废热锅炉薄管板防止塑性垮塌的安全评定

为评估废热锅炉薄管板的安全性,以ASMEⅧ第2册第5篇中规定的防止塑性垮塌方法为基础,利用有限元软件ANSYS Workbench对管板进行应力分析及评定。对比了三种方法(弹性应力分析法、极限载荷法、弹-塑性应力分析法)在对薄管板进行防止塑性垮塌评定时存在的差异及各自的优势。其中极限载荷方法不仅可以避免弹性应力分析中的应力分类问题,其过程较弹-塑性应力分析法也相对简单。相比之下,极限载荷方法更适合对薄管板进行防止塑性垮塌的安全评定。     

圆柱形容器接管塑性极限弯矩

对圆柱形容器在接管外载荷作用下的塑性极限载荷进行了研究。两台专门设计 ,制造的试验容器被用于进行试验 ,并将试验结果与三维有限元数值模拟结果进行了比较。研究表明上述两种方法获得的接管塑性极限载荷基本一致 ,均可用于确定设备的塑性极限外载荷     

肩部减薄缺陷三通塑性极限面内弯矩的研究

利用ANSYS有限元分析软件对含肩部减薄缺陷焊制三通进行了弹塑性有限元分析,确定了影响三通塑性极限面内弯矩的主要因素,建立了覆盖常用三通几何尺寸及缺陷尺寸的塑性极限面内弯矩有限元解数据库,并拟合得到形式简单且具有较高精度的塑性极限面内弯矩工程估算式。     

底部减薄焊制三通的塑性极限面外弯矩分析

利用ANSYS有限元分析软件对含底部减薄缺陷焊制三通进行了弹塑性有限元分析 ,确定了影响三通塑性极限面外弯矩的主要因素 ,建立了覆盖常用三通几何尺寸及缺陷尺寸的塑性极限面外弯矩有限元解数据库 ,并拟合得到形式简单且具有较高精度的塑性极限面外弯矩工程估算式。     

管件三通塑性极限载荷估算式研究进展

三通几何结构和受载较复杂,是管系中的薄弱环节,准确预测三通的塑性极限载荷,成为管道完整性评估的关键技术。综述了国内外三通塑性极限载荷的研究现状,对今后三通塑性极限载荷的研究和安全评定标准的制定具有一定的指导意义。     

大开孔锻制T型异径三通强度分析

以大开孔锻制T型异径三通为研究对象,分别采用应力分类法和塑性极限载荷法对三通进行了强度校核和分析。由于应力分类法无法完全区分弯曲应力中的一次和二次应力成份,所以采用不同的应力分类方法和许用极限所得的评定结果差别较大。塑性极限载荷法所得的许用载荷是唯一的,弥补了应力分类法的不足,许用载荷值也较应力分类法有所提高。塑性极限载荷法可以作为应力分类法静强度校核的有效补充。     

周向缺陷位置对弯管承载能力的影响

以弯管为研究对象,采用有限元法对弯管中间横截面应力分布规律和塑性极限载荷进行研究,给出了弯管在内压和弯矩载荷下的应力分布情况,指出了弯矩载荷下弯管中间截面最大轴向应力点位置和计算公式,分析了中间截面上不同位置周向裂纹缺陷对弯管塑性极限弯矩载荷的影响。结果表明,对于弯曲半径比较小,径厚比较大的弯管应将周向裂纹缺陷定位在最大轴向应力点确定弯管弯矩承载能力,为进一步研究弯管塑性极限弯矩,完善弯管失效评定奠定基础。     

等径三通+长径弯头组合管件的安全性能分析

采用有限元法分析了典型的组合管件——等径三通+长径弯头组合管件在内压作用下的力学特性和安全性能,并对其安全性做出了评价。结果表明,压力管道组合管件既安全又方便;不同转角半径对等径三通+长径弯头组合管件的塑性极限载荷有不同影响,其最佳三通转角半径与管外径之比为0.17～0.21;现有管件的塑性极限载荷估算公式不适用于组合管件,是偏危险的。     

内压作用下斜接管结构塑性极限载荷的试验研究

斜接管结构是石油、化工、能源及动力工程中常见的一种结构。由于其结构的特殊性,在连接处的应力集中要比具有相同结构参数的正交接管接管大得多。本语文对３０°大开孔斜接管容器进行了弹－塑性应力分析,及爆破试验,确定了这种结构最薄弱的部位,根据不同的准则确定了它的塑性极限载荷及其的爆破压力,为这种结构的极限设计提供了依据。     

底部减薄三通管件塑性极限内压的有限元分析

采用有限元分析研究了单一内压作用时局部减薄缺陷对三通管塑性极限内压的影响。总结出含底部缺陷三通管的塑性极限载荷随缺陷尺寸影响的变化规律。     

安全阀的开启压力和排放压力

介绍了安全阀的开启压力、排放压力与容器的工作压力、超压限度之间的关系;概括了超压限度的含义;指出采用最高允许工作压力作为超压起始压力的好处;提出气密性试验时,确定安全阀的开启压力应采取的方法。     

裂解气洗涤塔简体化学爆炸剖析

针对某合成气装置洗涤塔筒体爆炸的重大事故。计算了裂解气的理论爆炸极限、最大爆炸压力及筒体材料的爆炸压力。分析了爆炸前后的筒体材料的化学成分及金相组织，得出了爆炸事故的原因。提出了以人为本强化管理、加大安全投入、增设监控和紧急事故放空装置等防范措施。     

Detailed investigation on elastoplastic deformation and failure of carbon nanotube fibers by monotonic and cyclic tensile experiments

Monotonic and cyclic tensile loading experiments were conducted for analyzing elastoplastic deformation and failure of carbon nanotube (CNT) fibers. The deformation stages of the CNT fibers under tensile loads consist of a short elastic stage and a long-lasting plastic stage, while the elastic stage of the CNT fibers can be generally divided into two parts: a perfect-elastic stage and an elastic-like stage. Microstructural evolution for each deformation stage was interpreted by means of scanning electron microscope photos. An elastic limit and an offset yield point were discovered through the cyclic loading experiments. The elastic strain limit of the CNT fibers was determined at about 0.35% and the offset yield strain at about 1.2% for quasi-static loading. The effect of strain rates on the deformation and failure mode of CNT fibers was investigated as well.     

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。     

Chemical health and safety challenges in a new era of enlightenment

Based on the experience of the past 30 years, some trends in chemical health and safety can be expected to continue during the new century. More health and safety information will be collected on specific chemicals; exposure hazard (threshold limit values and permissible exposure limits) and environmental impact databases will be expanded as new research is carried out in these areas. The mission of safety professionals will be to make the job safe for employees, including the elimination of excessive employee exposure to hazardous chemicals. Some ways to accomplish this include increased use of personal protective equipment and more thorough health and safety information on Material Safety Data Sheets. The objective is not to ban use of specific chemicals but to develop procedures to work safely with materials of interest. There will be increasing demands for products and processes involving chemicals and chemical reactions. Where will researchers obtain the necessary health and safety knowledge? Chemical health and safety information must become an integral part of the undergraduate and graduate chemistry curriculum.     

原子荧光光谱法测定工业硫酸中砷含量

通过检出限测定,精密度实验,回收率测定对原子荧光光谱法测定工业硫酸中砷含量进行应用研究。结果表明该方法灵敏度高,检出限低,精密度和准确度高,操作简捷,可广泛用于工业硫酸中砷含量的测定。     

On the use of model-based tools to optimize in-line a pharmaceuticals freeze-drying process

This article is focused on the use of model-based tools to design and optimize in-line a pharmaceutical freeze-drying process. Two control systems have been compared, a predictive one that uses the pressure rise test to monitor the state of the system and to estimate in-line the values of model parameters, named LyoDriver in the previous literature, and a controller where a soft sensor uses the temperature measurement obtained by a thermocouple to get the same information and to calculate on-line the design space of the process. In both cases, the goal of the controller is to maintain product temperature as close as possible to a limit value, without trespassing it, throughout the primary drying stage. An extended experimental campaign has been performed, where various products, with different characteristics, have been processed, namely, aqueous solutions containing sucrose, mannitol, or polyvinylpyrrolidone. Results evidence that both systems are effective in optimizing in-line the freeze-drying process, but shorter cycles can be obtained using the soft sensor. This is due to the fact that the soft sensor is not responsible for any product overheating and, thus, product temperature can be maintained very close to the limit value, while when using the pressure rise test as monitoring tool, a safety margin has to be used, because of the temperature increase during the pressure rise test. Besides, when using the soft sensor no least-square optimization problem is solved to estimate model parameters, and this can improve the robustness of the system. The main drawback is represented by the fact that this system requires thermocouples to measure product temperature, and this can be difficult in industrial-scale freeze-dryers, used to process large batches of vials in sterile conditions, but it can be performed quite easily in lab-scale units used for process design.     

Heuristic framework for the debottlenecking of a palm oil-based integrated biorefinery

This paper presents a heuristic framework that can be used for the debottlenecking of a palm oil-based integrated biorefinery with multiple processes and products. In current industrial practice, any individual unit within these systems is generally designed for a required size. Besides, it also takes into account of an additional margin for safety to meet the requirement of the baseline state of the process. In case there is a variation in the quality of the supplied feedstock or an increase for product demand, it becomes necessary to identify the bottleneck process unit in order to handle the new variation and meet all requirements. In response, the system has to be debottlenecked by altering important operating parameters from the baseline state that limits the change. This stage entails formulating and solving a detailed model for this particular process. In this paper, frameworks are presented to aid decision makers to first identify a bottleneck and subsequently debottleneck the process. The frameworks are essentially a guide for design and safety engineers for decision making at conceptual design stage. A design stage palm oil-based integrated biorefinery case study is solved to demonstrate the proposed approach.     

Improving the Safety of a Pyrotechnic Igniter through a controlled experiment

One of the important goals of quality management in today's competitive marketplace is to build quality into products and processes at the development stage. The use of statistically controlled experiments, in which several parameters are studied simultaneously, can help accomplish this goal efficiently. This paper describes a case study that illustrates the utility of controlled experiments in product development. The customer required improvements in the safety of a pyrotechnic igniter used in one of the products they purchased. The safety improvements could be met by replacing the “match-head” initiator by a type IA/IW no fire initiator. However, there was concern that changing the initiator might degrade other important product performance characteristics. A controlled experiment was designed to compare three different initiators, the booster charge and the main charge. The experiment quickly and efficiently pointed to a superior initiator and the optimal charges to maintain high performance with enhanced product safety.