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大功率硬齿面减速机设计及零件的工艺安排,大功率,硬齿面,减速,设计,零件,工艺,安排

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河南理工大学本科毕业设计（论文）中期检查表指导教师： 王志阳 职称： 副教授 所在院（系）： 机械与动力工程学院 教研室（研究室）： 机械设计教研室 题 目大功率硬齿面减速机设计及零件的工艺安排学生姓名张兰兰专业班级机设3班学号0828070177一、选题质量：（主要从以下四个方面填写：1、选题是否符合专业培养目标，能否体现综合训练要求；2、题目难易程度；3、题目工作量；4、题目与生产、科研、经济、社会、文化及实验室建设等实际的结合程度） 1、本次设计过程中，综合运用了在本科学习中所学的专业知识，且通过本次设计，加深了对所对所学专业知识的认识。我认为此次设计选题符合机设专业培养目标，能锻炼和培养生产实际中分析问题的能力及动手操作能力，能充分体现综合训练要求；2、本题目符合本科毕业设计要求；3、该题目的工作量中等，需要考虑的问题主要是减速器齿轮的选取、材料的选取、工艺方案的选取等。4、本题目与生产、科研、日常生活等实际有较紧密联系，能够很好的解决各种传动速度的需要。二、开题报告完成情况：在初步分析完大功率减速器的类型，结构，所需运用的基本知识及可能面临的一些问题之后，开题报告也具有了很强的针对性、具体性，进而也显得特别的充实，对我们的总体设计具有很强的指导性和概括性。三、阶段性成果：1、收集并整理设计所需的相关资料，完成外文资料翻译、撰写开题报告； 2、完成系统方案设计及方案论证；3、完成了零部件的设计计算，论文说明书主体思路基本完成。四、存在主要问题：1、对于理论性的问题还可以处理，但对电脑知识了解的比较少，因此需要应用电脑时有点困难。2、所用的知识比较多，把他们有效地组织起来还是有一定难度的。3、有些地方理解的还不够透彻，还需要多多的学习。五、指导教师对学生在毕业实习中，劳动、学习纪律及毕业设计（论文）进展等方面的评语指导教师： （签名） 年 月 日译文题目: Mechanical Plant 机械装置 正文：外文资料翻译译文机械装置（摘自FAP项目输送设备技术要求）a) 设计基础托辊带式输送机应当遵循ISO1537，BS2890或者欧洲和国际的相关设计标准的要求。在实际的生产过程中，必须保证运输带的外边缘和旁边过道间的距离最少为1200mm，滚筒和平台之间的高度距离最少为300mm，并且中间不能有障碍物。相关负责人应当使传送带的宽度，槽的角度和带的速度与要传送原料的输送效率相适应，以保证不会溢出。滚筒的直径，滚筒之间的距离以及喂料皮带的相关具体数据的设计都应当和传送带相配合。所有的传送机械和相关的设备的设计能力应能够满足机器的满负荷运行。输送机是由各种必须的托辊，驱动装置，减速齿轮，联轴器，头部及尾部滚筒，张紧齿轮，皮带除尘器，防护装置，支撑架，盖板，头轮和尾轮的机罩，喂料和卸料管，侧边盖板，过道，栏杆扶手等组成。输送机设计的额定功率为1200tph，最大功率为额定功率的125%，机器设计的成产能力决定了以后的计算，皮带的宽度，皮带的速度，槽带，滚轮，皮带的材料和发动机等。b) 传送带传送带的选择应该和传送物料的相关性质相配合，皮带应当能够防火耐油。并且只能使用有边缘的皮带。制造商必须遵守最新修订的RMA或者同等级的国际标准。传送带的制造，封盖的厚度，安全系数等，建议使用皮带制造商所提供的数据。所有的连接处都应有切割的边缘并且经过硫化处理。皮带应在托辊和滚轮之间拉平。.为了防止腐蚀传送带，所有的连接处都应当光滑。被选用的传送带的在指定的设计能力下张紧力为允许的最大张紧力的80%。投标者应明确说明和原带相比结合板所要求的最小力。两个托辊组之间皮带的下垂度不应当超过两个托辊组之间距离的2%。c) 槽型回程托辊槽型托辊是由三段托辊首尾相连组成的，两端的托辊带有边缘翼。回行托辊应当能够向两端旋转。托辊的直径和长度应当遵循机器的功率，并应遵循适当的标准。在任何情况下，不管是前进方向还是回程方向，托辊的直径都不应当小于152mm。托辊间的排列，空隙，间距，轴端等，应当符合给定标准的要求。托辊应当防水，防尘，防潮湿。托辊的材料应为ERW钢管，板材厚度最低为4mm，并且应当安装在EN8或者等效的重型球轴承管状材料。轴应当伸长，使托辊向下拉，以构成钢铁支撑框架。所有的导轮在装配前都应当涂上油脂包装好，成为密封型号。应当采取轴承制造商的建议，选用滚子轴承或球形轴承，以达到国际标准化组织的推荐NO.R281推荐的最少50000小时。行程托辊和回程托辊的最小直径为30mm。所有导轮的零件，密封部分，润滑油和安装方法都应当符合轴承的额定寿命。传送带应当以箭头明确的标出进给方向和回程方向。物料的装载和传送，应当避免损坏传送带或者空载运行。由橡胶或者其他弹性材料制成的缓冲托辊，应当安装在传送机的装载点和传送点，防止冲击的部件应当用最少六个相互间隔最多为300mm的缓冲托辊组成，导轮在一个框架中支撑着，并当机器空载的时候，可以用类似的方法换掉。槽型传送托辊应当接近滑轮才能适当的支撑接近滚筒的负载皮带轮。传送托辊的设计应当具有可调整性，以适应槽型的边线。传送带长度和传送托辊数量的选择取决于张紧力，皮带的类型和尺寸等其他一些控制因素。d) 滚筒滚筒机构由一个低碳钢壳体焊接在固定的圆盘上。滚筒的通称直径和表面宽度应当遵行ISO1537的标准。应当尽力避免带的应力过大，直径的选择应遵循皮带制造商的建议。应特别注意的是设计带的应力集中点，例如滚筒的轮毂及与轮轮盘的接触面。如果在这些区域产生焊缝则应当用X射线检测故障。所有的滚筒硫化后排列在一起。滚筒的直径，外壳的厚度，硫化和轴的直径的选择应当符合FAP的要求，滚筒的偏心率不能超过其通称直径的5%。所有的滑轮都是静平衡的，为低碳钢，固定型，机械加工其表面和边缘。滚筒的表面和带接触的侧边，有延出的平板，来导向皮带的运动。带有侧边缘的滚筒，不应当用在多驱动系统的部分中，如带的反向弯曲和产生高应力的地方。传送滑轮轴的加工由EN-8钢铸造，平整或带肩的，并提供必要的加工键槽，或其他允许的制动装置。应根据电动机的功率设计传动轴，在屈服点处弯曲应力为扭转应力的四倍。这个数值是在有关设计标准和守则中最起码的的要求，在实际使用中，如果要求更高，则数值更高。尾部转向滚筒轴末端的最小拉力为T2 x3，安全系数比为4：1，这个数值是最起码的要求，根据有关设计标准，在实际中，要求越高，则这个数值越高。分离型轴承，轴承架，应优先使用实心型，这样有利于维修。每一个轴都要有一个定位和游隙的轴承。在驱动滚筒中，定位轴承应被安装在驱动轴的尾部。有自带轴承的滚筒不能使用。轴承座应当提供适当的油脂和和防尘迷宫油脂。e)张紧装置每个传输机都有张紧装置，以拉紧伸长变松的皮带，并提供必要的皮带张力。重物平衡张紧是采用张紧滑轮的首选。张紧滚筒应和尾部滚筒采用相同的直径。这些张紧装置应当尽可能有足够的运动，能够：（1）消除吸收带在工作中的弹性和伸长量。（2）提供足够的皮带，以使最少两个连接头硫化。（3）当带硫化时，调整任何带的初始松弛度。重锤式自动张紧装置应当拥有包括转向滚筒，张紧滚筒，重物砝码和其他各种的配件。垂直吊着的重物应当由一个有斜度的外壳保护着，以防止传送的堆积物刮到和溢出到上面。所有的张紧单元应当有一个合适的刻度用来观察皮带的伸长情况。有足够的空间做适当的维修保养，检查和维修，应有相配的楼梯，平台，扶手等。平台上能够安排清理堆积的物料。在皮带的改变，硫化过程中，保证对张紧滑轮和重物砝码的控制。所有的重力张紧装置应有具有弹性的安全链或者另外的可行装置，这样能够在如果皮带断裂时能够吸收落下的自重。在每个张紧装置的拉紧重物处应有带有门和锁的安全围栏，围栏的最低高度为2.5m。应规定，在工作中使张紧装置有足够的张紧力。在皮带启动后皮带驱动滚筒轮仍有足够的张紧力。在皮带发生伸长后应当能够显示皮带中张紧力的数值。各种的拉紧装置被集中在一处，可用一部小型移动式液压装置作为张紧装置。f)皮带清扫和滚筒清扫所有的传送设备都应拥有有效的清扫皮带传送带面的方法。设计的皮带清扫装置包含一个预刮片，尽可能得接近物料和皮带的分离处，刮片的正确位置在卸货滚筒的后面。由扁钢和橡胶支撑的V型犁式皮带清扫器应当在未运行之前安装好，如尾端滚筒，任何粘在回程皮带上的物料都有可能卡在皮带和滚轮之间。清扫装置包括各种必须的斜道来汇集和盛放被刮板刮下来的物料。g)倾斜角度传送机械的倾斜方向和倾斜角度的选择，应符合其规定的作用和物料的特性，以便与设计的经济效益相符合。h)驱动装置设计和制造的传送机械的驱动装置包括电动机和减速齿轮。驱动装置可以是单一电机或多电机式。串联的驱动不能在这里使用。驱动装置的主要组成部分应当尽量标准化。所有齿轮箱的额定工作情况为24小时/天连续运转。齿轮箱的输入功率应当小于电机铭牌上的额定功率。另外，计划出适当的资金来选择较好的齿轮箱，最好选用在工程实践中被推荐的品牌。在环境温度为40的情况下，减速齿轮的热量不应小于驱动电机的额定热量。不能使用带有冷却旋管的减速齿轮。用在电力传输上的可靠连接应当取决于其作用的要求。耦合的设计，应当在其休眠的情况下，不损耗其功率。齿轮联轴器应当提供对变速箱低速侧的传送带。该联轴器的功率不得小于驱动电机的额定功率。电机和变速箱之间为液力联轴器，总功率在40KW以上。不能使用带有冷却旋管液力联轴器。在任何情况下，电机和减速箱是被固定和排列好的，底座的支架被固定在刚性的机身上或者地面上。轴的排列应当遵循联轴器制造商的公差建议。驱动装置的支撑框架应被牢固的连接在传送装置上，用来支撑驱动皮带轮。驱动皮带轮轴和变速箱输出轴应当在制造商的建议公差下正确排列。电动液压制动装置应当安装在所有的传送机上，在紧急刹车后的自然停止状态，皮带仍能够往前运行，将皮带上剩余的物料转送到传送机之间的物料堆放管道。在刹车的地方应有电动液压制动器。他们应具备故障安全型或重量弹簧操作，并被安装在减速齿轮的减速侧。倾斜运输带，应装有一个合适的逆止装置，无论是电源故障或者正常运行的延迟情况下，能够防止皮带运行停在装载处的时候皮带的倒退。逆止装置应该是一个滚筒形状的装置，有逆止滚，钢臂，楔型盘，硬化钢制滚筒和自动对准平衡。当电力恢复或者延迟消失的时候，它应当瞬间无震动啮合释放。i)安全防护装置对于传送机械的紧急刹车，拉线手动重置型紧急开关应当提供整个皮带输送设备的应急。拉线应当安装在输送机械全长的走道上，开关之间的最大间隔为30m,并应提供拉线的变化显示。皮带摆动的限位开关应安装在间隔摆动处。皮带晃动的迹象应当在控制室里显示并传递在输送带全线，间隔带摆动开关为一对，每50米一对，每个传送机械应最少有2对。每个传送机械都有一个电子型零高速开关。它将安装在尾部滑轮，并会显示和停止皮带的运行当出现滑落和破损等后。j) 盖板在以下位置，上行带和下行带之间的硬性钢制盖板之间的最小厚度为3mm：装载点的下方和延长了一个最少相当于环形板的长度。高度较低的输送机，建筑物之间的输送机和附有图表的连续钢板等以上这些地方。盖板的设计应能防止皮带顶部钢绞线下物料的增大。并应当能够轻易拆除，整个装置易于清理。k) 遮雨板所有的输送机都应有防水和防尘的保护板。l) 过道输送机的两边都应有过道，过道的最小宽度为610m。接料点m)溜槽制造者设计的溜槽应充分考虑特定物质的性质。溜槽的设计形状和传送机的要素应根据实际符合要求，一般传送带详见于本规范第6.2.1组织和联系服从反复应力的变化应使用AISC手册的指南或者BS5400第10部分或相当于欧洲认可的标准。当设计成员和疲劳连接，考虑到在设计使用年限内设备有多少应力周期与应力范围和类型成员地点连接。机器的设计应最大限度的稳定在正常和可遇见的各种紧急情况的范围内，在可能的不稳定的情况下，警报装置应给予操作者应急方法。过道，平台和楼梯上应具备网格镀锌光栅。有斜面的过道，应花费比金属光栅更大的牵引力。通过楼梯来观察机器。附件：外文原文Mechanical Planta)Design Basis Troughed belt conveyors shall conform to the requirements of ISO 1537, BS 2890 or equivalent European/International standards. Wherever practical the line of the belt shall be a minimum of 1200mm above any walkway level and all pulleys shall have a minimum of 300mm clearance above platform level. The Contractor shall ensure that belt width, troughing angles and belt speeds are commensurate with the efficient carrying of the specified material, without spillage. Pulley diameters, idler spacings and belt feeding details shall be designed to minimise belt wear. All conveyors and their associated equipment shall be designed to be capable of starting when the conveyor belt is fully loaded. Conveyors shall be supplied complete with all necessary idlers, drives, reduction gears, couplings, head, tail and snub pulleys, take-up gear, belt cleaners, guards, stringers, stringer supports, decking plates, head and tail frames, feed and discharge chutes, skirt plates, gantries, walkways, handrailing etc. The rated capacity of the conveyor shall be1,200tph. The design capacity of the conveyor shall be 125% of the normal (rated) capacity ie, the design capacity shall be used for the calculation and selection of belt width, belt speed, drums and pulleys, belting and drives, etc.Conveyor beltingThe belts shall be chosen to suit the particular characteristics of the materials to be conveyed. The belts shall be moderately fire and oil retardant. Only belts with moulded edges shall be used.They shall conform to the latest revision of the Rubber Manufacturers Association (RMA) Cover Grade 2 or equivalent International Standard, wherever applicable.The belt construction, cover thickness, factor of safety etc, shall be that recommended by the belt manufacturer for the required duty.All joints shall be of the spliced type and vulcanised. The belts shall be stretched to remove the sag between idlers before vulcanising. The finish of the joints shall be such that they will not foul the belt scrapers.The belts shall be selected such that normal working tension at the specified design capacity does not exceed 80% of the maximum allowable working tension. The Tenderer shall clearly state the minimum strength requirement of the spliced joint in comparison to the original belt.The belt sag between idler sets shall not exceed 2% of the distance between the idler sets.Troughing and return idlersThe troughing idlers shall be of the 3 roll transom mounted type and shall be such that they can be turned end for end and can be used either as centre or wing idlers. The return idlers shall be capable of being turned end for end.The diameter and length of idlers shall be related to duty, and shall comply with the applicable standard. In no case, shall the diameter of the idler be less than 152mm for both carrying side and return side.The idler arrangements, clearance, spacing and shaft ends etc, shall conform to the requirement given in the appropriate standard.Idlers shall be water proof, dust proof and weather proof.Idlers shall be made from ERW steel tube. Wall thickness shall be minimum 4.0mm. The idlers shall be mounted on EN8 or equivalent material tubular spindles by means of heavy duty ball bearings. The spindles shall extend to allow the idlers to drop-in to fabricated steel support frames.All idlers shall be pre-packed with good quality grease before assembly and shall be of the sealed for life type.Ball or roller bearings shall be selected according to the bearing manufacturers recommendations to give a rated life of 50,000 hours minimum as defined by ISO Recommendations No.R281. Both carrying and return idlers shall have bearings of 30mm minimum diameter.All component parts of the idlers, seals, lubrication and method of mounting shall be compatible with the achievement of the full rated life of the bearings.The direction of travel of the belt shall be clearly marked by an arrow on both the carrying and return idler sets.Loading and transfer points, shall be designed to avoid damage to the conveyor belt or carrying idlers.Impact idlers, of rubber or other resilient material, shall be fitted at all conveyor loading and transfer points. An impact section shall consist of at least six impact idler sets spaced at a maximum pitch of 300mm. The idlers shall be supported in a frame and be interchangeable in a similar manner to that required for the normal carrying idlers.Transition type troughing idlers shall be used adjacent to all pulleys to permit proper support of the loaded belt near the pulleys without excessive stretch of the belt edges. The transition idlers shall be designed with adjustable concentrator (end) rolls, to suit the troughed belt contour between the last regular troughing idler and the adjacent pulley. The transition length and the number of the transition idlers shall be selected depending upon the tensions, type and size of belt, number of piles and other governing factors.PulleysThe pulley body shall comprise of a mild steel shell with welded on solid end discs.The nominal diameter and face width of the pulleys shall conform to ISO 1537. They shall be chosen so as not to overstress the belt. The diameters shall be selected in accordance with the recommendation of the belt manufacturer.Particular attention shall be given to the design of high stress concentration points such as hub and disc interfaces. If welds are used in these areas they shall be radiographically examined for faults.Suitable stiffening arrangements shall be provided in all pulleys. Selection of pulley diameter, shell thickness, stiffening and shaft diameter shall be subject to approval of FAP. The out of roundness shall not exceed 0.5 percent of nominal diameter of the pulley.All pulleys shall be statically balanced. They shall be of mild steel, solid end type, machined on faces and edges.Dependent upon the application, the pulley surface in contact with the belt may have a crowned profile where this will assist belt-tracking. Crowned pulleys should not be used on pulleys forming part of a multi-drive system where reverse bending of the belt at high stresses may occur.Conveyor pulley shafts shall be machined from EN-8 (or equivalent) forged steel, plain or shouldered and provided as necessary with machined keyways or other approved locking device.Drive shafts shall be designed for combined bending and twisting stresses incorporating a safety factor of 4 to 1 on the yield stress based on the motor power. This value is a minimum requirement should the relevant design standard or code, in use, require a higher then the higher value shall be applied.Tail end and bend pulley shafts shall be designed for a minimum pull of T2 x 3 (slack side tension) and a factor of safety of 4 to 1. This value is a minimum requirement should the relevant, design standard or code used require a higher value then this value shall be applied.Split type bearings, housings and plummer blocks shall be used in preference to the solid type in all locations where their use will facilitate maintenance.Each shaft shall be fitted with one locating and one non-locating bearing. On conveyor driving pulleys the locating bearing shall be fitted on the drive end of the shaft. Pulleys with integral bearings shall not be used.Bearing housings shall be provided with proper greasing arrangements and dust proof labyrinth grease seals.Take-up and tensioning gearEach conveyor shall be fitted with take-up and tensioning gear to compensate for any elongation of the belts and provide the necessary belt tension.Counterweighted take-up units of the vertical floating take-up pulley type are preferred. Take-up pulleys shall be of the same diameter as the tail pulley.These take-up units shall wherever possible have sufficient movement to allow them to:(i)Absorb the total elastic and permanent stretch of the belt during its working life.(ii)Provide sufficient belting to allow a minimum of two vulcanising repair joints to be made.(iii)Accommodate any initial slack belt present when the belt is vulcanised.Automatic take-up units of the gravity type shall be provided complete with bend pulleys, take-up pulleys, counter weights and all other accessories. Weights hanging vertically shall be protected with a sloping (self cleaning) cover to prevent the accumulation of conveyor scraping and spillage upon them. All take-up units shall have a suitable scale attached at a point which will allow monitoring of belt stretch. Adequate access for the proper maintenance, inspection and repair shall be allowed, with the provision of suitable staircases, platforming, hand rails etc. Arrangements for cleaning accumulated material from all platforms shall be provided.Provision shall be made to hold the take-up pulley complete with weights during belt changing, vulcanising etc.All gravity take-up units shall be provided with resiliently mounted safety chains or an alternative approved device capable of absorbing the shock from the falling deadweight unit in the event of a belt breakage.Safety fencing with a suitable gate and locking arrangement shall be provided around each gravity take-up. The fencing shall be a minimum of 2.5m high.Provision shall be made for sufficient tension to be applied at any take-up setting to allow the belt to stretch on start-up but still retain enough tension at the drive pulley. Indication shall be displayed of the amount of tension in the belt and provision made for easy retensioning of the belt after stretch has occurred. Hydraulic haul pumps may be used for tensioning. Where a number of take-ups are grouped in a single location such as on a mobile machine a single hydraulic pressurising unit may be used to serve more than one take-up.Automatic take-up units of the gravity type shall be provided complete with bend pulleys, take-up pulleys, counter weights and all other accessories. Weights hanging vertically shall be protected with a sloping (self cleaning) cover to prevent the accumulation of conveyor scraping and spillage upon them. All take-up units shall have a suitable scale attached at a point which will allow monitoring of belt stretch. Adequate access for the proper maintenance, inspection and repair shall be allowed, with the provision of suitable staircases, platforming, hand rails etc. Arrangements for cleaning accumulated material from all platforms shall be provided.Provision shall be made to hold the take-up pulley complete with weights during belt changing, vulcanising etc.All gravity take-up units shall be provided with resiliently mounted safety chains or an alternative approved device capable of absorbing the shock from the falling deadweight unit in the event of a belt breakage.Safety fencing with a suitable gate and locking arrangement shall be provided around each gravity take-up. The fencing shall be a minimum of 2.5m high.Provision shall be made for sufficient tension to be applied at any take-up setting to allow the belt to stretch on start-up but still retain enough tension at the drive pulley. Indication shall be displayed of the amount of tension in the belt and provision made for easy retensioning of the belt after stretch has occurred. Hydraulic haul pumps may be used for tensioning. Where a number of take-ups are grouped in a single location such as on a mobile machine a single hydraulic pressurising unit may be used to serve more than one take-up.Belt and pulley cleanersAll conveyors shall be provided with efficient means of cleaning the carrying side of the belt.The design of the belt cleaning system shall include a pre-scraper as close as possible to the point where the material naturally breaks away from the belt with the main cleaning being carried out using one or more scrapers in the normal position just after the belt has left the discharge pulley.V-plough type belt cleaners made of steel flats and rubber strips shall be fitted before any in-running nip, such as a tail pulley, where any material split onto the return belt could be trapped between the belt and pulley. The cleaning system shall include all necessary chutes to collect and contain the material removed by the scraper.Angle of inclinationWhere conveyors are inclined, the angle of inclination shall be selected to suit the specified conveyor duty and the characteristics of the material to be handled consistent with economy in layout and design. Driving gearThe driving gear of each conveyor shall include an electric motor and helical/bevel reduction gear of proven design and manufacturer.Drive units may be of a single or multi-motor type. Geared tandem drives shall not be used. Wherever possible the main components of the drives shall be standardised.All gear boxes shall be rated for 24 hour/day continuous duty. The input rating of the gear box shall not be less than the nameplate rating of the motor. In addition to the appropriate design allowances used when selecting gear boxes, the service factor as recommended and accepted as good engineering practice shall be considered. The thermal rating of each speed reduction gear at an ambient temperature of 40o shall not be less than the rating of its drive motor. Speed reduction gear with cooling coils are not acceptable.An approved type of coupling shall be used for power transmission depending upon duty requirements. The design of the coupling shall be such that it can take shock and misalignment without sacrificing its efficiency. Gear couplings shall be provided on the low speed side of the gearbox for all conveyors. The rating of couplings shall not be less than that of the drive motor.A traction type fluid coupling shall be included between the motor and the gearbox for all motors of 40kW and above.Cooling water coils for traction type couplings are not acceptable.In all cases, after the motor and gearbox are mounted and aligned, the assembly shall be dowelled onto a rigid machined and ground combination bedframe. The shafts shall be correctly aligned within the tolerances recommended by the coupling manufacturer.The support frame for the drive unit shall be rigidly connected to the conveyor structure supporting the drive pulley. The conveyor drive pulley shaft and the gearbox output shaft shall be correctly aligned within the tolerances recommenced by the manufacturer of the output coupling.Electro hydraulic brakes shall be fitted to any conveyor whose natural stopping time under emergency shutdown conditions exceeds that of the following conveyor by an amount that would lead to any build up of material in the transfer chute between the conveyors.Where brakes are fitted they shall be of the electro hydraulic type. They shall be of the fail safe type either weight or spring operated and shall be fitted at the high speed side of the reduction gear.Inclined conveyors shall be fitted with a suitable hold back device to prevent the belt running back when stopped in the loaded condition, due to either power failure or normal operational delays.Hold back devices shall be one of the roller type with hold back drum, steel side arms, wedge plate, hardened steel rollers and self aligning counter balance. It shall engage instantaneously without shock and shall be released instantly when power resumes or the delay is removed.Safety and protection equipmentFor the emergency stopping of conveyors, pull wire manually reset type emergency switches shall be provided which shall trip the entire conveying train of equipment.The pull wires shall be installed along all walkways for the entire length of the conveyor. Switches shall be spaced at maximum of 30m apart. Pull wire actuation indication shall be provided.Belt sway (misalignment) limit switches shall be installed at intervals to sense belt sway. Indication of belt sway shall be given in the control room and shall be used to trip the entire conveying train. The spacing of belt sway switches shall be one pair at 50m intervals and minimum of 2 pairs for each belt conveyor.Each conveyor shall be provided with an electronic type zero speed switch. This shall be mounted at the tail end pulley and shall indicate and stop the drive in event of belt slip or breakage etc.Decking platesA suitably stiffened steel decking plate of minimum thickness 3mm shall be provided between the upper and lower strands of the belt in the following locations:-Beneath their loading points and extending for a length at least equal to that of the skirt plates.-Low level conveyors, conveyors in buildings and enclosed galleries shall be fitted with continuous deck plates over these areas.The decking plate shall be designed to prevent material building up below the top strand of the belt. They shall be easily removable and the whole structure shall be easily cleaned.Weather coversAll conveyors shall be provided with water and dust proof covers.WalkwaysWalkways shall be provided on both sides. The walkways shall have a minimum width of 610mm.5.2.2Transfer pointsa)ChutesThe Tenderer shall ensure that the design of the chutes supplied takes full account of the specified material flow rates. The shape of the chute shall be the design of the belt conveyor elements of the machines shall as far as practical be compatible with the requirements for the general plant conveyors detailed in clause 6.2.1 of this specification.Members and connections subject to repeated stress variation shall be designed for fatigue using AISC manual or BS5400 Part 10 or equivalent European/International recognised standard. When designing members and connections for fatigue, consideration shall be given to the number of stress cycles expected during the design life of the equipment together with the stress range and the type and location of member or connection.The machine shall be designed for maximum stability under normal and all foreseeable emergency operating conditions, wherever possible warning devices shall be fitted to give the operator warning should the machine approach an unstable condition.Walkways, platforms and stair treads shall be of open mesh galvanised grating. Walkways on sloping surface shall be of expended metal grating for greater traction.Stairs shall be used for access.Automatic take-up units of the gravity type shall be provided complete with bend pulleys, take-up pulleys, counter weights and all other accessories. Weights hanging vertically shall be protected with a sloping (self cleaning) cover to prevent the accumulation of conveyor scraping and spillage upon them. All take-up units shall have a suitable scale attached at a point which will allow monitoring of belt stretch. Adequate access for the proper maintenance, inspection and repair shall be allowed, with the provision of suitable staircases, platforming, hand rails etc. Arrangements for cleaning accumulated material from all platforms shall be provided.Provision shall be made to hold the take-up pulley complete with weights during belt changing, vulcanising etc.All gravity take-up units shall be provided with resiliently mounted safety chains or an alternative approved device capable of absorbing the shock from the falling deadweight unit in the event of a belt breakage.Safety fencing with a suitable gate and locking arrangement shall be provided around each gravity take-up. The fencing shall be a minimum of 2.5m high.Provision shall be made for sufficient tension to be applied at any take-up setting to allow the belt to stretch on start-up but still retain enough tension at the drive pulley. Indication shall be displayed of the amount of tension in the belt and provision made for easy retensioning of the belt after stretch has occurred. Hydraulic haul pumps may be used for tensioning. Where a number of take-ups are grouped in a single location such as on a mobile machine a single hydraulic pressurising unit may be used to serve more than one take-up.Belt and pulley cleanersAll conveyors shall be provided with efficient means of cleaning the carrying side of the belt.The design of the belt cleaning system shall include a pre-scraper as close as possible to the point where the material naturally breaks away from the belt with the main cleaning being carried out using one or more scrapers in the normal position just after the belt has left the discharge pulley.V-plough type belt cleaners made of steel flats and rubber strips shall be fitted before any in-running nip, such as a tail pulley, where any material split onto the return belt could be trapped between the belt and pulley. The cleaning system shall include all necessary chutes to collect and contain the material removed by the scraper.Angle of inclinationWhere conveyors are inclined, the angle of inclination shall be selected to suit the specified conveyor duty and the characteristics of the material to be handled consistent with economy in layout and design. Driving gearThe driving gear of each conveyor shall include an electric motor and helical/bevel reduction gear of proven design and manufacturer.Drive units may be of a single or multi-motor type. Geared tandem drives shall not be used. Wherever possible the main components of the drives shall be standardised.All gear boxes shall be rated for 24 hour/day continuous duty. The input rating of the gear box shall not be less than the nameplate rating of the motor. In addition to the appropriate design allowances used when selecting gear boxes, the service factor as recommended and accepted as good engineering practice shall be considered. The thermal rating of each speed reduction gear at an ambient temperature of 40o shall not be less than the rating of its drive motor. Speed reduction gear with cooling coils are not acceptable.An approved type of coupling shall be used for power transmission depending upon duty requirements. The design of the coupling shall be such that it can take shock and misalignment without sacrificing its efficiency. Gear couplings shall be provided on the low speed side of the gearbox for all conveyors. The rating of couplings shall not be less than that of the drive motor.A traction type fluid coupling shall be included between the motor and the gearbox for all motors of 40kW and above.Cooling water coils for traction type couplings are not acceptable.In all cases, after the motor and gearbox are mounted and aligned, the assembly shall be dowelled onto a rigid machined and ground combination bedframe. The shafts shall be correctly aligned within the tolerances recommended by the coupling manufacturer.The support frame for the drive unit shall be rigidly connected to the conveyor structure supporting the drive pulley. The conveyor drive pulley shaft and the gearbox output shaft shall be correctly aligned within the tolerances recommenced by the manufacturer of the output coupling.Electro hydraulic brakes shall be fitted to any conveyor whose natural stopping time under emergency shutdown conditions exceeds that of the following conveyor by an amount that would lead to any build up of material in the transfer chute between the conveyors.Where brakes are fitted they shall be of the electro hydraulic type. They shall be of the fail safe type either weight or spring operated and shall be fitted at the high speed side of the reduction gear.Inclined conveyors shall be fitted with a suitable hold back device to prevent the belt running back when stopped in the loaded condition, due to either power failure or normal operational delays.Hold back devices shall be one