On offshore support vessels, tugboats, and wind turbine installation platforms, the azimuth thruster serves as the core propulsion and dynamic positioning equipment. The precision of its installation directly determines the vessel's vibration levels during turning maneuvers and the accuracy of its DP (Dynamic Positioning) system.
Key Procedure 1: Manual Scraping of the Base Plane
The mounting base flange of an azimuth thruster demands an exceptionally high degree of flatness, typically within 0.05 mm per meter. This level of precision cannot be achieved solely through milling, as welding-induced deformation of the base structure is inherently random. Our fitters must perform manual scraping and spotting. A thin layer of Prussian Blue is applied to a standard surface plate, which is then rubbed against the base flange to reveal the high spots. Using a flat scraper, the fitter meticulously removes these peaks, shaving off microns of metal at a time. This process is repeated dozens of times until the contact spots are uniformly distributed, achieving a density of 8 to 12 spots per 25mm × 25mm area.
Key Procedure 2: On-Site Reaming of Bolt Holes
To ensure an interference fit between the high-strength bolts and the mounting holes, on-site reaming is performed after the thruster is positioned. All mounting holes are finished using an adjustable pneumatic reamer. Throughout the reaming process, cutting fluid is continuously applied for cooling, and the reaming allowance is precisely controlled to guarantee the cylindricity of the holes.
Key Procedure 3: Scraping Fit of the Propeller Cone
The mating surface between the propeller hub and the tail shaft features a taper ratio of 1:10 or 1:15. We again employ the Prussian Blue spotting method to verify the contact area, which must exceed 75% . Simultaneously, strict control is exercised over the push-up distance. During the hydraulic keyless installation of the propeller, the axial displacement from the initial zero position to the final pressed position must be accurate to within 0.1 mm. This measurement is critical for calculating the radial interference force and ensuring a secure fit.
Key Procedure 4: Zero-Position Calibration
Following installation, we rotate the thruster unit and adjust the limit switches using a laser alignment tool. This ensures that when the rudder angle indicator reads 0, 90, and 180 degrees, the thrust vector of the propeller is absolutely parallel or perpendicular to the vessel's centerline. A zero-position deviation exceeding 1 degree will generate a constant yawing moment when the vessel is underway at full speed, negatively impacting course-keeping and fuel efficiency.