汽车轴承的失效模式及预防

汽车轴承在正确的使用下,可以有很长的寿命,如果过早的出现损伤,很可能是选型错误,使用不当、润滑不良、或安装不当造成。在选用轴承时,要根据安装的部位、润滑条件、周围的配合等条件进行选择。通过研究总结轴承的故障类型,问题出现时的环境,以避免故障再次发生。运转中无法直接观察轴承,但通过噪声、振动、润滑剂的变化等情况判断故障。     

粉末冶金制品在饲料机械上的应用

<正> 螺旋输送机内悬吊轴承是在大量粉尘的环境中工作的,要求轴承有良好的减磨性能。但补充润滑油进行润滑,不仅容易污染饲料,而且润滑油也容易变质而加速轴承损坏。因此对螺旋输送机悬吊轴承采用自润滑较好的含油轴承较为合适。一、含油轴承自动润滑原理当轴旋转时,轴与轴承接触表面微小的凹凸不平造成金属间的磨擦,产生磨擦热,轴承的温度上升。温度的升高使油的粘度降低而容易流动,从轴承孔隙中渗出形成油膜,保证轴工作时的正常润滑。当轴停止旋转,轴承的温度逐渐降低,油因冷却收缩在毛细作用下又被吸存在轴承的孔隙中,等     

凝结水泵无法盘车故障分析与处理

某核电站凝结水系统的3台凝结水泵在安装阶段出现泵轴无法盘车缺陷。通过长达三个月的分析处理,目前3台凝泵运行正常。本文主要结合凝结水泵的结构和装配,以及水润滑轴承特点进行分析研究,明确导致凝结水泵无法盘车的根本原因,并为今后同类型水润滑轴承立式泵盘车故障处理提供参考。     

论延长轴承寿命的具体措施

在机械领域内,轴承作为一种关键部件在机械设备运行中起到了重要的作用。考虑到轴承随设备一起运行的特性,只要设备保持运转,轴承就始终处于工作状态,因此,对轴承采取保护措施提高轴承寿命就显得十分重要。通常在轴承的使用和运行过程中,我们会通过观察设备状态、加强轴承养护、优化设备使用过程等手段来切实延长轴承的寿命。从根本上来说,轴承寿命的长短,一部分原因在于使用过程中的维护和保养,一部分原因也在于生产制造轴承的模具设计是否合理。只有从这两方面出发,才能有效延长轴承的使用寿命。     

真空泵润滑器工作原理及正确使用

真空泵润滑器工作原理及正确使用○中国农业机械化科学研究院（北京１０００８３）王茂祥真空泵润滑器工作质量是保证真空泵正常工作和持续运转的重要前提。真空泵的润滑方式归纳起来有三种：第一，自润滑式：真空泵旋片含油自润滑，轴承采用全密封含油轴承一次性使用；第...     

刮板运输机减速器的润滑设计及润滑保养探讨

刮板运输机减速器使用在条件恶劣的矿井下,刮板运输机减速器在工作时,齿轮和轴承等转动部件润滑状况,以及润滑保养,直接影响着刮板运输机减速器的及使用寿命,本文主要阐述刮板运输机减速器的润滑设计原理,润滑保养等。     

集中润滑系统在盾构机中的重要性分析

盾构机是地下隧道施工的一种工程机械,随着社会发展的步伐日益加快,盾构机在诸多地下工程施工中被广泛的采用。盾构机是机械设备,其中有传动、滚动、滑动的部位,在这些部位需要集中润滑帮助润滑,保证部件的工作能够正常运转。盾构机中的集中润滑是保证盾构顺利推进的重要装置,若集中润滑一旦故障引起唇口密封失效,泥沙容易进人大刀盘的轴承内,引起轴承咬死,会使盾构无法推进。     

动力机械传动轴径焊补修复

传动轴在生产使用过程中在轴承结合面处大轴与轴承结合面材质硬度不同;生产过程中热处理措施不好;轴承跑内套;轴承润滑不好等原因造成轴径出现磨损现象,影响设备正常运行.利用手工氩弧焊焊接工艺;采用氩气保护;合理打磨轴径表面(用车床加工);制订相应的的焊接工艺参数;选择适当的焊接材料;取得良好的焊接效果,使工件起到修旧利废的目的.     

机械设备中滚动轴承的装配浅析

轴承的装配至关重要,轴承装配的好坏与否,将影响到轴承的精度、寿命和性能。装配滚动轴承前要保证装配现场的清洁,根据设备装配图明确轴承型号,了解滚动轴承的轴向和周向定位方式,确定滚动轴承安装位置的轴孔配合要求等。本文从滚动轴承装配前的准备工作、装配方法、装配注意事项等方面做了探讨。     

颗粒机全程跟踪监控专用自动加油系统研究

颗粒机全程跟踪监控、专用自动加油系统,是为颗粒机的主轴轴承、偏心轴轴承和颗粒机的传动副轴轴承、喂料器主轴轴承、调质器主轴轴承的润滑,研究设计的。该系统可对颗粒机的主轴轴承、偏心轴轴承实行自动、定时、定量、分配加油,并同时发出加油全程跟踪监控信号。同时该系统可对颗粒机的传动副轴轴承、喂料器主轴轴承、调质器主轴轴承实行电动加油,同时发出加油全程跟踪监控信号。     

Phase I evaluation of CCNU (lomustine) in tumor-bearing cats

1-(2-Chloroethyl)3-cyclohexyl-1-nitrosourea (CCNU) is an alkylating agent in the nitrosourea subclass. A prospective evaluation of CCNU was done to determine the maximally tolerated dosage of CCNU in tumor-bearing cats. Response data were obtained when available. Twenty-five cats were treated with CCNU at a dosage of 50-60 mg/m3 body surface area. Complete hematologic data were available for 13 cats. Neutropenia was the acute dose-limiting toxicity. The median neutrophil count at the nadir was 1,000 cells/microL (mean, 2,433 cells/microL; range, 0-9,694 cells/microL). The time of neutrophil nadir was variable, occurring 7-28 days after treatment, and counts sometimes did not return to normal for up to 14 days after the nadir. Based on these findings, a 6-week dosing interval and weekly hematologic monitoring after the 1st treatment with CCNU are recommended. The nadir of the platelet count may occur 14-21 days after treatment. The median platelet count at the nadir was 43,500 cells/microL. No gastrointestinal, renal, or hepatic toxicities were observed after a single CCNU treatment, and additional studies to evaluate the potential for cumulative toxicity should be performed. Five cats with lymphoma and 1 cat with mast cell tumor had measurable responses to CCNU. Phase II studies to evaluate antitumor activity should be completed with a dosing regimen of 50-60 mg/m3 every 6 weeks.     

Furosemide continuous rate infusion in the horse: evaluation of enhanced efficacy and reduced side effects

Continuous rate infusion (CRI) of furosemide in humans is considered superior to intermittent administration (IA). This study examined whether furosemide CRI, compared with IA, would increase diuretic efficacy with decreased fluid and electrolyte fluctuations and activation of the renin-angiotensin-aldosterone system (RAAS) in the horse. Five mares were used in a crossover-design study. During a 24-hour period, each horse received a total of 3 mg/kg furosemide by either CRI (0.12 mg/kg/h preceded by a loading dose of 0.12 mg/kg IV) or IA (1 mg/kg IV q8h). There was not a statistically significant difference in urine volume over 24 hours between methods; however, urine volume was significantly greater after CRI compared with IA during the first 8 hours ([median 25th percentile, 75th percentile]: 9.6 L [8.9, 14.4] for CRI versus 5.9 L [5.3, 6.0] for IA). CRI produced a more uniform urine flow, decreased fluctuations in plasma volume, and suppressed renal concentrating ability throughout the infusion period. Potassium, Ca, and Cl excretion was greater during CRI than IA (1,133 mmol [1.110, 1,229] versus 764 mmol [709, 904], 102.7 mmol [96.0, 117.2] versus 73.3 mmol [65.0, 73.5], and 1,776 mmol [1,657, 2.378] versus 1,596 mmol [1,457, 1,767], respectively). Elimination half-lives of furosemide were 1.35 and 0.47 hours for CRI and IA, respectively. The area under the excretion rate curve was 1,285.7 and 184.2 mL x mg/mL for CRI and IA, respectively. Furosemide CRI (0.12 mg/kg/h) for 8 hours, preceded by a loading dose (0.12 mg/kg), is recommended when profound diuresis is needed acutely in horses.     

Prevalence of gastric lesions in racing Alaskan sled dogs

Human and equine athletes are reported to have a high prevalence of gastric disease, and anecdotal evidence suggests a similar phenomenon applies to racing sled dogs. To investigate the prevalence of gastric disease in racing sled dogs, we conducted 2 gastroscopy studies on dogs competing in the annual Iditarod Sled Dog Race. A pilot study of dogs that were either dropped from the 2000 Iditarod Sled Dog Race because of illness or that finished the race indicated that, approximately 5 days after competing, 10 of 28 dogs (35%) had endoscopic evidence of gastric ulceration, erosion, or hemorrhage. The next year, an endoscopic study of 73 dogs participating in the 2001 Iditarod race was performed in order to evaluate a larger population of dogs. Data from 70 of these dogs could be used; 34 (48.5%) had ulceration, erosion, gastric hemorrhage, or some combination of these findings. When this group of 70 dogs was compared retrospectively to a control group of 87 dogs presented to the Texas A&M University (TAMU) Veterinary Medical Teaching Hospital, the Iditarod sled dogs had a significantly higher prevalence (P = .049) of gastric lesions. These findings suggest that, similar to athletes of other species, elite canine athletes have an increased prevalence of gastric disease compared to the canine population at large.     

Internal Parasites and Haematological Values in Cattle Slaughtered in Buea Subdivision of Cameroon

Tropical Animal Health and Production -     

The Epidemiology of Gastrointestinal Nematodes of Dairy Cattle in Central Kenya

The epidemiology of H. placei and of other gastrointestinal nematodes in yearling dairy cattle was examined on two farms in Kiambu District, central Kenya during each of 13 one-month periods from April 1993 to April 1994. On each farm, 32 newly weaned dairy calves were given a single dose of albendazole and then placed on experimental pastures. Twelve of the animals were designated for bi-monthly slaughter (n = 2) and analysis of worm population characteristics and 20 were designated for blood and faecal collection and for weighing. Two parasite-free tracer calves were grazed alongside the weaner calves each month throughout the study period and were also slaughtered for analysis of worm populations. Faecal egg counts, haematological and serum pepsinogen determinations, herbage larval counts, and animal live weight changes were recorded monthly. The study revealed that Haemonchus placei, Trichostrongylus axei, Cooperia spp. and Oesophagostomum radiatum were responsible for parasitic gastroenteritis and that H. placei was the predominant nematode present in the young cattle on both farms. Faecal egg counts from resident cattle and necropsy worm counts revealed that pasture larval levels were directly related to the amount of rainfall. The total worm burdens in the animals were highest during the rainy season (March–June and October–December) and lowest during the dry seasons (July–September and January–February). The very low recovery of immature larvae of H. placei from the tracer calves indicated that arrested development is not a feature of the life cycle of this parasite in central Kenya. The maintenance of the parasite population depended on continuous cycling of infection between the host and the pasture. The agroclimatic conditions of the study area were such that, in general, favourable weather conditions for the development and survival of the free-living stages of gastrointestinal nematodes existed all year round.     

Diversity of Ectoparasites in Sheep Flocks in Sa~o Paulo,Brazil

The occurrence of ectoparasites in sheep flocks is frequently reported but seldom quantified. Sheep production used to be a predominantly family activity in the state of Sa~o Paulo (Brazil), but it began to become a commercial activity in the past decade. Thus, information about the ectoparasites existing in sheep flocks has become necessary. The present data were obtained by means of questionnaires sent to all sheep breeders belonging to the `Associaça~o Paulista de Criadores de Ovinos' (ASPACO; Sa~o Paulo State Association of Sheep Breeders). Response reliability was tested by means of random visits paid to 10.6% of the respondents. Most of the properties (89.5%) reported the presence of one or more ectoparasites. Screw-worm (Cochliomyia hominivorax) was the most frequent ectoparasite (72.5%), followed by bot fly larvae (Dermatobia hominis, 45.0%), ticks (Amblyomma cajennense) and Boophilus microplus, 31.3%) and finally lice (Damalinia ovis, 13.8%). Combined infestations also occurred, the most common one being screw-worm with bot fly larvae (36.0%) followed by bot fly larvae with ticks (13.9%), screw-worm with ticks (9.3%), bot fly larvae with lice (6.9%), and ticks with lice (5.0%). The most common triple combination was screw-worm, bot fly larvae and ticks (12.8%). Breeds raised for meat or wool were attacked by bot fly larvae and ticks more often than other breeds. Lice were only absent from animals of indigenous breeds. The relationships among these ectoparasites are discussed in terms of sheep breeds, flock size, seasonality and the ectoparasitic combinations on the host.     

Chemotaxis of macrophage in inflammation

Our particular attention in this article was given to natural mediators for macrophages isolated from the sites of tissue injury. A number of chemotactic factors, which may satisfy many criteria making them acceptable as inflammatory leucocyte chemotactic factors, has been separated. Among them, our laboratory has isolated three macrophage (monocyte) chemotactic factors (MCF-a, -b and -c). Their purification, characterization and functional specificity are discussed.     

Evaluation of biohydrogenation rate of canola vs. soya bean seeds as unsaturated fatty acids sources for ruminants in situ

An experiment was conducted to study disappearance of C14 to C18 fatty acids, lag times and biohydrogenation (BH) rates of C18 fatty acids of ground soya bean and canola seeds in situ. Three ruminally fistulated Dallagh sheep were used to determine ruminal BH of unsaturated fatty acids (UFAs). Differences in the disappearance of fatty acids through the bags and lag times were observed between the oilseeds. We saw that the longer the incubation time of the oilseeds in the rumen, the lower the content of C18:2 and C18:3. Significantly higher lag times for both C18:2 and C18:3 were observed in ground canola compared to ground soya bean. BH rates of C18:2 and C18:3 fatty acids in soya bean were three times higher than those of canola. These results suggest that the fatty acid profile of fat source can affect the BH of UFAs by rumen micro‐organisms. So that UFAs of canola had higher ability to escape from ruminal BH. It seems that fatty acid profile of ruminant products is more affected by canola seed compared to soya bean seed.     

Serum biochemical values and mineral element contents of tissues in yaks

Serum biochemical values and the wet weight to dry weight ratios of tissues were determined in yaks in Shandan county of Gansu province. The liver, kidney, heart and muscle contents of seven elements in yaks were also analysed. Most serum biochemical values were similar to those of cattle, camels and sheep, but the calcium concentration was considerably above the normal range for other ruminants. The liver contained the highest concentrations of copper, manganese and cobalt and the kidney of selenium, iron and calcium.Abbreviations Alb albumin - ALT alanine aminotransferase - AST aspartate aminotransferase - BUN blood urea nitrogen - Chol cholesterol - Glob globulin - -GT -glutamyl transpeptidase - IP inorganic phosphorus - TP total protein