【终稿全套】混凝土泵车回转机构及臂架油缸和回转台的设计【5张CAD图纸+文档】
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徐州工程学院毕业设计(论文)任务书 机电工程 学院 机械设计制造及自动化 专业设计(论文)题目 混凝土泵车回转机构、臂架油缸及回转台的设计 学 生 姓 名 聂海江 班 级 04机本(4) 起 止 日 期2008年2月25号2008年6月2号 指 导 教 师 仇文宁 教研室主任 李志 发任务书日期 2008 年 02月 25 日1.毕业设计的背景: 随着国民经济的快速发展,建筑结构的的大型化和复杂化对混凝土机械提出了越来越高的要求。具有众多优点和较高经济效益的混凝土泵车得到了普及和应用,混凝土泵车已成为当今建筑施工企业必不可少的专用设备。混凝土泵车的应用,将混凝土输送和浇注工序合二为一,节约了时间,节省了劳动力;同时完成水平和垂直输送,省去了起重环节,不需再设混凝土中间运转,保证了混凝土质量,同时与混凝土运输车相配合,实现了混凝土输送过程完全机械化大大提高了运输效率。2.毕业设计(论文)的内容和要求:本文首先介绍了混凝土泵车的结构和特点,重点对混凝土泵车的回转机构和回转液压部分及臂架油缸进行了设计;同时对回转头部件与油缸相连的部件进行了强度校核,并根据泵车零部件标准确定了回转头的主要尺寸及组成部件。回转机构采用液压马达驱动减速器带动回转支承进行旋转,回转头安装在回转支承上随着回转支承转动,从而带动臂架在回转平台上在0360范围内转动,臂架展开收拢及其混凝土浇注时定位均是由变幅油缸推(拉)动变幅机构的运动来实现的。本设计具体内容主要包括:1回转机构、回转液压部分的设计,回转支承装置的选型与计算。2回旋支承满足上车布料杆(含混凝土总量)的倾翻力矩的计算。3回转台的强度校核及臂架油缸设计系统方案可行,能满足泵车整体性能要求。本设计的主要特点是:机构简单,节省投资,控制方便。对目前国内的混凝土泵车的优化设计具有一定的参考价值。3.主要参考文献: 【1】张国忠.现代混凝土泵车及施工应用技术.北京:中国建材工业出版社,2004.【2】徐灏.机械设计手册.北京:机械工业出版社,1991【3】邱宣怀.机械设计.北京:高等教育出版社,2006.【4】李壮云.葛宜远.液压元件与系统.北京:机械工业出版社,2000【5】雷天觉.液压工程手册.北京:机械工业出版社,19904.毕业设计(论文)进度计划(以周为单位):起 止 日 期工 作 内 容备 注1-2 周3-4 周5-6 周7-8 周9-10 周11周12-14 周15周结合课题进行相关实地调研,明确设计原理与设计思想,查询相关文献,收集资料。综合分析与泵车有关的文献资料,提出总体的设计方案。主要完成泵车回转机构的设计计算。主要完成回转液压系统部分的设计计算。主要完成臂架液压油缸的设计计算与选型。完成回转台的选型与强度校核。绘制泵车回转机构及回转台主要装配及零件图。在综合设计的基础上,校核和改正设计的不完善之处,认真撰写毕业论文准备答辩。教研室审查意见: 室主任 年 月 日学院审查意见: 教学院长 年 月 日徐州工程学院毕业设计(论文)开题报告课 题 名 称: 混凝土泵车回转机构、臂架油缸及 回转台的设计 学 生 姓 名: 聂海江 学号:20040601436 指 导 教 师: 仇文宁 职称: 高级工程师 所 在 学 院: 机电工程学院 专 业 名 称: 机械设计制造及自动化 徐州工程学院2008 年 3 月 4 日说 明1根据徐州工程学院毕业设计(论文)管理规定,学生必须撰写毕业设计(论文)开题报告,由指导教师签署意见、教研室审查,学院教学院长批准后实施。2开题报告是毕业设计(论文)答辩委员会对学生答辩资格审查的依据材料之一。学生应当在毕业设计(论文)工作前期内完成,开题报告不合格者不得参加答辩。3毕业设计开题报告各项内容要实事求是,逐条认真填写。其中的文字表达要明确、严谨,语言通顺,外来语要同时用原文和中文表达。第一次出现缩写词,须注出全称。4本报告中,由学生本人撰写的对课题和研究工作的分析及描述,没有经过整理归纳,缺乏个人见解仅仅从网上下载材料拼凑而成的开题报告按不合格论。5. 课题类型填:工程设计类;理论研究类;应用(实验)研究类;软件设计类;其它。6、课题来源填:教师科研;社会生产实践;教学;其它课题名称混凝土泵车回转机构、臂架油缸及回转台的设计课题来源自拟课题类型工程设计选题的背景及意义随着国民经济的快速发展,建筑结构的的大型化和复杂化对混凝土机械提出了越来越高的要求。具有众多优点和较高经济效益的混凝土泵车得到了普及和应用,混凝土泵车已成为当今建筑施工企业必不可少的专用设备。混凝土泵车是在拖式混凝土输送泵的基础上发展起来的一种专用机械设备,混凝土泵车的应用,将混凝土输送和浇注工序合二为一,节约了时间,节省了劳动力;同时完成水平和垂直输送,省去了起重环节,不需再设混凝土中间运转,保证了混凝土质量。同时与混凝土运输车相配合,实现了混凝土输送过程完全机械化大大提高了运输效率。研究内容拟解决的主要问题研究内容:1. 通过对徐州混凝土机械厂的考察、调研,记录主要原始数据,以及其工作条件,对混凝土泵车、随车起重机等具体机械的比较,从而明确所要设计的泵车回转机构设计的思想及意义。2. 对所设计的泵车回转机构、回转液压部分、回转支承装置的选与计算进行较好的分析研究。3. 回转台的强度校核及臂架油缸设计系统方案可行,能满足泵车整体的性能要求。拟解决的主要问题:1 根据对具体机械制造厂的考察、调研,收集的主要原始数据,以及其工作条件,对于混凝土泵车的各种机构有感性的认识。2 对于混凝土泵车的回转支承装置、回转台等进行选型设计及验算。研究方法技术路线通过对混凝土泵车的实地考察,确定了其重要的数据及主要机构之后,首先进行回转支承装置的选型设计。然后进行回转液压部分的设计,同时所设计的系统安全可靠。然后进行臂架液压油缸及泵车回转台的选型计算。整体选型与计算结束后,接下来是对所选型号的泵车各设备的校核与修改,直至其满足要求为止。研究的总体安排和进度计划1-2周:结合课题进行相关实地调研,明确设计原理与设计思想,查询相关文献,收集资料。3-4周:综合分析与泵车有关的文献资料,提出总体的设计方案。5-6周:主要完成泵车回转机构的设计计算。7-8周:主要完成回转液压系统部分的设计计算。9-10周:主要完成臂架液压油缸的设计计算与选型。11周:完成回转台的选型与强度校核。12-14周:绘制泵车回转机构及回转台主要装配及零件图。15周:在综合设计的基础上,校核和改正设计的不完善之处,认真撰写毕业论文准备答辩。主要参考文献【1】张国忠.现代混凝土泵车及施工应用技术.北京:中国建材工业出版社,2004.【2】徐灏.机械设计手册.北京:机械工业出版社,1991.【3】紧固件设计手册编委会编.紧固件连接设计手册.北京:国防工业出版社,1990.【4】张展.减速器设计选用手册.上海:上海科学技术出版社,2002.【5】邱宣怀.机械设计.北京:高等教育出版社,2006.【6】刘忠.工程机械液压传动原理、故障诊断与排除.北京:机械工业出版社,2005.【7】李壮云.葛宜远.液压元件与系统.北京:机械工业出版社,2000.【8】朱宏涛.液压与气压传动.北京:清华大学出版社,2005.【9】杜国森.液压元件产品样本.北京:机械工业出版社,2000.【10】雷天觉.液压工程手册.北京:机械工业出版社,1990【11】何存兴.液压传动与气压传动.武汉: 华中科技大学出版社, 2000.【12】Charles.Wilson.Kinematics and Dynamics of MachineryJ.New York,2000, (6):120-132.指导教师意 见 指导教师签名: 年 月 日 教研室意见学院意见教研室主任签名:年 月 日 教学院长签名: 年 月 日徐州工程学院毕业设计(论文)摘要随着国民经济的快速发展,建筑结构的的大型化和复杂化对混凝土机械提出了越来越高的要求。具有众多优点和较高经济效益的混凝土泵车得到了普及和应用,混凝土泵车已成为当今建筑施工企业必不可少的专用设备。本文首先介绍了混凝土泵车的结构和特点,重点对混凝土泵车的回转机构和回转液压部分及臂架油缸进行了设计;同时对回转头部件与油缸相连的部件进行了强度校核,并根据泵车零部件标准确定了回转头的主要尺寸及组成部件。回转机构采用液压马达驱动减速器带动回转支承进行旋转,回转头安装在回转支承上随着回转支承转动,从而带动臂架在回转平台上在0360范围内转动,臂架展开收拢及其混凝土浇注时定位均是由变幅油缸推(拉)动变幅机构的运动来实现的。本设计的具体内容主要包括:1回转机构、回转液压部分的设计,回转支承装置的选型与计算。2回旋支承满足上车布料杆(含混凝土总量)的倾翻力矩的计算。3回转台的强度校核及臂架油缸设计系统方案可行,能满足泵车性能要求。本设计的主要特点是:机构简单,节省投资,控制方便。对目前国内的混凝土泵车的优化设计具有一定的参考价值。关键词:混凝土泵车;回转机构;回旋驱动部分;液压系统;臂架液压缸;回转台AbstractAs the rapid development of the national economy,incresing demands have been made by the large and complicated struction of the construction.Pump trucks with many advantages and economic benefits have been used widely and they have been the essential equipment during the contruction today. This paper firstly introduces the structur and features of the pump trucks with the most important of the design of the swing body and calculate the strength of the mechanical parts of the rotary and oil bank and make sure the main sizes and parts of the rotary head according the standard parts of the pump car. The-turn-around-organlitation,makes the decelation machine round by the liquid-press-machine,the rotary head which installed on rotary suface moves by it and makes the Arm turn around during 0360,the function of Arm machine is achieved by the moving of Oil Bank.The specific contents including:1. The specific of the Rotary and Rotarry hydraulic part,also the selection and calculation of the Rotarry support.2. The calculation of the rollover torqne of the Roundabout suport.3. The projct of thecalculation of rotarry base and the design of the oil urn is resonable and can meet the requirments.The main features of the design are:simle structure low investment convenient control.The design has some referent value to the domestic optinal design of pump trucks.Key word: Pumpcrete machine vehicle Swiveling mechanism Maneuver supporting Hydraulic system The tank of boom The turretII徐州工程学院毕业设计(论文)目 录1 绪论11.1 概述11.2 国内外混凝土泵车的发展概况11.3 混凝土泵车的选择与技术管理32 泵车的基本组成及主要技术参数确定52.1 混凝土泵车的基本组成与构造52.1.1 混凝土泵车基本组成52.1.2 混凝土泵车构造52.2 主要性能参数的确定63 混凝土泵车总体结构设计方案73.1 底盘系统设计与选型73.2 泵送系统设计73.3 臂架系统设计83.4 支腿油箱设计83.5 回转机构设计及回转台选型计算93.6 操纵控制系统设计104 回转机构设计114.1回转机构与回转支承装置简述114.2 回转支承装置的选择134.2.1 载荷的确定134.2.2 回转支承装置的受力分析134.2.3 回转支承装置的强度计算154.2.4 回转支承联接螺栓选型及强度校核164.3 回转驱动装置的传动分析174.3.1 回转阻力矩计算184.3.2 马达轴回转功率204.3.3 回转小齿轮设计204.4 减速器的选择234.4.1 明确选择所需技术要求234.4.2根据机械强度选规格234.4.3校核热功率234.4.4校核瞬时尖峰载荷234.4.5按机械设备总布局要求总体减速机型号235 泵车液压回转系统设计245.1 混凝土泵车液压系统简述245.2 电液比例换向阀在液压系统中的重要作用245.3 回转机构液压系统的设计255.4液压元件主要工作参数的计算与选择265.4.1 液压泵的选择计算265.4.2 液压马达的选择与计算275.4.3 液压控制阀的选择285.4.4 辅助装置的选择285.5 液压系统性能验算295.5.1 液压系统压力损失的验算295.5.2 液压系统总效率的验算305.5.3 液压系统发热温升的验算306 臂架液压油缸设计及回转台强度校核326.1 臂架液压缸的作用及结构326.1.1 液压缸的作用326.1.2液压缸的结构326.2 液压缸主要零件的材料及技术要求326.3 液压缸设计步骤336.4 液压缸主要零件的设计与计算336.4.1 缸筒计算336.4.2缸筒底部厚度计算346.4.3缸筒端部螺纹连接部分校核计算356.4.4 活塞杆及其部分计算356.4.5 最小导向长度的确定356.4.6 液压缸进、出油口尺寸的确定366.5 液压缸的强度校核366.5.1 缸筒壁厚校核366.5.2 活塞杆直径校核366.5.3 活塞杆的弯曲稳定性校核计算366.5.4 焊接缸筒的校核366.6 回转台的选型及强度校核376.6.1 回转台的主要结构376.6.2 回转台底板与回转支承联接螺栓处强度校核386.6.3 回转台油缸连接处的的强度校核39结论41致谢42参考文献43附录44英文原文44中文翻译59III徐州工程学院毕业设计(论文)1附录英文原文Talking About The Design of Hydraulic ConductorsEric SandgrenThis paper is account for uncertainty Mechanical Engineering, University of California, San Francisco, avialon 503 West Main Street, P .O. Box9625311.1 INTRODUCTIONIn a hydraulic system, the fluid flows through a distribution system consisting of conductors and fittings, which carry the fluid from the reservoir through operating components and back to the reservoir. Since power is transmitted throughout the system by means of these conducting lines (conductors and fittings used to connect system components), it follows that they must be properly designed in order for the total system to function properly.The choice of which type of conductor to use depends primarily on the systems operating pressures and flow rates. In addition, the selection depends on environmental conditions such as the type of fluid, operating temperatures, vibration, and whether or not there is relative motion between connected components.Conducting lines are available for handling work pressures up to 10,000 Pa or greater. In general, steel tubing provides greater plumbing flexibility and neater appearance and requires fewer fittings than piping. However, piping is less expensive than steel tubing. Plastic tubing is finding increased industrial usage because it is not costly and circuits can be very easily hooked up due to its flexibility. Flexible hoses are used primarily to connect components that experience relative motion. They are made from a large number of elastomeric (rubberlike) compounds and are capable of handling pressures exceeding 10,000 Pa.Stainless steel conductors and fittings are used if extremely corrosive environments are expected. However, they are very expensive and should be used only if necessary. Copper conductors should not be used in hydraulic systems because the copper promotes the oxidation of petroleum oils. Zinc, magnesium, and cadmium conductors should not be used either because they are rapidly corroded by water-glycol fluids. Galvanized conductors should also be avoided because the galvanized surface has a tendency to flake off into the hydraulic fluid. When using steel pipe or steel tubing, hydraulic fittings should be made of steel except for inlet, return, and drain lines, where malleable iron may be used.Conductors and fittings must be designed with human safety in mind. They must be strong enough not only to withstand the steady-state system pressures but also the instantaneous pressure spikes resulting from hydraulic shock. Whenever control valves are closed suddenly, this stops the fluid, which possesses large amounts of kinetic energy. This produces shock waves whose pressure levels can be two or four times the steady-state system design values. Pressure spikes can also be caused by sudden stopping or starting of heavy loads. These high-pressure pulses are taken into account by the application of an appropriate factor of safety.1.2 CONDUCTOR SIZING FOR FLOW-RATE REQUIREMENTSA conductor must have a large enough cross-sectional area to handle the flow-rate requirements without producing excessive fluid velocity. Whenever we speak of fluid velocity in a conductor such as a pipe, we are referring to the average velocity. The concept of average velocity is important since we know that the velocity profile is not constant. As shown in Chapter 5 the velocity is zero at the pipe wall and reaches a maximum value at the centerline of the pipe. The average velocity is defined as the volume flow rate divided by the pipe cross-sectional area:In other words, the average velocity is that velocity which when multiplied by the pipe area equals the volume flow rate. It is also understood that the term diameter by itself always means inside diameter and that the pipe area is that area that corresponds to the pipe inside diameter. The maximum recommended velocity for pump suction lines is 4 ft/s (1.2 m/s) in order to prevent excessively low suction pressures and resulting pump cavitation. The maximum recommended velocity for pressure lines is 20 ft/s (6.1 m/s) in order to prevent turbulent flow and the corresponding excessive head losses and elevated fluid temperatures. Note that these maximum recommended values are average velocities.EXAMPLE 1-1A pipe handles a flow rate of 30 gprn. Find the minimum inside diameter that will provide an average fluid velocity not to exceed 20 ft/s.Solution Rewrite Eq. (3-26), solving for D:EXAMPLE 1-2A pipe handles a flow rate of 0.002. Find the minimum inside diameter that will provide an average fluid velocity not to exceed 6.1 m/s.Solution Per Eq. 3-35) we solve for the minimum required pipe flow area:The minimum inside diameter can now be found, becauseSolving for D we have1.3 PRESSURE RATING OF CONDUCTORSA conductor must be strong enough to prevent bursting due to excessive tensile stress (called hoop stress) in the wall of the conductor under operating fluid pressure. The magnitude of this tensile stress, which must be sustained by the conductor material. we see the fluid pressure ( P ) acting normal to the inside surface of a circular pipe having a length (L). The pipe has outside diameter D0 , inside diameter Di, and wall thickness t. Because the fluid pressure acts normal to the pipes inside surface, a pressure force is created that attempts to separate one half of the pipe from the other half.Figure shows this pressure forcepushing downward on the bottom half of the pipe. To prevent the bottom half of the pipe from separating from the upper half, the upper half pulls upward with a total tensile force F. One-half of this force ( or F/2 ) acts on the cross-sectional area (tL) of each wall, as shown.Since the pressure force and the total tensile force must be equal in magnitude, we havewhere A is the projected area of the lower half-pipe curved-wall surface onto a horizontal plane. Thus, A equals the area of a rectangle of width Di and length L, as shown in Figure 4-1(b). Hence,The tensile stress in the pipe material equals the tensile force divided by the wall cross-sectional area withstanding the tensile force. This stress is called a tensile stress because the force (F) is a tensile force (pulls on the area over which it acts).Substituting variables we havewhere = Greek symbol (sigma) = tensile stress.As can be seen from Eq. the tensile stress increases as the fluid pressure increases and also as the pipe inside diameter increases. In addition, as expected, the tensile stress increases as the wall thickness decreases, and the length of the pipe does not have any effect on the tensile stress.Burst Pressure and Working PressureThe burst pressure (BP) is the fluid pressure that will cause the pipe to burst. This happens when the tensile stress () equals the tensile strength ( S ) of the pipe material. The tensile strength of a material equals the tensile stress at which the material ruptures. Notice that an axial scribe line is shown on the pipe outer wall surface in Fig. 4-1(a). This scribe line shows where the pipe would start to crack and thus rupture if the tensile stress reached the tensile strength of the pipe material. This rupture will occur when the fluid pressure (P) reaches BR Thus, from Eq. (4-2) the burst pressure isThe working pressure (WP) is the maximum safe operating fluid pressure and is defined as the burst pressure divided by an appropriate factor of safety (FS).A factor of safety ensures the integrity of the conductor by determining the maximum safe level of working pressure. Industry standards recommend the following factors of safety based on corresponding operating pressures:FS = 8 for pressures from 0 to 1000 PaFS = 6 for pressures from 1000 to 2500 PaFS = 4 for pressures above 2500 PaFor systems where severe pressure shocks are expected, a factor of safety of 10 is recommended.Conductor Sizing Based on Flow Rate and Pressure ConsiderationsThe proper size conductor for a given application is determined as follows:1. Calculate the minimum acceptable inside diameter (Di) based on flow-rate requirements.2. Select a standard-size conductor with an inside diameter equal to or greater than the value calculated based on flow-rate requirements.3. Determine the wall thickness (t) of the selected standard-size conductor using the following equation:4. Based on the conductor material and system operating pressure (P), determine the tensile strength (S) and factor of safety (FS).5. Calculate the burst pressure (BP) and working pressure (WP) using Eqs. (4-3) and (4-4).6. If the calculated working pressure is greater than the operating fluid pressure, the selected conductor is acceptable. If not, a different standard-size conductor with a greater wall thickness must be selected and evaluated. An acceptable conductor is one that meets the flow-rate requirement and has a working pressure equal to or greater than the system operating fluid pressure.The nomenclature and units for the parameters of Eqs. BP = burst pressure (Pa, MPa)Di = conductor inside diameter (in., m)D0 = conductor outside diameter (in., m)FS = factor of safety (dimensionless)P = system operating fluid pressure (Pa, MPa)S = tensile strength of conductor material (Pa, MPa)t = conductor wall thickness (in., m)WP = working pressure (Pa, MPa)= tensile stress (Pa, MPa)EXAMPLE 1-3A steel tubing has a 1.250-in, outside diameter and a 1.060-in, inside diameter. It is made of SAE 1010 dead soft cold-drawn steel having a tensile strength of 55.000 Pa. What would he the safe working pressure for this tube assuming a factor of safety of 8?Solution First, calculate the wall thickness of the tubing:Next, find the burst pressure for the tubing:Finally, calculate the working pressure at which the tube can safely operate:Use of Thick-Walled ConductorsEquations and apply only for thin-walled cylinders where the ratio Di / t is greater than 10. This is because in thick-walled cylinders (Di / t 10), the tensile stress is not uniform across the wall thickness of the tube as assumed in the derivation of Eq. (4-2). For thick-walled cylinders Eq. (4-6) must be used to take into account the nonuniform tensile stress,Thus, if a conductor being considered is not a thin-walled cylinder, the calculations must be done using Eq. (4-6). As would be expected, the use of Eq. (4-6) results in a smaller value of burst pressure and hence a smaller value of working pressure than that obtained from Eq. (4-3). This can be seen by comparing the two equations and noting the addition of the 1.2t term in the denominator of Eq. (4-6).Note that the steel tubing of Example 4-3 is a thin-walled cylinder because = 1.060 in./0.095 in. =11.2 10. Thus, the steel tubing of Example 4-3 can operate safely with a working pressure of 1230 Pa as calculated using a factor of safety of 8. Using Eq. (4-6) for this same tubing and factor of safety yieldsAs expected the working pressure of 1110 Pa calcu1ated using Eq. (4-6) is less than the 1230 Pa value calculated in Example 4-3 using Eq. (4-3).1.4 STEEL PIPESSize DesignationPipes and pipe fittings are classified by nominal size and schedule number, as illustrated in Fig. 4-2. The schedules provided are 40, 80, and 160, which are the ones most commonly used for hydraulic systems. Note that for each nominal size the outside diameter does not change. To increase wall thickness the next larger schedule number is used. Also observe that the nominal size is neither the outside nor the inside diameter. Instead, the nominal pipe size indicates the thread size for the mating connections. The pipe sizes given in Fig. 4-2 are in units of inches.Figure 4-3 shows the relative size of the cross sections for schedules 40, 80, and 160 pipes. As shown for a given nominal pipe size, the wall thickness increases as the schedule number increases.Thread Design Pipes have tapered threads, as opposed to tube and hose fittings, which have straight threads. As shown in Fig. 4-4, the joints are sealed by an interference fit between the male and female threads as the pipes are tightened. This causes one of the major problems in using pipe. When a joint is taken apart, the pipe must be tightened farther to reseal. This frequently requires replacing some of the pipe with slightly longer sections, although this problem has been overcome somewhat by using Teflon tape to reseal the pipe joins. Hydraulic pipe threads are the dry-seal type. They differ from standard pipe threads because they engage the roots and crests before the flanks. In this way, spiral clearance is avoided.Pipes can have only male threads, and they cannot be bent around obstacles. There are, of course, various required types of fittings to make end connections and change direction, as shown in Fig. 4-5. The large number of pipe fittings required in a hydraulic circuit presents many opportunities for leakage, especially as pressure increases. Threaded-type fittings are used in sizes up to in. in diameter. Where larger pipes are required, flanges are welded to the pipe, as illustrated in Fig. 4-6. As shown, flat gaskets or 0-rings are used to seal the flanged fittings.1.5 STEEL TUBINGSize DesignationSeamless steel tubing is the most widely used type of conductor for hydraulic systems as it provides significant advantages over pipes. The tubing can be bent into almost any shape, thereby reducing the number of required fittings. Tubing is easier to handle and can be reused without any sealing problems. For low-volume systems, tubing can handle the pressure and flow requirements with less bulk and weight. However, tubing and its fittings are more expensive. A tubing size designation always refers to the outside diameter. Available sizes include-in. increments from -in. outside diameter up to -in. outside diameter. For sizes from-in. to 1 in. the increments are -in. For sizes beyond 1 in., the increments are-in. Figure 4-7 shows some of the more common tube sizes (in units of inches) used in fluid power systems.SAE 1010 dead soft cold-drawn steel is the most widely used material for tubing. This material is easy to work with and has a tensile strength of 55,000 Pa. If greater strength is required, the tube can be made of AISI 4130 steel, which has a tensile strength of 75,000 Pa.Tube FittingsTubing is not sealed by threads but by special kinds of fittings, as illustrated in Fig. 4-8. Some of these fittings are known as compression fittings. They seal by metal-to-metal contact and may be either the flared or flareless type. Other fittings may use 0-rings for sealing purposes. The 370 flare fitting is the most widely used fitting for tubing that can be flared. The fittings shown in Fig. seal by squeezing the flared end of the tube against a seal as the compression nut is tightened. A sleeve inside the nut supports the tube to dampen vibrations. The standard 450 flare fitting is used for very high pressures. It is also made in an inverted design with male threads on the compression nut. When the hydraulic component has straight thread ports, straight thread 0-ring fittings can be used, as shown in Fig. 4-8(c). This type is ideal for high pressures since the seal gets tighter as pressure increases.Two assembly precautions when using flared fittings are:1.The compression nut needs to be placed on the tubing before flaring the tube.2. These fittings should not be over-tightened. Too great a torque damages the sealing surface and thus may cause leaks.For tubing that cant be flared, or if flaring is to be avoided, ferrule, 0-ring, or sleeve compression fittings can be used see Fig. 4-8(d), (e), (f). The O-ring fitting permits considerable variations in the length and squareness of the tube cut.Figure 4-9 shows a Swagelok tube fitting, which can contain any pressure up to the bursting strength of the tubing without leakage. This type of fitting can be repeatedly taken apart and reassembled and remain perfectly sealed against leakage. Assembly and disassembly can be done easily and quickly using standard tools. In the illustration, note that the tubing is supported ahead of the ferrules by the fitting body. Two ferrules grasp tightly around the tube with no damage to the tube wall. There is virtually no constriction of the inner wall, ensuring minimum flow restriction. Exhaustive tests have proven that the tubing will yield before a Swagelok tube fitting will leak. The secret of the Swagelok fitting is that all the action in the fitting moves along the tube axially instead of with a rotary motion. Since no torque is transmitted from the fitting to the tubing, there is no initial strain that might weaken the tubing. The double ferrule interaction overcomes variation in tube materials, wall thickness, and hardness.In Fig. 4-10 we see the 450 flare fitting. The flared-type fitting was developed before the compression type and for some time was the only type that could successfully seal against high pressures.Four additional types of tube fittings are depicted in Fig. 4-11: (a) union elbow, (b) union tee, (c) union, and (d) 45 male elbow. With fittings such as these, it is easy to install steel tubing as well as remove it for maintenance purposes.EXAMPLE 1-4Select the proper size steel tube for a flow rate of 30 gpm and an operating pressure of 1000 Pa. The maximum recommended velocity is 20 ft/s, and the tube material is SAE 1010 dead soft cold-drawn steel having a tensile strength of 55,000 Pa,Solution The minimum inside diameter based on the fluid velocity limitation of 20 ft/s is the same as that found in Example 4-1 (0.782 in.).From Fig. 4-7, the two smallest acceptable tube sizes based on flow-rate requirements are1-in. od , 0.049-in, wall thickness, 0.902-in. ID1-in. od , 0.065-in, wall thickness, 0,870-in. IDLets check the 0.049-in, wall thickness tube first since it provides the smaller velocity:This working pressure is not adequate, so lets next examine the 0.065-in, wall thickness tube:This result is acceptable, because the working pressure of 1030 Pa is greater than the system-operating pressure of 1000 Pa and10.1.6 PLASTIC TUBINGPlastic tubing has gained rapid acceptance in the fluid power industry because it is relatively inexpensive. Also, it can be readily bent to fit around obstacles, it is easy to handle, and it can be stored on reels. Another advantage is that it can be color-coded to represent different parts of the circuit because it is available in many colors. Since plastic tubing is flexible, it is less susceptible to vibration damage than steel tubing.Fittings for plastic tubing are almost identical to those designed for steel tubing. In fact many steel tube fittings can be used on plastic tubing, as is the case for the Swagelok fitting of Fig. 4-9. In another design, a sleeve is placed inside the tubing to give it resistance to crushing at the area of compression, as illustrated in Fig. 4-12. In this particular design (called the Poly-Flo Flareless Tube Fitting), the sleeve is fabricated onto the fitting so it cannot be accidentally left off.Plastic tubing is used universally in pneumatic systems because air pressures are low, normally less than 100 Pa. Of course, plastic tubing is compatible with most hydraulic fluids and hence is used in low-pressure hydraulic applications.Materials for plastic tubing include polyethylene, polyvinyl chloride, polypropylene, and nylon. Each material has special properties that are desirable for specific applications. Manufacturers catalogs should be consulted to determine which material should be used for a particular application.1.7 FLEXIBLE HOSESDesign and Size DesignationThe fourth major type of hydraulic conductor is the flexible hose, which is used when
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