外文翻译--带式输送机技术的最新发展

1 附录 英文文献翻译 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 ， 2004.9.27 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： 1、 托辊阻力 2 2、 节能 3、 动力分散 4、 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： a. 托辊阻力 b. 托辊与皮带的摩擦力 c. 材料或输送带弯曲下垂引起的阻力 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。 3 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 4 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。 5 图 4 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 6 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。 7 图 7 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。 8 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。 9 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。 10 图 -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 11 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 12 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）。 图 -17 垂直式输送装置 13 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 矿 动力分散 14 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 15 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， 16 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。 图 -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 17 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 18 引用 1散装材料的带式输送机 ,输送设备制造商协会 ,第五版 ,1997 年版 2宫 ,沃尔特 ,”亨德森粗矿石输送系统的调试 ,启动 ,和操作” ,由带式输送机 5散装材料处理 ,学会采矿、冶金和探索 ,Inc .,2004 年 3Goodnough Ryne” ,在 Wyodak 矿的矿井内输送 -吉列 ,怀俄明” ,由带式输送机5 散装材料处理 ,学会采矿、冶金和探索 ,Inc .,2004 年 4Neubecker,我。” ,一个陆上管道输送机 22 水平和 45 垂直曲线连接煤矿铁路负荷” ,散装固体处理 ,17 卷 (1997 年 ),4 号 5Crewdson,史蒂夫 ,“垂直皮带系统 Pattiki 2 矿” ,由带式输送机 5 散装材料处理 ,学会采矿、冶金和探索 ,Inc .,2004 年。 6Alspaugh,马克 ,“中间驱动带式输送机技术的发展” ,散装固体处理” ,23 卷(2003)3 号 7奥多 ,E.J.,“所有输送机动态分析 -效益” ,传送带工程煤炭和矿产开采行业 ,学会采矿、冶金和探索 ,Inc .,1993 年。 8Dewicki Grzegorz” ,散装材料处理和处理 ,数值模拟技术和颗粒材料” ,散装固体处理” ,23 卷 (2003)2 号 19 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: 5、 Idler Resistance 6、 Energy Efficiency 7、 Distributed Power 20 8、 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: d. Idler Resistance e. Rubber indentation due to idler support f. Material/Belt flexure due to sag being idlers g. 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. 21 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 22 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 23 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 24 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 25 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 26 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 27 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 28 (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. 29 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 30 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 31 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 32 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. 33 Figure