Blowout preventer device for offshore drilling exploitation

Abstract

The invention discloses a blowout preventer device for offshore drilling and production, and relates to the technical field of offshore oil and gas drilling and production equipment. The device comprises a BOP shell, a sealing shaft seat, a driving assembly, a shear ram assembly, a grease injection module and a sand prevention module. The shear flashboard A adopts a split structure, and a grease injection module comprising a grease storage cavity, a grease injection piston and an impact rod is integrated in the shear flashboard A; and the side wall of the BOP shell is vertically communicated with a bypass flow channel pipe provided with a sand prevention filter element. When a well is sealed in a shearing mode, the driving assembly is used for pushing the flashboard to be closed, the impact rod is pushed through mechanical kinetic energy at the tail end of the stroke to extrude the grease injection piston, and high-viscosity sealing grease is automatically injected into a shearing section through the grease injection micro-hole to repair a micro-gap; and meanwhile, the bypass flow channel is conducted by utilizing the groove in the side wall of the flashboard in a fully-closed state, so that filtration and pressure relief of sand-containing fluid are realized. The problems that sand-containing fluid erodes hard sealing, the shear section leaks and the bottom hole pressure building risks are effectively solved, and the self-repairing sealing and pressure stabilizing sand control device has the beneficial effects of self-repairing sealing and pressure stabilizing sand control.

Description

Technical Field

[0001] This invention relates to the field of marine oil and gas drilling and production equipment technology, and in particular to a blowout preventer device for marine drilling and production. Background Technology

[0002] In the exploration and development of offshore oil and gas resources, well control safety is paramount as operating depth increases and geological environments become increasingly complex. Blowout preventers (BOPs), as core equipment for ensuring wellhead safety, are primarily used to quickly seal the wellhead in emergency situations such as overflows or blowouts, preventing high-pressure oil and gas from spiraling out of control. Among these, the shear gate BOP is the last line of defense in well control operations, responsible for shearing the tubing string and sealing the wellbore in extreme conditions. However, offshore formation fluids are typically high-pressure and accompanied by mud and sand production, posing severe challenges to the sealing reliability and pressure control capabilities of equipment. Especially when considering extraction processes, balancing shearing efficiency with long-term sealing has become a thorny problem for existing equipment.

[0003] To address the aforementioned well sealing issues, several related designs have been developed in the existing technology. For example, Chinese patent document CN120007138A discloses a shear gate blowout preventer. This design works by hydraulically driving the gate to move relative to each other, using metal shear blades to cut the drill string, and relying on the deformation of the rubber sealing core at the front of the gate under compression to conform to the shear section and achieve wellhead sealing. This structure represents the current mainstream blowout preventer design concept, which mainly relies on a combination of hard metal seals and soft rubber seals for well sealing. Although it meets conventional shear requirements to a certain extent, its adaptability in complex sea conditions is still insufficient.

[0004] Although existing technologies can perform shearing operations, significant drawbacks remain in practical applications. First, there's the issue of hard seal damage. After shearing the tubing string, the high-speed flow of sand-laden fluid severely erodes the gate seal surface, leading to metal hard seal failure. Second, there's micro-gap leakage. The cross-section of the sheared tubing string is often highly irregular, and passive compression by rubber components alone cannot completely fill all gaps, resulting in insufficient airtightness. Finally, there's the risk of pressure buildup. Existing devices form a dead seal once the well is fully sealed. A rapid increase in bottomhole pressure could fracturing the formation. There's a lack of a mechanism for passive mechanical filtration and pressure relief during well sealing, making it difficult to achieve pressure stabilization and sand control. Summary of the Invention

[0005] (a) Technical problems to be solved To address the aforementioned technical shortcomings of existing offshore drilling blowout preventers (BOPs) in shear sealing operations—namely, the susceptibility of the hard seal of the metal shear blade to erosion by sand-laden fluids leading to failure, the difficulty in completely sealing the micro-gaps in the irregular cross-section after shearing through simple rubber compression resulting in leakage, and the lack of an emergency pressure relief mechanism after full well sealing, which can easily lead to formation pressure buildup and fracturing—this invention provides an offshore drilling BOP device with mechanical adaptive grease injection sealing and emergency sand control and pressure relief functions.

[0006] (II) Technical Solution To achieve the above objectives, the present invention provides the following technical solution: A blowout preventer (BOP) device for offshore drilling includes a BOP housing, a sealing shaft seat, a drive assembly, a shear gate assembly, a sealing gate assembly, a grease injection module, and a sand control module. The BOP housing has a vertically penetrating gate channel inside, and a sealing shaft seat communicating with the gate channel is provided on the side wall of the BOP housing; the drive assembly is located at the end of the sealing shaft seat away from the BOP housing.

[0007] The shear gate assembly includes shear gate A and shear gate B symmetrically slidably disposed within the lower gate channel of the BOP housing, with shear gate A and shear gate B respectively connected to drive assemblies on both sides. The closing gate assembly includes closing gate A and closing gate B symmetrically slidably disposed within the upper gate channel of the BOP housing. The grease injection module is integrated inside shear gate A and is used to inject sealing grease into the shearing end face via mechanical linkage when the shear gate is closed. The sand prevention module is disposed on the side of the BOP housing, and the BOP housing has a bypass channel pipe perpendicular to the gate channel. The sand prevention module is installed inside the bypass channel pipe and is used to filter fluid and relieve pressure under specific operating conditions.

[0008] As a further embodiment of the present invention, the shear gate A adopts a split structure, including a gate outer shell A and a gate inner shell A slidably disposed inside the gate outer shell A; the inner wall of the gate outer shell A is provided with a sliding groove along the axial direction, and the outer wall of the gate inner shell A is provided with a sliding block that cooperates with the sliding groove; a shearing blade A is integrally formed at one end of the gate inner shell A facing the center of the gate channel, and sealing rubber gaskets are provided on the end faces of the gate inner shell A and the gate outer shell A.

[0009] As a further embodiment of the present invention, the grease injection module includes a grease storage cavity integrally formed inside the inner shell A of the gate, a grease injection piston slidably disposed in the grease storage cavity, and an impact rod for driving the grease injection piston to move; the front end of the grease storage cavity is provided with a grease injection micro-hole penetrating to the end face of the shearing blade A, and the rear end of the grease storage cavity is provided with a guide hole penetrating the outer shell A of the gate, and the impact rod is movably disposed in the guide hole and connected to the grease injection piston.

[0010] As a further embodiment of the present invention, the grease injection module further includes a docking plate, a connecting sleeve B, and a spring; the connecting sleeve B is fixedly installed at the end of the gate outer shell A away from the shearing blade, the docking plate is fixedly connected to the outer end of the impact rod, and the spring is sleeved on the outside of the impact rod and located between the docking plate and the gate outer shell A; the bottom of the gate inner shell A is provided with an injection port communicating with the grease storage cavity, and a removable sealing cap is installed at the injection port.

[0011] As a further embodiment of the present invention, the structure of the shear gate B is mirror-symmetrical to that of the shear gate A. The shear gate B includes a gate outer shell B, a gate inner shell B, a shearing blade B, and a connecting bushing A. The gate outer shell B and the gate inner shell B are slidably connected by a sliding groove and a slider structure. The shearing blade B is located at the front end of the gate inner shell B and is configured to cooperate with the shearing blade A to cut the drill rod.

[0012] As a further embodiment of the present invention, both the side wall of the gate housing A of the shear gate A and the side wall of the gate housing B of the shear gate B are provided with grooves; the sand prevention module includes an mounting ring and a sand prevention filter ball disposed in the mounting ring; when the shear gate A and the shear gate B are closed at the center of the gate channel, the grooves on both sides are spliced ​​together to form a chamber for accommodating the sand prevention filter ball, and the upstream and downstream of the gate channel are connected through the bypass channel pipe and the sand prevention filter ball.

[0013] As a further embodiment of the present invention, the drive assembly includes a movable chamber disposed within a sealed shaft seat, a piston disc slidably disposed within the movable chamber, a drive rod connected to one side of the piston disc, and a guide sleeve disposed outside the sealed shaft seat; one end of the drive rod passes through the sealed shaft seat and connects to the corresponding gate plate, and the other end extends into the guide sleeve.

[0014] As a further embodiment of the present invention, the drive rod connected to one side of the shear gate A is a hollow structure, with an inner connecting rod passing through it; one end of the inner connecting rod is connected to the docking plate of the grease injection module, and is used to transmit driving force to push the grease injection piston.

[0015] As a further embodiment of the present invention, a spring-loaded overflow valve is connected to the bypass channel pipe to control the fluid pressure inside the bypass channel pipe.

[0016] As a further embodiment of the present invention, the BOP housing is a cross-shaped double-chamber structure, and the front ends of the sealing gate A and the sealing gate B are provided with mutually cooperating semi-circular sealing grooves for gripping and sealing the drill rod when closed.

[0017] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention effectively solves the problem of micro-gap leakage caused by sand-containing fluid erosion of hard seals and irregular shear cross-sections in existing technologies by integrating a mechanically linked grease injection module inside the shear gate. The device utilizes the kinetic energy at the end of the gate's closing stroke, and through the mechanical cooperation between the impact rod and the grease injection piston, automatically injects high-viscosity sealing grease into the sealing interface at the instant the shearing is completed. This adaptive grease injection method not only quickly fills the tiny gaps between the rubber gasket and the irregular drill pipe cross-section, greatly improving airtightness, but also forms a protective oil film on the gate sealing surface, significantly reducing the wear and erosion of the metal hard seal surface by sand-containing fluids. This achieves self-repair and protection of the sealing interface, thereby extending the service life of the blowout preventer and ensuring the reliability of well sealing.

[0018] 2. This invention overcomes the risk of formation pressure buildup and fracturing after full well sealing by setting a laterally linked sand control and pressure relief module. Utilizing the cooperation between the gate sidewall groove and the shell bypass channel, the device only opens the pressure relief channel when the gate is fully closed, and uses the built-in sand filter ball to filter the high-pressure fluid. This design constructs a passive mechanical pressure relief mechanism that is "sealed but not completely shut down," enabling controlled release of overpressure fluid while effectively preventing formation mud and sand from entering the downstream manifold through the filter ball. This achieves the dual functions of pressure stabilization and sand control, effectively protecting the wellbore integrity and formation structure, and is particularly suitable for the exploitation of deep-sea, high-pressure, high-sand-bearing oil and gas reservoirs.

[0019] 3. Furthermore, the present invention adopts a purely mechanical drive and control method, eliminating the dependence on complex electrical control systems or external grease injection pump stations, and significantly improving the operational reliability of the equipment in harsh deep-sea environments. By cleverly integrating the grease injection drive mechanism inside the gate drive rod and integrating the sand control module into the side wall of the BOP shell, the overall structure is compact and does not significantly increase the size of the equipment, making it easy to install and maintain on space-constrained offshore drilling platforms, and has high engineering application value. Attached Figure Description

[0020] The present invention will be further described below with reference to the accompanying drawings and embodiments: Figure 1 This is a perspective view of the present invention; Figure 2 This is a top view of the present invention; Figure 3 For the present invention Figure 2 AA section view in the middle; Figure 4 This is a structural diagram of shear gate A and shear gate B of the present invention; Figure 5 This is a top view of shear gate A and shear gate B of the present invention; Figure 6 For the present invention Figure 5 BB section view in the middle; Figure 7 This is a split diagram of shear gate A and shear gate B of the present invention; Figure 8 This is a cross-sectional view of the shear gate A of the present invention; Figure 9 This is a cross-sectional view of the shear gate B of the present invention.

[0021] Reference numerals: 1. BOP housing; 2. Sealing shaft seat; 3. Drive assembly; 31. Movable chamber; 32. Piston disc; 33. Drive rod; 34. Guide sleeve; 35. Inner connecting rod; 4. Sandproof module; 5. Gate channel; 6. Shear gate A; 61. Gate outer shell A; 62. Gate inner shell A; 63. Slide groove; 64. Sliding block; 65. Shearing blade A; 66. Sealing rubber gasket; 7. Shear gate B; 71. 72. Gate outer shell B; 73. Gate inner shell B; 74. Shearing blade B; 75. Connecting bushing A; 8. Grease injection module; 86. Grease reservoir; 87. Grease injection micro-hole; 88. Grease injection piston; 89. Guide hole; 80. Impact rod; 81. Connecting plate; 82. Connecting bushing B; 83. Spring component; 84. Injection port; 85. Sealing cap; 86. Sealing gate A; 87. Sealing gate B; 88. Bypass channel pipe; 89. Drill rod. Detailed Implementation

[0022] Please see Figures 1 to 3 This invention discloses a blowout preventer (BOP) device for offshore drilling, which mainly includes a BOP housing 1, a sealing shaft seat 2, a drive assembly 3, a sand control module 4, and a gate assembly disposed inside the BOP housing 1. The BOP housing 1 has a cross-shaped multi-directional interconnected structure, with a gate channel 5 vertically opened at its center for the drill pipe 12 to pass through. This gate channel 5 is the main path for downhole oil and gas flow. On the two side walls of the BOP housing 1, integrally formed or flange-connected sealing shaft seats 2 are symmetrically arranged. The internal space of the sealing shaft seat 2 is connected to the gate assembly. Channel 5 is horizontally connected; the inner cavity of the BOP housing 1 is divided into upper and lower layers in the vertical direction. The upper layer is equipped with a closed gate assembly for conventional annular sealing, and the lower layer is equipped with a shearing gate assembly with shearing and grease injection functions; the drive assembly 3 is installed at the end of the sealing shaft seat 2 away from the BOP housing 1, and is used to provide power for the opening and closing of the gate; in addition, a bypass channel pipe 11 is provided on the side of the BOP housing 1 (i.e., the side wall perpendicular to the direction of gate movement) and perpendicularly intersects the gate channel 5, and the sand prevention module 4 is installed in the bypass channel pipe 11.

[0023] Please refer to this carefully. Figure 4 , Figure 6 and Figure 8A shearing gate A6 and a shearing gate B7 are symmetrically slidably arranged within the lower gate channel 5. Taking the more complex shearing gate A6 as an example, it adopts a "split-type box" structure, including a gate outer shell A61 and a gate inner shell A62 fitted inside it. The inner wall of the gate outer shell A61 has a sliding groove 63 along the axial direction, and the outer wall of the gate inner shell A62 has a slider 64 that slides with the sliding groove 63. This guiding fit restricts the inner shell to only make a small amount of movement along the axial direction. A V-shaped or straight shearing blade A65 is integrally formed at one end of the gate inner shell A62 facing the center of the gate channel 5, and a sealing rubber gasket 66 is applied to the front end face of the gate outer shell A61 and the gate inner shell A62. The grease injection module 8 is integrated inside the shearing gate A6. Specifically, a cylindrical grease reservoir 81 is machined inside the solid body of the gate inner shell A62, and the grease reservoir 81 is filled with high viscosity grease. The grease reservoir 81 contains a grease injection piston 83, which is slidably installed inside the grease reservoir 81. An impact rod 85 is connected to the rear end of the grease injection piston 83. The impact rod 85 extends rearward through a guide hole 84 located at the rear end of the gate housing A61. A mating plate 86 is fixedly connected to the end of the impact rod 85. A spring 88 is fitted between the mating plate 86 and the rear end face of the gate housing A61 to keep the impact rod 85 in its reset state when not in operation. Several grease injection micro-holes 82 are opened at the front end of the grease reservoir 81. These micro-holes 82 pass through the metal entity near the shearing blade A65 and open directly into the sealing interface. To facilitate grease injection, an injection port 89 communicating with the grease reservoir 81 is provided at the bottom of the gate inner housing A62 and sealed by a sealing cap 810. The corresponding shearing gate B7 structure is mirror-symmetrical, including the gate housing B71, the gate inner housing B72, and the shearing blade B73 at the front end. A connecting bushing A74 is provided at its rear end for connection to the drive side.

[0024] Please see Figure 3 and Figure 9The drive assembly 3 includes a movable chamber 31 disposed within the sealed bearing 2. A piston disc 32 is slidably and sealed within the movable chamber 31, and a drive rod 33 is connected to one side of the piston disc 32. For the shear gate A6 side, the drive rod 33 is designed as a hollow tubular structure, with one end extending through the sealed bearing 2 and fixedly connected to the connecting sleeve B87 at the rear end of the gate housing A61, and the other end extending into the guide sleeve 34 outside the sealed bearing 2. An inner connecting rod 3 is coaxially inserted inside the hollow drive rod 33. 5; One end of the inner connecting rod 35 extends into the inside of the gate plate and abuts or is fixedly connected to the docking plate 86 of the grease injection module 8, while the other end is connected to the secondary drive mechanism of the hydraulic system, or it is designed to continue to move forward by inertia after the main drive rod 33 has reached its stroke position; This design of inner and outer rods ensures that the inner connecting rod 35 can continue to push the grease injection piston 83 only after the gate plate outer shell A61 drives the shearing blade A65 to complete shearing and close, thus realizing the sequential action of "shearing to seal the well first, then grease injection to seal".

[0025] Please see Figure 4 , Figure 5 and Figure 7 This invention utilizes the side of the gate to achieve a mechanically linked sand-proof and pressure-relief function; hemispherical or arc-shaped grooves 41 are provided on the side wall of the gate housing A61 of the shear gate A6 and the side wall of the gate housing B71 of the shear gate B7; the sand-proof module 4 includes an installation ring 42 fixedly installed in the bypass channel pipe 11 and a sand-proof filter ball 43 (which can adopt a multi-layer metal sintered mesh structure) disposed in the installation ring 42; when the gate is in the open state, the solid side wall of the gate housing The port of the bypass channel pipe 11 is blocked, and the pressure relief channel is closed. Only when the shear gate A6 and the shear gate B7 are completely closed at the center of the gate channel 5, the grooves 41 on both sides are just joined to form a cavity surrounding the sand filter ball 43, so that the high-pressure fluid upstream of the gate channel 5 can enter the cavity, be filtered by the sand filter ball 43, and then enter the bypass channel pipe 11. The outlet end of the bypass channel pipe 11 is connected to a spring-loaded relief valve (not shown in the figure), which opens to relieve pressure when the pressure exceeds the set threshold.

[0026] The working principle of this device is as follows: During normal drilling operations, the sealing gate A9, sealing gate B10, and shearing gates A6 and B7 are all in the retracted open state; when overflow occurs at the bottom of the well and conventional methods are ineffective, the drive assembly 3 inside the sealing shaft seat 2 is activated; the piston disc 32 pushes the drive rod 33 to drive the shearing gates A6 and B7 to move towards the center; when the front end of the gate contacts the drill pipe 12, the shearing blades A65 and B73 cooperate to cut the drill pipe 12; as the gate continues to move until it is completely closed, the sealing rubber gaskets 66 are squeezed against each other; at this time, the gate outer shell A61 stops moving, but the inner connecting rod 35 continues to move forward under hydraulic thrust or inertia, overcoming the resistance of spring 88 to push impact rod 85; impact rod 85 squeezes grease injection piston 83, spraying high-pressure sealing grease in grease storage chamber 81 through grease injection micro-hole 82 to the joint surface of shear section and sealing rubber gasket 66, filling tiny gaps and achieving zero-leakage sealing; at the same time, as the gate closes, the groove 41 of the side wall connects with the bypass channel pipe 11; if the downhole pressure continues to rise, the fluid is filtered out of mud and sand by sand filter ball 43 and then safely depressurized through bypass channel pipe 11, thereby protecting the sealing performance of blowout preventer and preventing formation pressure damage.

Claims

1. A blowout preventer device for offshore drilling, characterized in that, include: BOP housing (1) has a gate channel (5) that runs vertically through it. The side wall of the BOP housing (1) is provided with a sealing shaft seat (2) that communicates with the gate channel (5). The drive assembly (3) is located at the end of the sealed shaft seat (2) away from the BOP housing (1); The shear gate assembly includes a shear gate A (6) and a shear gate B (7) symmetrically slidably disposed in the lower gate channel (5) of the BOP housing (1), wherein the shear gate A (6) and the shear gate B (7) are respectively connected to the drive assemblies (3) on both sides; The closed gate assembly includes a closed gate A (9) and a closed gate B (10) symmetrically slidably disposed in the upper gate channel (5) of the BOP housing (1). The grease injection module (8) is integrated inside the shear gate A (6) and is used to inject sealing grease into the shear end face when the shear gate is closed. And a sand prevention module (4) is provided on the side of the BOP housing (1). The BOP housing (1) is provided with a bypass channel pipe (11) that is perpendicular to the gate channel (5). The sand prevention module (4) is installed in the bypass channel pipe (11).

2. The blowout preventer device for offshore drilling as described in claim 1, characterized in that, The shear gate A (6) includes a gate outer shell A (61) and a gate inner shell A (62) slidably disposed inside the gate outer shell A (61). The inner wall of the gate shell A (61) is provided with a sliding groove (63) along the axial direction, and the outer wall of the gate inner shell A (62) is provided with a sliding block (64) that cooperates with the sliding groove (63). The inner shell A (62) of the gate is integrally formed with a shearing blade A (65) at one end facing the center of the gate channel (5), and the end faces of the inner shell A (62) and the outer shell A (61) of the gate are provided with sealing rubber pads (66).

3. A blowout preventer device for offshore drilling and development according to claim 2, characterized in that, The grease injection module (8) includes a grease storage cavity (81) integrally formed inside the inner shell A (62) of the gate, a grease injection piston (83) slidably disposed in the grease storage cavity (81), and an impact rod (85) for driving the grease injection piston (83) to move. The front end of the grease reservoir (81) is provided with a grease injection micro-hole (82) that extends through to the end face of the shearing blade A (65). The rear end of the grease reservoir (81) is provided with a guide hole (84) that extends through the gate shell A (61). The impact rod (85) is movably inserted into the guide hole (84) and connected to the grease injection piston (83).

4. A blowout preventer device for offshore drilling as described in claim 3, characterized in that, The grease injection module (8) also includes a docking plate (86), a connecting bushing B (87), and a spring (88). The connecting bushing B (87) is fixedly installed on the end of the gate shell A (61) away from the shearing blade, the docking plate (86) is fixedly connected to the outer end of the impact rod (85), and the spring (88) is sleeved on the outside of the impact rod (85) and located between the docking plate (86) and the gate shell A (61). The bottom of the gate inner housing A (62) is provided with an injection port (89) that communicates with the grease storage chamber (81), and a removable sealing cap (810) is installed at the injection port (89).

5. A blowout preventer device for offshore drilling as described in claim 1, characterized in that, The structure of the shear gate B (7) is mirror-symmetrical to that of the shear gate A (6). The shear gate B (7) includes a gate outer shell B (71), a gate inner shell B (72), a shearing blade B (73), and a connecting bushing A (74). The gate outer shell B (71) and the gate inner shell B (72) are slidably connected by a sliding groove and a slider structure. The shearing blade B (73) is located at the front end of the gate inner shell B (72) and is configured to cooperate with the shearing blade A (65) to cut the drill rod (12).

6. A blowout preventer device for offshore drilling as described in claim 5, characterized in that, The side wall of the gate shell A (61) of the shear gate A (6) and the side wall of the gate shell B (71) of the shear gate B (7) are both provided with grooves (41). The sand-proof module (4) includes an installation ring (42) and a sand-proof filter ball (43) disposed in the installation ring (42). When shear gate A (6) and shear gate B (7) are closed at the center of the gate channel (5), the grooves (41) on both sides are spliced ​​together to form a chamber that accommodates the sand filter ball (43), and the upstream and downstream of the gate channel (5) are connected through the bypass channel pipe (11) and the sand filter ball (43).

7. A blowout preventer device for offshore drilling as described in claim 1, characterized in that, The drive assembly (3) includes a movable chamber (31) disposed in the sealed shaft seat (2), a piston disc (32) slidably disposed in the movable chamber (31), a drive rod (33) connected to one side of the piston disc (32), and a guide sleeve (34) disposed on the outside of the sealed shaft seat (2). One end of the drive rod (33) passes through the sealing shaft seat (2) and connects to the corresponding gate plate, while the other end extends into the guide sleeve (34).

8. A blowout preventer device for offshore drilling and development according to claim 7, characterized in that, The drive rod (33) connected to one side of the shear gate A (6) is a hollow structure, and an inner connecting rod (35) is inserted inside it. One end of the inner connecting rod (35) is connected to the docking plate (86) of the grease injection module (8) to transmit driving force to push the grease injection piston (83).

9. A blowout preventer device for offshore drilling and development according to claim 1, characterized in that, A spring-loaded relief valve is connected to the bypass channel pipe (11) to control the fluid pressure inside the bypass channel pipe (11).

10. A blowout preventer device for offshore drilling as described in claim 1, characterized in that, The BOP housing (1) has a cross-shaped double-chamber structure. The front ends of the closing gate A (9) and the closing gate B (10) are provided with semi-circular sealing grooves that cooperate with each other, which are used to hold and seal the drill rod when closed.

Images