A method for installing a rotary table of a drilling and production vessel

Abstract

The application provides a method for installing a drilling and production ship rotary table, which is based on a drilling and production ship rotary table base and a rotary table, and comprises the following steps: adjusting leveling pads of adjustable height on the drilling and production ship rotary table base to form an installation plane within a predetermined tolerance range; setting a stopper in a translation direction according to an outer contour of the rotary table and adjusting the height of the stopper; welding the leveling pads on the drilling and production ship rotary table base and adjusting the flatness and levelness of the installation plane; and installing the rotary table according to the limiting positions of the leveling pads and the stopper. The flatness and levelness of the rotary table are adjusted by the leveling pads and the stopper, which helps to solve the technical problem that there is no high-precision installation method for a drilling and production ship rotary table in the prior art.

Description

Technical fields:

[0001] This invention relates to the field of rotary table installation on drilling and production vessels, and in particular to a method for installing a rotary table on a drilling and production vessel. Background technology:

[0002] my country possesses abundant marine resources, but research and development of deep-sea mining technology started relatively late. In recent years, through continuous scientific research efforts, significant progress has been made in the research and development of mining technologies and equipment, narrowing the gap with international advanced levels.

[0003] The most commonly used drilling technology is rotary drilling, which consists of a derrick, top drive, hoisting system, blowout preventer, rotary blowout device, drill pipe, and drill string. The hoisting system lifts or lowers the drill string, which is then rotated by the rotary table or top drive. The drill bit then rotates to break up the rock until it reaches the resource extraction layer.

[0004] There is an urgent need for a method for installing the rotary table on a drilling vessel, which would help solve the technical problem of the lack of a high-precision installation method for the rotary table on a drilling vessel in the existing technology. Summary of the Invention:

[0005] In one embodiment, the present invention provides an installation method for a drilling and production vessel turntable, which uses leveling pads and blocks to level the flatness and horizontality of the turntable, helping to solve the technical problem of the lack of a high-precision installation method for drilling and production vessel turntables in the prior art.

[0006] Adjust the leveling pads on the rotary table base of the drilling vessel to form an installation plane within a predetermined tolerance range;

[0007] According to the outer contour of the turntable, a stop block is set in the translation direction, and the height of the stop block is adjusted;

[0008] The leveling pad is welded to the rotary table base of the drilling vessel, and the flatness and levelness of the mounting surface are adjusted.

[0009] The turntable is installed according to the limiting positions of the leveling pad and the stop block.

[0010] In one embodiment, installing the turntable according to the limiting positions of the leveling pad and the stop block includes:

[0011] The turntable is normally lifted and placed close to the installation position on the turntable base of the drilling vessel using the hooks on the turntable;

[0012] The turntable cover plate on the turntable is hoisted and removed;

[0013] The turntable is placed by securing it to the turntable after the turntable cover has been removed using lifting lugs.

[0014] In one embodiment, before the step of adjusting the leveling shim on the rotary table base of the drilling rig, the method further includes:

[0015] The installation reference for the turntable is calibrated.

[0016] In one embodiment, the step of securing the turntable to the turntable after the turntable cover has been removed using lifting lugs to complete the placement of the turntable includes:

[0017] The turntable cover plate is removed and slowly hoisted onto the leveling pad;

[0018] Alignment shall be performed according to the installation reference calibrated by the turntable and the alignment reference of the turntable base of the drilling vessel, and shall be within the predetermined deviation.

[0019] The stop block is fixed by spot welding;

[0020] Reinstall the turntable cover plate onto the turntable;

[0021] Holes are drilled at the bolt fixing positions on the turntable, and the turntable is then fixed with bolts.

[0022] In one embodiment, after drilling holes at the bolt fixing positions on the turntable and fixing it with bolts, the method further includes:

[0023] After repositioning the turntable and the base of the drilling vessel turntable, the lifting equipment was removed.

[0024] In one embodiment, the preload force when the bolt is tightened is less than 70% of the allowable stress.

[0025] In one embodiment, the bolts are tightened again after being left to stand for 24 hours after being fixed.

[0026] In one embodiment, the predetermined deviation is less than 2.5 mm, and the flatness and the levelness are within the range of ±0.5 mm.

[0027] In one embodiment, after the step of spot welding the stop block, the method further includes:

[0028] Temporary guide blocks and positioning blocks are used during installation to assist in the positioning of the turntable.

[0029] In one embodiment, the leveling pad includes a first leveling pad and a second leveling pad, which are laid flat on the rotary table base of the drilling vessel.

[0030] The stop blocks include a first set of stop blocks and a second set of stop blocks;

[0031] The first set of stops is located on both sides of the turntable to limit the movement of the turntable along the first direction;

[0032] The second set of stops is located on the other two sides of the turntable to limit the movement of the turntable in the second direction. Attached image description:

[0033] Figure 1 This is a top view of a rotary table on a drilling vessel according to an embodiment of the present invention.

[0034] Figure 2 This is a schematic diagram of the AA cross-sectional structure of a drilling and production vessel turntable according to another embodiment of the present invention;

[0035] Figure 3 This is a schematic diagram of the cross-sectional structure of a drilling and production vessel rotary table BB in another embodiment of the present invention;

[0036] Figure 4 This is a top view of the rotary table base of the drilling vessel in another embodiment of the present invention;

[0037] Figure 5 In another embodiment of the present invention Figure 2 A partially enlarged structural diagram;

[0038] Figure 6 This is a schematic diagram of the turntable hoisting in another embodiment of the present invention;

[0039] Figure 7 This is a schematic diagram of the installation of the eye ring after the turntable cover plate is removed, according to another embodiment of the present invention;

[0040] Figure 8 This is a schematic diagram of the tightening sequence of the turntable fixing bolts in another embodiment of the present invention.

[0041] Figure label:

[0042] Leveling pad 1

[0043] First leveling pad 11

[0044] Second leveling pad 12

[0045] Block 2

[0046] First group of blocks 21

[0047] Second set of blocks 22

[0048] Drilling vessel rotary table base 10

[0049] Spinning wheel 20

[0050] Turntable cover 201

[0051] 202 hanging ear

[0052] Bolt 3 Detailed implementation method:

[0053] Figure 1 This is a top view of a rotary table on a drilling vessel according to an embodiment of the present invention. Figure 2 This is a schematic diagram of the AA cross-sectional structure of a drilling and production vessel turntable according to another embodiment of the present invention; Figure 3 This is a schematic diagram of the cross-sectional structure of a drilling and production vessel rotary table BB in another embodiment of the present invention; Figure 4 This is a top view of the rotary table base of the drilling vessel in another embodiment of the present invention; Figure 5 In another embodiment of the present invention Figure 2 A partially enlarged structural diagram; Figure 6 This is a schematic diagram of the turntable hoisting in another embodiment of the present invention; Figure 7 This is a schematic diagram of the installation of the eye ring after the turntable cover plate is removed, according to another embodiment of the present invention; Figure 8 This is a schematic diagram of the tightening sequence of the turntable fixing bolts in another embodiment of the present invention.

[0054] like Figures 1 to 8 As shown, Figure 6 The winning bid item 1 is a 10-ton lifting eye ring (provided by the equipment), 2 is a lifting hook, and 3 is a 10-ton sling. The lifting slings used can be adjusted on-site according to the actual situation. Figure 8 1-2-3-4 is the tightening sequence of the turntable fixing bolts.

[0055] In one embodiment, the present invention provides a method for installing a rotary table on a drilling vessel, based on a rotary table base 10 and a rotary table 20. The method for installing the rotary table includes:

[0056] S101, Adjust the leveling pad 1 on the rotary table base 10 of the drilling vessel to form an installation plane within the predetermined tolerance range.

[0057] This step provides a specific procedure for adjusting the leveling pad 1. In this step, a mounting surface needs to be formed within a predetermined tolerance range. Multiple leveling pads 1 are used, and their specific arrangement will be disclosed later; it will not be repeated here.

[0058] S102, set the stop block 2 in the translation direction according to the outer contour of the turntable 20, and adjust the height of the stop block 2.

[0059] In this step, a stop block 2 is provided around the turntable 20 to limit the horizontal movement of the turntable 20.

[0060] S103, the leveling pad 1 is welded to the rotary table base 10 of the drilling vessel, and the flatness and levelness of the mounting surface are adjusted.

[0061] This step provides a specific procedure for fixing and welding the leveling pad 1.

[0062] S104, Install turntable 20 according to the limiting positions of leveling pad 1 and stop block 2.

[0063] This step provides a specific procedure for final leveling based on the mounting plane of the leveling pad 1 and the stop 2, and for ensuring that the stop 2 restricts the degree of freedom of horizontal movement.

[0064] This embodiment provides a specific implementation method for installing a rotary table on a drilling vessel. Before installation, tools and fixtures are prepared and fabricated, with the load-bearing fixtures required to pass inspection before use. The welding accuracy of the upper plane of the rotary table base structural beam is checked to determine the theoretical position of the rotary table leveling shims. If necessary, the structure can be modified to meet the equipment installation requirements. If the leveling shim 1 is too thick (i.e., its height), the length of the rotary table's fixing bolts will be insufficient. The height of the stop block 2 should be flush with the upper surface of the equipment base after welding. If the stop block 2 is too high, it will affect the installation and disassembly of the rotary table's anchor bolts. In addition to the aforementioned rotary table 20 and rotary table base 10 structures, the main iron drilling track on the table and the main iron drilling track on the drilling platform must be aligned and flush.

[0065] Installation tools and standard consumables.

[0066] The main tools and commonly used consumables are listed in the table below:

[0067]

[0068] In addition to the basic installation process, safety and construction constraints should also be established beforehand:

[0069] I. Safety Requirements

[0070] 1. Before starting work, construction workers must wear appropriate safety protective equipment.

[0071] 2. Touch-up painting, hot work, hoisting and other operations must be planned in advance and carried out in accordance with the installation requirements.

[0072] 3. A scaffolding platform must be erected in the area below the turntable and used only after it has passed inspection.

[0073] 4. During hot work operations, fireproof cloth must be laid on the scaffolding platform below the turntable.

[0074] 5. All tools used must meet the installation requirements, and load-bearing fixtures must be inspected and approved before use.

[0075] 6. Before construction, coordinate with the surrounding areas for cross-operations, such as cross-operations around the upper derrick area, the lower drilling platform reverse area, the moon pool area, etc., as well as nearby pipeline pressure testing, flaw detection and other operations, to avoid mutual interference.

[0076] 7. A warning line should be set up in the area where the turntable is installed, and unauthorized personnel are not allowed to enter. In particular, after the turntable is placed on the turntable beam, temporary protection should be set up in the gaps around the turntable and in the opening in the middle of the turntable to prevent people from falling.

[0077] 8. After the turntable is installed, and before the filler core is installed, a guardrail or cover plate must be installed at the turntable opening to prevent people from falling into the turntable opening.

[0078] II. Construction Conditions

[0079] 1. The ship's drilling rig structure has been installed and handed over for inspection.

[0080] 2. Once the well center baseline on the drilling platform is marked, well center baseline points A and B are set on the front and back sides of the drilling platform structure for use when positioning the rotary table. The heights of baseline points A and B can be determined on-site according to the actual situation, and the relevant values ​​are recorded.

[0081] 3. Equipment unpacking inspection and installation information verification completed.

[0082] 4. All relevant tools and fixtures are ready.

[0083] In one embodiment, the installation of the turntable 20 according to the limiting positions of the leveling pad 1 and the stop block 2 includes:

[0084] S201, the turntable 20 is normally lifted and placed close to the installation position of the turntable base 10 on the drilling vessel using the hook on the turntable 20.

[0085] This step provides specific steps to ensure that the turntable 20 is in a normal state during the hoisting process, that is, the relative position of the turntable 20 in the use state during the suspension process.

[0086] S202, the turntable cover plate 201 on the turntable 20 is hoisted and removed.

[0087] This step provides specific steps for hoisting and removing the turntable cover 201 on the turntable 20.

[0088] S203, the turntable 20 is fixed to the turntable 20 after the turntable cover plate 201 has been removed by the lifting lug 202 to complete the placement of the turntable 20.

[0089] This step provides the specific steps for using lifting lugs 202 to fix them to the holes on the original fixed turntable cover plate 201 for subsequent hoisting.

[0090] This embodiment provides a specific implementation method for hoisting and finally fixing the turntable 20. Before the derrick is installed, the turntable is pre-hoisted to the drilling platform and placed near the turntable installation position or directly on the turntable support beam. The hoisting state is normal hoisting; lateral or reverse hoisting of the equipment is prohibited.

[0091] The specific steps are as follows:

[0092] a) Before hoisting, check whether the eye rings are tightened, whether the slings are damaged or otherwise abnormal, and whether the hook and sling certificates are complete;

[0093] b) Remove the turntable filler core before installing the turntable and store it properly;

[0094] c) Refer to the turntable installation diagram for the turntable placement location;

[0095] d) Before lifting, check whether the equipment accessories and other items on the equipment are loose or have fallen off. If there are any problems, they should be dealt with in time to prevent items from falling during the lifting process.

[0096] e) Carefully inspect the surrounding environment to ensure personnel safety during the hoisting process;

[0097] f) When lifting the turntable, first lift it about 150mm off the ground and check whether the turntable is in a horizontal and stable state. If necessary, adjust the length of the slings. After confirming that everything is correct, continue the lifting operation.

[0098] In one embodiment, before the step of adjusting the leveling shim 1 on the rotary table base 10 of the drilling vessel, the method further includes:

[0099] The installation reference for turntable 20 is calibrated.

[0100] This embodiment provides a specific implementation method for calibrating the installation reference of the turntable 20, wherein the installation reference can be a crosshair method or a horizontal plane reference point.

[0101] In one embodiment, fixing the turntable 20 to the turntable 20 after removing the turntable cover plate 201 using the lifting lug 202 to complete the placement of the turntable 20 includes:

[0102] S301, slowly lift the removed turntable cover plate 201 onto the leveling pad 1.

[0103] This step provides a specific procedure for slowly lifting the removed turntable cover 201 onto the leveling pad 1.

[0104] S302, Align with the installation reference calibrated by the turntable 20 and the alignment reference of the drilling vessel turntable base 10, and ensure that the alignment is within the predetermined deviation.

[0105] This step provides a specific procedure for aligning the rotary table 20 with the alignment reference of the rotary table base 10 of the drilling vessel, ensuring that the alignment is within a predetermined deviation.

[0106] S303, Spot weld the stop block 2 to fix it.

[0107] This step provides a specific procedure for spot welding and fixing the stop block 2.

[0108] S304, reinstall the turntable cover 201 onto the turntable 20.

[0109] This step provides specific steps for reinstalling the turntable cover 201 onto the turntable 20.

[0110] S305, drill holes at the bolt 3 fixing position of turntable 20 and fix it with bolt 3.

[0111] This step provides a specific procedure for drilling holes at the bolt 3 fixing position of the turntable 20 and fixing it with the bolt 3.

[0112] This embodiment provides a specific implementation method for placing the turntable 20 by fixing it to the turntable 20 after removing the turntable cover plate 201 using the lifting lug 202.

[0113] Turntable cover hoisting

[0114] For ease of installation, the turntable cover can be temporarily lifted before installation; remove the cover's mounting bolts, and then lift the turntable cover. During lifting, use inching motions to slowly raise the cover, ensuring all connecting bolts have been removed.

[0115] In one embodiment, after drilling holes at the bolt 3 fixing positions on the turntable 20 and fixing it with bolt 3, the method further includes:

[0116] After repositioning the turntable 20 and the turntable base 10 of the drilling vessel, the lifting equipment was removed.

[0117] hoisting after the turntable cover is removed

[0118] Install the lifting eye rings into the screw holes below the cover plate, ensuring that all eye rings are tightened, and at the same time ensure lifting safety according to the above-mentioned turntable lifting requirements.

[0119] This embodiment provides a specific implementation method for removing the lifting device after re-correcting the position of the turntable 20 and the turntable base 10 of the drilling vessel.

[0120] In one embodiment, the preload of bolt 3 is less than 70% of the allowable stress when it is fixed.

[0121] This embodiment provides a specific implementation method in which the preload force of bolt 3 is less than 70% of the allowable stress when it is fixed.

[0122] In one embodiment, after the bolt 3 is fixed, it is left to stand for 24 hours before being tightened again.

[0123] This embodiment provides a specific implementation method for tightening bolt 3 again after it has been fixed for 24 hours.

[0124] In one embodiment, the predetermined deviation is less than 2.5 mm, and the flatness and the levelness are within the range of ±0.5 mm.

[0125] This embodiment provides a specific implementation of the predetermined deviation, and the flatness and levelness within the range of ±0.5mm.

[0126] In one embodiment, after the step of spot welding and fixing the stop block 2, the method further includes:

[0127] Temporary guide blocks and positioning blocks are used during installation to assist in the positioning of the turntable.

[0128] This embodiment provides a specific implementation method for using temporary guide blocks and positioning blocks to assist in the positioning of the turntable during installation.

[0129] In one embodiment, the leveling pad 1 includes a first leveling pad 11 and a second leveling pad 12, which are laid flat on the rotary table base 10 of the drilling vessel.

[0130] The stop block 2 includes a first set of stop blocks 21 and a second set of stop blocks 22;

[0131] The first set of stops 21 are located on both sides of the turntable 20 to limit the movement of the turntable 20 in the first direction;

[0132] The second set of stops 22 are located on the other two sides of the turntable 20 to limit the movement of the turntable 20 in the second direction.

[0133] This embodiment provides a specific implementation with a first leveling pad 11 and a second leveling pad 12. The first leveling pad 11 consists of eight pads arranged on the left and right sides respectively. Taking a horizontal plane coordinate system as an example, four are on the left, arranged along the Y direction and symmetrically with respect to the X-axis. After symmetry along the X-axis, two are positioned above and below. The second leveling pad 12 consists of two pads, one on the Y-axis and one above and one below the X-axis, ultimately forming a quadrilateral enclosed by the first leveling pad 11 and the second leveling pad 12. The first set of stops 21 consists of four blocks, divided into two opposing groups vertically. The second set of stops 22 also consists of four blocks, divided into two opposing groups horizontally, ultimately forming limits in the X and Y axis directions.

[0134] The following is a detailed explanation of the turntable installation process:

[0135] 1) Clean the surface of the turntable beam and pad, complete the touch-up painting work on the turntable beam area except for the upper surface of the pad, and ensure the cleanliness of the mounting surface on the back of the turntable. If there is any paint damage in other parts of the equipment, it needs to be touched up according to the paint specifications.

[0136] 2) Slowly lift the turntable to the leveling pad. When the turntable is close to the pad, adjust the position of the turntable. At this time, the weight of the turntable is still borne by the lifting sling.

[0137] 3) When the center line of the rotary table equipment coincides with the center line of the drilling rig, i.e., the deviation between the center crosshair of the rotary table and the center crosshair of the drilling rig is ≤2.5mm, lower the rotary table. After confirming that there is no error, place stop block I and stop block II in place and spot weld them in place. Temporary guide blocks and positioning blocks can be used to assist in the positioning of the rotary table during installation. They need to be removed after the installation and positioning are completed.

[0138] 4) Lift the turntable cover plate and install the lifting ring into the screw hole under the turntable cover plate, then tighten the lifting ring.

[0139] 5) Mark the drilling positions for the turntable fixing bolts.

[0140] 6) Based on the determined screw hole positions, use a magnetic drill to drill the turntable fixing bolt holes. The through holes should pass through the leveling pad and the turntable beam panel. If necessary, the turntable can be lifted to facilitate the drilling operation.

[0141] 7) Clean the turntable mounting base and the mounting bolt positions on the back of the turntable beam again, removing burrs, iron filings, rust and other debris.

[0142] 8) Hoist the turntable back to the installation position and slowly lower it until the fixed position of the turntable coincides with the position during inspection. Place the 8.8 grade fixing bolts into the bolt holes. Apply EP2 type grease before inserting the bolts. Install the washers and nuts in sequence, and initially tighten the fixing bolts until the nuts contact the washers.

[0143] 9) Double-check the center position of the turntable and the installation height of the upper surface. Once confirmed, remove the lifting equipment.

[0144] 10) The preload of the turntable fixing bolts shall not exceed 70% of the bolt's allowable stress and shall be tightened in two steps. The tightening sequence shall be diagonal and progressive (e.g., port bow position → starboard stern position → port stern position → starboard bow position).

[0145] 11) Step 2 completes the final tightening, and the tightening sequence is the same as in Step 1; however, the tightening operation in Step 2 must be left for 24 hours after Step 1 is completed before the final tightening operation is performed. After tightening, use a marker to mark the position of the nut.

[0146] 12) Clean the area around the turntable, remove oil stains, debris, temporary work clothes, etc., and touch up the paint as needed.

[0147] 13) Reinstall the turntable cover, remove the turntable lifting equipment, and set up temporary fences and other safety facilities at the turntable opening to prevent people from falling.

[0148] 14) Connect the hydraulic lines to the turntable drive motor. The turntable installation is now complete.

[0149] This invention outlines the construction conditions and safety precautions for installing a rotary table on a ship, clarifying the required installation accuracy. It comprehensively describes the preparatory work, installation process, tools, and common consumable materials. The technical solution provides significant guidance for rotary table installation.

[0150] 1. Verified on actual ships, this installation method is safe, reliable, and highly operable.

[0151] 2. The turntable is installed in place in one go, and the deviation between the center crosshair of the turntable and the crosshair of the well center is ≤

[0152] The turntable's flatness and levelness are within ±0.5mm, eliminating the need for repeated corrections.

[0153] 3. This technical solution can be used as a reference for the installation of turntables on similar engineering vessels and offshore platforms.

[0154] 4. Block 2 not only prevents the turntable from shifting horizontally, but also solves the problem of quick positioning when the turntable is disassembled and reinstalled.

Claims

1. A method for installing a rotary table on a drilling vessel, characterized in that, The installation method of the drilling vessel turntable, based on the drilling vessel turntable base (10) and the turntable (20), includes: Adjust the leveling pad (1) on the rotary table base (10) of the drilling vessel to form an installation plane within a predetermined tolerance range; According to the outer contour of the turntable (20), a stop block (2) is set in the translation direction, and the height of the stop block (2) is adjusted; The leveling pad (1) is welded to the rotary table base (10) of the drilling vessel, and the flatness and levelness of the mounting plane are adjusted. The turntable (20) is installed according to the limiting positions of the leveling pad (1) and the stop block (2). The installation of the turntable (20) according to the limiting positions of the leveling pad (1) and the stop block (2) includes: The turntable (20) is normally lifted and placed close to the installation position on the turntable base (10) of the drilling vessel using the hook on the turntable (20); The turntable cover plate (201) on the turntable (20) is hoisted and removed; The turntable (20) is placed by fixing it to the turntable (20) after the turntable cover plate (201) has been removed using the lugs (202); Before the step of adjusting the leveling pad (1) on the rotary table base (10) of the drilling vessel, the method further includes: The installation reference for the turntable (20) is calibrated; The placement of the turntable (20) by fixing it to the turntable (20) after the turntable cover plate (201) has been removed via the lugs (202) includes: Remove the turntable cover plate (201) and slowly lift it onto the leveling pad plate (1); Alignment shall be performed according to the installation reference calibrated by the turntable (20) and the alignment reference of the turntable base (10) of the drilling vessel, and shall be within the predetermined deviation. The stop block (2) is spot welded in place; Reinstall the turntable cover (201) onto the turntable (20); Drill holes at the bolt (3) fixing positions on the turntable (20) and fix it with the bolt (3); The leveling pad (1) includes a first leveling pad (11) and a second leveling pad (12), which are laid flat on the rotary table base (10) of the drilling vessel; The stop (2) includes a first set of stop (21) and a second set of stop (22); The first set of stops (21) are located on both sides of the turntable (20) to limit the movement of the turntable (20) in the first direction; The second set of stops (22) are located on the other two sides of the turntable (20) to limit the movement of the turntable (20) in the second direction.

2. The method for installing the rotary table of a drilling vessel according to claim 1, characterized in that, After drilling holes at the bolt (3) fixing positions on the turntable (20) and fixing them with the bolts (3), the method further includes: After repositioning the turntable (20) and the turntable base (10) of the drilling vessel, the lifting equipment was removed.

3. The method for installing the rotary table of a drilling vessel according to claim 2, characterized in that, When the bolt (3) is fixed, the preload is less than 70% of the allowable stress.

4. The method for installing the rotary table of a drilling vessel according to claim 3, characterized in that, After the bolt (3) is fixed, it is left to rest for 24 hours before being tightened again.

5. The method for installing the rotary table of a drilling vessel according to claim 4, characterized in that, The predetermined deviation is less than 2.5 mm, and the flatness and levelness are within ±0.5 mm.

6. The method for installing the rotary table of a drilling vessel according to claim 5, characterized in that, After the step of spot welding and fixing the stop block (2), the method further includes: Temporary guide blocks and positioning blocks are used during installation to assist in the positioning of the turntable.

Images