Hydraulic calculations of complex pipe networks are generally solved by professional software. This study investigates the process of recursively modeling complex pipe networks and solving their hydraulic calculations based on a recursive algorithm. An algorithm of oscillatory convergence and alternately driving recursion is proposed to address the multi-path recursive states arising from multi-inlet complex pipe networks, whose calculation results fully comply with the requirements for pipeline calculations in engineering fluid mechanics. The calculation program developed according to this algorithm enables one-click import of the pipe network models and directly calculate the flow rates and the pressure distribution of the pipe network. The program code is highly encapsulated and portable. In the final section, the fire-fighting system of a domestic luxury cruise ship is analyzed. The program directly calculates the flow rates and the pressure distribution after simplified modeling, determines the fire-pump parameters, and identifies the critical locations of the pipe network, which provides guidance for the design. The results show that the proposed algorithm and program can calculate complex pipe networks. It can provide a calculation reference for the design of complex pipe networks and even the determination of the principal parameters of the system.

The impact of the new strategy on reduction of greenhouse gas (GHG) emissions from ships by the International Maritime Organization (IMO) on the ship retrofitting market has been evaluated and studied. By analyzing the compliance with existing ship regulations and shipbuilding resource endowments at home and abroad, a detailed study is conducted on the impact of the implementation of the new strategy on the size, structure, regional differences, characteristics of the ship retrofitting market and the strategy of shipbuilding and ship repair enterprises. It shows that the implementation of IMO’s new strategy will promote the expansion of the global shipbuilding market based on green transformation, with an expected market size of 4 billion to 40 billion dollars. Additionally, it will drive the ship retrofitting market restructuring toward areas such as hydrodynamics, alternative fuels and post-processing technologies. It also promotes diversification, differentiation and customization in the shipbuilding and ship repair industry, providing data basis for market layout, strategic adjustment and resource allocation in the global shipbuilding and ship repair enterprises.

The Rules for the Classification of Trimarans by Lloyd's Register of Shipping are mainly for steel trimarans and are not applicable to aluminum-alloy trimarans. The fatigue life of a 120m aluminum-alloy trimaran is calculated by using the direct calculation method (spectral analysis method) based on the Miner linear cumulative damage theory. At the same time, the fatigue assessment results are corrected by the rain flow correction with consideration of the difference between treating the alternating stress process as a narrow band and the actual sea state. The results show that fatigue damage is easy to occur at the bridge of the aluminum-alloy trimaran, and hot spots have the different contributions to the fatigue damage under the different wave angle. The results of the fatigue life calculation are conservative if the alternating stress process is regarded as a narrow-band model. The conclusions can provide reference for the fatigue assessment of the aluminum-alloy trimaran.

In view of the oil and gas pollution caused by the ventilation of the fuel oil storage tank to the main deck, an optimal design scheme and a systematic design process have been proposed according to the characteristics of the closed overflow ventilation system of the fuel oil storage tank. It is proved that the optimal design scheme can meet the system design requirements and avoid the oil and gas pollution on the main deck through the combination of theoretical calculation and CFD simulation of a 2 200 TEU container ship.

The feasibility of offshore tandem lifting test for the semi-submersible lifting and disassembling unit has been discussed based on the procedure of the offshore tandem lifting with a 2 000 t crane, combining with the performance properties of the crane and the actual experiment environment. The operation of each segment in the procedure of the tandem lifting can be safe and reliable according to the characteristics of the unit. It can provide a theoretical basis for the later offshore tandem lifting test of the semi-submersible lifting and disassembling unit. The analysis results show that the tandem lifting procedures that meet the requirements of feasibility and safety can be tested at sea.

The demountable platform may have serious accidents during its operation, such as fire, instability, structure failure and load falling. It is necessary to arrange the evacuation and safe escape of platform personnel in time. A semi-submersible lifting demountable platform is examined to carry out the analysis of the possible serious accidents, the calculation of the escape time, the determination of the key points in the escape route, and the optimization of the escape route at the key points, as well as the analysis of the endurance time of the temporary refuge on the platform. The analysis results show that the personnel can evacuate in time with safeguards when an accident occurs on the platform.

This paper summarizes the basic principles of the general arrangement design for the dismantling platform. The arrangement of the lifting, power and accommodation, ballast and positioning systems are planned and designed around the lifting and accommodation functions of the platform. A design method for the key technology of the general arrangement of the semi-submersible crane dismantling platform has been presented to divide the general functional regions based on the implementation of the main functions of the platform. Under the requirements of the latest specification, the key systems of the platform is optimized and designed to provide experience and reference for the subsequent projects.