带式输送机自动张紧装置设计【含CAD图纸+文档】
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带式输送机自动张紧装置设计
自动张紧装置设计
张紧装置设计
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带式输送机输送带
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专题带式输送机胶带跑偏的原因与治理 带式输送机由于具有结构简单，造价低廉，并且维护方便，可以实现不同距离运送物料的要求等特点，因此，被广泛应用在矿山、冶金、电力、港口、煤炭等部门，是生产工程中最常用的一种输送机械。但带式输送机在工作过程中会出现不同情况的问题，其中以胶带在运行中跑偏最为常见。所谓胶带跑偏，就是带式输送机在运转过程中胶带中心线脱离输送机的中心线而偏向一边的现象称之为胶带跑偏。胶带跑偏可能造成物料撒落和浪费，使胶带的边缘与机架相互磨损，使胶带过早损坏，从而大大降低胶带的使用寿命。胶带又是输送机的重要组成部分，其用量大价格较高，在整个输送机的成本中占了很大的比重大约为50%。当胶带跑偏严重时胶带将脱离托辊掉下来，或者发生胶带划破等严重事故，使带式输送机不能正常工作。由于生产过程的连续性和设备之间的联锁性，如果其中一条带式输送机发生故障，就会影响其他设备的正常运转，造成整个生产过程的瓦解，因此，分析和研究带式输送机输送胶带跑偏的机理和原因，找出减小和消除胶带跑偏现象的方法，在实际生产过程中具有重要意义。 1.带式输送机胶带的跑偏机理 在带式输送机中，由于输送机胶带既是牵引构件，靠它来传递运动和动力，又是承载件，用来支承物料载荷。而在带传动中，传动带只是牵引构件，用来传递运动和动力。在实际工作中，根据不同的工作条件，可以选用不同质地的传送带，常用的传送带类型有：钢丝芯带、强力尼龙芯带、橡胶帆布带等。此处以平皮带为例加以分析，图1为平带传动原理图。 传送带不工作时，由于传送带张紧在两滚筒上，故传送带两边的拉力应相等，都等于初拉力F0。当传送带以顺时针方向转动工作时，紧边拉力为F1，松边拉力为F2。则传送带工作时的有效拉力Fe为 Fe=F1-F2。 如果近似地认为传送带工作时的总长度保持不变，则传送带的紧边拉力的增量，应等于传送带松边的减少量，即 F0=(F1+F2)/2。由上两式可得 F1=F0+Fe/2， F2=F0-Fe/2。 将柔韧体摩擦的欧拉公式F1= F2efa代入上式得 Fe0=2F0(efa-1)/(efa+1)。式中： F0输送带的初拉力； F1输送带的紧边拉力； F2输送带的松边拉力； f输送带与带轮之间的摩擦系数； a带在带轮上的包角； Fe0带所能传递的最大有效拉力。 由此可知：输送带的最大牵引力是与初拉力F0成正比的；最大牵引力随着包角A的增大而增大；最大牵引力随着摩擦系数的增大而增大。通常带式输送机胶带的宽度较宽，这是由带式输送机的工作所决定的。因此，带式输送机的牵引力和初拉力在带宽上的分布比较复杂，如果载荷在带宽上分布不均匀，就会使输送带跑偏。因此，在其他参数一定的情况下，输送胶带是否跑偏，主要由输送机的牵引力或初拉力在带宽上的分布状况决定。所有使力在输送胶带带宽方向上发生偏载的因素，都是使输送胶带跑偏的原因。 2 带式输送机胶带跑偏的原因 造成胶带跑偏的原因很多，但其根本原因就是使胶带的受力沿带宽方向分布不均造成的，根据生产现场的实际情况，找出胶带跑偏的主要原因有以下几个方面。 (1) 输送带自身的质量或制造质量问题。如：边缘成波纹状，带厚不均匀，或有小缺口等弊病。 (2) 输送机的安装方面存在问题。如：输送机头、尾部滚筒、托辊的轴线不平行；所有滚筒和托辊的轴线与输送机机架的中心线不垂直；各落料点不在胶带中心，使胶带承载面上受力不均。 (3) 在粘接胶带接口时，由于胶带接头不正，即接口与胶带中心线不垂直造成胶带受力不均而导致跑偏现象的发生。 (4) 托辊转动不灵活，托辊太稀或连续缺托辊，使胶带两侧受力不等。 (5) 清扫器不能充分发挥作用，造成物料粘结在托辊和改向滚筒上，使其形成了锥形或凸凹形状，从而胶带受到侧向水平分力，发生跑偏。3 防止胶带跑偏的主要措施 根据以上列举的影响胶带跑偏的众多因素，可以采取适当的措施加以防止。 (1) 边缘成波纹状，带厚不均匀等胶带自身制造过程中出现的问题，对于使用者来说，只有在选购胶带时，选择质量好的产品。 (2) 提高安装质量，把胶带跑偏控制在一定的范围。 带式输送机安装的质量标准如下： 头尾机架中心线对输送机纵向中心线不重合度不应超过3mm。 头尾机架(包括拉紧架)安装轴承座的2个平面应在同一平面内，其偏差不应大于1mm。 中间架支腿不垂直度或对建筑物地面的不垂直度不应超过0.3%。 中间架在铅垂面内的不直度应小于1%。 中间架接头处，左右、高低的偏移均不超过1mm。 中间架间距的偏差不应超过1.5mm，相对标高差不应超过间距的0.2%。 托辊横向中心与带式输送机纵向中心线的不重合度不应超过3mm；托辊架的轴线应与输送机中心线垂直，有凹凸弧的胶带应根据设计要求缓慢变向。 带式输送机的传动轴中心线与机架的中心线应垂直，使传动滚筒宽度的中心与机架的中心线重合，减速机的轴线与传动轴线平行，同时，所有轴线和滚筒都应找正，根据带式输送机的宽窄，轴的水平误差可以在0.5至1.5mm。 (3) 对于胶带接口不正的问题，除了加强人员的技术培训外，改善胶带的粘接工艺，由过去的冷粘方式改为采用热硫化胶阶梯斜角形接头方式。因为，斜角形接头的接触面积随截断角度的减小而增大，且斜角接头在运转时所受应力不会集中在同一横截面上，因此不易发生接头开裂现象，同时易于对合准确，并能较好地保证接头处中心线和胶带中心线保持一致，使其内部受力均匀，防止运行中跑偏。 (4) 在管道卸料点处增加一缓冲调整板，该装置不但可以对卸料点进行调整，还可以有效地将输送的物料均匀堆卸在胶带上，防止物料下落时对胶带产生不均匀的侧向力而导致胶带跑偏。 (5) 对于输送机由于托辊出现问题而导致胶带跑偏的，除了及时更换、安装、修理损坏的托辊外，还可以用以下措施进行纠正。即侧托辊向输送带运行方向前倾防跑偏法。 这种方法就是将两个册托辊均向输送带运行方向前倾一个角度，这个角度一般取2度到3度。 在输送机的任意部位安装一对跑偏监视器和一套调整部分，调整部分由纵梁支座、固定纵梁、移动纵梁、托辊组、驱动机构和电动机组成。驱动机构的右边与电动机连接，左边与移动纵梁连接，跑偏监视器安装在调整部分的前面，固定纵梁装在输送带的一侧，移动纵梁有支座装在机架的另一侧，移动纵梁的支座上的限位销与移动纵梁上的纵向导槽滑动配合，托辊组的两端分别挂在固定纵梁和移动纵梁上。当输送带因某种原因偏向一侧超过100m时，该侧的跑偏监控器发出报警信号，同时驱动调整部分纵向移动，从而改变托辊与输送带的交角，对输送带产生横向推力将输送带调整到允许的范围内运动。 ISO标准都规定前倾角小于3度，并给出由此而产生的附加阻力。受力分析如下图： 受力分析图 附加阻力F1为： 式中 摩擦系数； N1输送带对托辊的正压力； 输送带单位质量； 物料单位质量； B带宽； b1前倾托辊与输送带接触长度。 垂直于输送带运行方向的分力Fa1为： 式中 前倾角， 槽角。 同理可知Fa2。 当输送带向一侧跑偏时，则纠正偏力为： 在轴向纠偏力的作用力下，输送带向中间移动，直至达到平衡。 由于输送带的轴向纠偏力是两侧力的差值，数值较小。为了定心可靠，应将所有上托辊前倾2度到3度；也可以间隔几组不前倾的托辊放一组前倾托辊，阻力可减少许多，但纠正可靠性差一些。 (6) 对于清扫装置不能发挥充分的作用，要求维修人员要对清扫器进行定期的维护，保证清扫器与胶带始终保持良好的接触，使胶带表面的物料能够及时清理；在胶带回程要每隔30m安装一套清扫器，保证回程非工作面的清洁；另外，还在头尾部的增面滚筒处安装清扫器，可以随时清理增面滚筒上的粘煤，使胶带不受到侧向水平分力，避免胶带发生跑偏。 (7) 加强设备的改造，特别对使用尾部车式拉紧装置的带式输送机，我们自行对其进行重新设计安装，增强其自动纠偏性能，避免胶带从尾部滚筒处发生跑偏，具体的方案如下： 从力学分析及实践经验上来看，通过调整尾部拉紧滚筒轴心线与胶带纵向中心线间的夹角来纠正尾部胶带跑偏，效果最为明显。所以采取的第一个措施就是：改变目前拉紧装置钢丝绳曳拉方式和拉紧小车的受力情况，使其达到自动纠编的作用。 其自动纠偏机理为：在胶带跑正的情况下，A，B段钢丝绳与拉紧小车架构成了等腰三角形结构，且A，B段钢丝绳受力相当。假如尾部胶带向左侧跑偏，胶带中心线就会偏移拉紧滚筒长度上的中心线，拉紧小车因受胶带相对偏斜力的反作用，而相应产生顺时针角偏斜趋势，而由A，B段钢丝绳及小车架构成的等腰三角形就会遭到破坏，A段钢丝绳(因增长的趋势)成为紧边，B段钢丝绳(因缩短的趋势)成为松边，重锤力G在A段绳上分力大于B段，即G1G2，即产生一对令拉紧小车逆时针偏转的力偶。因此，在重锤与胶带拉力的共同作用下，小车就会产生逆时针角偏转，并向正中的趋势发展，皮带随之跑正，A，B段钢丝绳受力相当，如图2所示。 另外改进前，拉紧装置行走轮外缘面为圆柱型，与道轨配合为4条线接触，其内部滚动轴承选用为调心球轴承，这就决定了拉紧装置的导向性和运行稳定性较差。为提高拉紧小车在拉紧行程内具有良好的导向性与可靠性及弥补行走道轨安装中少量的误差，其行走轮外缘面改为内八字双曲面结构，道轨踏面改为与之适应的正三角形，内部轴承形式为向心球轴承。改进后行走轮与道轨配合为4个点接触，这样就不但保证了拉紧小车具备了一定左右、偏转运动方向上的自由度，而且减小了拉紧装置在纠偏时的摩擦阻力，增加了其灵活性。4 使用中如何调整胶带跑偏 在实际使用中，由于影响胶带跑偏的因素很多，随着各种情况的变化，仍可能会出现输送胶带的跑偏。胶带跑偏的规律是：当滚筒旋转轴线与胶带运行方向垂直时，胶带向紧边跑，即胶带向滚筒直径增大的方向跑；当滚筒或托辊旋转轴线与胶带运行方向不垂直时，胶带向滚筒或托辊先接触的那边跑。 掌握好了这个规律，工作中出现胶带跑偏现象时，应首先分析其原因，找出主要原因后，再动手调整，不要盲目行事。 调整胶带跑偏的工作应在空载运转时进行，一般从输送机头部卸载滚筒开始，沿着胶带运行方向先调整回程段，后调整承载段，切忌多人同时动手，每调整一次以后都要让胶带运行几圈后才能决定是否需要再调整。在滚筒处跑偏，可以调整滚筒，在其他地方跑偏，就调整托辊。调整托辊应在一侧，切勿两侧同时调，调整换向滚筒和托辊时的一般原则如图3所示。在换向滚筒处胶带往哪边跑即调紧哪边，如图3a所示；在托辊处胶带往哪边跑就在哪边将托辊朝胶带运动方向偏转一个角度，但一次不能调得太多，要根据胶带运动情况适当调整，如图3b所示。5 结束语 以上综述了有关胶带跑偏的机理、产生的原因、防止跑偏的措施以及使用者如何调整胶带跑偏，在以后的生产实践中如能对这一问题引起足够的重视，并能认真地在日常的维护中做好胶带跑偏工作，则对提高带式输送机的设备完好率和使用寿命都会产生明显的影响。 参考文献1机械工业部北京起重运输研究所.ISO工业标准.机械工业出版社，19832宋伟刚.带式输送机的动力学模型.连续输送技术，19953杨复兴.胶带输送机结构、原理与计算.煤炭工业出版社，19834张钺.新型带式输送机设计手册.冶金工业出版社，2003 毕 业 设 计 说 明 书学生姓名： 学 号： 学 院： 专 业： 题 目： 带式输送机自动张紧装置设计 指导教师： 职称: 职称: 20*年12月5日毕业设计（论文）任务书一、设计（论文）题目： 带式输送机自动张紧装置设计 二、专题题目： 带式输送机胶带跑偏的原因与治理 三、设计的目的和意义： 带式输送机主要用于输送煤炭、矿石、沙石、谷物等散装物料。其在连续装卸条件下能实现连续运输，所以生产率较高；另外皮带传送机结构简单，设备费用低；工作平稳可靠、噪音小，输送距离长，输送量大，能源消耗少；其应用范围相当广泛，遍及矿山、冶金、化工、建筑、轻工、港口和车站货场。而拉紧装置是带式传送机不可缺少的重要组成部分，它直接关系到带式传送机的安全运行及使用寿命，对于大运量、长距离等大型带式传送机而言更是如此。 到目前为止，在社会生产中有多种皮带拉紧装置得到应用。以往煤矿井下用带式传送机一般均采用固定绞车拉紧或重锤拉紧，很少见到别的类型。由于固定绞车拉紧装置只能定期张紧皮带，而皮带的张紧程度往往与操作者的经验有关，经常出现张紧力过大或者过小，并且直接影响到带式传送机的冲击动负荷，所以固定绞车拉紧装置对于传送机的安全及平稳运行极为不利。 因此，我们有必要研制成一种自动型的张紧装置来实现输送机的张紧过程。四、设计（论文）主要内容： 此次设计主要完成以下三方面的工作：（1）液压回路设计。（2）元件的确定。包括：油缸的选择和计算，液压油的确定，液压泵的选择及计算，电动机的确定，各种阀类的选择。（3）主要部件的设计及计算强度校核等。最终圆满完成毕业设计任务。五、设计目标： 研制成一种自动型的张紧装置来实现输送机的张紧过程。六、进度计划： 20*年3月13日至3月31日进行为期3周的生产实习；4月1日至4月10日完成对设计题目的资料收集与查询；4月11日至4月20日完成对张紧装置总体结构的初步布置；4月21日至5月7日完善张紧装置的设计；5月8日至5月31日进行设计图纸的绘制；6月1日至6月10日进行毕业设计说明书的编写；6月11日至6月20日最后的审稿及说明书和图纸的打印。 七、参考文献资料：张钺.新型带式输送机设计手册； 范存德.液压技术手册；杜国森.液压元件产品样本等22本书或论文。 附录A带式输送机技术的最新发展M. A. AlspaughOverland Conveyor Co., Inc.MINExpo 2004拉斯维加斯, 内华达州，美国 ，9，27, 2004摘要粒状材料运输要求带式输送机具有更远的输送距离、更复杂的输送路线和更大的输送量。为了适应社会的发展，输送机需要在系统设计、系统分析、数值仿真领域向更高层次发展。传统水平曲线和现代中间驱动的应用改变和扩大了带式输送机发展的可能性。本文回顾了为保证输送机的可靠性和可用性而运用数字工具的一些复杂带式输送机。前言虽然这篇文章的标题表明在皮带输送机技术中将提出“新”发展，但是提到的大多思想和方法都已存在很长时间了。 我们不怀疑被提出一些部件或想法将是“新”的对你们大部分人来说。所谓的“新”就是利用成熟的技术和部件组成特别的、复杂的系统； “新”就是利用系统设计工具和方法，汇集一些部件组成独特的输送机系统，并解决大量粒状原料的装卸问题；“新”就是在第一次系统试验(委任)之前利用日益成熟的计算机技术进行准确节能计算机模拟。同样，本文的重点是特定复杂系统设计及满足长距离输送的要求。这四个具体课题将覆盖： l 托辊阻力l 节能l 动力分散l 分析与仿真节能减小设备整体电力消费是所有项目的一个重要方面，皮带输送机是也不例外。 虽然与其他运输方法比较皮带输送机总是运输大吨位高效率的手段，但是减少带式输送机的功率消耗的方法还是很多的。 皮带输送机的主要阻力组成部分有：l 托辊阻力l 托辊与皮带的摩擦力l 材料或输送带弯曲下垂引起的阻力l 重力这些阻力加上一些混杂阻力组成输送材料所需的力。1 在一台输送长度400米的典型短距离输送机中,力可以分为如图1所示的几个部分，图中可以看出提升力所占比例最大，而阻力还是占绝大部分。 图1在高倾斜输送带中如矿用露天倾斜输送带，所受力可分解为图2所示的几个部分，其中提升力仍占巨大比例。由于重力是无法避免的，因此没有好的方法减少倾斜式输送机所受力。 图 2但是在长距离陆上输送机中，所受力更趋向图3所示的几个部分，不难看出摩擦力几乎是所受力的全部。这种情况下考虑主要受力才是最重要的。 图 3力量演算具体是超出本文的范围之外，但是值得一提的是，在过去几年对所有四个区域橡胶凹进、对准线和材料或者传送带弯曲等方面的重要研究都在进行。 并且，虽然在处理每特定区域时大家有不同意见，通常对整体项目经济是必要和重要的是被大家被接受的。在2004个SME年会上，MAN Takraf的Walter Kung介绍了题为“Henderson粗糙矿石输送系统回顾组装、起动和操作”2。 这个项目在1999年12月被实施并且包括一个24公里(3飞行)陆上转达的系统替换地下矿碾碎路轨货车使用系统。 图4 - Henderson PC2到PC3调动站最长的传动机在这个系统(PC2)是16.28公里长与475m升距。最重要的系统事实是提供的功率(4000千瓦在1783 mtph 和4.6 m/s)的50% 被要求用来转动一条空载的带子，因此输送系统的效率是很重要的。需密切注意托辊、传送带盖子橡胶和对准线。用文件说明有关的效率的差别是的一种方法， 使用相等的摩擦系数f的22101标准定义作为比较主要抵抗的总数的另一种方法。过去，象这样典型输送装置的综合设计噪音系数大约是0.016f。MAN Takraf正估计他们对力的敏感达到到0.011的f，超过30%的削减。这在减少设备建造成本上做出了重大贡献。通过六次的实际动态测量显示价值是0.0075，甚至比期望值低30%。 Kung先生强调这将在仅仅用电费用一项上每年减少费用10万美元。 线路优化图5 中国天津水平适应性当然最高效率的材料运输方式是从一点到下一点的直线输送。 但是，由于自然和认为障碍的存在，我们在长距离输送过程中直接直线输送的可能性越来越小。第一台水平弯曲输送机已在很多年前安装使用，但它今天似乎关于安装的每台陆上传动机在方向至少有一个水平变化。并且今天的技术允许设计师相对地容易地调整这些曲线。 图5和图6显示的是把煤从蕴藏地运输到中国天津港口管理处的陆上输送装置。这套运输机由E.J. ODonovan & Associates设计，由 Continental Conveyor Ltd of Australia 公司承建，长达9千米的输送距离4台1500千万电机驱动运输能力达6000 mtph 。 图6 天津输送线平面图Wyodak矿位于美国怀俄明州粉河流域，是记录中最古老的连续经营的煤矿，自1923年运营至今。它一般运用坡面(图7)从新的矿坑到装置756m (2,482 ft)与700m (2,300 ft)水平的半径。 这表明由于水平轮的应用输送机不需要设计太长3。 图7- Wyodak 煤矿隧道式如通过没有水平曲线线路，另一项产业，隧道挖掘，就不能使用带式输送机了。 隧道就想象废水和运输那样的基础设施在全世界有。 移动隧道粪肥的最有效率的方法通过把推进的输送装置和隧道机器的后部连结起来。但是这些隧道极少是直的。 这里有一个例子，西班牙10.9m直径隧道的在巴塞罗那之下作为地铁(火车)引伸项目一部分。大陆输送机机有限公司安装了前4.7km传动机如图8和9所显示和最近接受合同安装第二台8.39公里输送机。 图 8- 巴塞罗那隧道平面图图 9- 隧道内部另一个例子， 肯珀建设边境时，建设一个直径3.6米长6.18公里的隧道作为大都市圣路易斯的下水道区。鲍姆加特纳隧道(图10)将装有600毫米宽的用4个中间运动用带子系住的6.1 公里输送装置。图10- 鲍姆加特纳隧道平面图管状输送装置如果常规输送机不能满足必须的输送要求，带式输送机的一种管状输送机会是不错的选择。 图 11- 管状输送装置它最简单的描述，管状输送机就是由管状橡胶管和空转辊组成。这种设计具有其他传送方式的优点，更有自己的特点。托辊可以在各个方向传力允许更复杂的曲线输送。这些曲线可以是水平或垂直或混合形式。这样的输送机输送带与托辊之间的重力和摩擦力保证原料在输送管道内。 Figure 12管状输送机的另一个好处可以输送粉状原料并且可以减少溢出浪费，因为材料是在管道内部。一个典型的例子是环境效益和适应性特好的美国犹他州地平线矿（图12）。这个长3.38公里的管状输送机由ThyssenKrupp Robins 安装通过一个国家森林并且横断了22个水平段和45个垂直段。Metso 绳索输送机另一种由常规衍变来的是Mesto 绳索输送机（MRC），通常以缆绳传送带著名。这个产品以长途输送著名，在距澳大利亚30.4公里的沃斯利铝土矿上应用的输送带是最长的单个飞行输送机。在钢绳输送机上，驱动装置和运载媒介是分离的。 图13 - MRC-平直的部分这种驱动与输送装置的分离允许输送有小半径的水平弯曲，这种设计优于根距张紧力和地势的传统设计。图 14MRC与常规输送机水平曲线的不同图 15- 位于加拿大 Line Creek的MRC图15显示的是位于加拿大Line Creek河畔的一条长10.4公里水平半径430米的缆绳输送带立式输送装置有时材料需要被提升或下降而常规输送机被限制在1618度附近的倾斜角度内。但是带式输送机的非传统衍变不管是在增加角度还是平直方面都是相当成功的。 大角度输送机 第一台大角度输送机由Continental Conveyor & Equipment Co.公司生产，非常利用常规输送机零部件（图16）构成。当原料在两条带子之间输送时，被称为三明治输送装置。 图16Continental 公司的第100套大倾角输送装置采用独特的可平移式设计，作为Mexican de Canenea的堆过滤垫（图17）。 Figure 17垂直式输送装置第二种立式输送装置展现的是一种非常规的带式装置，它可以实现垂直输送（图18）。 这种Mesto 垂直输送机，2001年由Frontier Kemper 安装在白县煤矿Pattiki 2矿（图19），将煤由273米深的矿井输出并达到1,818 mtph的输送能力。 图18图19- Pattiki 2矿动力分散 在最近过去的一段时间里，一种最有趣的发展是电力沿输送道路的分配。看到输送机驱动装置安装在收尾末端，让尾端驱动完成输送带的拉紧输送工作。但是现在的发展观念是把驱动安装在任何需要的位置。 在带式输送机上多个位置安装动力源的想法已经存在很长一段时间了。第一次应用是1974年安装在美国Kaiser煤矿。紧接着是在地下煤矿中得到应用，而且长臂开采法也越来越体现它的优越性。采矿设备的效率和能力也得到巨大改善。矿工们也开始寻找大的矿区从而减少移动大型采矿设备的次数及时间。矿井宽度和矿井分格长度都得到增加。 当矿井分格长度增加后，输送问题开始出现。接近4-5千米的输送长度所需要的电力和输送带的强度比以前地下煤矿需要的大很多。问题是大号的高电力驱动装置安装及移动困难。虽然胶带技术能够满足胶带所需强度要求，它意味着需要比钢铁更重要的强度及加硫处理。由于长臂开采法的盘区传动机经常推进和后退，矿工需要经常增加或取消滚筒的正传与逆转。而且硫化结合需要长期维护以保证强度，因而失去的产品生产时间在一个完全盘区中是很严重的。现在需要超过风险，并且中间驱动的应用限制了输送带的伸长及张紧这样就允许纤维胶带在长距离输送机中应用。 现今，中间驱动技术被很好的接受并越来越广泛的应用于地下煤矿中。世界范围内的许多矿把这项技术整合到现在和未来矿业计划当中来增加他们的整体采矿效率和效益6。表20所示的张紧图显示了中间驱动的重大好处。这种平面前驱的输送机有简单的皮带张力分布如黑色线条所示。虽然平均皮带张力在每个周期期间只约为最大值的40%，但必须围绕最大估量值附近。黑色线条的急剧回落表示顶头滑轮要求的总扭矩和力量来启动输送机。 将受力分解到两个地点（红线），当总功率基本相同的情况下，皮带张力差不多减少40%。因此更小的输送带和更小的电源组可以得到运用。为了进一步扩展这种方式，增加第二中间驱动（绿线），皮带峰顶张力进一步下降。 隧道产业也迅速采用这种技术并且把这项技术提高到更好的水平，更复杂更先进。但挖隧道最需要的是水平曲线的进步。 通过中间驱动（图21）的一种应用例如Baumgartner 隧道如前图10所描述，皮带张紧力可以通过在重要的地点安装战略驱动来控制，从而实现输送带的小曲线换向。 图20图21在图22中，绿色投影区域代表弯曲结构的地点。蓝色线条代表输送带运载面，粉红色线条代表输送带返回面。可以发现在弯曲半径最小750米时输送带运载面和返回面所受张紧力均达到最小。 图22尽管到目前为止，这项技术陆上输送机中没有广泛的应用，一些倾向于水平曲线的技术却得到发展。图23显示了南美洲的一条长8.5千米硬岩层输送带，它需要4个中间驱动来实现4段2000米半径的曲线转向。 Figure 23- 平面图图24显示在弯曲段有与没有驱动时输送带的张紧力比较。分散驱动的优点在MRC缆绳输送带中也得到应用。然而张紧运载的绳索有别于负载传送带，安装中间驱动更加容易，输送的原料不用离开运载输送带的表面。张紧运载的绳索与输送带分开足够的距离，便利在安装中间驱动后继续工作。(图25). 图24- 张紧曲线图25分析与仿真许多人在争论我们建造以上描述的复杂输送机的能力时，归因于许多分析和仿真工具的发展。组件制造商可以通过测试他的产品以保证符合规格；然而系统工程师很少能测试完成的系统，知道它在站点完成。所以计算方法和工具在模仿各种各样不同学科和组分上的作用是绝对重要的。 动态开始和停止当进行开始和停止试验时，假设所有的质量单元同时加速；也就是把输送带看做一个刚体（非弹性体）。实际上，推进扭矩通过滑轮产生的压力波传递给输送带，并通过压力波的传播带动输送带运行。压力在输送带上传播时发生由阻碍输送带运行的阻抗产生的纵波引起的变化。7从1959开始许多出版物都指出弹性输送带的大输送量、长距离输送机在停止和启动时会导致传动装置、驱动装置、张紧装置的选择等错误。对弹性瞬变响应的疏忽可能导致不精确的后果： l 输送带最大压力l 滑轮上的最大压力l 输送带的最小压力及原料泄漏l 提升压力要求l 提升行程和速度要求l 驱动轮 l 启动转矩l 制动转矩 l 各驱动间的负载分担 l 原料在斜面上的稳定性为了长期应用，通过数学模型对弹性输送带在开始和停止时的状态进行模拟是非常重要的。 一部完整输送机系统的模型可通过划分输送机为一系列的有限元素来实现。每个元素由一个质量和一个流变弹簧组成，如图26所示。 图 26许多分析输送带无力性能的方法都在研究，如把它看做一个流变弹簧，而且大量的技术也被用来这方面的研究。一个合适的模型需要包含以下几个方面： 1. 传送带纵向拉伸量的弹性模数2. 对从属运动的阻抗3. 凹陷处的粘弹性损失4. 由于输送带的下垂引起的输送带模数变动因为纯数学解决这些动态问题是非常复杂的，它的目标不是详述基础的动态理论分析。相反，它的目的是让长距离输送、水平弯曲、分散驱动在输送机上更普遍，对传送带停止和开始进行弹性动态分析的重要性是开发适当的控制算法。 以图23 8.5千米输送机为例，两个虚拟开始被模拟来比较它们的控制算法。一种是两个1000千瓦的驱动安装在头部尾端，二个1000千瓦驱动安装在输送面的中点，另一个1000千瓦驱动安装在尾部，要极端小心保证所有驱动的协调与维护。 图27显示一个不协调并严重摆动输送机120秒启动的扭矩图及其相应的速度输送带摆动图。T1/T2滑动比率表明推进滑动可能发生。图28显示对应的一个180秒启动图，并能够安全和顺利的加速输送机。 图27-120 秒恶劣启动 图 28- 180 良好启动转运站的质流运用中间驱动和链板输送能长期使用的一个原因就是消除转运站。许多最困难的问题在带式输送机装货和卸载附近集中。传送溜槽通常选在输送机高效维护区域，同时重大生产风险在这里集中。 l 堵塞l 输送带和滑道损伤和磨蚀物质退化 l 粉尘l 装货/溢出偏心过去，没有分析工具，反复试验和经验是设计工程师唯一可用的设计方法；现在，数值仿真方法的存在允许设计师在制造之前测试他们的设计。 数字仿真是根据一个实际的物理系统设计的模型，并在计算机上模拟和分析结果。仿真体现在实践中学习的精神。为了了解现实及其复杂性，我们在计算机上建立虚拟物体并动态的观察它们间的相互作用。 分离元素法是解决工程学和应用科学如粒状材料流等不连续的机械行为问题的一种数字模拟技术。值得注意的是，由非连续行为引起的行为不能依靠传统基基于计算机的连续流塑造方法例如有限元素分析、有限差规程和甚而计算流体动力学(CFD)的来进行模拟。 DEM系统模仿每个部件或微粒的动态行为和机械互作用，并提供分析期间每个部件和微粒的位置、速度、和力量的详细描述。8 在分析过程中，微粒被塑造成有形状的物体，这些物体之间及于界限表面、运载表面互相作用，这些物体接触和碰撞形成他们之间法向、切向力. 正常接触分力在碰撞过程中引起一个线性有弹性恢复的组分和一个粘阻力来模拟能量损失。线性有弹性组分系数根据自身属性确定，正常粘滞系数可以根据一个等效恢复系数的弹簧来塑造（图29）。 图29图30显示颗粒下落通过传送带溜槽。图示中颗粒的颜色代表他们的速度。红色代表零速度，而绿色代表最高速度。也许这些工具的最大好处就是一位老练的工程师能通过形象化表示设计施工前有个行像的表现。有了这个形象的感觉在施工过程中可以尽量减少不必要的工作。 其他定量数据也可能被隐藏包括在输送带或滑道墙壁的冲击和剪切力。 图30前景更大的带式输送机本文提到了一台最长的唯一飞行常规输送机，长16.26公里的Henderson PC2。但一台19.1公里的输送机在美国正在建设中，并且一台23.5公里的飞行式输送机在澳洲被设计。其他长30-40公里的输送机在世界其他地区讨论研究。 当定量凹进的方式为人所知，输送带制造商开发了低辗压抗压储力10-15%的橡胶输送带。与改进的设施方法和对准线一起作用，节能是可以实现的。地下煤矿和隧道承包商将继续使用已经证明对他们有好处的分散驱动方式；至少有两种在表面输送机中安装中间驱动的输送机在2005年运行。 在德国，RWE Rheinbraun 使煤矿用输送机输送量达到30,000 tph ，并且其他表面煤矿也在有计划的接近这个输送量。随着输送两的增加，输送带的速度也在增加，这样就要求更好的设备、工艺公差、阻力和动力分析。我们希望输送机能够更远、更宽、更高、更快，采用所有分析工具来分析系统性能。因为每台输送机都是独特的，我们唯一的预见方式就是外面的数据分析和模仿工具。因此由于外面的目标越来越大，我们有必要改进设计工具。 附录BLatest Developments in Belt Conveyor Technology M. A. AlspaughOverland Conveyor Co., Inc.Presented at MINExpo 2004Las Vegas, NV, USA September 27, 2004Abstract Bulk material transportation requirements have continued to press the belt conveyor industry to carry higher tonnages over longer distances and more diverse routes. In order keep up, significant technology advances have been required in the field of system design, analysis and numerical simulation. The application of traditional components in non-traditional applications requiring horizontal curves and intermediate drives have changed and expanded belt conveyor possibilities. Examples of complex conveying applications along with the numerical tools required to insure reliability and availability will be reviewed. Introduction Although the title of this presentation indicates “new” developments in belt conveyor technology will be presented, most of the ideas and methods offered here have been around for some time. We doubt any single piece of equipment or idea presented will be “new” to many of you. What is “new” are the significant and complex systems being built with mostly mature components. What is also “new” are the system design tools and methods used to put these components together into unique conveyance systems designed to solve ever expanding bulk material handling needs. And what is also “new” is the increasing ability to produce accurate Energy Efficiency computer simulations of system performance prior to the first system test (commissioning). As such, the main focus of this presentation will be the latest developments in complex system design essential to properly engineer and optimize todays long distance conveyance requirements.The four specific topics covered will be: l Idler Resistance l Energy Efficiency l Distributed Power l Analysis and Simulation Energy EfficiencyMinimizing overall power consumption is a critical aspect of any project and belt conveyors are no different. Although belt conveyors have always been an efficient means of transporting large tonnages as compared to other transport methods, there are still various methods to reduce power requirements on overland conveyors. The main resistances of a belt conveyor are made up of:l Idler Resistancel Rubber indentation due to idler supportl Material/Belt flexure due to sag being idlersl AlignmentThese resistances plus miscellaneous secondary resistances and forces to over come gravity (lift) make up the required power to move the material.1 In a typical in-plant conveyor of 400m length, power might be broken into its components as per Figure 1 with lift making up the largest single component but all friction forces making up the majority.Figure 1In a high incline conveyor such as an underground mine slope belt, power might be broken down as per Figure 2, with lift contributing a huge majority. Since there is no way to reduce gravity forces, there are no means to significantly reduce power on high incline belts. Figure 2But in a long overland conveyor, power components will look much more like Figure 3, with frictional components making up almost all the power. In this case, attention to the main resistances is essential. Figure 3The specifics of power calculation is beyond the scope of this paper but it is important to note that significant research has been done on all four areas of idlers, rubber indentation, alignment and material/belt flexure over the last few years. And although not everyone is in agreement as to how to handle each specific area, it is generally well accepted that attention to these main resistances is necessary and important to overall project economics.At the 2004 SME annual meeting, Walter Kung of MAN Takraf presented a paper titled “The Henderson Coarse Ore Conveying System- A Review of Commissioning, Start-up and Operation”2. This project was commissioned in December 1999 and consisted of a 24 km (3 flight) overland conveying system to replace the underground mine to mill rail haulage system. Figure 4- Henderson PC2 to PC3 Transfer House The longest conveyor in this system (PC2) was 16.28 km in length with 475m of lift. The most important system fact was that 50% of the operating power (4000 kW at 1783 mtph and 4.6 m/s) was required to turn an empty belt therefore power efficiency was critical. Very close attention was focused on the idlers, belt cover rubber and alignment. One way to document relative differences in efficiency is to use the DIN 22101 standard definition of “equivalent friction factor- f” as a way to compare the total of the main resistances. In the past, a typical DIN fused for design of a conveyor like this might be around 0.016. MAN Takraf was estimating their attention to power would allow them to realize an f of 0.011, a reduction of over 30%. This reduction contributed a significant saving in capital cost of the equipment. The actual measured results over 6 operating shifts after commissioning showed the value to be 0.0075, or even 30% lower than expected. Mr. Kung stated this reduction from expected to result in an additional US$100, 000 savings per year in electricity costs alone. Route Optimization Figure 5- Tiangin ChinaHorizontal Adaptability Of course the most efficient way to transport material from one point to the next is as directly as possible. But as we continue to transport longer distances by conveyor, the possibility of conveying in a straight line is less and less likely as many natural and man-made obstacles exist. The first horizontally curved conveyors were installed many years ago, but today it seems just about every overland conveyor being installed has at least one horizontal change in direction. And todays technology allows designers to accommodate these curves relatively easily. Figures 5 and 6 shows an overland conveyor transporting coal from the stockpile to the shiploader at the Tianjin China Port Authority installed this year. Designed by E.J. ODonovan & Associates and built by Continental Conveyor Ltd of Australia, this 9 km overland carries 6000 mtph with 4x1500 kW drives installed. Figure 6- Tiangin China Plan ViewThe Wyodak Mine, located in the Powder River Basin of Wyoming, USA, is the oldest continuously operating coal mine in the US having recorded annual production since 1923. It currently utilizes an overland (Figure 7) from the new pit to the plant 756m long (2,482 ft) with a 700m (2,300 ft) horizontal radius. This proves a conveyor does not need to be extremely long to benefit from a horizontal turn. 3 Figure 7- Wyodak CoalTunneling Another industry that would not be able to use belt conveyors without the ability to negotiate horizontal curves is construction tunneling. Tunnels are being bore around the world for infrastructure such as waste water and transportation. The most efficient method of removing tunnel muck is by connecting an advancing conveyor to the tail of the tunnel boring machine. But these tunnels are seldom if ever straight. One example in Spain is the development of a 10.9m diameter tunnel under Barcelona as part of the Metro (Train) Extension Project. Continental Conveyor Ltd. installed the first 4.7km conveyor as shown in Figures 8 and 9 and has recently received the contract to install the second 8.39 km conveyor. Figure 8- Barcelona Tunnel Plan ViewFigure 9- Inside TunnelIn another example, Frontier Kemper Construction is currently starting to bore 6.18 km (20,275 ft) of 3.6m (12 foot) diameter tunnel for the Metropolitan St. Louis (Missouri) Sewer District. The Baumgartner tunnel (Figure 10) will be equipped with a 6.1 km conveyor of 600mm wide belting with 4 intermediate drives. Figure 10- Baumgartner Tunnel Plan ViewPipe Conveyors And if conventional conveyors cannot negotiate the required radii, other variations of belt conveyor such as the Pipe Conveyor might be used. Figure 11- Pipe ConveyorIn its simplest description, a pipe conveyor consists of a rubber conveyor belt rolled into a pipe shape with idler rolls. This fundamental design causes the transported material to be totaled enclosed by the belt which directly creates all the advantages. The idlers constrain the belt on all sides allowing much tighter curves to be negotiated in any direction. The curves can be horizontal, vertical or combinations of both. A conventional conveyor has only gravity and friction between the belt and idlers to keep it within the conveyance path. Figure 12Another benefit of pipe conveyor is dust and/or spillage can be reduced because the material is completely enclosed. A classic example where both environment and adaptability to path were particularly applicable was at the Skyline Mine in UT, USA (Figure 12). This 3.38 km (11,088 ft) Pipe Conveyor was installed by ThyssenKrupp Robins through a national forest and traversed 22 horizontal and 45 vertical curves.4Metso Rope Conveyor Another variation from conventional is the Metso Rope Conveyor (MRC) more commonly known as Cable Belt. This product is known for long distance conveying and it claims the longest single flight conveyor in the world at Worsley Alumina in Australia at 30.4 km. With Cable Belt, the driving tensions (ropes) and the carrying medium (belt) are separated (Figure 13). Figure 13- MRC- Straight SectionThis separation of the tension carrying member allows positive tracking of the ropes (Figure 14) which allow very small radius horizontal curves to be adopted that defeat the traditional design parameters based on tension and topography. Figure 14MRC vs. Conventional Conveyor in Horizontal CurveFigure 15- MRC at Line Creek, CanadaFigure 15 shows a 10.4 km Cable Belt with a 430m horizontal radius at Line Creek in Canada. Vertical Adaptability Sometimes material needs to be raised or lowered and the conventional conveyor is limited to incline angles around 16-18 degrees. But again non-traditional variations of belt conveyors have been quite successful at increased angles as well as straight up. High Angle Conveyor (HAC.) The first example manufactured by Continental Conveyor & Equipment Co. uses conventional conveyor components in a non-conventional way (Figure 16). The concept is known as a sandwich conveyor as the material is carried between two belts. Figure 16Continentals 100th installation of the HAC was a unique shiftable installation at Mexican de Caneneas heap leach pad (Figure 17). Figure 17Pocketlift. The second example shows a non-traditional belt construction which can be used to convey vertically (Figure 18). This Metso Pocketlift. belt was installed by Frontier Kemper Constructors at the Pattiki 2 Mine of White County Coal in 2001 (Figure 19). It currently lifts 1,818 mtph of run-of-mine coal up 273 m (895 ft). 5 Figure 18Figure 19- Pattiki 2 MineDistributed Power One of the most interesting developments in technology in the recent past has been the distribution of power along the conveyor path. Is has not been uncommon to see drives positioned at the head and tail ends of long conveyors and let the tail drive do the work of pulling the belt back along the return run of the conveyor. But now that idea has expanded to allow designers to position drive power wherever it is most needed. The idea of distributing power in multiple locations on a belt conveyor has been around for a long time. The first application in the USA was installed at Kaiser Coal in 1974. It was shortly thereafter that underground coal mining began consolidating and longwall mines began to realize tremendous growth in output. Mining equipment efficiencies and capabilities were improving dramatically. Miners were looking for ways to increase the size of mining blocks in order to decrease the percentage of idle time needed to move the large mining equipment from block to block. Face widths and panel lengths were increasing. When panel lengths were increased, conveyance concerns began to appear. The power and belt strengths needed for these lengths approaching 4 -5 km were much larger than had ever been used underground before. Problems included the large size of high power drives not to mention being able to handle and move them around. And, although belting technology could handle the increased strength requirements, it meant moving to steel reinforced belting that was much heavier and harder to handle and more importantly, required vulcanized splicing. Since longwall panel conveyors are constantly advancing and retreating (getting longer and shorter), miners are always adding or removing rolls of belting from the system. Moreover, since vulcanized splicing takes several times longer to facilitate, lost production time due to belt moves over the course of a complete panel during development and mining would be extreme. Now the need surpassed the risk and the application of intermediate drives to limit belt tensions and allow the use of fabric belting on long center applications was actively pursued. Today, intermediate drive technology is very well accepted and widely used in underground coal mining. Many mines around the world have incorporated it into their current and future mine plans to increase the efficiency of their overall mining operations. 6 The tension diagram in Figure 20 shows the simple principal and most significant benefit of intermediate belt conveyor drives. This flat, head driven conveyor has a simple belt tension distribution as shown in black. Although the average belt tension during each cycle is only about 40% of the peak value, all the belting must be sized for the maximum. The large drop in the black line at the head pulley represents the total torque or power required to run the conveyor. By splitting the power into two locations (red line), the maximum belt tension is reduced by almost 40% while the total power requirement remains virtually the same. A much smaller belt can be used and smaller individual power units can be used. To extend the example further, a second intermediate drive is added (green line) and the peak belt tension drops further. The tunneling industry was also quick to adopt this technology and even take it to higher levels of complexity and sophistication. But the main need in tunneling was the necessity of using very tight horizontal curves. By applying intermediate drives (Figure 21) to an application such as the Baumgartner Tunnel as described in Figure 10 above, belt tensions can be controlled in the horizontal curves by strategically placing drives in critical locations thereby allowing the belt to turn small curves. Figure 20Figure 21In Figure 22, the hatched areas in green represent the location of curved structure. The blue line represents carry side belt tensions and the pink line represents return side belt tensions. Notice belt tensions in both the carry and return sides are minimized in the curves, particularly the tightest 750m radius. Figure 22Although aboveground overland conveyors have not used this technology extensively to date, applications are now starting to be developed due to horizontal curve requirements. Figure 23 shows a South American, 8.5km hard rock application which requires an intermediate drive to accommodate the four relatively tight 2000m radii from the midpoint to discharge. Figure 23- Plan ViewFigure 24 shows a comparison of belt tensions in the curved areas with and without distributed power. The benefit of distributed power is also being used on the MRC Cable Belt. However, since the tension carrying ropes are separate from the load carrying belt, installing intermediate drives is even easier as the material never has to leave the carry belt surface. The tension carrying ropes are separated from the belt long enough to wrap around drive sheaves and the carry belt is set back on the ropes to continue on (Figure 25). Figure 24- Tension DiagramFigure 25Analysis and Simulation Many will argue the major reason for our ability to build complex conveyors as described above is advancements in the analysis and simulation tools available to the designer. A component manufacturer can usually test his product to insure it meets the specification; however the system engineer can seldom test the finished system until it is completed on site. Therefore computational methods and tools are absolutely critical to simulate the interactions of various diverse disciplines and components. Dynamic Starting and Stopping When performing starting and stopping calculations per CEMA or DIN 22101 (static analysis), it is assumed all masses are accelerated at the same time and rate; in other words the belt is a rigid body (non-elastic). In reality, drive torque transmitted to the belt via the drive pulley creates a stress wave which starts the belt moving gradually as the wave propagates along the belt. Stress variations along the belt (and therefore elastic stretch of the belt) are caused by these longitudinal waves dampened by resistances to motion as described above. 7 Many publications since 1959 have documented that neglecting belt elasticity in high capacity and/or long length conveyors during stopping and starting can lead to incorrect selection of the belting, drives, take-up, etc. Failure to include transient response to elasticity can result in inaccurate prediction of: l Maximum belt stresses l Maximum forces on pulleys l Minimum belt stresses and material spillage l Take-up force requirements l Take-up travel and speed requirements l Drive slip l Breakaway torque l Holdback torque l Load sharing between multiple drives l Material stability on an incline It is, therefore, important a mathematical model of the belt conveyor that takes belt elasticity into account during stopping and starting be considered in these critical, long applications. A model of the complete conveyor system can be achieved by dividing the conveyor into a series of finite elements. Each element has a mass and rheological spring as illustrated in Figure 26. Figure 26Many methods of analyzing a belts physical behavior as a rheological spring have been studied and various techniques have been used. An appropriate model needs to address: 1. Elastic modulus of the belt longitudinal tensile member 2. Resistances to motion which are velocity dependent (i.e. idlers) 3. Viscoelastic losses due to rubber-idler indentation 4. Apparent belt modulus changes due to belt sag between idlers Since the mathematics necessary to solve these dynamic problems are very complex, it is not the goal of this presentation to detail the theoretical basis of dynamic analysis. Rather, the purpose is to stress that as belt lengths increase and as horizontal curves and distributed power becomes more common, the importance of dynamic analysis taking belt elasticity into account is vital to properly develop control algorithms during both stopping and starting. Using the 8.5 km conveyor in Figure 23 as an example, two simulations of starting were performed to compare control algorithms. With a 2x1000 kW drive installed at the head end, a 2x1000 kW drive at a midpoint carry side location and a 1x1000kW drive at the tail, extreme care must be taken to insure proper coordination of all drives is maintained. Figure 27 illustrates a 90 second start with very poor coordination and severe oscillations in torque with corresponding oscillations in velocity and belt tensions. The T1/T2 slip ratio indicates drive slip could occur. Figure 28 shows the corresponding charts from a relatively good 180 second start coordinated to safely and smoothly accelerate the conveyor. Figure 27-120 Sec Poor Start Figure 28- 180 Sec Good Start Mass Flow at Transfer Points One of the reasons for using intermediate drives and running single flight conveyors longer and longer is to eliminate transfer points. Many of the most difficult problems associated with belt conveyors center around loading and unloading. The transfer chute is often sited as the highest maintenance area of the conveyor and many significant production risks are centered here. l Plugging l Belt and Chute Damage and Abrasion l Material Degradation l Dust l Off Center Loading/Spillage In the past, no analytical tools have been available to the design engineer so trial-and-error and experience were the only design methods available. Today, numerical simulation methods exist which allow designers to “test” their design prior to fabrication. Numerical simulation is the discipline of designing a model of an actual physical system, executing the model on a computer, and analyzing the results. Simulation embodies the principle of “learning by doing. To understand reality and all of its complexity, we build artificial objects in the computer and dynamically watch the interactions. The Discrete Element Method (DEM) is a family of numerical modeling techniques and equations specifically designed to solve problems in engineering and applied science that exhibit gross discontinuous mechanical behavior such as bulk material flow. It should be noted that problems dominated by discontinuum behavior cannot be simulated with conventional continuum based computer modeling methods such as finite element analysis, finite difference procedures and/or even computational fluid dynamics (CFD). The DEM explicitly models the dynamic motion and mechanical interactions of each body or particle in the physical problem throughout a simulation and provides a detailed description of the positions, velocities, and forces acting on each body and/or particle at discrete points in time during the analysis. 8 In the analysis, particles are modeled as shaped bodies. The bodies can interact with each other, with transfer boundary surfaces and with moving rubber conveyor belt surfaces. The contact/impact phenomena between the interacting bodies are modeled with a contact force law which has components defined in the normal and shear directions as well as rotation. The normal contact force component is genera
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