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第三章 机械部分设计第三章 机械部分设计2.1 电机的选择：2.2.1 常用交流异步电动机的特性和用途： 异步电动机主要用途 异步电机主要用作电动机，去拖动各种生产机械。例如，在工业方面，用于拖动中小型轧钢设备、各种金属切削机床、轻工机械、矿山机械等；在农业方面，用于拖动水泵、脱粒机、粉碎机以及其它农副产品的加工机械等；在民用电器方面的电扇、洗衣机、电冰箱、空调机等也都是用异步电动机拖动的。 异步电动机的特点 异步电动机的特点是结构简单、容易制造、价格低廉、运行可靠、坚固耐用、运行效率较高和具有适用的工作特性。缺点是功率因数较差。异步电动机运行时，必须从电网里吸收落后性的无功功率，它的功率因数总是小于1。由于电网的功率因数可以用别的办法进行补偿，这并不妨碍异步电动机的广泛使用。 对那些单机容量较大、转速又恒定的生产机械一般采用同步电动机拖动为好。因为同步电动机的功率因数是可调的(可使cos=1或领先)。但并不是说，异步电动机就不能拖动这类生产机械，而是要根据具体情况进行分析比较，以确定采用哪种电机。异步电动机运行时，定子绕组接到交流电源上，转子绕组自身短路由于电磁感应的关系，在转子绕组中产生电动势、电流，从而产生电磁转矩。所以，异步电机又叫感应电动机。电机系列名称：1. J2、JO2系列三相异步电动机： 特点：外型小，重量轻，效率高，温升低，使用方便，运行可靠，易于检修。但J2,JO2系列电动机系老产品，已经逐渐被新产品所取代，故新设计不宜再选用。本2JO3系列三相异步电动机：JO3系列电动机为封闭风扇自冷式三相鼠笼型异步电动机，能阻止机座内外的空气自由交换，但不完全密封。采用了新型电磁材料及优质绝缘材料，因此体积较JO2系列的小，重量也较轻。3. Y系列三相异步电动机：Y系列电动机是封闭风扇自冷式鼠笼型三相异步电动机。是全国统一设计的新的基本系列，是我国80年代JO2系列的更新换代产品。Y系列电动机高效，节能，起动转矩高，噪声低，振动小，运行安全可靠。安装尺寸和功率等级完全符合国际标准（IEC）。Y系列电动机为一般用途的电机，适合于驱动无特殊要求的各种机械设备，如金属切削机床、鼓风机、水泵、运输机械、搅拌机、农业机械和食品机械等。4.JZ,JZR系列起重用三相异步电动机：JZ及JZR为自扇冷式三相异步电动机，允许有较显著的震动及冲击，转动惯量小，过载能力大，工作方式为断续额定运行，适用于驱动各种型式的起重机械。通过以上比较，本设计选用Y系列异步电动机作为驱动部件。Y系列异步电动机主要派生和专用电机的特点和适用范围序号产品名称性能和结构特点适用范围1防暴安全型异步电动机YA(JA)在正常运转时便产生电火花，电弧或危险温度的电机中，采取适当措施，如降低各部件的文升限度，增强绝缘，提高导体连接的可靠性，以及提高对固体异物与水的防护等级等，以提高防爆安全性适用于Q-2和Q-3有爆炸性危险的场所2隔爆型异步电动机YB(JB)封闭自扇冷式。增强外壳的机械强度，并保证组成外壳的部件之间的各接合面上具有一定的间隙参数一旦电机内部爆炸，亦不致引起周围环境的爆炸性混合物爆炸。适用于石油，化工，煤矿井下有爆炸危险的场所3起重及冶金用异步电动机YZ(JZ)断续定额。封闭自扇冷式。采用高电阻铝在浇铸的笼型转子。起动转矩大，能频繁起动，过载能力大，转差率较高适用于冶金和一般起重设备4起重冶金用绕线转子异步电动机YZR(JZR)转子为绕线型，其余和YZ相同同上5高转差率异步电动机YH(JH)结构和外型尺寸与基本系列相同，转子采用高电阻铝合金浇铸适用于惯性矩较大且具有冲击性负荷机械的传动，如剪床，压力机，锻压机及小型起重机等6电磁调速异步电动机YCT(JZT)由异步电动机和电磁转差离合器组合而成，通过控制器控制离合器的励磁电流来调节转速适用于恒转矩和风机类型设备的无级调速7变极多速异步电动机YD(JD)改变定子绕组的接线方法以改变极对数，得到多种转速，结构和外型尺寸，与基本系列相同，但引出线数为612根适用于机床，印染机，印刷机等需要变速的设备8齿轮减速异步电动机YCJ(JTC)由通用的异步电动机与两级圆柱齿轮减速箱合成一整体适用于矿山，轧钢，造纸，化工等部门需要低速，大转矩的各种机械设备，电机可用联轴器或正齿轮与传动机构联接9摆线针论减速异步电动机YXJ(JXJ)由通用的异步电动机与摆线针减速器直接合成一体，结构紧凑，体积小，重量轻，速比大，一级减速比有9种范围，为1187同上10旁磁制动异步电动机YEP(JZD)带有断电制动的结构；通电时，转子端部的分磁块吸合导磁环压缩弹簧，打开制动装置适用于单梁吊车，或机床仅给系统11高起动转矩异步电动机YQ(JQ)结构和外型尺寸与基本系列相同，转子采用双笼或深沟，启动力矩大适用于静止负荷或惯性矩较大的机械，如压缩机，柱塞式水泵，粉碎机等12力矩异步电动机YLJ(JLJ)机械特性很软，能在堵转到接近同步转速的范围内稳定运行，转子导条采用高电阻黄铜条，一般装有独立的鼓风机适用于恒张力线速（卷绕）传动和恒转矩（导辊）传动 防爆电机和普通电机的区别：1、 防爆电机一般应用在易燃易爆的场合。2、 防爆电机接线盒的密封较普通电机要好。3、 防爆电机防护等级最低为IP55，而普通电机有IPIP23、IP44、IP54、IP55、IP56不等，故而从外形可以分辨出。 防爆电机是一种可以在易燃易爆厂所使用的一种电机,运行时不产生电火花。防爆电机主要用于煤矿、石油天然气、石油化工和化学工业。此外，在纺织、冶金、城市煤气、交通、粮油加工、造纸、医药等部门也被广泛应用。防爆电机作为主要的动力设备，通常用于驱动泵、风机、压缩机和其他传动机械。随着科技、生产的发展，存在爆炸危险的场所也在不断增加。例如，食用油生产过去是用传统的压榨法工艺，20世纪70年代以后，我国开始引进国外先进的浸出油工艺，但此工艺中要使用含有己烷的化学溶剂，己烷是易燃易爆物质；因此浸出油车间就成了爆炸危险场所，需要使用防爆电机和其他防爆电气产品。又如，近年来我国公路发展迅速，一大批燃油加油站出现，也给防爆电机提供了新的市场。产品分类1 按电机原理分可分为防爆异步电机、防爆同步电机及防爆直流电机等。2 按使用场所分可分为煤矿井下用防爆电机及工厂用防爆电机。3 按防爆原理分可分为隔爆型电机、增安型电机、正压型电机、无火花型电机及粉尘防爆电机等。4 按配套的主机分可分为煤矿运输机用防爆电机、煤矿绞车用防爆电机、装岩机用防爆电机、煤矿局部扇风机用防爆电机、阀门用防爆电机、风机用防爆电机、船用防爆电机、起重冶金用防爆电机及加氢装置配套用增安型无刷励磁同步电机等。此外，还可以按额定电压、效率等技术指标来分，如高压防爆电机、高效防爆电机、高转差率防爆电机及高起动转矩防爆电机等。本文按防爆原理分类介绍。产品系列及其特点1 隔爆型电机它采用隔爆外壳把可能产生火花、电弧和危险温度的电气部分与周围的爆炸性气体混合物隔开。但是，这种外壳并非是密封的，周围的爆炸性气体混合物可以通过外壳的各部分接合面间隙进入电机内部。当与外壳内的火花、电弧、危险高温等引燃源接触时就可能发生爆炸，这时电机的隔爆外壳不仅不会损坏或变形，而且爆炸火焰或炽热气体通过接合面间隙传出时，也不能引燃周围的爆炸性气体混合物。我国当前广泛应用的低压隔爆型电机产品的基本系列是YB系列隔爆型三相异步电机，它是Y系列(IP44)三相异步电机的派生产品。防爆性能符合GB3836183爆炸性环境用防爆电气设备通用要求和GB3836283爆炸性环境用防爆电气设备隔爆型电气设备“d”，的规定；电机功率范围为O55200kW，相对应的机座号范围是机座中心高为80315nun；防爆标志为dI、dIIAT4、dIIBT4，分别适用于煤矿井下固定式设备或工厂IIA、IIB级，温度组别为T1T4组的可燃性气体或蒸气与空气形成的爆炸性混合物的场所；主体外壳防护等级为IP44，也可制成IP%4，接线盒防护等级为IP54；额定频率为50Hz，额定电压为380、1660、1140、380660、660140V；电机绝缘等级为F级，但按B级考核定子绕组的温升，具有较大的温升裕度。低压隔爆型三相异步电机派生系列的主要型号有：YB系列(dIIcT4)(机座中心高为80315mm)，YBSO系列(小功率，机座中心高为6390mm)，YBF系列(风机用，机座中心高为63160mm)，YBH系列(船用，机座中心高为80280mm)，YB系列(中型，机座中心高为355450mm)，YBK系列(煤矿用，机座中心高为100315mm)，YBW、BTH、YBWTH系列(机座中心高为80315mm)，YBDFWF系列(户外防腐隔爆型电动阀门用，机座中心高为80315mm)及YBDC系列(隔爆型电容起动单相异步电机，机座中心高为71100mm)和YBZS系列起重用隔爆型双速三相异步电机。另外，还有YB系列高压隔爆型三相异步电机(机座中心高为355450mm，560710mm)。行业联合设计的YB2系列已于1四年底通过了全国鉴定，将逐步取代YB系列，成为我国隔爆型三相异步电机的基本系列。YB2系列共15个机座号(机座中心高为63、355nmm)，功率范围为O12315kW。其主要特点是：(1) 功率等级、安装尺寸及转速的对应关系与DIN42673一致，同时考虑到与YB系列的继承性和Y2系列的互换性，作了必要调整，更加有效和适用。(2) 全系列采用F级绝缘，温升按B级考核。(3) 噪声限值比YB系列低，接近YB系列的I级噪声，振动限值与YB系列相当。(4) 外壳防护等级提高到IP55。(5) 全系列选用低噪声深沟球轴承，机座中心高在180mm以上电机设注排油装置。(6) 电机散热片有平行水平分布和辐射分布两种，以平行水平分布为主。(7) 主要性能指标达到20世纪90年代初国际先进水平。2.增安型电机它是在正常运行条件下不会产生电弧、火花或危险高温的电机结构上，再采取一些机械、电气和热的保护措施，使之进一步避免在正常或认可的过载条件下出现电弧、火花或高温的危险，从而确保其防爆安全性。我国当前应用的低压增安型的基本系列是YA系列增安型三相异步电动机，它是Y系列(IP44)三相异步电机的派生产品。防爆性能符合GB3836183爆炸性环境用防爆电气设备通用要求和GB3836383爆炸性环境用防爆电气设备增安型电气设备“e”的规定；功率范围为O5590kW，相对应的机座中心高为80280mm；防爆标志为eIITl、eIIT2、eIIT3，分别适用于工厂中具有温度组别为TlT3组爆炸性混合物并具有轻微腐蚀介质的场所；主体外壳的防护等级为IP54，接线盒防护等级为IP55；额定频率为50Hz，额定电压为380V；电机采用F级绝缘。低压增安型电机派生系列的主要型号有：YASO系列小功率增安型三相异步电机(机座中心高为5690mm)，YAW、YAWFl系列户外、户内防腐增安型三相异步电机(机座中心高为80280mm)。其特点是：(1)满足增安型防爆电机的要求，采取一系列可靠的防止火花、电弧和危险高温的措施，可以安全运行于2区爆炸危险场所。(2)采用无刷励磁，设置旋转整流盘和静态励磁柜，励磁控制系统可靠；顺极性转差投励准确，无冲击；励磁系统失步保护可靠，再整步能力强；线路设计合理，放电电阻在工作中不发热；励磁电流调节范围宽。(3)同步机、交流励磁机及旋转整流盘同轴。整流盘位于主电机和励磁机之间，或置于轴承座之外。(4)外壳防护等级为IP54。(5)采用F级绝缘，温升按B级考核。(6)改变传统的下水冷为上水冷，即水冷却器置于电机上部。(7)设增安型防潮加热器，固定在电机底部的罩内，用于停机时加热防潮用。(8) 选优质原材料，电气及机械计算留有较大裕度，能满足运行可靠性和增安型电机的温度要求。(9)设置有完善的监控措施；主接线盒内设置用于差动保护的增安型自平衡电流互感器；定子绕组埋设工作和备用的铂热电阻，分度号为Pt100；设漏水监控仪，监控水冷却器的泄漏；两端座式滑动轴承分别设现场温度显示仪表和远传信号端子。2.1.2 仪器- 13 -第二章 设计思路与论证第二章 设计思路与解决关键问题的方法 2.1运行条件与参数：（一）物料1、物料形态特征：（1）湿污泥，半固态不流动膏状粘稠物（2）干污泥，固态颗粒物（挤压易粉碎）（二）热解反应1、温度（炉内）：干燥段200450，热解段450650，残渣冷凝段650250；排出口温度：小于200。2、压力：微负 -300Pa0Pa；3、停留时间：干燥段12小时，热解段11.5小时，残渣冷凝段11.5小时。（三）燃料燃料为天然气。 动停止控制及PLC程序；变频器的选用及使用等。2.2 设计中主要解决的关键问题：2.2.1 怎样将污染环境的油泥处理成对环境无污的物质： 在第一章中提到，污泥的主要成分是水、有机物及挥发性物质、泥沙。本设计采用利用热解炉加热的方法将它们分离。分离原理为：利用水、有机挥发物气化后冷凝温度的不同进行组分分离。如水在超过100C时将转化成气态，挥发性物质在400C600C时将从液态变成气态。利用上述方法可将它们分离。此过程中最重要的任务是将含有污染性物质的挥发性物质从油泥中分离。轻质油回收2.2.2 热解炉密封问题： 热解炉内温度很高，在加热的过程中，油泥的状态发生变化，使窑内外产生压强差，在高温和负压状态下，当密封装置密封效果不好时，便会有冷风漏入，同是氧气也会进入热解炉反应筒内，因为含油污泥中含有有机可燃烧物质，这些物质在高温和氧气充足的条件下很容易爆炸，另一方面外界气体进入热解炉中从而增加了系统废气量，减少了合理条件下的有用烟气通过量，并且增加了系统能耗。所以在热解炉的窑头和窑尾部应安装密封装置。本设计采用机械密封装置。2.2.3 热解炉的转速控制： 设计的热解炉转速大约在1r/min0.3r/min。因此采用变频控制器调节热解炉的转速。2.2.4 热解炉温度压力控制： 为便于了解热解炉各个不同部分的温度情况，在热解炉的燃烧室内安装温度传感器，具体位置布置将在传感器的选择中介绍。2.2.5 热解炉的压力控制： 为了控制热解炉内压力，在热解炉出现故障时便于判断故障点，在热解炉的窑头，窑尾，排气口出分别安装不同类型的压力传感器，具体情况见传感器的选择章节。2.2.6 反应室内燃烧器的布置和点火方式，及PLC程序：燃烧器采用燃气燃烧器，其点火方式采用PLC程序控制，这用可保证燃烧器按一定顺序启动。同时在燃烧器加热的过程中，采用热电偶传感器对燃烧室内温度数据进行采集，然后经过PLC程序停止在燃烧室中超过要求温度的地方的燃烧器，同时，还可启动燃烧室内温度低于要求温度地方的燃烧器。2.3 整体方案可行性分析：2.2.3.1炉型的选择：本设计燃气燃烧器加热，间接加热式热解炉。选则此窑型的原因是：将加热点布置在窑底面和上面，由于窑炉回环筒是匀速旋转的，筒壁受热均匀，因此，不影响热解炉热效率和正常工况条件。在电、油、气三种加热方式中，燃气加热是一种最清洁的加热方式，除了取用和分配方便之外，还具有，很好地解决了加热元件方便修换的问题，有成本低，热效高、无污染烟气、窑体结构简单紧凑、散热面积小、散热损失少、易于自动控制调节等特点。2.2.3.2 控制方式：采用西门子PLC可编程控制器，控制燃气燃烧器的燃烧。控制方式的自动化程度高，节省劳动力。节省能源的消耗，更合理利用能源。2.2.3.3 窑体均匀加热： 采用PLC控制，使筒体内的温度分布符工艺要求的温度曲线。使分布在窑体上的加热点按顺序启动，停止。防止窑体产生过大的热胀，使热解炉发生变形。- 9 - 英文翻译Walter Gebhart, Phillips Kiln Services, USA discusses the philosophy of lubricating between the tyre and kiln shell.(Reprinted from World Cement, December 1995)Lubricate between tyre and shellIntroductionTo lubricate or not to lubricate? The area under discussion is the mating surface between the bore of a migrating kiln tyre and the shell or shell bars that the tyre sits on. This issue has been controversial for some years now. To be perfectly clear, this discussion does not involve the lubrication of the rolling surface of the tyre. This surface which contacts the face of the rollers, should only see dry graphite as a lubricant and is a separate issue. Although lubricating the tyre bore may seem to be a natural requirement of good rotary kiln operation, some experts in the industry advise against it. Their case is presented with the article by Mr. Robert P. Chapman. His arguments are that a grease type lubricant attracts dust and other debris which acts as a grinding compound which accelerates wear. Secondly, an argument is made that a lubricant promotes slippage and creep which then itself causes more wear since wear is presumed to be proportional to creep and slippage. Promotion of these ideas has led to considerable controversy among those who have been faced with deciding whether to apply lubricant or not. If the action between the tyre and the shell it supports was one of pure rolling, that is the shell rolling within the tyre, then there would be some merit to Chapmans arguments. This article argues however, that this is clearly not the case and can never be so. The nature of the overwhelming majority of kiln designs dictates this as will be seen. It is believed that statistical or scientific investigation has never been done on this subject. However, the author believes that the action and reaction between the tyre bore and its supporting elements, be that the shell or intermediate spacer bars, is only a variation of combined rolling and sliding action between surfaces of similar metals. The common knowledge associated with rolling and sliding is applied, and the special circumstances imposed by a kiln tyre are discussed. The following anecdotal incidents and personal experiences though not proof in themselves, help to illustrate the issue. Case study 1 Case study 2 Comparisons What is creep and why is it necessary? Some creep is actually desirable Tyre retainers Lubrication The real culprit References Case study 1In the first case study, pier no. 2 (from the hot end) of a 4 pier cement kiln had to have the shell under the riding ring and the riding ring replaced. The kiln had been in operation for approximately ten years and the gap between the shell and the tyre had grown to about 2.5 in. This was an intolerable condition and seriously damaged the refractory, considering only a 0.125 in. gap is considered normal during a kilns operation. Once the old components had been removed the damage was fully exposed. The gouges scarfed from both the bore of the tyre and the surface of the pads were remarkable because they were so deep. Some of the shell support pads had grooves so deep they were almost cut in half. The mating surface on the inside of the tyre was in similar condition which, if it were made of soft butter, looked as it is had been systematically subjected to an ice cream scoop. It is believed that no lubrication was ever applied to the mating areas of the tyre and its support elements. Case study 2In the second example, pier No. 2 (from the hot end) of a 4 pier lime kiln had to have the shell under the riding ring changed out. This kiln had also been in operation for about ten years but the gap, shell to tyre was normal. Improperly proportioned shell plate thickness and/or lack of tapers where the plate thickness changes had caused severe circumferential weld cracking on each side of the tyre. Inability to keep these cracks from re-appearing, resulted in the decision to replace the shell under the tyre with extended heavy plate which would be fully tapered to meet the thinner plate of the existing kiln shell. The tyre would be re-used. Once the tyre was slipped back to allow removal of the damaged shell, its bore was fully visible. The exposed mating surfaces were as remarkable in appearance, for opposite reasons, as those described in the first case study. These surfaces were not only smooth and relatively unmarked but the inside of the tyre had the appearance of being chrome plated. The result was striking and was due to the application of a lubricant. Further investigation showed that the gold coloured grease was a commercially available lubricant specifically formulated for kiln tyres. After ten years of operation, the condition of these surfaces were visibly better than the originally machined surfaces, suggesting the adage, better to lubricate than not to lubricate, those areas in contact between the kiln tyre and its support elements. ComparisonsThe reason for failure in the first case study could have been lubrication since the author only observed the mating surfaces at the time of repair. They were dry, rusty and had the general appearance of never having seen any lubricant of any type. The reason for the chronic scarfing of material was naturally the subject of many discussions. Although it was claimed that areas were not lubricated, no one could prove it. Case study 2, however, allows a more concrete conclusion. For the sake of impartiality, one should not conclude that systematic lubrication maintained those parts for ten years or arguably improved them, even though it is an irresistible conclusion. Instead, one can simply say that periodic lubrication with proper materials had in no way contributed to any premature wear of the mating surfaces simply because there was no wear visible. What is creep and why is it necessary?Due to thermal expansion, a typical kiln grows in length by 4-6 in. from dead cold to its operating condition. Similarly the circumference also increases in size. Because the tyre is much thicker than the kiln shell and somewhat proud of the general body of the kiln, its average temperature rise is less than that of the shell. Thermal expansion, therefore, increases the diameter of the shell by a greater amount than it does the tyre. If this differential expansion is not carefully accommodated the tyre may restrict shell expansion, distort it permanently and the refractory in this area can be crushed, yielding undesirable results. Hence the tyre must be loose on the shell. As the kiln warms to operating conditions, the shell circumference grows to more closely match the tyre. It is desirable for this shell growth to never quite catch up with the tyre. Damage to either shell or refractory is thus avoided. If there was an ideal process wherein the operating temperatures were completely constant, it would be possible to design it in such a way that at operating conditions the shell just matches, but is not pinched by the tyre. (The splined tyre support designs, although an expensive capital cost, do eliminate this problem. But since they are very few in number, they are not the subject of discussion here.) Such an ideal process would then avoid having to deal with the problems associated with the differential motion of the tyre and the shell. Ideal processes may be theoretically possible but reality dictates that a range of operating temperatures must be accommodated. A residual gap between shell and tyre is therefore a matter of safety. Some creep is actually desirableSince there is a difference between the bore diameter of the tyre and the diameter of the surface it runs on (the tyre to shell gap), a revolution for the tyre takes proportionately longer than it does for the shell. This is usually relatively small but measurable and is seen as a slow migration of the tyre around the shell. This differential motion is commonly referred to as creep. Excessive gap is as much of a problem as no gap. The tyre not only facilitates the rotary motion of the kiln but is also responsible for maintaining its roundness and consequently the mechanical integrity of refractory. The shell at the points of support would collapse were it not for the girdling effect of the tyre. The shell can be thought of as a bag of water filling the confines of its supporting tyre. The difference in diameters therefore manifests itself near the top and is not distributed as cotangent circles. In other words when the gap becomes large, there is a flattening effect at the top. This continuous change of curvature during rotation, analogous to the flat spot of a car tyre where it contacts the road, can aggravate the mechanical integrity of the refractory to the point of collapse. Good kiln operationtherefore requires that the correct tyre to shell fit or gap of which creep is the normal indicator, must be maintained. Tyre retainersSince the tyres are loose around the shell they must be retained from shifting along the length of the shell. This is done in a variety of ways but is usually accomplished by a simple set of blocks welded to the support pads or directly to the shell on either side of the tyre. Kiln tyres will normally sit against the uphill side retaining blocks. The migration of the tyre produces a circumferential sliding action of the tyre against its retainers. The force with which the tyre sits against its retainers depends on a number of factors, mainly roller skew, slope and alignment. Radial sliding between the retainers and the tyre also occurs due to the gap discussed previously. Consequently the scoring marks on the side of the tyres caused by the retaining blocks are a combination of radial and circumferential sliding and look like the pattern shown in Figure 1. LubricationGraphite is most frequently used for this application. Lubricants specifically formulated for this service are colloids containing graphite as well as molybdenum, copper, aluminium etc. These are solid lubricating materials in a carrier that is designed to flash off at low temperatures. In no way should this carrier be confused with grease implying that a high lubricity grease is being applied. The carrier quickly dissipates leaving the solids as a non sticky residue which closely adheres to (at the microscopic level) the surface of the steel components as witnessed in case study 2. These lubricants are far superior to graphite alone but are correspondingly more expensive. Kilns, as has already been indicated, are not ideal machines. The action between the tyre and the support pads and how to measure it is widely understood and aptly described by Chapman. Chapman also astutely points out that due to heat distortion the support surface presented to the tyre is not circular but has localized perturbations. Because this mechanism is not ideal, slippage will occur with or without lubrication. True rolling action can never be assured and at best is a transient condition. Lubrication therefore is not applied to induce slippage but to prevent any local area from galling and hanging up to the point where metal failure occurs. A greater amount of creep may be seen with the use of a lubricant than without, which if it acts to polish the surfaces is infinitely more desirable than creep which is limited because it tears metal as it proceeds . The real culpritWhether an attempt should be made to eliminate slippage and hopefully achieve pure rolling action between tyre and shell is admittedly at the centre of the lubrication controversy. But is that not skirting the real issue? The action between the tyre retainer blocks and the sides of the tyre is always sliding as long as the tyre is not in the undesirable condition of being locked to the shell due to excessive thermal expansion. Debris getting into the mating surface between the tyre and the shell pads has been cited as the origin of galling and creating self-enlarging slugs that plow through the bore zone. Over the average thirty year life of a kiln in operation it is not weld rod stubs nor air borne material that cause most of the problems. The occasional weld rod stub may in some cases be at fault but how often are they present over the years? Only infrequently. Air borne material, usually kiln product, is gritty and will be ground up, especially at the discharge end tyre. But this grinding action crushes the debris which is brittle and friable, consuming it rather than galling the steel. Galling occurs when dry steel slides against dry steel and the surfaces attach themselves on the microscopic level thereby destroying each other. The mutual destruction of these surfaces causes the steel to ball up forming slugs or spitzers. These particles are overwhelmingly created at the sides of the tyre where they contact the retaining blocks. These then can fall between the tyre bore and its mating surface causing further and potentially more severe damage to the shell pads etc. Even where poor alignment conditions do not cause excessive force, the nature of a typical kiln design necessitates that sliding action exists in these areas. Getting a tyre to float between its uphill and downhill retaining blocks is every operators objective but is commonly not achieved. Some of the forces causing the tyre to sit towards the feed end of the kiln or towards the discharge end of the kiln, the operator simply cannot control. Lubricating here is as essential to preventing undercutting the tyre and consuming the stop blocks as is vigilant control of alignment. With that accomplished, the bore will unavoidably also see lubrication. Lubricating the bore in this context may seem almost secondary. However, few practitioners doing the lubricating will make such subtle distinctions, so lubricating the complete area, short of letting lubricant hit the rolling surfaces, is completely appropriate. Understanding how a kiln is designed, and all kiln manufacturers must cope with the same laws of nature and mechanics of materials, is the first step to understanding the benefits of maintenance procedures such as lubrication. Lubrication does not correct misalignment, alignment does not correct poor operating habits and poor operating habits should not be excused for poor kiln conditions and so on. All maintenance procedures are important and contribute to achieve a reliable operation. Lubrication in the areas discussed, with appropriate solid lubricants is one such step contributing to a well-maintained kiln. Roller and Tire Lubrication：Why should the contact surfaces of the rollers and tires not be lubricated with oil or grease?There is little chance that the meeting of the mating surfaces of the tire and the rollers through the pinch points is one of pure rolling action. There are several reasons for this. The most obvious is that the rolling axis of the roller is not parallel to that of the tire. It would be exceptional for this to prevail for any significant period of time given the nature of the equipment both in its design, installation and operation. Additionally there is always axial movement of the tire on the rollers caused by either or both thermal expansion and mechanical clearance between tire and shell and tire and thrust rollers. Then there is also tire wobble which is always present to some degree. Tire wobble at the pinch points is axial movement that cycle back and forth with each rotation. All of the above detracts from the surfaces meeting in pure rolling by introducing some amount of face dragging or skidding. Lubrication therefore is mandated to prevent surface gall