Marine gearbox is the core parts of the ship's power transmission system, which is used to transfer the power of the engine to the propeller, while realizing the adjustment of speed and torque to ensure the efficient and stable operation of the ship.

The main functions include: - Transfer and distribute power. - Adjust speed and torque. - Achieve positive and negative rotation and clutch operation. - Provides overload protection.

Gears are usually made of high-strength alloy steels such as 20CrMnTi, 18Cr2Ni4WA and 42CrMo to ensure high strength, wear resistance and impact resistance.

When designing, consider: - Load type (static, dynamic, impact load). - Working environment (seawater corrosion, high temperature, high humidity). - Transmission ratio and efficiency requirements. - Reliability and ease of maintenance.

The main processing technology includes: - Forging : Ensure material density and fiber flow. - Roughing : preliminary forming, leaving a margin for finishing. - Finishing : Using high precision CNC machine tools for tooth shape machining. - Grinding teeth : improve tooth shape accuracy and surface quality. - Heat treatment : carburizing quenching, tempering and nitriding treatment.

The housing is usually made of high-strength cast iron or cast steel to ensure sufficient rigidity and vibration resistance.

Test items include: - Dimensional inspection : Use a coordinate measuring instrument to detect geometric dimensions and form and position tolerances. - Tooth shape detection : Use the gear detection center to detect tooth shape, tooth direction and tooth pitch accuracy. - Hardness test : Test surface and core hardness. - Non-destructive testing : Using magnetic particle testing or ultrasonic testing to check internal defects.

The quality control follows international standards (such as ISO, AGMA) or industry specifications to ensure that the dimensional accuracy, hardness, surface quality and mechanical properties of the gearbox meet the design requirements.

Factory acceptance test (FAT) is a series of performance tests carried out before the delivery of the gearbox to ensure that it meets the design requirements and relevant standards, including no-load test, load test, noise test, vibration test, etc.

The purpose of the factory acceptance test (FAT) is: - Verify the performance and reliability of the gearbox. - Ensure that the gearbox complies with design specifications and customer requirements. - Identify and resolve potential problems to avoid failures in subsequent use.

Factory acceptance test (FAT) usually follows the following standards: - International standards such as ISO, IEC, AGMA. - Industry specifications: such as classification society specifications (CCS, DNV, ABS, etc.). - Enterprise standards: specific test specifications developed according to customer needs.

The main test items include: - No-load test. - Load test. - Noise test. - Vibration test. - Sealing test. - Temperature rise test.

No-load test is to run the gearbox under no load conditions and check the following: - Whether the operation is smooth and there is no abnormal noise. - Whether the clutch operation is smooth. - Lubricating oil system is working properly.

The load test is to run the gearbox under simulated actual working conditions and check the following: - Gearbox transmission efficiency and power loss. - Bearing capacity and stability of each gear. - Whether the temperature rise meets the requirements.

Mainly used in: - Commercial vessels (cargo ships, tankers, container ships). - Engineering vessels (dredgers, cranes). - Military ships (frigates, submarines). - Yachts and fishing boats.

Need to consider when selecting: - Engine power and speed. - Vessel type and purpose. - Transmission ratio and efficiency requirements. - Working environment (e.g. seawater corrosion, temperature change).

Note when installing: - Ensure accurate alignment of gearbox with engine and propeller. - Use appropriate installation tools and methods to avoid damaging the gearbox. - Check lubricating oil system to ensure proper lubrication.

Maintenance measures include: - Check gear meshing and surface wear regularly. - Keep the lubrication system working properly and use suitable lubricating oil. - Change the filter element and lubricating oil regularly. - Avoid overload operation and ensure that the gearbox works within the rated load.

Common faults include: - Gear wear or pitting. - Bearing damage. - Lubricating oil contamination or insufficient. - Excessive vibration or noise of the box.

Troubleshooting steps include: - Check gear meshing and surface quality. - Check bearing status and replace if necessary. - Check lubricating oil system and oil quality, replace lubricating oil and filter element. - Check gearbox fixing and alignment, adjust or reinstall.

The design life is usually 10-20 years, depending on working conditions, load and maintenance.

Noise control methods include: - Improve gear machining accuracy and surface quality. - Use high-precision bearings and alignment mounting. - Optimize the box structure and increase the vibration reduction design.