大型双金属壁LNG低温储罐超厚抗压环预制安装技术

建造安全可靠的液化天然气(LNG)储罐一直是建造企业所面对的难题,而抗压环作为LNG储罐的主要承压部件,其预制及安装质量的控制将成为整个施工过程的重点。本文针对超厚抗压环的预制焊接、组对安装等施工工艺进行详细描述,可为今后类似的LNG储罐的建造提供参考。

立式拱顶储罐抗压环结构与弱顶性能分析

以1台690m3拱顶储罐为研究对象,对GB 50341—2003《立式圆筒形钢制焊接油罐设计规范》和API 650 2005《Welded Steel Tanks for Oil Storage》中规定的4种型式的抗压环建立了拱顶储罐非线性有限元模型,采用罐底和地基材料接触单元的方法替代罐底和地基材料弹性杆单元法模拟罐底和地基材料的接触力,分析了不同抗压环结构的储罐弱顶性能规律,研究结果表明,a型抗压环弱顶系数达到2.096,弱顶效果最好。

提高低压储罐抗压环施工质量

根据施工运行压力0.088MPa低压储罐图纸及标准要求要求,施工抗压环时采用焊接对称焊、分段跳焊,预制严格把关,焊前预热充分的措施,提高施工精度,获得令人满意的效果。

新型LNG储罐抗压环施工工序及控制要点

液化天然气储罐是天然气储运中非常重要的一个环节,储存量大、储存安全,适用性强的LNG储罐受到了众多企业的追捧,单包容罐、双包容罐和全包容罐得到了广泛应用。新型LNG储罐在造价、工期和技术上的优势虽然已经在国外广泛采用,但国内尚未有投产应用先例。新型LNG储罐的抗压环与以往9%镍钢LNG储罐不同,整体结构形式为56边形。因此,如何控制抗压环的制作安装质量,成为新型LNG储罐的施工重点。

大型薄膜罐抗压环施工工序及控制要点

液化天然气储罐是天然气储运中非常重要的一个环节,近年来LNG储存的方式及安全可靠性成为现在越来越多的建造企业共同的难题,储存量大、储存安全、适用性强的LNG储罐收到了众多企业的追捧,现如今单包容罐、双包容罐、全包容罐都以其相应特点得到了广大的应用,新型的薄膜型储罐因其在造价、工期和技术上的优势已经在国外广泛采用,而国内尚未有投产应用先例,以天津南港在建的22万m^(3)薄膜罐为例,其抗压环与以往9%镍钢LNG储罐不同,整体结构形式为56边形结构,如何控制抗压环制造安装质量,成为薄膜罐抗压环施工重点。

全自动MAG焊在20万m^3LNG储罐抗压环结构焊接中的应用

简要介绍了江苏LNG项目二期工程20万m^3LNG储罐的抗压结构形式和16MnDR压力容器钢板的机械性能,通过选用合理的焊接工艺实现了抗压环结构现场的高效制作,对施工过程中遇到的问题提出解决方案。

LNG储罐抗压环焊缝的射线检测

抗压环是LNG储罐外罐的结构件。在射线检测中,由于上焊缝过渡段厚度不均匀,按常规射线检测所得底片无法满足要求。通过采用试块补偿法补偿焊缝不均匀的几何尺寸,使透照厚度均匀,所得底片黑度满足标准要求。

储罐设计标准中对抗拉(压)环截面积相关规定的研究

考察了现今国、内外常用的储罐设计标准,包括:GB 50341—2003《立式圆筒形钢制焊接油罐设计规范》、SH 3046—1992《石油化工立式圆筒形钢制焊接储罐设计规范》、API 650—1998《钢制焊接石油储罐》及API 650—2009《钢制焊接石油储罐》。针对标准中拱顶储罐抗拉(压)环截面积的相关规定,介绍了各公式的推导过程与系数取值。采用规范计算方法对八种工程直径的储罐进行了对比计算,讨论其在工程实际中的可行性。

Strength of copolymer grouting material based on orthogonal experiment

Using the orthogonal experimental design method involving three factors and three levels, the flexural strength and the compressive strength of copolymer grouting material were studied with different compositions of water-cement ratio （mass fraction of water to cement）, epoxy resin content, and waterborne epoxy curing agent content. By orthogonal range and variance analysis, the orders of three factors to influence the strength, the significance levels of different factors, and the optimized compound ratio scheme of copolymer grouting material mixture at different curing ages were determined. An empirical relationship among the strength of copolymer grouting material, the water-cement ratio, the epoxy resin content, and the waterborne epoxy curing agent content was established by multivariate regression analysis. The results indicate that water-cement ratio is the most principal and significant influencing factor on the strength. Epoxy resin content and waterbome epoxy curing agent content also have a significant influence on the strength. But epoxy resin content has a greater influence on the 7-day and 28-day flexural strength, and waterborne epoxy curing agent content has a greater influence on the 3-day flexural strength and the compressive strength. The copolymer grouting material with water-cement ratio of 0.4, epoxy resin content of 8% （mass fraction） and waterbome epoxy curing agent content of 2% （mass fraction） is the best one for repairing of cement concrete pavement. The flexural strength and the compressive strength have good correlation, and the ratio of compressive strength to flexural strength is between 1.0 and 3.3.

Mechanical and electrical properties of coarse-grained soilaffected by cyclic freeze-thaw in high cold regions

To evaluate the geotechnical properties of coarse-grained soil affected by cyclic freeze-thaw,the electrical resistivity and mechanical tests are conducted.The soil specimens are prepared under different water contents,dry densities and exposed to 0?20 freeze-thaw cycles.As a result,the stress?strain behavior of the specimen(w=14.0%andρd=1.90 g/cm^3)changes from strain-hardening into strain-softening due to the freeze-thaw effect.The electrical resistivity of test specimen increases with the freeze-thaw cycles change,but the mechanical parameters(the unconfined compressive strength qu and the deformation modulus E)and brittleness index decrease considerably at the same conditions.All of them tend to be stable after 7?9 cycles.Moreover,both the dry density and the water content have reciprocal effects on the freeze-thaw actions.The failure and pore characteristics of specimens affected by freeze-thaw cycles are discussed by using the image analysis method.Then,an exponential function equation is developed to assess the electrical resistivity of specimens affected by the cyclic freeze-thaw.Linear relations between the mechanical parameters and the electrical resistivity of specimens are established to evaluate the geotechnical properties of the soil exposed to freeze-thaw actions through the corresponding electrical resistivity.

Effect of Freeze-Thaw Cycles on Mechanical Properties and Permeability of Red Sandstone under Triaxial Compression

Geological disasters will happen in cold regions because of the effects of freeze-thaw cycles on rocks or soils, so studying the effects of these cycles on the mechanical characteristics and permeability properties of rocks is very important. In this study, red sandstone samples were frozen and thawed with o, 4, 8 and 12 cycles, each cycle including 12 h of freezing and 12 h of thawing. The P-wave velocities of these samples were measured, and the mechanical properties and evolution of the steady-state permeabilities were investigated in a series of uniaxial and triaxial compression tests. Experimental results show that, with the increasing of cyclic freeze-thaw times, the P-wave velocity of the red sandstone decreases. The number of freeze-thaw cycles has a significant influence on the uniaxial compressive strength, elastic modulus, cohesion, and angle of internal friction. The evolution of permeability of the rock samples after cycles of freeze-thaw in a complete stress-strain process under triaxial compression is closely related to the variation of the microstructure in the rock. There is a highly corresponding relationship between volumetric strain and permeability with axial strain in all stages of the stress-strain behaviour.

Strength and thermal behavior of low weight foam geopolymer using circulating fluidized bed combustion fly ash

A comparative study of the influence of elevated temperature on foam geopolymer using circulating fluidized bed combustion fly ash（CFA） was reported. Foam geopoymers were prepared with different amounts of foam agent and different Si O2/Al2O3 molar ratios of 3.1, 3.4, and 3.8. The mechanical, thermo-physical properties and microstructure of the foam geopolymers before and after exposure to elevated temperature of 800, 1000, and 1200 ℃ were investigated. The specimen with Si O2/Al2O3 molar ratio of 3.8 exhibits the highest compressive strength, better microstructure and dimension stability before and after firing. Carnegeite, nepheline, and zeolite crystalline phases appearing after exposure may contribute to the good post-exposure strength. Low weight foam geopolymer using CFA can increase strength and maintain higher stability as high as 1000 ℃.

Prevalence of Anti-endothelial Cell Antibodies in Patients with Pulmonary Arterial Hypertension Associated with Connective Tissue Diseases

Objective To investigate the prevalence of anti-endothelial cell antibodies (AECAs) in the sera of connective tissue diseases (CTD) patients with pulmonary arterial hypertension (PAH) and its correlation with clinical manifestations. Methods AECAs in sera of 39 CTD patients with PAH,22 CTD patients without PAH,and 10 healthy donors as controls were detected with Western blotting. The prevalence of different AECAs in different groups was compared and its correlation with clinical manifestations was also investigated. Results The prevalence of AECAs was 82.1% in CTD patients with PAH,72.7% in CTD patients without PAH,and 20.0% in healthy donors. Anti-22 kD AECA was only detected in CTD patients with PAH (15.4%). Anti-75 kD AECA was more frequently detected in CTD patients with PAH than in those without PAH (51.3% vs. 22.7%,P<0.05). In CTD patients with PAH,anti-75 kD AECA was more frequently detected in those with Raynaud’s phenomenon or with positive anti-RNP antibody. Conclusion AECAs could be frequently detected in CTD patients with or without PAH,while anti-22 kD and anti-75 kD AECA might be specific in CTD patients with PAH.

Use of Magnesium Oxide-cement Binder in Composites Based on Hemp Shives

In this paper, it presented the results of experimental study of utilization of MgO cement as calcium hydrate replacement in lightweight composites based on hemp shives. The results of selected characteristics （compressive strength and coefficient of thermal conductivity） of hardened composites show that MgO cement based on the milled caustic magnesite is suitable alternative in comparison to conventional binders used in hemp concrete. This material leads to new environmentally products as non-load bearing building materials.

对立式圆筒形储罐标准GB 50341—2014中某些问题的探讨

GB 50341—2014在执行过程中,被发现某些规定条款存在问题、个别计算公式存在笔误。文章结合工程实际,将该标准实施以来所遇到的主要问题以及个人的理解和修改建议归纳为八个部分,即自支撑式罐顶顶与壁的非弱连接属性、罐顶与罐壁连接处有效截面面积A计算公式对于不同材料的适用性、计算破坏压力P f计算公式错误、外压储罐在拱顶板计算厚度及其抗压(拉)环所需面积A r无需满足常压储罐的要求、标准正文与附录B关于罐壁稳定计算不一致、外压储罐罐壁的设计风压W计算值过小、外压增加时罐壁加强圈数量不增反降以及对带肋拱顶计算公式的修改建议等,并分别加以分析与讨论。

Damage model of fresh concrete in sulphate environment

A model of damage to fresh concrete in a corrosive sulphate environment was formulated to investigate how and why the strength of corroded concrete changes over time. First, a corroded concrete block was divided into three regions: an expanded and dense region; a crack-development region; and a noncorroded region. Second, based on the thickness of the surface corrosion layer and the rate of loss of compressive strength of the corroding region, a computational model of the concrete blocks' corrosion-resistance coefficient of compressive strength in a sulphate environment was generated. Third, experimental tests of the corrosion of concrete were conducted by immersing specimens in a corrosive medium for 270 d. A comparison of the experimental results with the computational formulae shows that the calculation results and test results are in good agreement. A parameter analysis reveals that the corrosion reaction plays a major role in the corrosion of fresh concrete containing ordinary Portland cement,but the diffusion of the corrosion medium plays a major role in the corrosion of concrete mixtures containing fly ash and sulphate-resistant cement. Fresh concrete with a high water-to-cement ratio shows high performance during the whole experiment process whereas fresh concrete with a low water-to-cement ratio shows poor performance during the late experiment period.

Workability Tests on Fresh Concrete Formulated with Eco-friendly Admixture

Extra-cellular compounds, secreted by microorganisms into their surroundings, can be integrated in concrete composition as admixtures. These substances are important in biofilm formation and some of them can be used as corrosion inhibitor of concrete reinforcement. This paper deals with products made with biological surface active compounds/agents allowing the development of more eco-friendly concrete. The influence of this environmentally friendly bio admixture on setting time, workability, bending and compressive strengths of various mortar based materials made of CEM I, CEM III and CEM V was studied. Mechanical tests were carried out to highlight the influence of admixture in workability and hardening of samples containing the biological product with ratio in the range of 0-2.5%. It was demonstrated that the presence of the new bio-compound admixture in mortar decreases their compressive strength after 28 days of standard curing, in spite of remaining higher than standard minimal strength. Furthermore, Vicat needle experiments have shown a tendency of this admixture to decrease the setting time. A discussion was finally proposed in order to correlate the setting times and the decrease of the mortar compressive strength, corresponding in fact to a hardening delay. This setting time delay could be linked to a delay of the admixtured mortar to increase its resistance. The slump results highlight the action of bio-admixture as a plasticizer on mortars because it increases their workability for a same water-cement ratio. This effect seems variable according to the added amount.