Subsea templates are steel structures used to support subsea well components.Normally,offshore crane vessels are employed to install them to the target location on the seabed.Crossing the splash-zone during the ...Subsea templates are steel structures used to support subsea well components.Normally,offshore crane vessels are employed to install them to the target location on the seabed.Crossing the splash-zone during the lowering of a subsea template is considered the most critical phase during the installation due to slamming loads and needs to be studied to provide the operational weather criterion during the planning phase.In this study,dynamic response analysis has been carried out to evaluate the allowable sea states for the plash-zone crossing phase of the subsea templates.The numerical model of the lifting system,including the crane vessel and the subsea template,is firstly built in the state-of-the-art numerical program SIMA-SIMO.Then,dynamic analysis with time-domain simulations is carried out for the lifting system under various sea states.The disturbed wave field due to the shielding effects from the installation vessel is considered when calculating the hydrodynamic forces on the template.Statistical modelling of the dynamic responses from different wave realizations is used to estimate the extreme responses of various sea states.The application of the generalized extreme value distribution and Gumbel distribution in fitting the extreme responses is discussed.Moreover,the influence of the shielding effects from the vessel,as well as the influence of the changing size of the suction anchor on the hydrodynamic responses and the allowable sea states are studied.展开更多
在海水飞溅区对实验室冶炼的Ni-Cu-P钢、含Cu低合金钢和碳钢进行660 d的挂片实验,评价Ni-Cu-P钢的耐蚀性能;采用Fourier变换红外(FTIR)光谱、电感耦合等离子体原子发射光谱(ICP-AES)、电子探针(EPMA)、SEM和EDAX等技术,分析3种钢表面的...在海水飞溅区对实验室冶炼的Ni-Cu-P钢、含Cu低合金钢和碳钢进行660 d的挂片实验,评价Ni-Cu-P钢的耐蚀性能;采用Fourier变换红外(FTIR)光谱、电感耦合等离子体原子发射光谱(ICP-AES)、电子探针(EPMA)、SEM和EDAX等技术,分析3种钢表面的锈层特征.结果表明,Ni Cu P钢表现出比碳钢优越的耐全面腐蚀和点蚀能力.对锈层成分分析发现,在宏观阴极区,钢的内、外锈层均主要由α-FeOOH,β-FeOOH,γ-FeOOH,δ-FeOOH,Fe_3O_4和少量非晶氧化物组成,但内锈层的Fe_3O_4含量更高,而γ-FeOOH和β-FeOOH的含量更低.与碳钢相比,Ni-Cu-P钢宏观阴极区和蚀坑内的锈层更致密.对锈层中的合金元素分析发现,Ni-Cu-P钢中的合金元素Ni,Cu和P主要分布在宏观阴极区的内锈层和蚀坑内,Cu和P在蚀坑内有富集.在宏观阴极区,合金元素Cu可细化内锈层的晶粒,从而促进保护性锈层的形成.在蚀坑内,Cu富集在锈层中的夹杂物周围,对锈层中的裂纹和孔洞起修复作用.合金元素Cu和Ni可提高蚀坑内基体的电位,P有助于降低钢蚀坑内基体的腐蚀速度,因此,Ni-Cu-P钢比碳钢表现出强的耐点蚀性能.展开更多
文摘Subsea templates are steel structures used to support subsea well components.Normally,offshore crane vessels are employed to install them to the target location on the seabed.Crossing the splash-zone during the lowering of a subsea template is considered the most critical phase during the installation due to slamming loads and needs to be studied to provide the operational weather criterion during the planning phase.In this study,dynamic response analysis has been carried out to evaluate the allowable sea states for the plash-zone crossing phase of the subsea templates.The numerical model of the lifting system,including the crane vessel and the subsea template,is firstly built in the state-of-the-art numerical program SIMA-SIMO.Then,dynamic analysis with time-domain simulations is carried out for the lifting system under various sea states.The disturbed wave field due to the shielding effects from the installation vessel is considered when calculating the hydrodynamic forces on the template.Statistical modelling of the dynamic responses from different wave realizations is used to estimate the extreme responses of various sea states.The application of the generalized extreme value distribution and Gumbel distribution in fitting the extreme responses is discussed.Moreover,the influence of the shielding effects from the vessel,as well as the influence of the changing size of the suction anchor on the hydrodynamic responses and the allowable sea states are studied.
文摘在海水飞溅区对实验室冶炼的Ni-Cu-P钢、含Cu低合金钢和碳钢进行660 d的挂片实验,评价Ni-Cu-P钢的耐蚀性能;采用Fourier变换红外(FTIR)光谱、电感耦合等离子体原子发射光谱(ICP-AES)、电子探针(EPMA)、SEM和EDAX等技术,分析3种钢表面的锈层特征.结果表明,Ni Cu P钢表现出比碳钢优越的耐全面腐蚀和点蚀能力.对锈层成分分析发现,在宏观阴极区,钢的内、外锈层均主要由α-FeOOH,β-FeOOH,γ-FeOOH,δ-FeOOH,Fe_3O_4和少量非晶氧化物组成,但内锈层的Fe_3O_4含量更高,而γ-FeOOH和β-FeOOH的含量更低.与碳钢相比,Ni-Cu-P钢宏观阴极区和蚀坑内的锈层更致密.对锈层中的合金元素分析发现,Ni-Cu-P钢中的合金元素Ni,Cu和P主要分布在宏观阴极区的内锈层和蚀坑内,Cu和P在蚀坑内有富集.在宏观阴极区,合金元素Cu可细化内锈层的晶粒,从而促进保护性锈层的形成.在蚀坑内,Cu富集在锈层中的夹杂物周围,对锈层中的裂纹和孔洞起修复作用.合金元素Cu和Ni可提高蚀坑内基体的电位,P有助于降低钢蚀坑内基体的腐蚀速度,因此,Ni-Cu-P钢比碳钢表现出强的耐点蚀性能.
