高压甲铵泵轴端密封系统故障原因分析及对策

高压甲铵泵机械密封动静环、O形圈易失效,通过对密封冲洗水和缓冲水、介质、O形圈材质以及操作参数等方面的分析计算,论证了机械密封失效的原因。在保证密封水的压力、流量符合设计要求的前提下,提高密封水供应的可靠性,可以避免介质在密封腔内结晶,有效地解决机械密封过早失效问题。     

双氧水工作液泵泄漏故障分析及对策

针对双氧水生产中的工作液输送泵的机械密封泄漏故障进行了失效分析。经过密封理论计算和输送的工作液中所含的主要成分的化学物理特性的研究,发现引起密封失效的主要原因是密封冲洗方案和“O”型圈材料的选择有误。经调整机械冲洗方案格更换“O”型圈材料后,机械密封泄漏问题解决。     

高温循环冷却洗涤水泵机械密封技术改造

分析了高温循环冷却洗涤水泵机械密封频繁泄漏的原因,主要是介质特殊、原机械密封结构不合理、冲洗方案不完善、橡胶密封材料不相容等。采用集装式、整体环、螺旋槽端面、增加冲洗方案,选配全氟橡胶O形圈等新技术,对原机械密封进行了技术改造,取得了成功。     

高粘度浆液齿轮泵机械密封失效分析

针对进口的二醋酸纤维高粘度浆液齿轮泵的机械密封在使用过程中出现密封端面磨损、密封面变形、波纹管失弹、波纹管断裂、O形圈失效等故障进行了失效分析,对机械密封的结构、材质、安装工艺进行了改进.结果表明:采用静环、动环用浸渍聚四氟乙烯树脂,波纹管由导向套引导,导向套设有密封槽及石墨填料环等措施后,解决了高粘度浆液齿轮泵在高压...     

双端面机械密封泄漏原因分析

阐述并分析了泵用双端面机械密封的结构及特点,对密封失效原因进行了简要的分析。结合实际工况,分析了其失效原因(如O形圈材质选用不合理,搅拌同轴度偏大,密封面变形),提出了改进措施及使用中的注意事项。并就如何提高机械密封运行周期,从维修质量控制、运行操作的控制、密封水系统等方面进行了阐述,为双端面机械密封长周期运行提供了参考。     

改进型聚四氟乙烯O形圈在机械密封中的应用

随着机械密封在石油、化工等领域的广泛采用,作为机械密封中的辅助密封,在不同的工况条件下要求有着可靠的密封性能。目前,国内在机械密封中采用的辅助密封主要型状有 O 形圈、V 形圈、楔形圈等。辅助     

机械密封失效的原因探讨

机械密封意外失效对企业运行的经济性、安全性危害极大。失效的原因可以归纳为：冲洗原因，静密封失效，动密封失效等。     

常温蜡油泵机械密封失效分析及改进

本文对常温蜡油泵机械密封失效现象进行分析总结,指出由于密封流体——蜡油的粘度较大,从而导致弹性元件失弹并分析得出蜡油粘附摩擦副端面是机械密封失效的主要原因,提出了通过调整密封结构及冲洗方案,可解决机械密封失效的问题。     

悬臂化工泵输送低温二氯甲烷机封泄漏的解决

针对低温二氯甲烷输送泵用机械密封的故障进行了失效分析,发现机械密封的选型和O型圈材料的选择有误。经调整机械密封比压和更换O型圈材料后,机械密封泄漏问题解决。     

常减压蒸馏装置常二线中段回流泵机械密封冲洗方案的改造

针对石油二厂常减压蒸馏装置常二线中段回流泵的机械密封短周期内频繁出现的失效问题,通过对泵机械密封的选型、机械密封冲洗方案和结构等几个方面进行改造,延长了机械密封的使用寿命,为泵的长周期运行创造了条件.     

Many Drugs of Abuse May Be Acutely Transformed to Dopamine,Norepinephrine and Epinephrine In Vivo

It is well established that a wide range of drugs of abuse acutely boost the signaling of the sympathetic nervous system and the hypothalamic–pituitary–adrenal (HPA) axis, where norepinephrine and epinephrine are major output molecules. This stimulatory effect is accompanied by such symptoms as elevated heart rate and blood pressure, more rapid breathing, increased body temperature and sweating, and pupillary dilation, as well as the intoxicating or euphoric subjective properties of the drug. While many drugs of abuse are thought to achieve their intoxicating effects by modulating the monoaminergic neurotransmitter systems (i.e., serotonin, norepinephrine, dopamine) by binding to these receptors or otherwise affecting their synaptic signaling, this paper puts forth the hypothesis that many of these drugs are actually acutely converted to catecholamines (dopamine, norepinephrine, epinephrine) in vivo, in addition to transformation to their known metabolites. In this manner, a range of stimulants, opioids, and psychedelics (as well as alcohol) may partially achieve their intoxicating properties, as well as side effects, due to this putative transformation to catecholamines. If this hypothesis is correct, it would alter our understanding of the basic biosynthetic pathways for generating these important signaling molecules, while also modifying our view of the neural substrates underlying substance abuse and dependence, including psychological stress-induced relapse. Importantly, there is a direct way to test the overarching hypothesis: administer (either centrally or peripherally) stable isotope versions of these drugs to model organisms such as rodents (or even to humans) and then use liquid chromatography-mass spectrometry to determine if the labeled drug is converted to labeled catecholamines in brain, blood plasma, or urine samples.     

Insect antifeedant properties of anthranoids from the genusVismia

Vismiones and ferruginins, representatives of a new class of lypophilic anthranoids from the genusVismia were found to inhibit feeding in larvae of species ofSpodoptera, Heliothis, and inLocusta migratoria.     

Direct observation of freeze-thaw instability of latex coatings via high pressure freezing and cryogenic SEM

Despite its industrial importance, the subject of freeze-thaw (F/T) stability of latex coatings has not been studied extensively. There is also a lack of fundamental understanding about the process and the mechanisms through which a coating becomes destabilized. High pressure (2100 bar) freezing fixes the state of water-suspended particles of polymer binder and inorganic pigments without the growth of ice crystals during freezing that produce artifacts in direct imaging scanning electron microscopy (SEM) of fracture surfaces of frozen coatings. We show that by incorporating copolymerizable functional monomers, it is possible to achieve F/T stability in polymer latexes and in low-VOC paints, as judged by the microstructures revealed by the cryogenic SEM technique. Particle coalescence as well as pigment segregation in F/T unstable systems are visualized. In order to achieve F/T stability in paints, latex particles must not flocculate and should provide protection to inorganic pigment and extender particles. Because of the unique capabilities of the cryogenic SEM, we are able to separate the effects of freezing and thawing, and study the influence of the rate of freezing and thawing on F/T stability. Destabilization can be caused by either freezing or thawing. A slow freezing process is more detrimental to F/T stability than a fast freezing process; the latter actually preserves suspension stability during freezing. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004 in Chicago, IL. Tied for first place in The John A. Gordon Best Paper Competition.     

Ethanol and (−)-α-Pinene: Attractant Kairomones for Bark and Ambrosia Beetles in the Southeastern US

In 2002–2004, we examined the flight responses of 49 species of native and exotic bark and ambrosia beetles (Coleoptera: Scolytidae and Platypodidae) to traps baited with ethanol and/or (−)-α-pinene in the southeastern US. Eight field trials were conducted in mature pine stands in Alabama, Florida, Georgia, North Carolina, and South Carolina. Funnel traps baited with ethanol lures (release rate, about 0.6 g/day at 25–28°C) were attractive to ten species of ambrosia beetles (Ambrosiodmus tachygraphus, Anisandrus sayi, Dryoxylon onoharaensum, Monarthrum mali, Xyleborinus saxesenii, Xyleborus affinis, Xyleborus ferrugineus, Xylosandrus compactus, Xylosandrus crassiusculus, and Xylosandrus germanus) and two species of bark beetles (Cryptocarenus heveae and Hypothenemus sp.). Traps baited with (−)-α-pinene lures (release rate, 2–6 g/day at 25–28°C) were attractive to five bark beetle species (Dendroctonus terebrans, Hylastes porculus, Hylastes salebrosus, Hylastes tenuis, and Ips grandicollis) and one platypodid ambrosia beetle species (Myoplatypus flavicornis). Ethanol enhanced responses of some species (Xyleborus pubescens, H. porculus, H. salebrosus, H. tenuis, and Pityophthorus cariniceps) to traps baited with (−)-α-pinene in some locations. (−)-α-Pinene interrupted the response of some ambrosia beetle species to traps baited with ethanol, but only the response of D. onoharaensum was interrupted consistently at most locations. Of 23 species of ambrosia beetles captured in our field trials, nine were exotic and accounted for 70–97% of total catches of ambrosia beetles. Our results provide support for the continued use of separate traps baited with ethanol alone and ethanol with (−)-α-pinene to detect and monitor common bark and ambrosia beetles from the southeastern region of the US.     

ICP-MS法测定地球化学样品中As、Cr、Ge、V等18种微量痕量元素的研究

建立了测定地球化学样品中包括As、Cr、Ge、V等18种微量、痕量元素的ICP-MS方法。地化试样用HF-HNO3混酸分解后,以1 1 HNO3溶解干渣。由于制样不使用盐酸,避免了Cl对As、Cr、Ge、V的质谱干扰。用国家一级地球化学标准物质GBW 07309制备溶液优化仪器工作参数,并用于校准。方法测定限(6s)为:0.007~6.4μg/g,精密度(RSD%,n=12)为:29%~9.4%,经过国家一级地球化学标准物质的分析验证,结果与标准值吻合。方法已应用于国土资源调查的试样分析。