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电动执行机构的可靠性及维护保养

2010-03-31 12:37:56 阅读8 评论0 字号:

译文:
电动执行机构可分为直行程和角行程两大类,它是自动控制系统中不可缺少的重要设备,其主要任务是将调节器送来的控制信号成比例地转换成直线位移或角位移去带动阀门、挡板等调节机构,以实现自动控制。因而广泛用于电力、冶金、石油、化工等工业部门的自动控制领域。 近10年来,由于广泛采用和吸收微计算机控制、微机械等新技术、新成果与成熟经验,电动执行机构得到迅速发展,现已广泛使用“微机+随动系统”结构模式的微机型电动执行机构,由微处理器完成信号传递、调节参数切换、状态指示、控制量的输出,以提高调节性能、使用及维护保养等方面的灵活性。 一电动执行机构的可靠性 电动执行机构的可靠性是指它在规定的条件下、规定时间内完成规定功能的能力。 “规定的条件”一般可概括为: (1)环境条件:指能影响电动执行机构性能的环境特性,如温度、湿度、气压、磁场、机械冲击、振动、粉尘等。 (2)动力条件:指能影响电动执行机构性能的动力特性。 (3)负载条件:指能影响电动执行机构性能的负载特性,如力矩、被控对象的类型与特性等。 (4)使用和维护条件:电动执行机构的可靠性只有在使用中得以实现,并在维护中得到提高,对于使用和维护条件而言,首先要注意的是完善的使用和维护保养;其次是必须要求操作者达到相应的技术水平。 “规定的条件”是电动执行机构可靠性定义中最重要而又最容易忽略的部分。不同条件下,其可靠性是绝然不同的,离开具体条件谈可靠性将毫无意义。而“规定的功能”是表征电动执行机构完成任务的各参量,如力矩、开/关及时间、行程、不动时间、死区等。 电动执行机构在寿命期内的可靠性变化规律是研究其可靠性的基础,取决于早期失效、随机失效及耗损失效。理论上常用可靠度(R)这一定量指标来表征设备的可靠性,它是指设备在规定条件和时间内完成规定功能的概率。为简便直观起见,电动执行机构行业在实际使用时,简单地用平均无故障时间(MTBF)来表征可靠性的特征量,并作为代表电动执行机构可靠性的性能指标。 电动执行机构的可靠性一般受下列主要因素的制约与影响:系统选择与设计、元件/组件适用性、动作参数、机械构造、制造技术、装配xx度、运行与维护人员能力、操作与维护程序、操作正确性、维护结果、现场装配与施工条件、备品性能的退化、运输及使用影响等。 为使电动执行机构具有众多功能与优异性能,常常不得不增加系统结构的复杂性,为保证这些功能与性能在使用时付诸实践,使得可靠性问题更为突出。由于电动执行机构直接控制着机组的运行过程,影响着机组及发电厂的安全与经济运行,因此研究、分析电动执行机构的可靠性十分重要且有意义。 二电动执行机构的故障分析 提高电动执行机构的可靠性,就要尽可能减少和xx故障,而事实上这种故障是多种多样的。有的是某一元件失灵引起的,有的是系统中元件/组件综合因素引起的,有的则是电气、二次回路以及外界因素引起的。有些故障通过调整的方法就可以解决,有的则是由于使用时间长、xx度差,需要修配、更换部件才能恢复其性能,也有些是因原始设计不周,需改进才能排除。 1.电动执行机构的故障特征 (1)调试阶段故障 新电动执行机构的故障问题比较复杂,其特征是设计、制造、安装及管理等质量问题交织在一起。常见故障有泄漏严重、速度难以调整稳定,脏物或油污使传动机构卡涩或动作失灵。某些组件漏装或装错弹簧、密封件,也有属于设计欠妥,元件选择不当,动作不平稳、定位xx度差等,对待这类故障,应耐心细致、慎重处理,逐一排除。 (2)运行初期和中期故障 调试后进入正常生产阶段的故障特征有:少数密封件由于装配质量和材料质量问题短期内损坏而漏油;原先粘附在管壁、孔壁上的毛刺、粘沙、杂质和脏物脱落导致某些元件工作不稳定。一般到运行中期,系统元件/组件处于{zj0}运行工作状态,故障率较低。 (3)运行后期故障 电动执行机构运行一段时间后,各类元件/组件因工作频率和负载条件的差异,各易损件先后磨损超标。这个阶段的故障特征是位置反馈接触不良、定位xx度差、稳定性下降、效率显著降低、故障率逐渐增加。这时应全面检查,更换失效部件,不应有凑合、对付想法,应科学、严格地下决心投资,予以全面修复,否则可能给运行人员带来很多麻烦,甚至严重影响机组的正常调节和控制。 2.偶发性、突发性故障 这类故障在时间上表现为偶然突变,故障区域及产生原因较为明显,由非人为和人为因素造成,如位置反馈器件接触不良、刹车片磨损及“抱死”、零部件损坏、线圈烧坏、密封件失效等。 三电动执行机构的维护保养 电动执行机构主要由电动机、轴承、齿轮传动系统和电子部分等组成。根据美国军标MIL-HDBK-338发表的可靠性数据表明,执行器故障主要集中在电动机和轴承方面,在电动机故障中:绕组失效占20%,轴承失效占45%,滑环、电刷、整流子损坏占5%,其他占30%;在轴承故障中:润滑剂变质、消失占45%,污染占30%,剥蚀占5%,误调占5%,腐蚀占5%,其他占10%。因此,良好的维护保养能补充电动执行机构的可靠性不足,提高其有效性。 1.加强润滑油的清洁度管理 电动执行机构{zd0}特点是需使用润滑油。其黏度随油温变化,黏度过低,涡轮蜗杆及齿轮等传动部件磨损会增大,传动xx度下降;黏度过高,动作不良。而润滑油脂清洁度管理更为困难,涡轮蜗杆及齿轮等传动部件磨损、老化产生的杂质与水分的渗入,内部涂层的脱落、锈蚀等都会影响润滑油清洁度。 2.及时xx润滑油脂泄漏 由于电动执行机构动作频率高、速度快,难以避免受冲击,这是导致润滑油脂泄漏的一个重要原因,一旦润滑油脂泄漏,需要及时加以解决。 3.改善工作环境和使用条件 可靠性和寿命与使用情况、所处环境条件、人员知识等因素有着直接关系。只有在维护管理上改善其工作环境与使用条件,才可能使之延长寿命。 4.故障初期特别要加强维护 在所有故障中,初期故障比例一般都较高。初期故障大多是由设计、制造、安装上的初步误差而引起。这些初期故障的发现需要花费一定功夫,解决也需要时间。因此,初期故障期间要特别加强维护管理。 5.做好数据管理以防偶发故障 偶发故障一般较难预测。为防止偶发故障,要定期检查和保养,掌握某阶段维护资料和历史档案数据,这对于准确实施故障判断和日常维护十分重要。 6.提高运行维护人员的专业知识 运行维护人员专业知识的掌握程度直接影响维护管理。近年来,由于结构变化,使得运行维护人员对电动执行机构的知识、技术水平有了较大提高,然而,仍有不少仍缺乏应有的专业知识和技术。对电动执行机构处于“似懂非懂”的状况,这也是维护管理薄弱的环节所在。 为使运行维护人员方便地进行现场维护管理,在进行电动执行机构系统设计时要有超前意识,要充分考虑到便于维护管理的实施,努力做到:系统要简化;标准化程度高、互换性好、容易修复;集成化、组合化;调整、检查方便;引入故障诊断和定位、容错/纠错等新技术。 四RK-Z系列智能电动执行机构介绍 1.装置概况 从国产电动执行机构使用情况分析,虽然在某些技术指标上与国外同类产品相媲美,但可靠性和稳定性问题却长期得不到根本性解决,其主要原因有:长期忽视基础技术的研究和开发;国产通用件和基础件质量不过关;企业对产品质量控制和管理不力。 针对上述问题,上海锐凯仪表有限公司花大力气开发了新一代RK-Z系列智能电动执行机构,较好解决了这些缺陷和不足。RK-Z系列智能电动执行机构系统构成见图1所示。它采用全封闭、一体化结构,配以单相永磁式交流同步电动机,体积小、重量轻、结构简单、传动惯量小、转矩大等特点。限位和刹车采用逐步逼近电子技术,实现了阀门“柔性全开”和“柔性全关”,取消了限位开关和刹车片,解决了长期以来困扰的限位开关易失灵、刹车片易“抱死”以及刹车时易产生大冲击电流烧坏电动机等老大难问题。为提高整机可靠性,采用了可靠性设计、可靠性试验、失效分析和严格的筛选、老化等工艺措施,并{zd0}限度地减少了可动部件,使整机MTBF值达到40000万小时以上。 2.控制软件 控制软件采用C语言,为提高程序的可靠性和可理解性,将程序设计成相对独立的子程序,有利于程序的移植和修改。控制软件主要功能是接收来自控制中心的指令或控制器上开、关键指令;接受阀门开度反馈信号,计算后输出控制信号;向控制中心反馈信息;实时显示阀门开度;故障报警、故障处理, 3.装置特点 (1)可接受0~10mA、4~20mA、0~5V、1~5V等多种模拟信号,输入信号的选择和正、反行程的切换以及上、下限的定位调整等,无需开盖,只需通过显示窗的触摸式按键,就可完成所有调试。 (2)具有多种控制方式:输入模拟量控制、无源开关量远程控制(内、外置24VDC,10mA)、有源(220V,10mA交流)开关量远程控制等。 (3)采用智能化技术控制过力矩和超限位保护,取消了需要进行复杂调整的机械式力矩开关和限位开关。 (4)可实现阀门全行程任意设定。 (5)频繁通断次数可达1200次/h。 (6)防护等级:IP66。 4.装置自诊断功能 (1)当输出轴位移到行程起始点(0%)或行程终点({bfb})时,电动执行机构会输出无源常开触点各一副,供控制系统选用。 (2)当电网电压骤降或停电时,执行机构内部控制电路会使执行机构停留在当前位置,并自动记忆此前瞬间的有关现场数据,一旦电压恢复正常,执行机构能自动恢复有关数据而继续正常工作。 (3)当机械部件发生故障卡涩,致使电动机超负荷时,其输出轴会维持在原来位置上,控制电路会切断电动机电源,并发出显示报警信号(但仍保持反向运动方式),同时输出无源常开触点一副。当故障排除后,自动进入正常工作。 (4)碰到自动化系统故障时,可根据工艺过程要求设定阀门的全开、关闭和保持原位3种状态,省略了系统的一些联锁保护措施,使运行更稳定。 (5)具有多“协议”通信功能:根据用户要求可设置RS-485等其他通信协议,通过接口,挂接到数据总线上,接收来自系统的指令、数据等,并协同工作。 五结束语 在自动控制系统中,选择高质量的电动执行机构,对“寿命周期费用”是很重要的,如果电动执行机构选择不当或质量不过关,再xx的控制思路、高超的控制策略也难以达到预想的控制效果。为此,生产、制造和选用高可靠性的产品日益受到过程控制界的重视。本文介绍的RK-Z系列智能电动执行机构目前已在杨树浦、崇明、南市、高桥、洛河、汇源等电厂以及冶金、化工等行业运行,其以人为本的设计思路、便利的维护调整方式,得到了现场技术人员的青睐。

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原文:
Electric actuator can be divided into two straight stroke and rotary type, which is not the lack of automatic control systems important equipment, whose main task is to control the signals sent regulator in proportion to convert the angular displacement to linear displacement Huo driven valves, baffles and other regulatory agencies, in order to achieve automatic control. Which is widely used in electric power, metallurgy, petroleum, chemical and other industrial sectors field of automatic control. Over the past 10 years, due to widespread adoption and absorption of micro-computer control, micro-mechanical and other new technologies, new achievements and experiences of, the rapid development of electric actuators are now widely used "computer + servo" mode microprocessor-based power structure of the implementation of institutions, from the microprocessor to complete signal transduction, regulation parameter switch, status indication, control the amount of output, to improve the regulation performance, use and maintenance aspects of flexibility. A reliability of electric actuators The reliability of electric actuators is it under the conditions, the provisions of functions within the stipulated time capacity. "Prescribed conditions" generally can be summarized as: (1) Environmental conditions: the implementing agencies that can affect the electrical properties of environmental characteristics, such as temperature, humidity, pressure, magnetic field, mechanical shock, vibration, dust and so on. (2) dynamic conditions: the implementing agencies that can affect the electrical properties of the dynamic characteristics. (3) load conditions: the implementing agencies that can affect the performance of electric load characteristics, such as torque, the plant type and characteristics. (4) the use and maintenance conditions: the reliability of electric actuators can be realized only in the use and maintenance have been improved, for the use and maintenance conditions, the first thing to note is to improve the use and maintenance; followed must require the operator to achieve the appropriate level of technology. "Prescribed condition" is the definition of actuator reliability of the most important and most easily neglected. Under different conditions, their reliability are radically different from the specific conditions on the reliability would be meaningless. The "required function" is characterized by electric actuator to complete each task parameters such as torque, on / off and time schedule, fixed time, dead zones. Actuator reliability of lifetime change in the law is the basis of its reliability depends on early failure, random failure and degradation failure. Reliability theory commonly used (R) The quantitative indicators to characterize the reliability of equipment, it refers to the equipment within the stipulated time of completion of the conditions and provisions of the probability function. Simple and intuitive for the sake of industry, electric actuators used in practice, simply use the average time to failure (MTBF) reliability features to characterize the amount and as a representative of the reliability of electric actuator performance. The reliability of electric actuators generally subject to the following major factors and the impact of: system selection and design, component / components of fitness, movement parameters, mechanical construction, manufacturing technology, precision assembly, operation and maintenance personnel capacity, operation and maintenance procedures, operation accuracy, maintain the results, on-site assembly and construction conditions, spare performance degradation, transport and use of effects. In order to actuator has many features and outstanding performance, and often have to increase the complexity of system structure, function and performance to ensure they put into practice when in use, so reliability is more prominent. As the electric actuator unit directly controls the operation of the process unit and power plant affecting the safety and economic operation, so the research, analysis of the reliability of electric actuators is very important and meaningful. Second, the failure of actuator Improve the reliability of electric actuators, it is necessary to minimize and eliminate the fault, and in fact this failure are varied. Some are caused by a component failure, some system components / components caused by a combination of factors, some of them are electric, the secondary circuit and external factors. Failure by adjusting the way some can be resolved, and some were due to long period of use, accuracy, complementary repair, replacement parts to restore its performance, but also some of the original design due to poor planning, needs to be improved to 排除. 1. Actuator fault feature (1) debugging phase fault The new actuator failure problem is rather complicated, characterized by the design, manufacture, installation and management of quality issues intertwined. Fault leakage serious, difficult to adjust the speed and stability, dirt or oil to make jam or action transmission failure. Some components missing or placed incorrectly installed spring, seals, there are design defects, improper component selection, action is not smooth, accurate positioning and poor, to treat such failure, be patient and meticulous, careful handling, one by one rule. (2) Run the early and mid-term failure After commissioning into the normal production phase fault features are: a small number of seal assembly quality and materials as quality short-term damage to oil spills; originally adhere to the wall, the wall of the burr hole, sticky sand, dirt off impurities and lead to job insecurity in some parts. The general to run the interim, the system components / components running at its best working condition, low failure rate. (3) failure to run late Electric Actuator running for some time, various components / components and load conditions due to frequency differences, all wearing parts have wear out. This stage is characterized by position feedback fault poor contact, poor positioning accuracy, stability, decrease efficiency significantly lower failure rate increased. At this time should be a comprehensive inspection, replacement of failed components, should not make do, deal with ideas, to be scientific, strictly determined to invest in, be fully repaired, or it may bring a lot of trouble to run the staff, or even seriously affect the normal regulation and control unit. 2. Incidental, sudden failure The performance of such failures in time for the occasional mutation, fault area and the cause is more obvious, from the non-human and human factors such as poor contact position feedback devices, brake pad wear and the "locking" parts damaged, coil burnout , seal failure and so on. 3 Maintenance of Electric Actuators Mainly by the electric actuator motor, bearings, gear drive system and electronic parts and other components. According to the U.S. military standard MIL-HDBK-338 reliability of published data show that the actuator failure mainly to the motor and bearings, the failure of the motor: 20% of winding failure, bearing failure, 45%, slip ring, brush, commutator damage to 5%, other 30%; in the bearing failure in: lubricant deterioration, disappearance of 45%, 30% pollution, erosion, 5%, 5% false transfer, corrosion, 5%, other 10 %. Therefore, good maintenance can add less than the reliability of electric actuators to improve their effectiveness. 1. Strengthen the management of lubricant cleanliness Actuator is required to use most features of oil. The viscosity changes with the oil temperature, viscosity is too low, turbine and other worm and gear wear will increase transmission parts, transmission accuracy down; viscosity is too high, adverse action. The grease cleanliness management more difficult, such as turbine worm and gear transmission parts wear, aging and water produced by the infiltration of impurities, internal coating of the loss, corrosion, etc. will affect the oil cleanliness. 2. In a timely manner to eliminate grease leakage As the frequency of actuator movement, fast, hard to avoid the impact, which is leading to the leakage of lubricating grease an important reason, once the lubricant leakage, need to be addressed in a timely manner. 3. To improve the working environment and conditions of use And use of reliability and life, in which environmental conditions, staff has a direct relationship between knowledge and other factors. Only in the maintenance management to improve their working environment and conditions of use before to make it live longer. 4. Failure to strengthen the maintenance of the initial special In all failures, are generally higher proportion of early failures. Most of the initial failure by the design, manufacture, installation caused the initial error. The discovery of these early failures take some effort to address the need of time. Therefore, during the initial failure to strengthen the maintenance management in particular. 5. Good data management to prevent the accidental failure Occasional failures generally difficult to predict. To prevent accidental failure to regular inspection and maintenance of master data and maintain a certain stage of historical archives data, accurate implementation of Trouble for the daily maintenance is very important. 6. Improve the operation and maintenance of professional knowledge Operation and maintenance of staff specialized knowledge levels directly affect the maintenance and management. In recent years, due to structural changes, making operation and maintenance personnel of the electric actuator of knowledge, technology has been greatly improved, however, there are still many still lack the expertise and technology. Of the electric actuator in a "half-comprehended" situation, and this is where the maintenance and management of weak links. To enable easy operation and maintenance personnel to conduct on-site maintenance and management, conducting electric actuator system design have advanced awareness and taking fully into account the implementation of easy maintenance, and strive to: The system should be simplified; high standardization, interchangeability good, easy to repair; integration, combination; adjustment, check the convenience; the introduction of fault diagnosis and location, fault / error correction and other new technologies. 4 RK-Z series intelligent electric actuator Introduction 1. Device Overview From the domestic use of electric actuators, although in some technical indicators are comparable with similar foreign products, but the long-term reliability and stability problems are not a fundamental solution, the two main reasons: a long-term neglect of basic technology research and development; made the basis of common parts and parts with low quality standards; business-to-poor quality control and management. In response to these problems, Kai Instrument Co., Ltd. Shanghai Rui great efforts to develop a new generation of RK-Z series intelligent electric actuator, a better address these shortcomings and deficiencies. RK-Z series intelligent electric actuator system structure shown in Figure 1. It is a fully enclosed, integrated structure, together with the single-phase permanent magnet AC synchronous motor, small size, light weight, simple structure, drive inertia is small, torque and so on. Limit and brake gradually approaching electronic technology, the valve "soft opening" and "soft fully closed" to remove the limit switch and the brake pads, to solve the chronic problem of limit switch failure prone, easy to brake "Locking" and the brake is easy to produce such a large impact on current burn motor chronic problem. To improve machine reliability, with reliability design, reliability testing, failure analysis and rigorous selection and aging process measures, and minimizes moving parts, so that machine to reach 400 million hours MTBF values above. 2. Control Software Control software using C language, to improve the reliability and intelligibility of the program, a program designed independent of the subroutine is conducive to the transplant procedure and modified. Main function is to control the software from the control center to receive instructions or controller to open the key command; accept the valve opening degree feedback signal, calculated output control signal; feedback to the control center; real-time display of the valve opening; failure alarm , fault handling, 3. Device characteristics (1) accept 0 ~ 10mA, 4 ~ 20mA, 0 ~ 5V, 1 ~ 5V and other analog signals, input signal selection, and positive and negative trip switch and the upper and lower limit position adjustment without opening the lid, only need to touch through the display window buttons, you can complete all the debugging. (2) with a variety of control modes: analog input control, passive remote volume control switch (internal, external 24VDC, 10mA), active (220V, 10mA AC) switch the remote control. (3) The control over torque and intelligent technology overrun bit protection, eliminating the need for complex mechanical adjustments torque switches and limit switches. (4) can be arbitrarily set to achieve full travel valve. (5) the number of frequent on-off up to 1,200 times / h. (6) Protection grade: IP66. 4. Device self-diagnosis function (1) When the output shaft displacement to travel starting point (0%) or stroke end point ({bfb}), the electric actuator will output passive normally open contact each one for control system selection. (2) When the grid voltage sag or power outage, the implementing agency executive body within the control circuit will remain at the current location, and automatic memory of the scene moments after the data, once the voltage is back to normal, the implementing agencies to automatically restore the data continues to work. (3) When the mechanical parts failure jam, resulting in motor overload, the output shaft will remain in the original position, the control circuit will turn off the power and send alarm signals (but still maintain the backward motion mode), while a passive normally open contact output. When troubleshooting, the work automatically. (4) met automation system failure, according to process requirements set valve fully open, close and maintain the in situ three kinds of states, omitted a number of interlocking protection system to run more stable. (5) has more "protocol" communication function: can be set according to user requirements, and other RS-485 communication protocol, through the interface, attached to the data bus to receive commands from the system, data, and work together. 5 Conclusion In the automatic control system, select high-quality electric actuator body right, "life cycle cost" is very important, if the electric actuator options, but inappropriate or Zhi Liang Guan, perfect for the control of ideas, superb in the control Celue also Nanyidadao expected control effect. To this end, production, manufacture and use highly reliable process control products have become an increasing emphasis on community. This article describes the RK-Z series intelligent electric actuators currently in Yangshupu, Chongming, Nanshi, Takahashi, Luo, Huiyuan and other power plants and metallurgical and chemical industries to run, its people-oriented design ideas, convenient way to maintain adjustment , received on-site technical staff of all ages.


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