Tubing pressure test valve for deep water well operations

Abstract

The deep water well operation tubing pressure testing valve disclosed by the application comprises a valve outer cylinder, a closing mechanism, and a connecting sleeve is arranged in the inner cavity of the valve outer cylinder, one end of the connecting sleeve is connected with a valve plate through the closing mechanism and is used for closing the connecting sleeve, one side of the valve plate is further provided with a valve plate sealing seat and is used for forming a sealing structure with the valve plate, a power mechanism is further arranged and is used for controlling the opening of the valve plate, and a locking mechanism is further arranged and is used for limiting the valve plate and making the valve plate in a normally open state. The valve plate is closed through the closing mechanism, the valve plate is opened through the power mechanism, and the valve plate is limited to the normally open state through the locking mechanism, so that the technical problems that the valve plate is not tightly sealed due to repeated opening and closing of the pipe string pressure testing valve in the prior art and the valve plate is damaged by fluid flushing after being opened are solved.

Description

Technical Field

[0001] This invention belongs to the technical field of oil and gas testing equipment, and relates to a tubing pressure testing valve for deep water well operations. Background Technology

[0002] In the field of deepwater and ultra-deepwater testing technology, tubing test valves are a crucial testing tool. Due to the depth of the well and the length of the test tubing, the sealing performance of the tubing must be reliably tested to avoid operational failures that could result in severe economic losses and safety risks.

[0003] Ball valve-type pressure testing valves cannot automatically grout; fluid needs to be injected from the wellhead above the ball valve. Therefore, a more efficient baffle valve structure is used. Baffle valves can achieve automatic grouting, while ball valves, to ensure the diameter of the ball, have higher pressure resistance for the same specifications.

[0004] Because of its automatic grouting function, during the lowering process, fluid below the valve plate will force open the valve plate and flow above it, resulting in the valve plate being repeatedly opened and closed throughout the drilling process. The existing valve plate uses a metal-fit seal, and repeated opening and closing can easily lead to leakage, affecting the assessment of the sealing above the tubing string.

[0005] We developed and implemented a multi-functional tubing pressure testing valve to improve operational efficiency, increase the success rate of operations, reduce production and maintenance costs, and enhance overall competitiveness. Summary of the Invention

[0006] The purpose of this invention is to provide a tubing pressure testing valve for deep water well operations, which solves the technical problem in the prior art where the tubing pressure testing valve is prone to leakage due to repeated opening of the valve plate during the lowering process.

[0007] The technical solution adopted in this invention is a tubing pressure test valve for deep water well operations, including an outer cylinder and a closing mechanism. The inner cavity of the outer cylinder is provided with a connecting sleeve, and one end of the connecting sleeve is connected to a valve plate through the closing mechanism for closing the connecting sleeve. A valve plate sealing seat is also provided on one side of the valve plate for forming a sealing structure with the valve plate.

[0008] It also includes a power mechanism, which is configured to control the opening of the valve plate;

[0009] It also includes a locking mechanism, which is configured to limit the valve plate to a normally open state.

[0010] The invention is further characterized in that the closing mechanism includes a torsion helical spring disposed on the connecting sleeve, and the valve plate is connected to the torsion helical spring by a fixed pivot pin.

[0011] The power mechanism includes a power outer cylinder, which is snapped into the valve outer cylinder. One end of the power outer cylinder that extends into the valve outer cylinder is abutted against the valve plate sealing seat by a connecting short section.

[0012] The outer cylinder of the power cylinder is equipped with a flow tube mandrel and a power mandrel that are interlocked with each other. The power mandrel extends into the inner cavity of the outer cylinder of the valve. The outer cylinder of the power cylinder has a through hole in its circumference, which is used to drive the power mandrel to drive the flow tube mandrel to move toward the valve plate through external pressure so as to open the valve plate.

[0013] A rupture disc is installed at the circumferential opening of the outer cylinder of the power unit.

[0014] The end of the flow tube mandrel near the valve plate is designed as an arc structure tangent to the non-sealing area of ​​the valve plate.

[0015] The tubing pressure test valve also includes data modules located at both ends of the valve outer cylinder, the data modules including a first data module and a second data module;

[0016] The first data module includes an upper carrier that is snapped into the outer cylinder of the valve. A pressure and temperature acquisition device is provided on the upper carrier. The pressure and temperature acquisition device is connected to an internal monitoring adapter or an external monitoring adapter. A coil mounting section is sleeved on the end of the upper carrier away from the outer cylinder of the valve. An upper connector is sleeved on the end of the coil mounting section away from the upper carrier. An induction coil is provided between the upper connector and the coil mounting section.

[0017] The second data module includes a lower connector that snaps into the power outer cylinder. The end of the power spindle away from the flow tube spindle extends into the inner cavity of the lower connector. The lower connector extends into the power outer cylinder and abuts against the split-type locking block. A coil mounting section is sleeved on the end of the lower connector away from the power outer cylinder. The coil mounting section extends into the lower connector. An induction coil is provided between the coil mounting section and the lower connector. A lower carrier is snapped into the inner cavity of the coil mounting section. A pressure and temperature acquisition device is provided on the lower carrier. The pressure and temperature acquisition device is connected to an internal monitoring adapter or an external monitoring adapter.

[0018] The power spindle has a double-sealed structure between the power outer cylinder and the lower connector.

[0019] The locking mechanism includes a limiting and fixing sleeve disposed in the circumferential direction of the power spindle, the side wall of the limiting and fixing sleeve abutting the inner wall of the power outer cylinder, and a shearing pin connecting the limiting and fixing sleeve and the power spindle.

[0020] The power spindle is also equipped with a split locking block in the circumferential direction. The split locking block is equipped with a tension spring, and the outer wall of the power spindle is equipped with a locking groove that cooperates with the split locking block.

[0021] The end of the connecting section near the power outer cylinder is provided with a spline groove, and the end of the power outer cylinder near the connecting section is provided with a spline. The spline and spline groove are designed for a sealed fit.

[0022] The sealing surface of the valve plate sealing seat is a metal surface, and a non-elastic sealing ring is snapped onto the metal surface. The non-elastic sealing ring is designed to form a sealing structure with the valve plate.

[0023] The beneficial effects of this invention are:

[0024] This invention solves the technical problems in the prior art where repeated opening and closing of the tubing test valve leads to poor valve sealing and fluid scouring damage to the valve plate after it is opened. It closes the valve plate by setting a closing mechanism to prevent the valve plate from shaking when it is not pressurized. The valve plate is opened by a power mechanism and locked to the normally open state by a locking mechanism. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the tubing pressure testing valve for deep water well operations according to the present invention;

[0026] Figure 2 yes Figure 1 Schematic diagram of the structure at point A;

[0027] Figure 3 yes Figure 1 Schematic diagram of the structure at point B;

[0028] Figure 4 yes Figure 1 Schematic diagram of the structure at point C;

[0029] Figure 5 This is a schematic diagram of the closing mechanism in the tubing pressure test valve for deep water well operations according to the present invention;

[0030] Figure 6 This is a schematic diagram of the power mechanism and locking mechanism in the tubing pressure testing valve for deep well operations according to the present invention.

[0031] In the diagram, 1. Upper connector, 2. Coil mounting section, 3. Induction coil, 4. Upper carrier, 5. Pressure and temperature acquisition device, 6. Screw, 7. Internal monitoring adapter in the tubing, 8. External monitoring adapter in the tubing, 9. Valve outer cylinder, 10. Closing mechanism connecting sleeve, 11. Torsional helical spring, 12. Fixing pin, 13. Valve plate, 14. Non-elastic sealing ring, 15. Valve plate sealing seat, 16. Connecting section, 17. Flow tube mandrel, 18. Power outer cylinder, 19. Buffer pad, 20. Power mandrel, 21. Rupture disc, 22. Shear pin, 23. Limiting and fixing sleeve, 24. Split-type locking block, 25. Tension spring, 26. Lower connector, 27. Lower carrier. Detailed Implementation

[0032] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0033] Example 1

[0034] like Figure 1-4As shown, the present invention provides a tubing pressure test valve for deep water well operations, including an outer valve cylinder 9 and a closing mechanism. The inner cavity of the outer valve cylinder 9 is provided with a connecting sleeve 10. One end of the connecting sleeve 10 is connected to a valve plate 13 through the closing mechanism for closing the connecting sleeve 10. A valve plate sealing seat 15 is also provided on one side of the valve plate 13 for forming a sealing structure with the valve plate 13.

[0035] It also includes a power mechanism, which is configured to control the opening of the valve plate 13;

[0036] It also includes a locking mechanism, which is configured to limit the valve plate 13 so that the valve plate 13 is in the normally open state.

[0037] In existing technologies, the valve plate of the pressure testing valve repeatedly opens and closes during drilling, impacting the valve seat and hindering the protection of the sealing surface. Furthermore, when the valve plate is open, fluid flows through the slots on the mandrel, scouring the valve plate. This invention addresses this issue by using a closing mechanism to close the valve plate 13, preventing it from shaking under no-pressure conditions. A power mechanism opens the valve plate 13 and isolates it from fluid erosion, while a locking mechanism limits the valve plate 13 to its normally open position. This solves the technical problem in existing technologies where the repeated opening and closing of the valve plate during the drilling process leads to poor sealing.

[0038] Example 2

[0039] Based on Example 1, such as Figure 5 As shown, the closing mechanism includes a torsion coil spring 11 mounted on the connecting sleeve 10, and the valve plate 13 is connected to the torsion coil spring 11 via a fixed pivot pin 12.

[0040] The power mechanism includes a power outer cylinder 18, which is snapped into the valve outer cylinder 9. One end of the power outer cylinder 18 extending into the valve outer cylinder 9 is abutted against the valve plate sealing seat 15 by a connecting short section 16.

[0041] The power outer cylinder 18 is provided with a flow tube spindle 17 and a power spindle 20 that are interlocked. The power spindle 20 extends into the inner cavity of the valve outer cylinder 9. The power outer cylinder 18 has a through hole in the circumference, which is used to drive the power spindle 20 to further drive the flow tube spindle 17 toward the valve plate 13 to open the valve plate 13 by external pressure.

[0042] The power spindle 20 is inserted into the inner hole of the power outer cylinder 18 to form an upper air chamber. The power outer cylinder 18, the power spindle 20, and the lower connector 26 form a lower air chamber. The above forms an air chamber mechanism. The air chamber structure ensures that the power spindle 20 has a pressure differential surface when the power source is generated by the annular pressure during downhole operation.

[0043] A rupture disc 21 is installed at the circumferential through-hole of the power outer cylinder 18 to prevent the valve plate 13 from opening prematurely and accidentally. An opening and locking mechanism is added to prevent the valve plate 13 from closing due to accidents or air leakage. By pressurizing the annulus and breaking through the rupture disc 21, the annular fluid pressure pushes the power spindle 20 to further push the flow tube spindle 17 to open the valve plate 13.

[0044] The end of the flow tube mandrel 17 near the valve plate 13 is designed with an arc structure that is tangent to the non-sealed area of ​​the valve plate 13, so as to prevent the flow tube mandrel 17 from being damaged or deformed due to excessive movement speed when the tool moves.

[0045] The flow tube mandrel 17 is designed with a matching tangential arc surface at its front end, based on the specifications of the valve plate 13 and the sealing area. This design ensures that the end of the flow tube mandrel 17 does not contact the sealing area throughout the valve opening process, thus solving the problem of contact scratches on the sealing surface caused by the flow tube mandrel 17 opening the valve plate 13. This avoids the unavoidable scratches on the valve plate sealing surface caused by the flat end face and small arc of the central shaft in existing technologies. Specifically, the flow tube mandrel 17 is completely isolated from the sealing area during the opening of the valve plate 13 to 90°, minimizing the risk of contact scratches on the sealing area by ordinary flow tube mandrels. The flow tube mandrel 17 is a complete cylindrical surface design, unlike the guide groove design in existing technologies. In this invention, the flow tube mandrel 17 moves to the stepped inner hole of the upper carrier 4, isolating the fluid from the closing valve plate, valve seat, and other parts, eliminating the erosion of critical components by the fluid.

[0046] The oil pipe pressure test valve also includes data modules located at both ends of the valve outer cylinder 9. The data modules include a first data module and a second data module.

[0047] The first data module includes an upper carrier 4 that is snapped into the outer cylinder 9 of the valve. A pressure and temperature acquisition device 5 is provided on the upper carrier 4. The pressure and temperature acquisition device 5 is connected to an internal monitoring adapter 7 or an external monitoring adapter 8. A coil mounting section 2 is sleeved on the end of the upper carrier 4 away from the outer cylinder 9. An upper connector 1 is sleeved on the end of the coil mounting section 2 away from the upper carrier 4. An induction coil 3 is provided between the upper connector 1 and the coil mounting section 2.

[0048] The second data module includes a lower connector 26 that snaps into the power outer cylinder 18. One end of the power spindle 20 away from the flow tube spindle 17 extends into the inner cavity of the lower connector 26. The lower connector 26 extends into the power outer cylinder 18 and abuts against the split locking block 24. A coil mounting section 2 is sleeved on the end of the lower connector 26 away from the power outer cylinder 18. The coil mounting section 2 extends into the lower connector 26. An induction coil 3 is provided between the coil mounting section 2 and the lower connector 26. A lower carrier 27 is snapped into the inner cavity of the coil mounting section 2. A pressure and temperature acquisition device 5 is provided on the lower carrier 27. The pressure and temperature acquisition device 5 is connected to an internal monitoring adapter 7 or an external monitoring adapter 8. The internal monitoring adapter 7 or the external monitoring adapter 8 is installed on the upper carrier 4 and the lower carrier 27 by screws 6.

[0049] In this invention, the first and second data modules can simultaneously read the real-time pressure and temperature inside the upper and lower tubing of the pressure test valve closing mechanism on the ground, and simultaneously read the external pressure and temperature of the tubing. When the tubing is pressure tested, this allows for the most timely determination of whether the leakage is in the tubing above valve plate 13 or in the valve plate 13 area, thus solving the problem of the inability to accurately determine tubing leakage due to the lag in pressure transmission between the pressure test valve area and the wellhead.

[0050] The surface can directly read downhole pressure and temperature data, which can promptly and accurately determine the bottom hole condition. Before the valve is opened, the reliability of the tubing pressure test results can be judged by directly reading the pressure difference data above and below the valve, and the leakage of the valve plate 13 itself can be investigated. This solves the problem of uncertain causes of leakage in the downhole tubing and valve plate 13.

[0051] The power spindle 20 has a double-sealed structure with respect to the power outer cylinder 18 and the lower connector 26.

[0052] The valve plate's sealing performance under low pressure is enhanced by increasing the valve plate's sealing contact area. The sealing part of the power spindle 20 that contacts the formation fluid adopts a double-groove seal. The first groove is used to withstand the absolute pressure difference, and the second groove is used to improve reliability under absolute pressure, thus solving the risk of leakage from the air chamber isolated by the sealing ring.

[0053] Example 3

[0054] Based on Example 2, such as Figure 6 As shown, the locking mechanism includes a limiting and fixing sleeve 23 disposed in the circumference of the power spindle 20. The side wall of the limiting and fixing sleeve 23 abuts against the inner wall of the power outer cylinder 18. A shear pin 22 is connected between the limiting and fixing sleeve 23 and the power spindle 20.

[0055] The power spindle 20 is also provided with a split locking block 24 in the circumference. The split locking block 24 is provided with a tension spring 25. The outer wall of the power spindle 20 is provided with a locking groove that cooperates with the split locking block 24.

[0056] The locking mechanism ensures that the flow tube mandrel 17 is locked after the valve plate 13 is opened. The air chamber sealing part is designed for safety, which solves the risk of the flow tube mandrel 17 oscillating downward and shutting off the flow path due to air chamber leakage.

[0057] The end of the connecting section 16 near the power outer cylinder 18 is provided with a spline groove, and the end of the power outer cylinder 18 near the connecting section 16 is provided with a spline. The spline and the spline groove are configured to make contact fit.

[0058] The flow tube mandrel 17 and power mandrel 20 are designed without a guide structure. The arc-shaped flow tube mandrel 17 and valve plate 13 are correspondingly designed in the cooperation between the closing mechanism and the power outer cylinder 18. After the arc-shaped flow tube mandrel 17 is installed in the power outer cylinder 18, the closing mechanism is aligned with the arc-shaped flow tube mandrel 17, and then inserted into the spline groove at the lower end of the short section 16 of the sealing seat in the closing mechanism, which is then inserted into the spline at the upper end of the power outer cylinder 18. This replaces the structure of designing a guide groove on the flow tube mandrel 17, making the outer circle of the flow tube mandrel 17 complete and solving the problem of adverse erosion of the valve plate 13 under the action of fluid scouring caused by the slotted flow tube mandrel 17.

[0059] The sealing surface of the valve plate sealing seat 15 is a metal surface, and a non-elastic sealing ring 14 is snapped onto the metal surface. The non-elastic sealing ring 14 is configured to form a sealing structure with the valve plate 13.

[0060] In this invention, the valve plate 13 is improved from a single planar metal seal to a dual seal consisting of a metal plate and a non-elastic seal. When closed, it contacts the non-elastic seal, mitigating impact forces. The non-elastic seal ring 14 preferentially seals against the metal surface, reducing impact and collisions on the sealing surface of the valve plate 13 caused by repeated opening and closing during automatic downhole injection. Under low-pressure sealing, it preferentially presses against the non-elastic seal ring 14 for sealing; under high pressure, the non-elastic seal ring 14 is pressed against the metal surface, creating a dual-seal function and solving the problem of easy seal failure in low-pressure valve plate 13.

[0061] The working principle of the tubing pressure testing valve for deep water well operations of this invention is as follows:

[0062] Data module working principle: Pressure and temperature acquisition device 5 detects the pressure and temperature inside / outside the tubing string and transmits the data wirelessly upwards to the ground receiving system via transmitter. If the well depth is too deep, repeaters are added as needed in the middle of the tubing string.

[0063] The double-seal principle of the closing mechanism: The valve plate sealing seat 15 adopts a non-elastic polymer sealing element, namely a non-elastic sealing ring 14 and a high-precision ground metal sealing surface. The valve plate 13 adopts a metal sealing surface. After the valve plate 13 is closed, it will preferentially contact the non-elastic sealing ring 14, achieving a low-pressure seal under the action of the valve plate 13's own weight, the initial torque of the torsion coil spring 11, and the fluid pressure above the valve plate 13. When the pressure above the valve plate 13 is high, the non-elastic sealing ring 14 allows for slight elastic deformation, and the valve plate 13 moves downward through the unique waist-shaped pin hole until the valve plate 13 contacts the metal sealing surface for sealing, thereby generating a double seal.

[0064] Isolation Mechanism Principle: When the power spindle 20 moves to its upper limit and contacts the buffer pad 19, the front section of the flow tube spindle 17 inserts into the stepped inner hole at the lower end of the upper carrier 4, thus forming an isolation structure. After the valve plate 13 is opened, the flow tube spindle 17 moves upward into the stepped inner hole of the upper carrier 4, completely isolating the valve plate 13 from the flow path. This protects the formation fluid from directly scouring the valve plate 13. During fluid scouring, the flow tube spindle 17 isolates the valve plate 13 and the valve seat's double sealing surfaces from the fluid. During the process of the flow tube spindle 17 opening the valve plate 13, the special arc surface design of the front section of the flow tube spindle 17 prevents it from contacting the actual sealing area of ​​the valve plate 13, avoiding scratches on the sealing surface and leakage.

[0065] Locking mechanism working principle: Initially, the power spindle 20 is constrained by the preset shear pin 22, which is then broken by the rupture disc 21. Fluid pressure causes the power spindle 20 to move upward. After reaching the limit, the split locking block 24 falls into the locking groove of the power spindle 20 under the tightening force of the tension spring 25. With the inclined surface of the split locking block 24 contacting the opposite inclined surface of the lower connector 26, the split locking block 24 tightens inward to clamp the locking groove of the power spindle 20. The thickness of the split locking block 24 is stuck between the power spindle 20 and the lower connector 26, thereby locking the valve plate 13 in the open position. Opening test valve principle: Pressurization of the outer annulus of the tubing breaks the rupture disc 21, and the pressure enters the lower air chamber. The hydraulic pressure pushes the power spindle 20 upward, and the flow tube spindle 17 at the upper end of the power spindle 20 pushes open the valve plate 13 through the upper arc surface.

Claims

1. A tubing pressure test valve for deep water well operations, characterized by, Includes an outer valve cylinder (9) and a closing mechanism. The inner cavity of the outer valve cylinder (9) is provided with a connecting sleeve (10). One end of the connecting sleeve (10) is connected to a valve plate (13) through the closing mechanism for closing the connecting sleeve (10). A valve plate sealing seat (15) is also provided on one side of the valve plate (13) for forming a sealing structure with the valve plate (13). It also includes a power mechanism, which is configured to control the opening of the valve plate (13); It also includes a locking mechanism, which is configured to limit the valve plate (13) so that the valve plate (13) is in the normally open state; The closing mechanism includes a torsion helical spring (11) provided on the connecting sleeve (10), and the valve plate (13) is connected to the torsion helical spring (11) through a fixed pivot pin (12); The power mechanism includes a power outer cylinder (18), which is engaged with the valve outer cylinder (9). One end of the power outer cylinder (18) extending into the valve outer cylinder (9) abuts against a connecting short section (16) between it and the valve plate sealing seat (15). The power outer cylinder (18) is provided with a flow tube spindle (17) and a power spindle (20) that are interlocked with each other. The power spindle (20) extends into the inner cavity of the valve outer cylinder (9). The power outer cylinder (18) has a through hole in the circumference, which is used to drive the power spindle (20) to further drive the flow tube spindle (17) toward the valve plate (13) to open the valve plate (13) by external pressure. The end of the flow tube mandrel (17) near the valve plate (13) is set as an arc structure tangent to the non-sealing area of ​​the valve plate (13). The flow tube mandrel (17) is a complete cylindrical surface. The flow tube mandrel (17) and the power mandrel (20) have no guiding structure. The locking mechanism includes a limiting and fixing sleeve (23) disposed in the circumference of the power spindle (20), the side wall of the limiting and fixing sleeve (23) abuts against the inner wall of the power outer cylinder (18), and a shear pin (22) is connected between the limiting and fixing sleeve (23) and the power spindle (20). The power spindle (20) is also provided with a split locking block (24) in the circumferential direction. The split locking block (24) is provided with a tension spring (25). The outer wall of the power spindle (20) is provided with a locking groove that cooperates with the split locking block (24). The sealing surface of the valve plate sealing seat (15) is a metal surface, and a non-elastic sealing ring (14) is snapped onto the metal surface. The non-elastic sealing ring (14) is configured to form a sealing structure with the valve plate (13).

2. The tubing pressure testing valve for deep water well operations according to claim 1, characterized in that, A rupture disc (21) is provided at the circumferential through hole of the power outer cylinder (18).

3. The tubing pressure testing valve for deep water well operations according to claim 1, characterized in that, The oil pipe pressure test valve also includes data modules disposed at both ends of the valve outer cylinder (9), the data modules including a first data module and a second data module; The first data module includes an upper carrier (4) that is snapped into the outer cylinder of the valve (9). A pressure and temperature acquisition device (5) is provided on the upper carrier (4). The pressure and temperature acquisition device (5) is connected to an internal monitoring adapter (7) or an external monitoring adapter (8) of the tubing. A coil mounting section (2) is sleeved on one end of the upper carrier (4) away from the outer cylinder of the valve (9). An upper connector (1) is sleeved on one end of the coil mounting section (2) away from the upper carrier (4). An induction coil (3) is provided between the upper connector (1) and the coil mounting section (2). The second data module includes a lower connector (26) that snaps into the power outer cylinder (18). The end of the power spindle (20) away from the flow tube spindle (17) extends into the inner cavity of the lower connector (26). The lower connector (26) extends into the power outer cylinder (18) and abuts against the split locking block (24). A coil mounting section (2) is sleeved on the end of the lower connector (26) away from the power outer cylinder (18). The coil mounting section (2) extends into the lower connector (26). An induction coil (3) is provided between the coil mounting section (2) and the lower connector (26). A lower carrier (27) is snapped into the inner cavity of the coil mounting section (2). A pressure and temperature acquisition device (5) is provided on the lower carrier (27). The pressure and temperature acquisition device (5) is connected to an internal monitoring adapter (7) or an external monitoring adapter (8).

4. The tubing pressure testing valve for deep water well operations according to claim 3, characterized in that, The power spindle (20) has a double-sealed structure with respect to the power outer cylinder (18) and the lower connector (26).

5. The tubing pressure testing valve for deep water well operations according to claim 1, characterized in that, The connecting short section (16) is provided with a spline groove at one end near the power outer cylinder (18), and the power outer cylinder (18) is provided with a spline at one end near the connecting short section (16). The spline and the spline groove are configured for a sealed fit.

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