BE1030459A1 - Procedure for installing a telescopic azimuth thruster on a ship - Google Patents

Abstract

The present invention discloses a method for installing a telescopic azimuth thruster on a ship, comprising the following steps: step 1: manufacturing an azimuth thruster base comprising a top plate, a core and a tubular body ; step 2: carrying out a pre-welding wire draw to position the azimuth thruster base before its installation on a ship; step 3: fixing the azimuth thruster base to the tubular body; step 4: fixing the azimuth thruster base to the tubular body: Welding and fixing the core to the tubular body; Step 4: Performing machining and leveling for the azimuth thruster base top plate and machining the sealing groove; Step 5: Installing the Azimuth Thruster onto the Azimuth Thruster Base; Step 6: Before welding the lower ends of the two azimuth thruster lifting cylinders to the hull permanent connection arc plate, the lower ends of the azimuth thruster cylinders are positioned and aligned vertically; step 7: Lift the propulsion unit by means of the azimuth thruster's own hydraulic cylinder and lifting pump and carry out vertical alignment of the lifting cylinders by this lifting operation; Step 8: Once the vertical alignment of the lift cylinders is complete, the installation of the azimuth thruster is completed by welding the permanent connection of the lift cylinders and guide bars to the hull. Using this procedure, the installation of the azimuth thruster is carried out, which can achieve better installation accuracy and efficiency, which can well meet the design requirements.

Description

Procedure for installing a telescopic azimuth thruster on a ship

TECHNICAL AREA

The present invention relates more particularly to a method of installing a telescopic azimuth thruster on a ship.

STATE OF THE TECHNIQUE

In recent years, there has been a growing trend towards the use of an azimuth thruster as a ship propulsion device. The azimuthal thruster is a construction in which the thrusters are mounted on a nacelle that rotates 360 degrees in the horizontal direction, which allows the ship to move in any direction and correctly maintain its current position, unlike the propulsion by propellers and fixed shaft rudder.

There is therefore a need for faster and more practical installation of azimuth thrusters,

CONTENT OF THE PRESENT INVENTION

With regard to the defects in the prior art, the purpose of the present invention is to provide an installation method for a telescopic azimuth thruster on a ship.

To achieve the above objective, the present invention uses the following technical solution: a procedure for installing a telescopic azimuth thruster on a ship, comprising the following steps:

Step 1: Fabricate an azimuth thruster base, which is an annular structure including a top plate, a lug, and a tubular body;

Étane 2: Carry out a pre-welding wire pull to position the base of the azimuth thruster before its installation on a ship;

Step 3: Weld and secure the azimuth thruster base bar to the tube body;

Step 4: Carry out machining and leveling for the top plate of the azimuth thruster base and machining of the joint groove after the azimuth thruster base has been welded;

Step 5: Install the azimuth thruster on the azimuth thruster base;

Step 6: Before welding the lower ends of the two azimuth thruster lifting cylinders to the permanent connection arc plate of the fuselage, the lower ends of the azimuth thruster cylinders are correctly positioned and vertically aligned;

Step 7: Lift the propulsion unit by means of its own hydraulic cylinder and the azimuth thruster lifting pump and perform vertical alignment of the lifting cylinders through this lifting operation:

Step &: Once the vertical alignment of the lift cylinders is complete, the installation of the azimuth thruster is completed by welding the permanent connection of the lift cylinders and guide bars to the hull.

Step 1 includes the following: (1) Loading the upper plate in one piece; {2} make a special console or steel platform {3} the special console or steel platform must be provided with buckles to fix the top plate before installing the walkway; (4) use a sectional symmetrical welding process for the fillet weld between the core and the cover plate, in which the welding is carried out by an even number of welders and in a symmetrical manner, and in which the length d 'a single weld is 200 to 300 mm, and in which the welding sequence is adjusted in real time according to the deformation of the tubular body; (5) it is a fillet weld of the web and the cover plate; (6) Perform 100% ultrasonic inspection at the end of welding.

(7) Make 4 ocean punch marks on the surface of the base flange.

For welding between the core and the cover plate, it is necessary to place a series of vertical angle templates both on the interior face and on the exterior face of the core. Step 2, the central axis of the azimuth thruster base and the central axis of the screw of the azimuth thruster lifting and rotating system component are determined by drawing a natural vertical from the longitudinal section of the fuselage to the plane of clarity and ensuring that the natural vertical is perpendicular to the longitudinal center line of the fuselage, while finding the central position on the base of the azimuth thruster and ensuring, when installing and positioning the azimuth thruster base, that the natural vertical on the center line of the azimuth thruster lifting and rotating system component spindle is at the center of the azimuth thruster base azimuth thrust.

Step 4 includes the following: 1} Modify the flange plan; 2} Machine the inside diameter; 3} Machine the gasket groove in the plane of the flange; 4) Drill the plane of the flange.

In step 6, a temporary jack or screw is welded to the end portion of the lifting jack and the fuselage, with the lower end of the jack being finely adjusted in four directions - forward, aft, left and right - when the drive unit is in three different positions - high, medium and low - to finally achieve a permanent connection between the lifting cylinder and the fuselage at the optimal position via the connection hoop plate.

Step 7 includes the following: (1) Make preparations for alignment; {2} Prepare four pieces of three steel tubes of different lengths each; (3) Place the four shorter steel tubes evenly on the closing cover when the propulsion unit is in a low position, in which, along the length direction of the ship, a first screw is installed at the upper end of the first guide rod, and wherein, along the width direction of the ship, a second screw is installed at the upper end of the second guide rod, and wherein, along the width direction of the ship, a third screw is installed at the lower end of the lifting cylinder, and in which, along the length direction of the ship, a fourth screw is installed at the lower end of the cylinder lifting; (4) Perform initial positioning for the guide bars and lifting cylinders by fine-tuning using the four screws; {5} respectively installing a dial gauge along the length direction of the ship and the width direction of the ship on the closing cover, the values of the dial gauges being recorded; {6} start the lifting cylinders, in which the azimuth thruster propulsion unit is raised to a second height, and in which! the propulsion unit is supported using 4 steel tubes of medium length, and in which the values of the two comparators are recorded; {7) Raise the azimuth thruster propulsion unit again to an elevated position, supporting the propulsion unit using the longer steel tubes, and recording the comparator values ; (8) Compare the recorded comparator values three times, the difference between them should be less than 1.5mm, otherwise replace the screw and check again according to the above steps until the difference is less than 1 .5mm.

The present invention has the following advantages: by using this method, the installation of the azimuthal thruster is carried out, thereby achieving better installation precision and installation efficiency, which can well meet the requirements of design.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows a schematic diagram of the position of the ship and the entire a

BE2023/5177 segment in which the azimuth thruster is located.

Figure 2 shows a schematic diagram of the installation and welding details of the Azimuth Thruster base.

Figure 3 shows a schematic diagram of the cylinder verticality adjustment. Figure A shows a schematic diagram of detecting the verticality of the main guide bar when the drive unit is in the down position.

DETAILED DESCRIPTION

In connection with the figures in the embodiment of the present invention, the technical solutions in the embodiment of the present invention are explained clearly and completely below. Obviously, the explained embodiments do not constitute all embodiments, but only part of the embodiments of the present invention Exhaust gas purification unit. All other embodiments obtained by the average person skilled in this field based on the embodiments of the present invention without creative work should be considered outside the scope of protection of the present invention.

It should be noted that all direction indications (such as up, has, left, right, forward, backward......) in the exemplary embodiments of the present invention are only used to explain position relationships relative, movements, etc. between the components in a particular position (as shown in the figures}, and when this particular position is changed, the direction indications change accordingly.

The telescopic azimuth thruster has a power of 1300 kW, is driven at variable frequency, has fixed rudder blades and is mounted on the front of a ship and inserted into the chamber. The azimuth thruster is of the Azimuth ThrusterSULE155 FP model with a total weight of — 17,400 kg, conditioned and manufactured by Kongsberg, which uses a Rolls-Royce fixed-screw full-rotation thruster and a control system with ABB frequency variation. The azimuth thruster includes a lifting and rotating system component (i.e. the drive unit), two hydraulic cylinders for lifting and lowering movements, a main guide bar and two secondary guide bars, as well as a full rotation FPP thruster and other components.

The azimuth thruster is located inside the entire BOA segment, and its base must be installed after the general assembly of sub-segments 801, 802 and 810 has been completed, and it is also necessary to ensure that the platform 2930 is flat. As shown in Figure 1, the maximum deployed position of the azimuth thruster from the fuselage is 2700 mm below the fuselage baseline. As the azimuth thruster must be installed and commissioned during the general assembly phase, room must be provided for the full rotation thruster to exit the fuselage, so the entire segment must be elevated more than 3000 mm from the base of the general assembly platform.

Method of installing a telescopic azimuth thruster on a ship according to the present invention, comprising the following steps:

Step 1: make an azimuthal thruster base, which is an annular structure including an upper plate, a bar and a tubular body;

The base of the azimuth thruster is a ring structure with a diameter of up to 2940, as shown in Figure 2. As the tubular body of the azimuth thruster leads directly to the sea, the tubular body with a height of 129 mm and with a thickness of 20 mm needs to be connected to the top plate with a thickness of 35 mm by through-hole welding, and the welding workload is large, while the flatness of the top surface of the base requires a high level of 1.5 mm, which requires the development of effective measures in terms of welding deformation control.

Step 1: {1} Loading the one-piece cover plate; that is, the 35mm thick annular cover plate should be loaded at one time in order to avoid interference between the joints and the evenly distributed 48 bolt holes, and also to facilitate checking overall flatness; {2} make a special console or steel platform to ensure the flatness of the foundations

{3} The special console or steel platform should be provided with buckles to fix the cover plate before installing the spacer, to prevent the cover plate from bending upward when welding of the cover plate and spacer; To ensure the verticality of the core and cover plate, several vertical angle templates must be placed evenly inside and outside the core to ensure that the core does not tilt towards the inside or outside when tensions appear following welding; in order to guarantee the circularity of the cover slab and the core in the form of a tubular body, a temporary acler reinforcement with crossed angles must be placed in places located under the cover slab; (4) use a sectional symmetrical welding process for the fillet weld between the core and the cover plate, in which the welding is carried out by an even number of welders and in a symmetrical manner, and in which the length d 'a single weld is 200 to 300 mm, and in which the welding sequence is adjusted in real time according to the deformation of the tubular corn: (5) This is a core weld for welding of angle of the core and the cover plate, the quality of the weld must be taken into account. In particular, it is necessary to ensure that the weld slag is eliminated between several weld layers and several weld passes; single-sided welding with double-sided forming can be used, and the use of reverse carbon planes, which increases linear energy input and the risk of tension and deformation, should be avoided: (6 ) Carry out a 100% ultrasonic check at the end of the weld to ensure that there are no weld defects such as slag, cracks, etc. Welding defects that appear must be corrected in time;

Step 2: Perform a pre-weld wire draw to position the azimuth thruster base before installation on a vessel; after the azimuth thruster base has been manufactured and passed Inspection, it is lifted

* BE2023/5177 to be installed throughout the 80A segment; at that time, the tubular body of the lower opening of the azimuth thruster base is permanently installed as part of the segment 801 of the hull during the segment manufacturing phase; At this time, the installation of the base is mainly to align the core with a height of 129mm and a thickness of 20mm at the bottom opening of the base with the pre-assembled tubular body on the segment ; Before installing the base, wire drawing should be carried out for positioning to ensure the accuracy of the installation, with the center line of the azimuth thruster base determined as FR184-30; the center line of the azimuth thruster lifting and rotating system component spindle is FR183+400;at the point FR183+400 of the longitudinal section in the fuselage, a natural vertical is drawn on the plane of clarity and we ensure that the natural vertical is perpendicular to the longitudinal center line of the fuselage; at the same time, a central position is found in advance on the basis of the azimuth thruster; When installing and positioning the base, it must be ensured that the natural vertical of the ER183+400 point is in the center of the base, with a precision tolerance of +1mm;

Step 3: Weld and attach the azimuth thruster base bar to the tube body; welding is carried out using pairs of welding machines, by section welding and symmetrical welding, which helps to reduce deformation after welding, and for alignment between the core of the base and the tubular body of the hull, it is also advisable to use welding — symmetrical in sections; Alignment welding is a transverse welding on site, and the welding slopes must be prepared in advance to ensure that the angles and roots are left as required on the plans. cross welding is on-site welding, the welding position is low and it requires a lot of labor, so manpower and work plans need to be arranged to ensure the welding quality; after welding, it must be 100% photographed for inspection;

Step 4: Carry out machining and leveling for the top plate of the azimuth thruster base and machining of the joint groove after the azimuth thruster base has been welded;

Q

BE2023/5177

Machining focuses on the upper surface of the flange plate to ensure the precise dimensions of the joint surface and groove, and the specific details of requirements are as follows:

Flange plane machining, the inner diameter is 32740, the outer diameter is@2940, and the flatness is 1.5mm after machining.

Inner diameter machining, the inner hole is machined to 2740mm, and the machining length is 120mm.

Machining the gasket groove in the plane of the flange, groove width 25mm, groove depth 11+0.3mm, groove bottom smoothing Ra6.3, two sides smoothing Ra12.5.

Fastening of the flange plane, hole diameter 27mm, number 48, uniformly distributed, PCD 2880 mm, concentricity 1.5mm,

To ensure the requirements for machining accuracy, it is necessary to use special mechanical machining equipment capable of machining a series of flange holes with an outer diameter of up to 3 m, while being equipped with an additional precision measuring tool. Here is a list of the equipment needed for this type of machining: Mechanical machining equipment: MT4500 portable flange machining machine;

Measuring instruments: comparator, caliper, inner diameter ruler, laser leveling instrument.

A perfect machining process is a prerequisite for ensuring machining accuracy and cost control, including preparing tools and other machining conditions, as well as carrying out the entire process strictly compliance with it. The following points are at the heart of this process. 1} Preparation before treatment: scaffolding should be installed at the construction site to provide lighting, 380 V power supply, compressed air, etc.; before machining, machining marks should be made on the flange surface, 4 test points are machined on the surface; 2} Overview of Machining Accuracy: As mentioned above, Machining Indicators include surface flatness and smoothness, equipment rigidity and operator fog for tools and cutting speed determine whether the equipment can machine with high precision; 3) Equipment installation and adjustment: the mounting bracket is fixed to the inner hole of the flange with screws, and each support leg is adjusted approximately so that the mounting bracket is approximately at middle of the inside hole of the flange and remains approximately horizontal to the plane of the flange; the swing crosshead and counterweight section of the movable flange machine are installed on the seat; the flange machine is leveled using adjustable support feet; once leveling is completed, the movable flange cutter is centered around the flange using a comparator (or a caliper} and ensures that it is concentric with the reference provided by the shipyard; after leveling and centering are completed, the milling head drive unit is installed and the parallelism of the milling head with the plane to be machined is adjusted; after installation and level completed, the drive device is connected and the machine runs empty; at the end of the period of inactivity, it is checked again whether the amount of level and center adjustment meets the requirements, if not is not the case, the adjustment must be repeated until it meets the requirements;

Start the machine and perform rough machining of the flange surface until the plane is machined as a whole;

Mark the surface of the flange, including the center line of the hole and the center line of the gasket groove;

Drill the flange surface according to the drawn center;

Install the shank cutter and machine the joint groove to a depth of 11.5 mm, in accordance with the marking;

Finishing the flange surface to ensure that the depth of the gasket groove is machined according to the drawing requirements;

Adjust the machine arm and machine the inner bore of the flange according to the drawing requirements; once machining is completed, the equipment is dismantled for final inspection; for this purpose, the 190 diameter of the inner bore of the flange, the width and depth of the seal groove are measured and the flatness of the flange surface is checked by laser; 4} Measurement control;

Laser level/measuring dial: level control;

Vernier caliper: check the thickness of the plate as well as the depth and width of the joint groove;

Inner Diameter Ruler: Measure the diameter of the inner hole of the flange;

After drilling the flange surface and machining the joint groove, the 48 bolt hole positions evenly distributed on the top plate of the base are set according to the plan requirements, and the wiring is completed on site; the installation of the azimuth thruster mainly includes the initial installation, the connection of the lower end of the lifting cylinder to the fuselage structure and the alignment of the lifting cylinder, with emphasis on the alignment of the lifting cylinder to ensure smooth upward and downward movement of the lifting and rotating system components of the

T; ï - x - azimuth thruster within the normal system pressure range during the subsequent commissioning phase.

Step 5: Install the azimuth thruster on the azimuth thruster base;

° BE2023/5177

Check the flatness of the base sealing surface (1.5 mm flatness). The flatness measurement report must be approved by the Kongsberg service technician of the manufacturer of this azimuth thruster.

Install the O-ring into the groove of the azimuth thruster base and use a sealant, for example Permatex, and apply it to the machined surface of the flange to protect the surface.

Attach the well cover to the top base plate and use a torque wrench to secure it to the thickness prescribed by the manufacturer.

Install 2 tapered locating pins onto the flange. The diameter is 12mm. (The tapered locating pins are supplied by Kongsberg and drilled by the shipyard);

Step 6: Before welding the lower ends of the two azimuth thruster lifting cylinders to the hull permanent connection arc plate, the lower ends of the azimuth thruster cylinders are correctly positioned and vertically aligned; a temporary elevator or screw is welded to the end part of the cylinder and the hull, the lower end of the oil cylinder being finely adjusted in four directions - forward, aft, left and right - as the propulsion unit shifts found in three different positions - high, medium and low - to ultimately achieve a permanent connection between the oil cylinder and the hull at the optimal position via the linkage cell arc plate. The arrangement of adjustable screws is shown in Figure 6. The procedure of permanent connection and positioning between the upper end of the two auxiliary guide bars and the fuselage is the same as the procedure of positioning the lower end of the cylinder d 'oil ;

Step 7: Lift the propulsion unit by means of its own hydraulic cylinder and the azimuth thruster lifting pump and perform vertical alignment of the lifting cylinders through this lifting operation; all lowering and lifting movements during the installation phase must be checked on site, the starter included in the azimuth thruster equipment must be connected to all safety devices, The main stages of alignment cylinders of its

C BE2023/5177 lifting are indicated below.

Make preparations for alignment: This involves checking that the azimuth thruster equipment is fully oiled and never performing lift cylinder alignment before properly filling the system with oil; check the cleanliness of both welding bars to avoid iron shavings and other adhesions and apply lubricant after cleaning; Check the voltage of the AC hydraulic pump motor and connect it to the power supply via the switch; start the pump motor, run it for 1 to 2 seconds and check that the direction of rotation corresponds to the arrow indication; remove the pressure gauge from the end of the oil cylinder and vent the air from the lifting cylinder during the first short stroke of the oil cylinder;

Prepare in advance 4 steel tubes of 3 different lengths A (400 mm), B {1450 mm) and € (2500 mm}, strong enough to support the weight of the entire upper part of the unit, approximately 13 tons.

When the propulsion unit is in the down position, the four steel tubes A are placed evenly on the closing cover to support the propulsion unit. Along the length direction of the ship, a first screw is installed at the upper end of the guide bar 1, while along the width direction of the ship, a second screw is installed at the end upper of the second guide bar 2, and that along the direction of the width of the ship, a third screw is installed at the lower end of the lifting cylinder, and that along the direction of the length of the ship, a fourth screw is installed at the lower end of the lift cylinder.

The initial positioning of the guide rods and oil cylinders is done by fine adjustment of the four screws, which can be aided for example by a falling hammer.

Install a dial indicator in the ship's length direction and in the ship's width direction on the closing cover to detect the verticality of the main guide bar, recording the values of the dial indicators. It should be noted that a zero position must be set for the indicator so that the needle has enough room to move in both the positive and negative directions. For the steps

; © BE2023/5177 above, we can refer to Figure 7. the starting of the oil cylinders, the propulsion unit of the azimuth thruster being raised to a height of 1450 mm, and the propulsion unit being supported using 4 steel tubes B with a length of 1450 mm, and the values of the two comparators being recorded.

Raise the azimuth thruster propulsion unit again to a height of 2500 mm, then support the propulsion unit using steel C-tubes, while recording the comparator values.

Compare the recorded comparator values three times, checking that the difference between them is less than 1.5 mm, otherwise finely adjust the four screws and check again according to the steps above, until the difference is controlled as being less than 1.5 mm.

Step 8: Once the vertical alignment of the lift cylinders is complete, the installation of the azimuth thruster is completed by welding the permanent connection of the lift cylinders and guide bars to the hull. After the vessel is launched, commissioning and test use of the azimuth thruster begins, including a full rotation test and a low speed sailing test with the azimuth thruster as propulsion forward, to check the ship's class symbol for propulsion power redundancy {RP}. The RP sailing test is ordered from a third-party company, with the participation and proof of representatives of the shipyard, classification society and ship owner, the sailing speed reaches 7.46 knots, which fully corresponds to the design requirements.

The exemplary embodiments should not be considered as a limitation of the present invention, but all improvements based on the spirit of the present invention fall within the scope of protection of the present invention,

Claims (7)

PROTECTION CLAIMS 1. method of installing a telescopic azimuth thruster on a ship, characterized in that it comprises the following steps: Step 1: manufacturing an azimuth thruster base, which is an annular structure comprising an upper plate, a bar and a tubular body; Step 2: Perform a pre-weld wire draw to position the azimuth thruster base before installation on a vessel; Step 3: Weld and attach the azimuth thruster base bar to the tube body; Step 4: Perform machining and leveling for the azimuth thruster base top plate and joint groove machining after the azimuth thruster base has been welded: Step 5: Install the azimuth thruster azimuth based on azimuth thruster; Step 6: Before welding the lower ends of the two azimuth thruster lifting cylinders to the permanent connection arc plate of the fuselage, the lower ends of the azimuth thruster cylinders are correctly positioned and aligned vertically; Step 7: Lift the propulsion unit by means of its own hydraulic cylinder and the lifting pump of the azimuth thruster and carry out vertical alignment of the lifting cylinders using this lifting operation: Step 8: once the With the vertical alignment of the lifting cylinders complete, the installation of the azimuth thruster is completed by welding the permanent connection of the lifting cylinders and guide bars to the hull. 2. method of installing a telescopic azimuth thruster on a ship according to claim 1, characterized in that step 1 comprises the following: {1} Loading the upper plate in one piece; (2) make a special console or steel platform {3} the special console or steel platform must be provided with buckles to secure the top plate before installing the walkway; (4) use a sectional symmetrical welding process for the fillet weld between the core and the cover plate, in which the welding is carried out by an even number of welders and in a symmetrical manner, and in which the length d 'a single weld is 200-300mm, and in which the welding sequence is adjusted in real time according to the deformation of the tubular body; (5) it is a fillet weld of the core and the cover plate; (6) Perform 100% ultrasonic inspection at the end of welding. io (7) Make 4 ocean punch marks on the surface of the base flange. 3. method of installing a telescopic azimuth thruster on a ship according to claim 2, characterized in that, for the weld between the core and the deck plate, a series of vertical angie templates must be arranged both on the interior side and on the exterior side of the soul. 4. Method of installing a telescopic azimuth thruster on a ship according to claim 1, characterized in that, in the step, the center line of the base of the azimuth thruster and the center line of the pin of the component of the lifting and rotation system of the thruster azimuth are determined by tracing a natural vertical from the longitudinal section in the hull (to the plane of the hold and ensuring that, that the natural vertical is perpendicular to the longitudinal center line of the fuselage, while the central position is found on the azimuth thruster base, and must be ensured when installing and positioning the azimuth thruster base , that the natural vertical on the centerline of the azimuth thruster lifting and rotating system component spindle is at the center of the azimuth thrust base. 5. method of installing a telescopic azimuth thruster on a ship according to claim 1, characterized in that step 4 comprises the following: 1} Modify the plane of the flange; 2} Machine the inside diameter; 3} Machine the gasket groove in the plane of the flange; 4) Drill the plane of the flange. 6. method of installing a telescopic azimuth thruster on a ship according to claim 1, characterized in that, in step 6, a temporary elevator or screw is welded to the end part of the cylinder lifting and to the hull, the lower end of the cylinder being finely adjusted in four directions - forward, aft, left and right - when the propulsion unit is in three different positions - high, medium and low - to finally achieve a connection permanent between the lifting cylinder and the hull at the optimal position via the connecting arc plate. 7. method of installing a telescopic azimuth thruster on a ship according to claim 1, characterized in that step 7 comprises the following: (1) Making preparations for alignment; {2} Prepare four pieces of three steel tubes of different lengths each; (3) Place the four shortest steel tubes evenly on the closing cover when the propulsion unit is in a low position, in which, along the length direction of the ship, a first screw is installed at the upper end of the first guide rod, and in which, along the width direction of the ship, a second screw is installed at the upper end of the second guide rod, and in which, along of the ship's width direction, a third screw is installed at the lower end of the lifting cylinder, and in which, along the ship's length direction, a fourth screw is installed at the lower end of the lifting cylinder; {4) Perform initial positioning for the guide bars and lifting cylinders by performing fine adjustment using the four screws; (5) respectively installing a dial gauge along the ship length direction and the ship width direction on the closing cover, the values of the dial gauges being recorded; (6) start the lifting cylinders, in which the azimuth thruster propulsion unit is ; © BE2023/5177 raised to a second height, and in which the propulsion unit is supported using 4 steel tubes of average length, and in which the values of the two comparators are recorded; {7) Raise the azimuth thruster propulsion unit again to an elevated position, supporting the propulsion unit using the longer steel tubes, and recording the comparator values ; (8) Compare the recorded comparator values three times, the difference between them should be less than 1.5mm, otherwise replace the screw and check again according to the above steps until the difference is less than 1 .5mm.