As the main material used in ships and their equipment, steel is prone to corrosion due to working in high-salinity seawater environment for a long time, which affect its service life. In China, the annual loss of the hull steel caused by seawater corrosion even exceeds 50% of the total loss, which imposes significant hindrance on the development of the marine industry. The effects of the ultrasonic-aided quenching (USQ) heat treatment process on the microstructure and corrosion resistance of the sample is studied by the metallographic analysis, grain size statistics and electrochemical corrosion test of the 35CrMo steel used in rudder stock. The results show that in the microstructure of the USQ sample, the residual austenite disappears, the size and the uniformity of the grains are improved together with the significantly enhanced corrosion resistance.

For the working ships without power, the mooring system not only meets the requirements of the positioning of a ship, but also enables the ship to move. The moving and rotating operations of a cutter suction dredger are analyzed in the time-domain based on the three-dimensional potential theory. An appropriate mooring system is then designed to ensure the economy of the ship operation. It provides reference for the design of the enginearing ship operation system.

Air compressor is an important equipment for ships. The capacity and quantity of the air compressor must match the capacity of the relevant air reservoir and the gas consumption of the main engine and auxiliary engine, and meet the requirement of the inflation time and the start-ups of the main engine and the auxiliary engine, thus to be approved by the classification societies. The rational selection of the capacity and quantity of the air compressor can greatly save the procurement cost and the energy cost by reducing the frequent start-ups of the air compressor. It analyzes the advantages and disadvantages, optimization and redundancy of the selection of the air compressor for several container ships. It can provide reference for the ship design in future.

A three-dimensional entity model and its flow field model are established for a four-layer sintered metal mesh of the filter screen by adopting CFD software. The filter screen is numerically simulated according to the different filtering velocities of the filter screen. The simulation results are compared with the experimental results to obtain the fitting calculation equation and analyze the internal flow field characteristics of the filter screen. It shows that the difference between the simulation results and the experimental results is not significant, confirming the reliability of the method for the filter simulation. It can provide reference for the performance analysis, the prediction and the design of the filter screen.

The configuration and working principle of the vacuum condensate system for the cargo pump turbine of a oil tanker are described combining with the liquid level alarm faults occurred during the sea trail. The possible reasons that cause faults are analyzed and finally found out based on the simulation by AFT Fathom and troubleshooting for the real ship, enabling the elimination of the faults. It is of great significance to study and summarize the vacuum condensate system and its faults because of the complexity of the vacuum condensate system and the typicality of its faults. It can provide references for the ship design and fault elimination in the future.

The design of sacrificial anode cathodic protection lacks optimization approaches for the dimensions of single anode and the overall scheme. The concepts of slenderness and flatness are firstly introduced to solve this problem. The relationship between the dimensions of the sacrificial anode without coating and the total quantity and the mass of the required sacrificial anode is deduced based on the specifications. The feasible region of the dimensions of the sacrificial anode is then determined according to the polarization requirement of the structure and the consumption requirement of the sacrificial anode material. Finally, an integrated optimization model is established with the economic index in order to give the solution. This optimal design method can determine the dimensions of the sacrificial anode and get the general scheme with the optimized economy.