基于FAD技术的含裂纹缺陷压力管道安全评定

裂纹缺陷是压力管道在服役过程中频繁产生的缺陷,对其进行安全评定就显得格外重要。对含裂纹缺陷进行安全评定方法很多,本文主要研究基于失效评定图技术的含裂纹缺陷压力管道的安全评定方法。     

含缺陷锅炉蒸汽管道的安全评定

以某热电厂在用含缺陷锅炉蒸汽管道为研究对象，采用超声相控阵检测方法确定缺陷类型和尺寸，应用ANSYS Workbench软件对蒸汽管道进行有限元分析，采用GB/T 19624—2019《在用含缺陷压力容器安全评定》推荐的安全评定方法对存在未熔合、裂纹和未焊透三种缺陷的蒸汽管道进行安全评定，结果表明：该锅炉蒸汽管道中未焊透缺陷不能满足GB/T 19624—2019的评定要求，蒸汽管道存在安全隐患，应对缺陷进行返修处理。     

基于CAESAR的含未焊透缺陷压力管道的安全评定

根据TSGD7005—2018《压力管道定期检验规程——工业管道》对一条含未焊透缺陷的压力管道进行安全评定,发现该未焊透缺陷属于4级缺陷。使用单位不便对该管道进行返修,因此根据GB/T19624—2004《在用含缺陷压力容器安全评定》对其进行了安全评定。在安全评定的过程中,采用了CAESAR软件对该管线在复杂工况下的弯矩进行了计算。结果表明,该管道满足安全要求,可以继续使用。     

LF2铝制压力容器的失效评定

对石化企业的深冷设备中用铝镁合金制造压力容器材料 LF2的性能进行了试验研究,分析探讨了含缺陷铝制压力容器失效评定的方法,得到了 LF2材料的失效评定曲线和失效评定图。研究结果表明,含缺陷铝制压力容器的失效评定可以采用 R6通用失效评定曲线,其结果是偏安全的。     

造纸用铸铁烘缸超声波测厚研究

造纸用铸铁烘缸作为一种压力容器,在使用过程中应进行超声测厚,但由于铸铁材料的特殊性,普通测厚仪无法准确测量铸铁厚度。利用带A扫信号的超声波检测仪,在铸铁阶梯试块上进行比对实验,得知在一定的压力和温度范围内,铸铁声速、硬度和金相基本保持不变,因此可以利用烘缸凸缘部位校准声速。通过对不同超声波探头的比对实验,得知不同频率、不同晶体尺寸探头的优缺点,对提高铸铁烘缸测厚的精确度有较大帮助。     

含局部减薄缺陷X80长输管线的安全评定

为了准确评价含局部减薄缺陷管道的剩余强度,研究了API579-2007标准含局部减薄缺陷管道剩余强度的评价方法,针对长输管线,对评价流程进行了优化。以X80长输管线为研究对象,基于API579标准,完成了对含局部减薄缺陷管线的安全评定,得到的给定局部减薄缺陷下管道最大运行压力真实反映了含局部减薄缺陷管道的承载能力,二级评价的结果比一级评价更为精确,证明了API579标准评价含局部减薄缺陷管道的剩余强度的合理性。开发出含局部减薄缺陷的长输管线安全评定软件,该软件大大减少了安全评定过程中计算的工作量,提高了长输管线的安全评定工作效率,降低了评定的难度。     

球罐安全评定方法的比较

利用CVDA-1984《压力容器缺陷评定规范》及《在用舍缺陷压力容器安全评定》对含缺陷的球罐进行断裂与塑性失效安全评定,并分析比较所运用的评价方法。结果表明,《在用含缺陷压力容器安全评定》标准更具有优越性。     

含焊接缺陷压力管道安全评定系统--基于BS7910的理论及方法

针对含焊接缺陷压力管道评定中存在的不确定性,提出了建立在BS7910确定性评定基础上的可靠性评定方法,并开发出含焊接缺陷压力管系安全评定系统。该系统不仅能对含焊接缺陷管系进行确定性评定,而且能获得管系内每个缺陷的失效概率和整个管系的失效概率,具有极大的工程应用价值。     

氮气净化罐凹坑缺陷安全评定

某企业在压力容器定期检验过程中,发现一台氮气净化罐存在凹坑缺陷。依据GB/T 19624—2004《在用含缺陷压力容器安全评定》,利用ANSYS有限元分析软件对该设备进行了安全评定。结果表明,该设备的凹坑缺陷是可以接受的。     

在役含缺陷蒸汽及氨气管道应力分析及安全评估

对某石化厂蒸汽/氨气管道开展检验检测，并针对UT发现含超标缺陷压力管道进行应力分析及安全评估，结果表明，蒸汽/氨气管道上的9处超标缺陷(未焊透、未熔合等)均能够通过GB/T 19624—2019《在用含缺陷压力容器安全评定》中压力管道环向平面缺陷(U因子评定)的评定。上述检验所发现的超标缺陷不影响压力管道在操作工况的安全使用，允许在一定条件下保留。     

Effect of age on splitting tensile strength and fracture resistance of concrete

Concrete cylinders aged 1,2,3,5,7,14 and 28 days were loaded to failure in indirect tension. Similar cylinders, but with a central notch cast in the diametral plane of loading, were also loaded to fracture. The splitting tensile strength of the notched cylinders was determined, and its behavior with age was compared with that of unnotched cylinders. Apparent fracture toughness values were calculated as a function of age. It appears that strength and fracture resistance follow similar aging patterns for the concrete tested.     

Estimation of insitu strength of concrete

Twelve concretes of low, medium and high strength, with and without a fly ash and with and without a proprietary superplasticizer were designed. From each concrete 375 × 375 × 150 mm slabs and 100 × 200 mm cylinders were cast. The slabs were stored in out-door exposure conditions and 75 × 150 mm cores were extracted after 28, 91 days and 6 months duration. The moulded cylinders were cured in a fog room, control room maintained at 45% R.H. and placed alongside the slabs.

The concrete strength is known to be highly variable and depends on a great many factors. Nonetheless, the results suggest that the insitu strength can be estimated by dividing the strength of the fog cured cylinders by a factor of 1.25. Similarly, for most concretes it can also be assumed that the core strength is equal to the strength of the field-cured cylinders. In spring/summer-like ambient conditions, the core strength is 80% of the strength of the standard cured cylinders instead of 85% required by some codes of practice.     

X-ray microtomography (microCT) of the progression of sulfate attack of cement paste

High-resolution X-ray computed tomography (i.e., microCT or microtomography) was used to study the sulfate attack of cylinders of Type I cement paste cast with water-cement (w/c) ratios of 0.45, 0.50 and 0.60. Damage levels in samples exposed to a Na₂SO₄ solution with 10,000 ppm sulfate ion concentration were qualitatively rated from 0 (no damage) to 4 (extreme damage) based upon visual examination of the samples' exteriors and microtomography of the samples' interiors. The greater the w/c ratio, the more rapid the onset of sulfate damage. The corners of the cylinders appeared to be particularly susceptible to spalling, and damage may have continued into the cement paste by formation of subsurface cracks.     

ENAMELING DEFECTS DUE TO CAST IRON

A discussion of Malinovszky's paper on enameling defects due to cast iron. Problems are suggested for further investigation on the subject.     

Quality assessment of foundry coke

Possible methods for quality assessment of foundry coke are evaluated with a view to predicting the smelting characteristics and the properties of the cast iron produced. This involves defining what is meant by the quality assessment of foundry coke; a literature review of existing methods of coke assessment; and the identification of possible methods for the quality assessment of foundry coke. Analysis in terms of the macrostructure, the electrical resistance, the structure of the cast iron in a cupola furnace, and the coke consumption indicates that compliance with State Standard GOST 3340-88 does not ensure satisfactory quality of foundry coke. The quality of foundry coke may be assessed in terms of the yield of volatiles, the reactivity, the mean piece size, the macroporosity, and the electrical resistance. The resistance is greatest for samples in the size class 40–60 mm and is least for the size class 60–80 mm. It increases with increase in the moisture, ash, and sulfur content. Quality assessment may be based on the content of <0.1 mm and 0.1–0.2 mm pores in unit length of the coke surface or on the wall thickness of the pores (<0.05 mm, >0.3 mm, and 0.2–0.3 mm), and also on the structural parameters of the cast iron: the shape and size of the graphite inclusions, which depend on the ash content, total sulfur content, and total moisture content in the coke. Voluntary certification may be used for the quality assessment of foundry coke.     

Geometry of crack network and its impact on transport properties of concrete

This paper investigates the crack network geometry in concretes subjected to cyclic axial loading. A total of 24 cylinder specimens of two concretes (OPC and HVFC) were cast and eight levels of cracking extents were created for each concrete. Disks were extracted from the cylinders and the crack geometry was evaluated for sections both perpendicular and parallel to loading. The crack geometry is quantified by crack density, length, orientation and connectivity. The crack length is found to obey log-normal distribution, and the crack orientation and connectivity are correlated strongly with crack density. The volumetric density is identified as a consistent parameter to describe the impact of crack network on altered transport properties. The effective porosity, capillary sorptivity, gas permeability and electrical conductivity all have strong dependence on crack density. In particular, the gas permeability is proved to be sensitive to both small range and large range of crack density.     

Quantitative Characterization of Internal Defects in RDX Crystals

Size, shape, internal defects are very important properties of explosives crystals. These parameters play a role on both the explosive formulation processing and the detonic behavior of the explosive formulations. The use of explosive crystals free of solvent inclusions leads to decrease the shock sensitivity of cast explosive formulations. Many efforts for processing such high quality explosive crystals have been done and are still in progress. Qualitative observations of internal crystal defects can be performed by optical microscopy with matching refractive index. The purpose of this paper is to provide two accurate quantitative tools for internal crystal defects measurements. The first method is based on accurate measurements of the crystal apparent density. The second method records the mass of the species entrapped in the crystal internal cavities. Experiments are performed on two RDX batches. The strong correlation recorded between the results of the two complementary methods validates the measurements. Apparent density measurements provide an accurate global characterization of the internal defects population of a crystal batch sorting the crystals in function of their apparent density. The second method is a tool to identify the species entrapped in the crystals.     

立磨耐磨材料的选择

在用立磨粉磨物料时,磨辊和磨盘的磨损比较大。国外一些立磨生产厂在磨辊和磨盘等易损件上使用了更耐磨的材料,因此,其生产的立磨成功地用于水泥和矿渣粉磨中。总结了这些立磨的易损件材料选择的一些成功经验,并对其性能及其磨损情况进行了对比分析。结合国内立磨生产的实际情况和立磨生产中的磨损情况,提出了用于易损件的材质和结构。对于挤压磨损,推荐使用高铬合金铸铁制作辊套,并采用类似于DUOCAST的结构形式或再生补焊技术;对于喷射磨损,最有效的是使用复合式耐磨钢板UP-PLATE,以获得高的性价比。     

含缺陷压力管道的失效模式与缺陷评定方法分析

本文介绍了含缺陷压力管道失效模式,分析了三种缺陷失效评定方法,即脆性断裂失效评定、弹塑性断裂失效评定及塑性极限载荷失效评定,其中,以ＮＳＣ准则为基础的塑料极限载荷失效评定方法,使用非常方便,有广泛的适用价值。     

VITREOUS ENAMEL AND ITS DEFECTS1

Causes for various defects in enameled cast iron ware are traced in the enamel Photographs show the iron defects.