjustment between the two. The thread (female buckle) of the pulling head and the thread (male buckle) of the drawing rod are always in a normal matching state, thereby effectively avoiding the breakage of the thread tooth root or the adhesion of the thread tooth surface or the damage or sticking of the thread, making the valve seat pulling and extraction operation more reliable and safe, effectively improving the efficiency of equipment maintenance operations, and ensuring the good operation of on-site equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the prior art structure of the present invention;

[0028] Figure 2 This is a schematic diagram of the thread tooth surface bonding structure of the present invention;

[0029] Figure 3 It is a schematic diagram of the improved structure of the present invention;

[0030] Figure 4This is a schematic diagram of the structure of the pull nut of the present invention when viewed from above;

[0031] Figure 5 It is a schematic diagram of the cross-sectional structure of the pull-out nut of the present invention;

[0032] Figure 6 It is a schematic diagram of the structure of the drawing head of the present invention;

[0033] Figure 7 It is a schematic diagram of the cross-sectional structure of the limit block of the present invention;

[0034] Figure 8 This is a schematic diagram of the structure of the limit block of the present invention when viewed from above;

[0035] Fig. 9 It is a schematic diagram of the cross-sectional structure of the locking ring of the present invention.

[0036] Figure markings: 1-pull nut, 11-notch, 12-threaded hole, 2-pull cylinder, 3-liquid inlet pipe, 4-valve box body, 5-valve seat body, 6-pull head, 61-inner wall, 62-barb, 7-pull screw rod, 8-limit block, 81-inner step, 9-locking ring, 91-through hole. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0038] Example 1

[0039] like Figure 1 As shown, a conventional hydraulic valve seat puller is generally composed of the following main components: a pulling nut 1, a pulling cylinder 2, a liquid inlet pipe 3, a valve box body 4, a valve seat body 5, a pulling head 6 and a pulling wire rod 7, wherein the pulling wire rod 7 is threadedly connected to the pulling head 6, and the pulling nut 1 is threadedly connected to the pulling wire rod 7. The hydraulic pump injects liquid through the liquid inlet pipe 3 to form high pressure, and the piston of the pulling cylinder 2 drives the pulling wire rod 7 upward, thereby providing a pulling force F1 for pulling out the valve seat body 5;

[0040] The drawing screw rod 7 is connected to the drawing head 6 at the lower end and to the drawing nut 1 at the upper end, and its function is to open the drawing head 6 and drive the drawing head 6 to pull out the valve seat body 5 upward;

[0041] The drawing head 6 is connected to the drawing screw rod 7, and after the drawing screw rod 7 is screwed, the drawing head 6 opens and hooks the lower end surface of the valve seat body 5, and the valve seat body 5 is hooked upward under the drive of the drawing screw rod 7 to realize the function of pulling out the valve seat body 5;

[0042] Among them, the drawing nut 1 is located on the piston of the drawing hydraulic cylinder 2 and is connected to the drawing screw rod 7, and can drive the drawing screw rod 7 to move upward.

[0043] Example 2

[0044] like Figure 2 As shown, in a traditional hydraulic valve seat puller, the core part is the pulling head 6. The current mainstream design of the pulling head 6 structure adopts a clamp plus a threaded opening pulling head 6. The pulling head 6 of this clamp structure uses a pair of clamps to clamp the upper ends of the two pulling heads 6. In actual use, it is found that this pulling head 6 has a defect. When the matching thread of the pulling head 6 is stressed, it will form a tendency to open the clamp under the action of the radial component force F2 of the thread tooth surface. When the component force F2 is large enough, it will cause the connecting screw of the clamp to deform elastically, so that the actual inner diameter of the clamp is increased and cannot fully guarantee the normal matching of the thread of the pulling head 6 and the thread of the drawing screw 7. Wherein F1 = the upward force of the piston of the hydraulic pulling, which is used to overcome the interference of the valve seat and pull out the valve seat. The size can be controlled by injecting liquid through the hydraulic pump;

[0045] F2=Tan(θ) Formula (1)

[0046] F=Sec(θ) Formula (2)

[0047] If the threads do not fit properly, it will easily lead to root fracture of the threads (commonly known as slippage), or excessive contact stress on the thread surface will cause plastic deformation of the surface and lead to sticking. These will seriously affect the safety and smoothness of the extraction and maintenance work of the valve seat body 5, and bring considerable pressure to the maintenance work and equipment operation management.

[0048] After analysis, the root cause of the above problems is the strength and rigidity defects of the screw connection in the clamp structure itself. When the valve seat body 5 works for a long time or works under high pressure conditions, the interference force of the valve seat body 5 will increase, resulting in an increase in the F2 component force, because the clamp screw bears a stress σ of:

[0049] σ=0.5×F2 / A, where A is the effective cross-sectional area of ​​the screw. Formula (3)

[0050] It can be seen from formula (3) that the larger the F2, the greater the stress σ, which is likely to cause serious elastic deformation, plastic deformation or even fracture of the screw, resulting in abnormal thread matching between the drawing rod 7 and the drawing head 6, causing corresponding thread damage, and easily reducing the working life of the thread. In theory, this problem can also be solved by increasing the clamp to connect the screw, but this must be corresponding to increasing the thickness of the clamp, which will increase the volume of the drawing head. However, due to the limited size of the inner cavity of the valve box body 4, this improvement measure cannot be implemented.

[0051] Example 3

[0052] For the problems in Examples 1 and 2, Figure 3 As shown, a hydraulically-acting valve seat puller in this embodiment comprises a valve seat body 5, a pulling head 6 and a pulling screw rod 7. The outer wall of the valve seat body 5 is provided with an O-ring groove. The valve seat body 1 is conical. The O-ring groove is located at the center of the outer wall of the valve seat body 5. An O-ring is installed in the O-ring groove. One end of the pulling screw rod 7 is connected with the inner thread of the pulling head 6. The lower end of the pulling head 6 is formed with a barb 62. The upper surface of the barb 62 cooperates with the lower surface of the valve seat body 5. The valve seat puller acting by hydraulic pressure also includes The limit block 8 and the locking ring 9 are included. The limit block 8 is located at the upper end of the drawing head 3. The limit block 8 is connected to the upper end of the drawing head 6 by screws. The locking ring 9 is located on the outer wall of the drawing head 6. The inner wall of the locking ring 9 contacts and cooperates with the outer wall of the drawing head 6. The lower end surface of the limit block 8 is provided with an inner step 81. The inner step 81 is formed by the geometric center of the limit block 8 in the radial outward direction. The inner step 81 presses the upper end of the drawing head 6. The cooperation between the locking ring 9 and the drawing head 6 is a basic hole clearance cooperation. The cooperation relationship between the two is as follows:

[0053] The inner diameter of the locking ring 9 is φ50-100mm, the outer diameter is φ65-120mm, and the height is 20-50mm. The material of the locking ring 9 is any one of 40CrNiMo, 45CrNiMoV or 30CrMnSiNi2A. The locking ring 9 and the drawing head 6 are matched to address the shortcomings of the hoop structure drawing head 6. The high-strength and rigid locking ring 9 is used to lock the drawing head. Fig. 9 As shown, through holes 91 are formed through the inner and outer walls of the locking ring 9 . There are four through holes 91 . The through holes 91 are arranged in a circular array and evenly distributed about the longitudinal axis of the locking ring 9 .

[0054] like Figure 6 As shown, there are two pulling heads 6, and the pulling head 6 has an inner circumferential wall 61, and the inner circumferential wall 61 has a thread. The two inner circumferential walls 61 are butted, and after the inner circumferential walls 61 are butted, an opening is formed from the upper end to the lower end of the pulling head 6, and the angle between the lower end and the upper end of the two inner circumferential walls 61 in the opening shape is 20°. The upper end of the pulling head is radially opened, and the lower end of the pulling head is radially opened at the same time, so that the upper surface of the barb on the pulling head and the lower surface of the valve seat body The matching area is increased.

[0055] like Figure 7 , 8As shown, the limit block 8 is crescent-shaped and has a through hole 82. The screw passes through the through hole 82 and the threaded hole at the upper end of the drawing head 6 from the upper end of the limit block 8, so that the limit block 8 is threadedly connected to the drawing head 6. There are three through holes 82 and they are evenly distributed along the crescent-shaped arc direction of the limit block 8.

[0056] like Figure 4 , 5 As shown, the upper end of the valve seat puller acted by hydraulic pressure has a pulling nut 1 which is threadedly connected to the other end of the pulling wire rod 7. The outer circumferential wall of the pulling nut 1 is provided with a notch 11, and the outer circumferential wall is also drilled with a threaded hole 12. The number of the notch 11 and the threaded hole 12 is 4, and the notch 11 and the threaded hole 12 are arranged in a ring array on the pulling nut 1. The notch 11 and the threaded hole 12 are cross-arranged and the included angle is 45°, which facilitates the removal of the pulling nut from the pulling wire rod, and the notch is matched with a special tool or the screw is matched with the threaded hole for rotation and removal.

[0057] Example 4

[0058] The hydraulic valve seat puller of the present invention provides some test data and the test of the maximum bearing tension F1:

[0059] In the factory test, the maximum F1 force of 3 sets of valve seat pullers with the new locking ring 9 structure and 3 sets of valve seat pullers with the clamp structure were compared and tested. The data are shown in the following table:

[0060]

[0061] It can be seen that the valve seat puller with the novel locking ring 9 structure has a structural strength and rigidity far exceeding that of the valve seat puller with a clamp structure, and works more safely and reliably.

[0062] Main technical parameters of valve seat puller with new locking ring structure:

[0063] The matching relationship between the locking ring and the pull hook block

[0064] The inner diameter range of the locking ring is φ50-100mm; the outer diameter range is φ65-120mm; the height range is 20-50mm.

[0065] The application range of the external thread of the drawing rod 7 and the internal thread of the drawing head 6:

[0066] M36×4——M56×5.5; Tr36×6——Tr60×9, ensure that the thread matching between the drawing screw rod and the drawing head is always in normal state, prevent abnormal conditions such as slipping and sticking, and improve the safety and reliability of the operation.

[0067] Mechanical performance requirements for locking rings, drawing screws, and drawing heads:

[0068] Tensile strength δb ≥ 900MPa, yield strength δs ≥ 800MPa.

[0069] Example 5

[0070] The difference between Example 5 and Example 1 is that the working principle of Example 5 is as follows: Figure 3 As shown: the drawing rod 7 can be inserted into the upper end of the drawing head 6 by the limit block 8 at the upper end of the drawing head 6 to ensure that the lower end of the drawing rod 7 is not eccentric, and the upper end of the drawing head 6 is radially opened; the drawing rod 7 is rotated to push the barb 62 at the lower end of the drawing head 6 downward to squeeze the upper end of the valve seat body 5, and the middle part of the drawing head 6 is deformed, and the barb 62 is continuously pushed forward until the upper surface of the barb 62 cooperates with the lower surface of the valve seat body 5; when the lower end of the drawing rod 7 is inserted into the middle end of the drawing head 6, that is, the middle end position of the opening formed by the inner peripheral wall 61 Liquid is introduced into the upper end of the drawing wire rod 7, and the lower end of the drawing wire rod 7 expands and fits with the threaded position of the middle opening of the inserted drawing head 6. The middle ends of the two drawing heads 6 move radially and open. When the outer wall of the drawing head 6 contacts the inner wall of the locking ring 9, the locking ring 9 limits the radial movement and opening of the middle end of the drawing head 6. The upper surface of the barb 62 at the lower end of the drawing head 6 increases the matching area with the lower surface of the valve seat body 5, and the drawing fluid cylinder 2 pushes the drawing nut 1 to move the drawing wire rod 7 upward, driving the valve seat body 5 to move upward.

Claims

1. A hydraulically-acting valve seat puller, comprising a valve seat body (5), a pulling head (6) and a pulling screw rod (7), wherein the outer wall of the valve seat body (5) is provided with an O-ring groove, the valve seat body (5) is conical, the O-ring groove is located at the center of the outer wall of the valve seat body (5), an O-ring is installed in the O-ring groove, one end of the pulling screw rod (7) is connected to the inner thread of the pulling head (6), the lower end of the pulling head (6) is formed with a barb (62), the upper surface of the barb (62) cooperates with the lower surface of the valve seat body (5), and is characterized in that: It also includes a limit block (8) and a locking ring (9), wherein the limit block (8) is located at the upper end of the drawing head (6), the limit block (8) is connected to the upper end of the drawing head (6) by screws, the locking ring (9) is located on the outer wall of the drawing head (6), the inner wall of the locking ring (9) is in contact with the outer wall of the drawing head (6), and the lower end surface of the limit block (8) is provided with an inner step (81), the inner step (81) is formed by the geometric center of the limit block (8) in the radial outward direction, and the inner step (81) covers the upper end of the drawing head (6); The inner diameter of the locking ring (9) is in the range of φ50-100 mm, the outer diameter is in the range of φ65-120 mm, the height is in the range of 20-50 mm, and the material of the locking ring (9) is any one of 40CrNiMo, 45CrNiMoV or 30CrMnSiNi2A; The locking ring (9) and the drawing head (6) are matched in a basic hole clearance fit, and the matching relationship between the two is H9 / f9; The limit block (8) is crescent-shaped and has a through hole (82). The screw passes through the through hole (82) and the threaded hole at the upper end of the drawing head (6) from the upper end of the limit block (8) so that the limit block (8) and the drawing head (6) are threadedly connected. The through holes (82) are three in number and are evenly distributed along the crescent-shaped arc direction of the limit block (8).

2. A hydraulically-acting valve seat puller according to claim 1, characterized in that: Through holes (91) are formed through the inner and outer walls of the locking ring (9), and the number of the through holes (91) is 4. The through holes (91) are arranged in a circular array and evenly distributed about the longitudinal axis of the locking ring (9).

3. A hydraulically-acting valve seat puller according to claim 1, characterized in that: The number of the drawing heads (6) is two. The drawing heads (6) have an inner circumferential wall (61). The inner circumferential wall (61) has a thread. The two inner circumferential walls (61) are butt-jointed. After the inner circumferential walls (61) are butt-jointed, an opening is formed from the upper end to the lower end of the drawing head (6). The angle between the lower end and the upper end of the two inner circumferential walls (61) in the opening shape is 20°. The external thread range of the drawing screw rod (7) is M36×4-M56×5.5, and the internal thread range on the inner circumferential wall (61) of the drawing head (6) is Tr36×6-Tr60×9.

4. A hydraulically-acting valve seat puller according to claim 1, characterized in that: The upper end of the valve seat puller is provided with a pulling nut (1), and the pulling nut (1) is threadedly connected to the other end of the pulling screw rod (7). The outer circumferential wall of the pulling nut (1) is provided with a notch (11), and the outer circumferential wall is also drilled with a threaded hole (12). The number of the notch (11) and the threaded hole (12) is 4. The notch (11) and the threaded hole (12) are arranged in a ring array on the pulling nut (1), and the notch (11) and the threaded hole (12) are cross-arranged and the included angle is 45°.

5. The method for using a hydraulically-acting valve seat puller according to claim 1, characterized in that: The steps include: Step S1: When the drawing rod (7) is at the upper end of the drawing head (6), the limit block (8) limits the lower end of the drawing rod (7) to be inserted into the upper end of the drawing head (6) without eccentricity, and the upper end of the drawing head (6) is radially opened; Step S2: Rotate the wire drawing rod (7) to push the barb (62) at the lower end of the drawing head (6) downward to squeeze the upper end of the valve seat body (5), so that the middle part of the drawing head (6) is deformed, and continue to push until the upper surface of the barb (62) matches the lower surface of the valve seat body (5); Step S3: When the lower end of the drawing rod (7) is inserted into the middle end of the drawing head (6), i.e., the middle end of the opening formed by the inner peripheral wall (61), liquid is introduced into the upper end of the drawing rod (7), the lower end of the drawing rod (7) expands and is threadedly engaged with the middle end opening of the drawing head (6), the middle ends of the two drawing heads (6) move radially and open, and the upper surface of the barb (62) at the lower end of the drawing head (6) and the lower surface of the valve seat body (5) increase in the engagement area; Step S4: The drawing fluid cylinder (2) pushes the drawing nut (1) to move the drawing screw rod (7) upward, thereby driving the valve seat body (5) upward.

6. The method for using a hydraulically-acting valve seat puller according to claim 5, characterized in that: In the step S3, when the middle end of the pulling head (6) moves radially and opens until the outer wall of the pulling head (6) contacts the inner wall of the locking ring (9), the locking ring (9) restricts the middle end of the pulling head (6) from moving radially and opening.

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