China Classification Society Research Articles

Physical correction factor in ultimate strength calculation of deep-sea pressure-resistant cylindrical shells made of TC4, Ti80 and 18Ni(250)

ABSTRACT The increase in design depth of deep-sea equipment leads to new requirements for material selection criterion, so it is necessary to pay attention to the rationality of the coefficient values in the design formula based on material performance. In this paper, based on three candidate high-strength materials, TC4, Ti80 and 18Ni(250), a number of pressure-resistant cylindrical shell calculation models are designed according to the pressure vessel code, and the physical correction coefficients, Cs, in the calculation of the ultimate strength of the cylindrical shells are derived through theoretical and finite element calculations. The results are compared with the curve recommended by the China Classification Society as well as finite element analysis results. The deviations and material suitability between different methods are clearly demonstrated. The theoretical calculation basis for three alternative materials for pressure-resistant shells is extended, thus compensating for the small range of material applicability in current submersible specifications.

A method for improving the hydrostatic pressure testing of the compressive strength of solid buoyancy materials used at full ocean depth

The current optimized synthesis methods for solid buoyancy materials used in manned submersibles at full ocean depth fail to meet the safety factor requirement of 1.5 specified in China Classification Society rules. To address this issue, this study proposes a novel method for enhancing the compressive strength and safety margin of such materials using hydrostatic pressure to screen hollow glass microspheres and eliminate those with low compressive strength. The as-prepared solid buoyancy material is free of surface cracks and has a water absorption rate of <0.1% after a 24-h hydrostatic pressure test at 175 MPa, satisfying the required safety performance standards for buoyancy materials used at full ocean depth. This study highlights the feasibility of using hydrostatic pressure testing to enhance the compressive strength and safety of solid buoyancy materials for full-ocean-depth applications, paving the way for the development of more advanced and reliable buoyancy materials for deep-sea exploration.

Significant contribution of inland ships to the total NOx emissions along the Yangtze River

Abstract. Despite the large number of domestic inland river vessels in China, information on inland ship emissions is very limited, since legislation for shipping emission control is limited and there is no monitoring infrastructure. Taking the Yangtze River in the region of Nanjing as a research area, we compiled a ship emission inventory based on real-time information received from automatic identification system (AIS) signals combined with ship-related data provided by the China Classification Society (CCS) database. The total ship emissions we derived for the Jiangsu section of the Yangtze River from September 2018 to August 2019 for NOx, SO2, PM10 and PM2.5 were 83.5, 0.04, 0.006 and 0.005 kt yr−1, respectively. This ship emission inventory we constructed was compared with the Multi-resolution Emission Inventory for China (MEIC), the Shipping Emission Inventory Model (SEIM) and the satellite-derived emissions using the Daily Emissions Constrained by Satellite Observations (DECSO) algorithm. The results show a consistent spatial distribution, with riverine cities having high NOx pollution. With this comparison we analyzed the relative impact of ship emissions on densely populated regions along the river. Inland ship emissions of NOx are shown to contribute significantly, accounting for at least 40 % of air pollution close to the river.

A Function-Oriented Electronic and Electrical Architecture of Remote Control Ship on Inland River: Design, Verification, and Evaluation

The remote control is an important function of intelligent ships. In this article, first, the functions and communication requirements of remote control ships are sorted out based on the “Rules for Intelligent Ships (2020)” issued by the China Classification Society (CCS). Second, a domain controller-based electronic and electrical architecture (EEA) for inland remote control ships is proposed. The functional domain of the ship is divided, combined with the physical layout of the ship, into the perception domain, communication domain, motion control domain, marine bridge domain, deck domain, cargo management domain, and cabin domain. Third, the real-time network communication system and the central gateway controller are designed, and the efficient information interaction between domain controllers is realized through a service-oriented communication architecture. The simulation experiment shows that the designed domain controller architecture and communication network can meet the information interaction requirements of the ship. Compared with the traditional distributed architecture, the ship EEA based on the domain controller has apparent advantages in system cost, system redundancy, functional load distribution, architecture scalability, communication load distribution, and information security and can give a design reference for inland remote control ships.

A time-dependent corrosion wastage model for the partial structure of mobile offshore platforms

ABSTRACT Offshore mobile platforms are important facilities for the development of deep-water offshore oil and gas resources. In life-cycle safety assessment of offshore mobile platforms, there remains a lack of effective structural corrosion models to guide design evaluation. From a large amount of corrosion data provided by the China Classification Society regarding the operation of offshore mobile platforms, relevant data were statistically analysed, and available corrosion data were selected for analysis and comparison. By analysing the experimental data of offshore mobile platforms, it was verified that the corrosion rate of local components of offshore mobile platforms follows the Weibull distribution, which is consistent with Paik's verification that the corrosion rate of local components of marine mobile platforms follows Weibull distribution. Therefore, the corrosion evolution model of local components of offshore mobile platforms was established by referring to the ship corrosion rate model.

Four Points of View on the Designation of the Navigation Area for Yachts

Usually, the need for research arises when there is a discrepancy between the theoretical and practical data. For example, the RINA (Registro Italiano Navale) Rules describe two navigation areas for yachts: unrestricted navigation and a navigation area with a significant wave height of not more than 4 m. In the GL (Germanischer Lloyd) Rules, it is proposed to assign the maximum wave height that a ship can meet, taking into account its speed and design features. The CCS (China Classification Society) Rules consider five categories of yachts for different navigational conditions. The significant wave height range is from 0.5 m to 6 m, and the distance from the place of refuge is from 5 to 200 nautical miles or more. Directive of the European Parliament and of the Council does not consider the distance from the place of refuge for the ship, and significant wave heights from 0.3 m to 4 m or more are proposed. In practice, the following situations may arise: it is necessary to determine the maximum value of the wave height at which the ship will be able to move against the wave or a possible decrease in the speed of the ship; to determine the height of the wave at which the wetness of the deck will begin; to study the relationship between the allowable values of the design accelerations and technical characteristics of the ship; to determine the distance from the emergency ship to the mooring place of the rescue ship; and calculate the minimum time to render assistance to people. These four situations will be considered in the article by using the energy wave criterion EWC, the recommendations of classification societies, and modeling the behavior of a vessel on a head wave.

Conceptual design of a long-range autonomous underwater vehicle based on multidisciplinary optimization framework

The endurance of a deep-sea AUV is closely related to its sailing resistance, the amount of carrying batteries and equipment load, which involves interactions among multiple disciplines. In this paper, in order to develop the conceptual design of a long-range AUV in the early stage, a multidisciplinary optimization design framework is presented for decision-makers to explore the given design space, which takes into account the coupling between the disciplines of hull form, structural design and energy use. A Self-adaptive Surrogate Ensemble (SASE) method is proposed to replace the expensive process of hydrodynamic analysis, a recommended approach by the China Classification Society (CCS) specification is applied to carry out the design of metallic pressure hulls, and the classical lamination theory and Tsai–Wu criteria are adopted in the design of composite pressure hulls. Finally, the evaluation model of AUV endurance is created from the perspective of energy capacity and consumption. The conceptual design of a 200 kg-class AUV is executed to maximize the endurance based on the proposed multidisciplinary optimization design framework. The results show that the most important factors that affect AUV endurance are the velocity and diameter, and the optimum velocity of the AUV increases with the load power. The Sea-Whale 2000 AUV was developed based on the optimal result and the excellent endurance performance in the sea trial validated the effectiveness of the proposed design method in the preliminary design process.

Finite element analysis of typical structure of side stringer skeleton under ice load

Objectives The force on the typical side skeleton nodes of a cross-skeleton icebreaker under ice load action is explored through the numerical analysis of such nodes. Methods First, based on a PC2 heavy icebreaker, according to china classification society (CCS) specifications, the ice load is calculated according to the relevant ice load specifications; next, MSC/PATRAN software is used to create a finite element model of the typical side skeleton nodes, and a representative ice load is applied to the outer plates of the icebreaker so as to obtain the stress state of the typical nodes; finally, by constantly changing the forms of the typical nodes, the stress distribution difference in the area of interest is obtained. Results The stress levels of different typical node forms are compared and analyzed, and it is concluded that the superior choices are ribs that cross through the side stringer area, and a structural form of rib disconnection in the deck area. Conclusions This paper summarizes and puts forward the design points of the typical structure form of an icebreaker's side skeleton, providing useful references for rib-crossing structural design.

Failure analysis of a marine intermediate shaft

A bulk-ship was not working normally when anchoring to wait for entering port. Inspection in site found that the intermediate shaft fractured. The intermediate shaft had accumulatively serviced for 43,000 h before fractured. Fractographic investigation indicated that the multiple origins fatigue fracture was the dominant failure mechanism of the shaft. The cracking propagated on two fracture planes at approximately ± 45° with respect to the shaft axis. The material of failed shaft was found to be a low carbon steel of type ASTM 1020, rather than the specified the medium carbon steel of type ASTM 1035. The average values of yield strength and ultimate strength of shaft material were respectively 16% and 20% lower than the lower limit of technical specification due to low carbon content, as a result of the decreased fatigue strength of shaft material. The fracture occurred at the fillet root of flange connected to the propeller-shaft, where high stress concentration was caused by geometry design. Deep circumferential machining grooves were present on the fillet root of flange for additive stress concentration. The inhomogeneities acted as potential sites for fatigue crack initiation. The low fatigue strength of shaft material promoted initiation and propagation of fatigue cracks in the weaker region under the reversed torsion loading. The static strength analysis of intermediate shaft was performed to assess the design implications. The measured average ultimate strength of failed intermediate shaft was 12% lower than the lower limit in Rule for Classification of Sea-going Steel Ships issued by China Classification Society. The safety factor of the failed intermediate shaft is lower than the permitted one.

Research on the Emission Inventory and Pollution Characteristics of Air Pollutants from Ships in Beijing-Tianjin-Hebei Area

As the key areas of China’s air pollution control, Beijing-Tianjin-Hebei region are the busiest sailing area for ships. Therefore, the impact of air pollution caused by ships cannot be ignored. The bottom-up “dynamic method” was used in this study and the ships’ navigation process was divided into three processes: docking, entering and exiting port and cruising, and the emission of air pollutants from ships was calculated respectively, and the calculation method of air pollutants emission inventory for ships with high temporal and spatial resolution was established. Based on the ships’ basic information data from maritime database of China Classification Society and Lloyd’s Register, the Automatic Identification System data and the emission factor data for ships, the emission inventory for ships in 2014 in Beijing-Tianjin-Hebei area was calculated. In addition, the study also analyzed emission share rate of air pollutants from ships and the uncertainty of emission inventory.

Reliability analysis of hull girder ultimate strength for large container ships under whipping loads

The two incident reports for MSC (Mediterranean Shipping Company) Napoli in 2008 and MOL (Mitsui O.S.K. Lines) Comfort in 2015 both pointed out that whipping response was one main reason for inducing the catastrophes. Subsequently, International Association of Classification Societies (IACS) proposed a Unified Requirement (UR) S11A for ultimate strength evaluation of container ships, and main classification societies also updated their guidelines for whipping response. However, there are big differences in these requirements, and the safety level of ultimate strength under whipping loads is still unclear. This article is to find the effect of the whipping loads on hull girder reliability. Two large container ships 14500TEU and 19000TEU designed by China Classification Society (CCS) Rules are selected as case studies. Hull girder ultimate capacity in mid-ship section under hogging conditions is adopted as the dangerous failure mode, which is predicted by the increment-iterative method in IACS Common Structural Rules (CSR). The whipping effect on hull girder reliability is accounted for by a factor attaching on wave-induced moment. Then, a new evaluation criterion is proposed to evaluate hull girder ultimate strength for container ships under whipping loads, and sensitivity analysis of whipping effect is carried out. The conclusions in this article can provide a guidance for revising rule requirements in classification societies and optimising container ship structural design.

The wind load prediction and comparative study of asmmetric semi-submersible lifting platform based on CFD

In order to accurately predict the wind load of asymmetric offshore structures, this paper studied the wind load of an asymmetric semi-submersible lifting platform based on the CFD software FINE/MARINE, and calculated the wind load of operation state, lifting state and survival state respectively, and compared the results with those of China Classification Society(CCS) specification. The results show that under the same wind speed, the change of wind direction angle has a great influence on the distribution of wind field around the platform. The specification calculation can not fully consider the influence of the shielding effect between the components of the superstructure, therefore, the results are larger than the numerical simulation value. In addition, the wind field distribution near the platform can be used to analyze the variation of wind load, which provides an effective method for wind load prediction and wind field analysis of asymmetric offshore structures.

Summary of Technical Specifications for Offshore Wind Farm Facilities

[Introduction] This paper aims to promote the establishment of a complete technical standards system for offshore wind farms. [Method] The problems existing in the construction of offshore wind farms in China were pointed out, the standards for offshore wind farm facilities at home and abroad were summarized, and the exploration and effectiveness of the technical specifications for offshore wind power facilities by China Classification Society(CCS) were introduced. [Result] Despite the rapid development of offshore wind power in China, the supporting technical specifications for offshore wind power facilities have not been followed up in time, and the whole life cycle technical specifications system, including design, construction, installation, operation and maintenance and abandonment, has not been established. Although Europe has a mature specifications system for offshore wind power facilities, it cannot be completely copied and used, such as the LRFD method of structural design which is related to the environmental conditions and reliability index of the sea area, and the partial factor applicable to the European sea area is not applicable to the Chinese sea area. [Conclusion] Therefore, the technical specification system for the domestic offshore wind power facilities requires the joint efforts and cooperation of the industry, traditional ocean engineering specialty should play a greater role in this field, and the research achievements by CCS in this field can provide some reference values for the establishment of the technical specification system.

China Classification Society - Sailing Gloriously to the Farthest End of the Earth, CCS is on the Way

China Classification Society - Sailing Gloriously to the Farthest End of the Earth, CCS is on the Way

A study on sidewall penetration of cable-type welding wire electrogas welding

Cable-type welding wire (CWW) electrogas welding (EGW) is an innovative process in which CWW is used as the consumable electrode. Seven wires can be melted simultaneously with only one welding power source, one wire feeder, and one welding torch. This paper reports a study of the sidewall penetration of CWW EGW. The results showed that all the mechanical properties of CWW EGW welded joints met the standards of the China Classification Society (CCS). The arc heating area of CWW EGW was large and that the unique rotating arc of CWW EGW had a strong stirring effect, enhancing convective motion of the molten pool and accelerating heat transfer between the superheated molten pool and the sidewall. The droplet of the CWW EGW appeared to be non-axial transfer due to the rotating force. The superheated droplet transferred to the sidewall or the molten pool near the sidewall directly, promoting the heating and melting of the base metal.

Pollution from EOLV dismantling and the corresponding countermeasures

There are problems associated with dismantling vessels that have reached the end of their life, when pollution problems associated with the process need to be addressed. The first problem in “end-of-life vessels” (EOLV) is to define their legal frameworks. The second problem is their dismantlement for recycling of ships. In order to reduce the effects of pollution caused by EOLV dismantling, the International Maritime Organization (IMO) adopted the Hong Kong Convention on 15 May 2009. While preparing for implementing the obligations under the Hong Kong Convention, China shall make effort on five aspects: (i) establish an ISRT for the safe and environmentally sound recycling of ships, (ii) improve the competitiveness of ship dismantling plants, (iii) strengthen international exchanges, (iv) amend the domestic laws and regulations, and (v) support from the China Classification Society.

Intelligentized Interception type Separation And Recycle equipment for oil spillage

This text introduce interception oil-remove new technology developed by Nanjing bidun environmental protection technology Co., Ltd and the equipment “International No.1” used for offshore spilled oil treatment. This equipment adopt interception oil-removal technology, can separate and purify oil-water on site, recycle spilled oil with high quality and speed, meanwhile let the sewage discharge reaching the required standard. This treatment technology is pure physical process without any chemical, so will not cause secondary pollution. Offshore spilled oil treatment equipment”International No.1” can recycle spilled oil as original quality, application range is wide, from crude oil to light oil, and all mineral oil. It applies to oil content from trace to 100 percent; oil gathering concentration ≥95%, oil content of effluent ≤5mg/L. This equipment also has characteristics of small volume and low energy consumption. This equipment was highly evaluated by PCT, and get invention patent license of America, Russia and South Korea, also obtained the "Certificate of Type Approval " issued by IMO and China Classification Society.

Optimum Structural Design of the Hull on Jack-up Platform

The system design and optimization of the hull of a jack-up platform was presented in the paper, based on finite element method and size optimization theories. Three-dimensional model of the hull was made by the design parameters, the size and the layout of the various compartments were determined. The finite element model was built, the analysis and calculation of the hull in some load-cases requested in the China Classification Society were done. The thickness of the steel plates were optimized to be less based on the analysis results. The results show that a big displacement of the side plate is produced because of the wind load, there is large stress at the main deck and the inner bottom deck due to the variable load and ballast water. After finishing the size optimization, the stress of hull increases and the stress is more evenly distributed, and the mass of hull is down. The utilization of material increases effectively.

The Fatigue Strength Assessment for Hull Structure of Steel Fishing Vessel

According to the norms “the fatigue strength assessment for hull structures in 2007” issued by China Classification Society, the combined computing platform established is composed of mature hydrodynamic software SESAM from Det NorskeVeritas(DNV)and MSC.PATRAN/NASTRAN, the fatigue strength assessment for hull structure of a steel fishing vessel is studied.

Structural Optimization for a Spherical Pressure Hull of a Deep Manned Submersible Based on an Appropriate Design Standard

As the most critical component of a deep manned submersible, the manned pressure hull provides a safe living space for pilots and scientists under the deep sea pressure, and its weight occupies almost 1/3 total weight of the manned submersible. So the pressure hull should be designed to have enough strength and should be as light as possible. However, a comparison of the current available design rules from various classification societies indicated significantly different results among these design rules and many existing spherical pressure hulls are found to be not in compliance with most of the current design rules. This indicates that current design rules need to be updated and unified, similarly to the Common Structural Rules for tankers and bulk carriers. To update the design rules, a systematic study is carried out. Then, a new design standard based on this study is proposed to the China Classification Society (CCS) for consideration of updating their rules. The main purpose of this paper is to briefly summarize the study on this new design standard and to present the structural optimization of the manned spherical pressure hull of a new 4500-m rating manned submersible based on this new standard.