真空辊螺栓断裂初步分析

针对牡丹江恒丰纸业PM T 2纸机的真空辊螺栓断裂情况,分析并找出真空辊螺栓断裂的原因,初步分析故障的主要原因有以下两点:一是纸机使用盐水为辅助助剂使螺栓自身发生一定腐蚀,降低了螺栓的使用强度;二是真空辊筒与内芯为间隙配合.今后将整改操作规程及完善纸机辊件自身不足之处,预防此类事件的发生.     

毛布导辊轴承座螺栓断裂原因分析及应对措施

正岳阳林纸股份有限公司岳阳分公司特种纸事业部(PM3)压榨部1#毛布导辊,2017年10月在生产过程中出现导辊基座螺栓断裂,并造成毛布损坏。经过分析查找原因发现主要是更换毛布时,拆开操作侧轴承座,用千斤顶顶起毛布辊,这样使传动侧基座螺栓受力过大,     

真空压榨辊的改进

正真空压榨辊表面通过设置盲孔来提高纸机压榨部的脱水作用,从而有效地消除压花现象。但是,过多地开孔会影响真空压榨辊的整体强度和在纸上留下"影痕"。因此真空压榨辊表面的最大开孔率只有16.5%左右。现有技术的真空压榨辊对提高纸机压榨部的脱水能力有限。在此,提供一种改良的真空压榨辊。如图1所示,改良的真空压榨辊包括辊壳体,辊壳体     

纸机导辊的尺寸确定与选材

1引言 各类型辊筒的最终用途大同小异，辊筒的基本设计要求为：（1）提供运动的表面；（2）与纸机车速保持同步；（3）支承织物或纸幅。但是．辊筒在设计时并不一定要求运动的表面为圆形．在实际应用中可以通过缸体绕轴旋转加以实现。如果压榨辊的辊表面不是圆形．可能对提高纸机效率更为有利．在宽压区压榨中加入一层毛毯即可提高压榨效率。有些使用情况．可将辊筒替换为一些拥有静止表面的部件。     

Sym概念技术介绍(续)

四、Sym复合压榨 Sym复合压榨的设计有以下特点:布置紧凑,全封闭引纸,适用于高车速;第一压区由沟纹辊和真空辊组成,采用双毛布;第二、三压区由大直径中心石辊分别与真空辊和沟纹辊组成;快速更换毛布和辊子;真空压榨辊采用枪钻技术,内齿轮传动;沟纹辊用异型不锈钢带卷绕而成;辊筒用特种钢材制造,强度高,耐磨和耐腐蚀性能好;配用蒸汽箱,提高出压榨的纸页干度,降低汽耗。     

导纸辊轴头断裂的原因分析及改进措施

昆山钞票纸厂新安装的牵引压榨部等设备在正式投入试生产的初期,牵引压榨部的导纸辊操作面轴头频繁地出现断裂情况,严重影响了纸机的正常生产。对多个断裂轴头进行详尽分析后,发现该导纸辊在设计上存在不足之处:导纸辊操作侧轴头的疲劳强度过低,导致承受交变应力的轴头产生疲劳断裂。为此,针对提高轴头疲劳强度和降低交变应力,从2方面进行了相应的改进。改进后的导纸辊投入使用后,效果良好,经半年多运行,未发生轴头断裂现象。     

压榨导毯辊断轴原因分析及解决措施

我厂纸机压榨部是由一道三辊两压区的复合压榨和一道沟纹压榨组成,其中复合压榨是由加拿大GL&V公司进行改造,结构如图1所示。运行几年来,主要存在以下问题:多根导毯辊轴承位置轴头磨损,使退卸套及圆螺母松脱,造成整根辊子振动大;上毛布有一根导毯辊轴头靠辊子端面处断裂,造成毛布损坏、真空吸移辊和网部的真空伏辊辊壳砸扁的严重事故;轴承座端盖螺栓松掉,容易掉进压区,损坏辊子和毛毯。这些问题已成为制约纸机进一步提速的重要因素。1断断轴原因分析我厂M=qb(L-b/2)/4=Q(L-b/2)/4我厂已知L=7.061m,b=6.496m,我厂则M=36580N·m我厂辊筒的…     

造纸机负荷分配系统分析

岳阳造纸厂1号纸机，幅宽4m，速度600m／min。传动系统是德国AEG公司提供的MIDISEMI可控硅直流系统。纸机在网部、压榨部、1组供缸采用了多电机传动，应用了负荷分配自动控制电路。本文将对压榨部负荷控制的线路、原理、稳定性进行分析。1压榨部的多点传动及负荷分配原因压榨部由5台电机传动，其中一压电机是主导电机。真空引纸辊、一压、二压共带一床毛毯，三压带一床毛毯。一压沟纹辊与真空辊摩擦带另一床毛毯。二压、三压靠与石辊的相互摩擦传递力矩。见图1。要求二压、三压速度必须严格协调。我们先分析它们的负荷分配方式。直流电…     

开式压榨改为简易传递压榨

我厂有一台1880／130长网多缸纸机，压榨部为二道正压榨，一道反压榨，一道光压榨的开式压榨，这种纸机对浆料的选择性较强。浆料纯净，强度好，抄造就顺利；洗涤不好，杂细胞多，纤维短，强度差的浆料，抄造时在压榨部粘辊断纸多，特别是在一、二压榨处更为严重。该纸机用竹浆生产胶版印刷纸，投产10多年来，由于浆料原因，生产不稳定。我们根据传递压榨的特性，结合纸机现有结构，将压榨改为简易传递压榨，获得较好效果。1改进情况简易传递压榨示意图l一真空伏报；2一真空压榨辊；3—一压上肢辊；4一清洗报；5一吸水箱；6、7一二压榨根山…     

聚酯复合纤维牵伸机传动辊结构的改进设计

为了解决聚酯复合纤维牵伸机传动辊辊筒变形、断裂及齿轮断齿等问题,从原牵伸机传动辊结构入手,分析导致问题的原因,并提出针对性的改进方案。指出:将原辊筒连接处的连接方式由V形焊接改为U形焊接,并增加筋板、辊筒套和挡边等辊筒支撑,解决传动辊从焊道处断裂问题;采用右端轴承定位,并在轴上设计安装双螺母固定套及密封结构,解决传动轴轴向窜动问题;改进后的牵伸机传动辊结构能有效避免辊筒变形、断裂和轴向窜动等问题,且安装维修方便。     

Reliable identification of grapevine rootstock varieties using RAPD PCR on woody samples

Since grapevine ( Vitis spp .) rootstock material is being traded increasingly as disbudded woody material a lack of distinctive morphological features on such material necessitates an alternative and reliable means of identification. Methods described here were developed for rapid and efficient extraction of DNA from woody samples rich in phenolic compounds and polysaccharides, and for subsequent identification of varieties by RAPD PCR. Using these methods, and with the application of only one selected RAPD primer, we were able to differentiate sixteen rootstock varieties, including the seven varieties most commonly used in Germany. Problems commonly encountered with reproducibility of RAPD patterns were avoided by choosing primers with a dinucleotide sequence and a high G/C content that allowed a rather high annealing temperature of 45°C. Methods described here should also be useful for other horticultural crops, especially those with woody tissues rich in phenolic compounds and polysaccharides.     

An internet compendium of analytical methods and spectroscopic information for monomers and additives used in food packaging plastics

An internet website (http://cpf.jrc.it/smt/) has been produced as a means of dissemination of methods of analysis and supporting spectroscopic information on monomers and additives used for food contact materials (principally packaging). The site which is aimed primarily at assisting food control laboratories in the European Union contains analytical information on monomers, starting substances and additives used in the manufacture of plastics materials. A searchable index is provided giving PM and CAS numbers for each of 255 substances. For each substance a data sheet gives regulatory information, chemical structures, physico-chemical information and background information on the use of the substance in particular plastics, and the food packaging applications. For monomers and starting substances (155 compounds) the infra-red and mass spectra are provided, and for additives (100 compounds); additionally proton NMR are available for about 50% of the entries. Where analytical methods have been developed for determining these substances as residual amounts in plastics or as trace amounts in food simulants these methods are also on the website. All information is provided in portable document file (PDF) format which means that high quality copies can be readily printed, using freely available Adobe Acrobat Reader software. The website will in future be maintained and up-dated by the European Commission's Joint Research Centre (JRC) as new substances are authorized for use by the European Commission (DG-ENTR formerly DGIII). Where analytical laboratories (food control or other) require reference substances these can be obtained free-ofcharge from a reference collection housed at the JRC and maintained in conjunction with this website compendium.     

Chlorohydrins of bisphenol A diglycidyl ether (BADGE) and of bisphenol F diglycidyl ether (BFDGE) in canned foods and ready-to-drink coffees from the Japanese market

BADGE.2HCl and BFDGE.2HCl were determined in 28 samples of ready-to-drink canned coffee and 18 samples of canned vegetables (10 corn, 5 tomatoes and 3 others), all from the Japanese market. HPLC was used as the principal analytical method and GCMS for confirmation of relevant LC fractions. BADGE.2HCl was found to be present in one canned coffee and five samples of corn, BFDGE.2HCl in four samples of canned tomatoes and in one canned corn. No sample was found which exceeded the 1mg/kg limit of the EU for the BADGE chlorohydrins. However the highest concentration was found for the sum of BFDGE.2HCl and BFDGE.HCl.H₂O at a level of 1.5mg/kg. A Beilstein test confirmed that all cans containing foods contaminated with BADGE.2HCl or BFDGE.2HCl had at lest one part coated with a PVC organosol.     

European priorities for research to support legislation in the area of food contact materials and articles

A strong science base is required to underpin the planning and decision-making process involved in determining future European community legislation on materials and articles in contact with food. Significant progress has been made in the past 5 years in European funded work in this area, with many developments contributing to a much better understanding of the migration process, and better and simpler approaches to food control. In this paper this progress is reviewed against previously identified work-areas (identified in 1994) and conclusions are reached about future requirements for R&D to support legislation on food contact materials and articles over the next 5 or so years.     

Aroma characterization of various apricot varieties using headspace–solid phase microextraction combined with gas chromatography–mass spectrometry and gas chromatography–olfactometry

The characterization of the aromatic profile of several apricot cultivars with molecular tracers in order to obtain objective data concerning the aromatic quality of this fruit was undertaken using headspace–solid phase microextraction (HS–SPME). Six apricot cultivars were selected according to their organoleptic characteristics: Iranien, Orangered, Goldrich, Hargrand, Rouge du Roussillon and A4025. The aromatic intensity of these varieties measured by HS–SPME–Olfactometry were defined and classified according to the presence and the intensity of grassy, fruity and apricot like notes. In the six varieties, 23 common volatile compounds were identified by HS–SPME–GC–MS. Finally, 10 compounds, ethyl acetate, hexyl acetate, limonene, β-cyclocitral, γ-decalactone, 6-methyl-5-hepten-2-one, linalool, β-ionone, menthone and (E)-hexen-2-al were recognized by HS–SPME–GC–O as responsible of the aromatic notes involved in apricot aroma and considered as molecular tracers of apricot aromatic quality which could be utilized to discriminate apricot varieties.     

Textural Properties of Cold-set Gels Induced from Heat-denatured Whey Protein Isolates

A 9% whey protein (WP) isolate solution at pH 7.0 was heat-denatured at 80°C for 30 min. Size-exclusion HPLC showed that native WP formed soluble aggregates after heat-treatment. Additions of CaCl2 (10–40 mM), NaCl (50–400 mM) or glucono-delta-lactone (GDL, 0.4–2.0%, w/v) or hydrolysis by a protease from Bacillus licheniformis caused gelation of the denatured solution at 45°C. Textural parameters, hardness, adhesiveness, and cohesiveness of the gels so formed changed markedly with concentration of added salts or pH by added GDL. Maximum gel hardness occurred at 200 mM NaCl or pH 4.7. Increasing CaCl2 concentration continuously increased gel hardness. Generally, GDL-induced gels were harder than salt-induced gels, and much harder than the protease-induced gel.     

Tests of potential functional barriers for laminated multilayer food packages. Part I: Low molecular weight permeants

The advent of the functional barrier concept in food packaging has brought with it a requirement for fast tests of permeation through potential barrier materials. In such tests it would be convenient for both foodstuffs and materials below the functional barrier (sub-barrier materials) to be represented by standard simulants. By means of inverse gas chromatography, liquid paraffin spiked with appropriate permeants was considered as a potential simulant of sub-barrier materials based on polypropylene (PP) or similar polyolefins. Experiments were performed to characterize the kinetics of the permeation of low molecular weight model permeants (octene, toluene and isopropanol) from liquid paraffin, through a surrogate potential functional barrier (25 μm-thick oriented PP) into the food simulants olive oil and 3% (w/v) acetic acid. These permeation results were interpreted in terms of three permeation kinetic models regarding the solubility of a particular model permeant in the post-barrier medium (i.e. the food simulant). The results obtained justify the development and evaluation of liquid sub-barrier simulants that would allow flexible yet rigorous testing of new laminated multilayer packaging materials.     

Occurrence of bisphenol-F-diglycidyl ether (BFDGE) in fish canned in oil

The levels of bisphenol-F-diglycidyl ether (BFDGE) were quantified as part of a European survey on the migration of residues of epoxy resins into oil from canned fish. The contents of BFDGE in cans, lids and fish collected from all 15 Member States of the European Union and Switzerland were analysed in 382 samples. Cans and lids were separately extracted with acetonitrile. The extraction from fish was carried out with hexane followed by re-extraction with acetonitrile. The analysis was performed by reverse phase HPL C with fluorescence detection. BFDGE could be detected in 12% of the fish, 24% of the cans and 18% of the lids. Only 3% of the fish contained BFDGE in concentrations considerably above 1mg/kg. In addition to the presented data, a comparison was made with the levels of BADGE (bisphenol-A-diglycidyl ether)analysed in the same products in the context of a previous study.     

Contribution of European research to risk analysis

The European Commission's, Quality of Life Research Programme, Key Action 1—Health, Food & Nutrition is mission-oriented and aims, amongst other things, at providing a healthy, safe and high-quality food supply leading to reinforced consumer confidence in the safety of European food. Its objectives also include the enhancing of the competitiveness of the European food supply. Key Action 1 is currently supporting a number of different types of European collaborative projects in the area of risk analysis. The objectives of these projects range from the development and validation of prevention strategies including the reduction of consumers risks; development and validation of new modelling approaches; harmonization of risk assessment principles, methodologies, and terminology; standardization of methods and systems used for the safety evaluation of transgenic food; providing of tools for the evaluation of human viral contamination of shellfish and quality control; new methodologies for assessing the potential of unintended effects of genetically modified (genetically modified) foods; development of a risk assessment model for Cryptosporidium parvum related to the food and water industries; to the development of a communication platform for genetically modified organism, producers, retailers, regulatory authorities and consumer groups to improve safety assessment procedures, risk management strategies and risk communication; development and validation of new methods for safety testing of transgenic food; evaluation of the safety and efficacy of iron supplementation in pregnant women; evaluation of the potential cancer-preventing activity of pro- and pre-biotic ('synbiotic') combinations in human volunteers. An overview of these projects is presented here.