带式输送机技术的最新发展@中英文翻译@外文翻译

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： 托辊阻力 节能 动力分散 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： 托辊阻力 托辊与皮带的摩擦力 材料或输送带弯曲下垂引起的阻力 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 14 MRC 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 16 18 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 16 Continental 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： 输送带最大压力 滑轮上的最大压力 输送带的最小压力及原料泄漏 提升压力要求 提升行程和速度要求 驱动轮 启动转矩 制动转矩 各驱动间的负载分担 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。 堵塞 输送带和滑道损伤和磨蚀物质退化 粉尘 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 B Latest Developments in Belt Conveyor Technology M. A. Alspaugh Overland Conveyor Co., Inc. Presented at MINExpo 2004Las Vegas, NV, USA September 27, 2004 Abstract 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: Idler Resistance Energy Efficiency Distributed Power Analysis and Simulation Energy Efficiency Minimizing 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: Idler Resistance Rubber indentation due to idler support Material/Belt flexure due to sag being idlers Alignment These 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 1 In 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 2 But 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 3 The 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 China Horizontal 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 View The 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 Coal Tunneling 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 View Figure 9- Inside Tunnel In 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 View Pipe 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 Conveyor In 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 12 Another 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.4 Metso 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 Section This 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 14 MRC vs. Conventional Conveyor in Horizontal Curve Figure 15- MRC at Line Creek, Canada Figure 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 16 Continentals 100th installation of the HAC was a unique shiftable installation at Mexican de Caneneas heap leach pad (Figure 17). Figure 17 Pocketlift. 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 18 Figure 19- Pattiki 2 Mine Distributed 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 20 Figure 21 In 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 22 Although 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 View Figure 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 Diagram Figure 25 Analysis and Simulation Many will argue the major reason for our ability to build complex conveyo rs 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: Maximum belt stresses Maximum forces on pulleys Minimum belt stresses and material spillage Take-up force requirements Take-up travel and speed requirements Drive slip Breakaway torque Holdback torque Load sharing between multiple drives 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 26 Many 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. Plugging Belt and Chute Damage and Abrasion Material Degradation Dust 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 generated with a linear elastic restoring component and a viscous damping term to simulate the energy loss in a normal collision. The linear elastic component is modeled with a spring whose coefficient is based upon the normal stiffness of the contact bodies and the normal viscous damper coefficient is defined in terms of an equivalent coefficient of restitution (Figure 29). Figure 29 Figure 30 shows particles falling through a transfer chute. The colors of the particles in the visualization represent their velocity. T