阀门执行机构的应用选型与安装维护

译文：
1、何为“执行机构”？ 对于执行机构最广泛的定义是：一种能提供直线或旋转运动的驱动装置，它利用某种驱动能源并在某种控制信号作用下工作。 执行机构使用液体、气体、电力或其它能源并通过电机、气缸或其它装置将其转化成驱动作用。基本的执行机构用于把阀门驱动至全开或全关的位置。用与控制阀的执行机构能够精确的使阀门走到任何位置。尽管大部分执行机构都是用于开关阀门，但是如今的执行机构的设计远远超出了简单的开关功能，它们包含了位置感应装置，力矩感应装置，电极保护装置，逻辑控制装置，数字通讯模块及PID控制模块等，而这些装置全部安装在一个紧凑的外壳内。 因为越来越多的工厂采用了自动化控制，人工操作被机械或自动化设备所替代，人们要求执行机构能够起到控制系统与阀门机械运动之间的界面作用，更要求执行机构增强工作安全性能和环境保护性能。在一些危险性的场合，自动化的执行机构装置能减少人员的伤害。某些特殊阀门要求在特殊情况下紧急打开或关闭，阀门执行机构能阻止危险进一步扩散同时将工厂损失减至最少。对一些高压大口径的阀门，所需的执行机构输出力矩非常大，这时所需执行机构必须提高机械效率并使用高输出的电机，这样平稳的操作大口径阀门。 2、阀门与自动化 为了成功的实现过程自动化，最重要的是要确保阀门自身能够满足过程及管道内介质的特殊要求。通常生产过程和工艺介质能够决定阀门的种类，阀芯的类型以及阀内件和阀门的结构和材料。 阀门选择好后接下来就要考虑自动化的要求即执行机构的选择。可以简单的按两种基本的阀门操作类型来考虑执行机构。 .旋转式阀门（单回转阀门） 这类阀门包括：旋塞阀、球阀、蝶阀以及风门或挡板。这类阀门需要已要求的力矩进行90度旋转操作的执行机构 2.多回转阀门 这类阀门可以是非旋转提升式阀杆或旋转非提升式杆，或者说是他们需要多转操作去驱动阀门到开或关的位置。这类阀门包括：直通阀（截止阀）、闸阀、刀闸阀等。作为一种选择，直线输出的气动或液动气缸或薄膜执行机构也开来驱动上述阀门。 目前共有四种类型的执行机构，它们能够使用不同的驱动能源，能够操作各种类型的阀门。 1.电动多回转式执行机构 电力驱动的多回转式执行机构是最常用、最可靠的执行机构类型之一。使用单相或三相电动机驱动齿轮或蜗轮蜗杆最后驱动阀杆螺母，阀杆螺母使阀杆产生运动使阀门打开或关闭。 多回转式电动执行机构可以快速驱动大尺寸阀门。为了保护阀门不受损坏，安装在在阀门行程的终点的限位开关会切断电机电源，同时当安全力矩被超过时，力矩感应装置也会切断电机电源，位置开关用于指示阀门的开关状态，安装离合器装置的手轮机构可在电源故障时手动操作阀门。 这种类型执行机构的主要优点是所有部件都安装在一个壳体内，在这个防水、防尘、防爆的外壳内集成了所有基本及先进的功能。主要缺点是，当电源故障时，阀门只能保持在原位，只有使用备用电源系统，阀门才能实现故障安全位置（故障开或故障关） 2.电动单回转式执行机构 这种执行机构类似于电动多回转执行机构，主要差别是执行机构最终输出的是1/4转记90度的运动。新一代电动单回转式执行机构结合了大部分多回转执行机构的复杂功能，例如：使用非进入式用户友好的操作界面实现参数设定与诊断功能。 单回转执行机构结构紧凑可以安装到小尺寸阀门上，通常输出力矩可达800公斤米，另外应为所需电源较小，它们可以安装电池来实现故障安全操作。 3.流体驱动多回转式或直线输出执行机构 这种类型执行机构经常用于操作直通阀（截止阀）和闸阀，它们使用气动或液动操作方式。结构简单，工作可靠，很容易实现故障安全操作模式。 通常情况下人们使用电动多回转执行机构来驱动闸阀和截止阀，只有在无电源时才考虑使用液动或气动执行机构。 4.流体驱动单回转式执行机构 气动、液动单回转执行机构非常通用，它们不需要电源并且结构简单，性能可靠。它们应用的领域非常广泛。通常输出从几公斤米到几万公斤米。它们使用气缸及传动装置将直线运动转换为直角输出，传动装置通常有：拨叉、齿轮齿条，杠杆。齿轮齿条在全行程范围内输出相同力矩，它们非常适用于小尺寸阀门，拨叉具有较高效率在行程起点具有高力矩输出非常适合于大口径阀门。气动执行机构一般安装电磁阀、定位器或位置开关等附件来实现对阀门的控制和监测。 这种类型执行机构很容易实现故障安全操作模式。 3、执行机构选择要素 选择一台合适的阀门执行机构类型和规格时必须考虑下列要素： 1.驱动能源 最常用的驱动能源是电源或流体源，如果选择电源为驱动能源，对于大尺寸阀门一般选用三相电源，对于小尺寸阀门可选用单相电源。一般电动执行机构可有多种电源类型供选择。有时也可选直流供电，此时可通过安装电池实现电源故障安全操作。 流体源种类很多，首先可以是不同的介质如：压缩空气、氮气、天然气、液压流体等，其次它们可以具备各种压力，第三执行机构具有各种尺寸以提供输出力活力矩。 2.阀门类型 当选择阀门用执行机构时，必须要知道阀门的种类，这样才可以选择正确的执行机构类型。有些阀门需要多回转驱动，有些需要单回转驱动，有些需要往复式驱动，它们影响了执行机构类型的选择。 通常多回转的气动执行机构比电动多回转执行机构价格要贵，但是往复式直行程输出的气动执行机构价格比电动多回转执行机构便宜。 3.力矩大小 对于90度回转的阀门如：球阀、碟阀、旋塞阀，最好通过阀门厂商获得相应阀门力矩大小，大部分阀门厂商是通过测试阀门在额定压力下阀门所需的操作力矩，他们将这一力矩提供给客户。对于多回转的阀门情况有所不同，这些阀门可分为：往复式（提升式）运动-阀杆不旋转、往复式运动-阀杆旋转、非往复式-阀杆旋转，必须测量阀杆的直径，阀杆连接螺纹尺寸已决定执行机构规格。 4.执行机构选型 一旦执行机构类型和阀门所需驱动力矩确定了，就可以使用执行机构厂商提供的数据表或选型软件进行选型。有时还需考虑阀门操作的速度和频率。 流体驱动的执行机构可调节行程速度，但是三相电源的电动执行机构只有固定的行程时间。 部分小规格的直流电动单回转执行机构可调节行程速度。 开关控制 自动控制阀最大的好处是可以远距离的操作阀门，这就意味着操作人员可以坐在控制室控制生产过程而不需要亲临现场去人工操作阀门的开和关。人们只需铺设一些管线连接控制室和执行机构，驱动能源通过管线直接激励电动或气动执行机构，通常用的4-20mA信号来反馈阀门的位置。 连续控制 如果执行机构被要求用于控制过程系统的液位、流量或压力等参数，这是要求执行机构频繁动作的工作，可以用4-20mA信号作为控制信号，然而这个信号可能会和过程一样频繁的改变。如果需要非常高频率动作的执行机构，只有选择特殊的能频繁启停的调节型执行机构。当一个过程中需要多台执行机构时，可以通过使用数字通讯系统将各个执行机构连接起来，这样可大大降低安装费用。数字通讯回路可以快速高效的传递指令和收集信息。目前有多种通讯方式如：FOUNDATIONFIELDBUS、PROFIBUS、DEVICENET、HART和专为阀门执行机构设计的PAKSCAN等。数字通讯系统不单单可以降低投资费用，它们还可以收集大量阀门信息，这些信息对于阀门的预测性维护程序非常有价值。 4、预测性维护 操作人员可以借助内置的数据存储器来记录阀门每次动作时力矩感应装置测得的数据，这些数据可以用来监测阀门运行的状态，可以提示阀门是否需要维修，也可以用这些数据来诊断阀门。 针对阀门可以诊断如下数据： 1.阀门密封或填料摩擦力 2.阀杆、阀门轴承的摩擦力矩 3.阀座摩擦力 4.阀门运行中的摩擦力 5.阀芯的所受的动态力 6.阀杆螺纹摩擦力 7.阀杆位置 上述大部分数据存在于所有种类的阀门，但着重点不同，例如：对于蝶阀，阀门运行中的摩擦力是可以忽略的，但对于旋塞阀这个力数值却很大。 不同的阀门具有不同的力矩运行曲线，例如：对于楔式闸饭，开启和关闭力矩都非常大，其它行程时只有填料摩擦力和螺纹摩擦力，关闭时，液体静压力作用在闸板上增加了阀座摩擦力，最终楔紧效应使力矩迅速增大直到关闭到位。所以根据力矩曲线的变化可以预测出将会发生的故障，可以对预测性维护提供有价值的信息。 智能变频控制 执行机构在工作过程中，由于电机的频繁启动，导致工作时额定频率的变化，通过智能变频控制可使频率达到额定值 例如：由于电阻或外力原因，电机启动速度变慢，导致执行机构行程控制的误差，运用智能变频控制，可以改变输入转速，从而使执行机构的工作更可靠和稳定。

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原文：
1, What is "executing agency"? The executing agency for the broadest definition is: one can provide linear or rotary movement of the drive unit, which uses some kind of drive energy and the role of certain control signals to work. Implementing agencies to use liquid, gas, electricity or other energy through the motor, cylinder or other device will convert it into a driving force. The basic implementing agencies used to drive the valve to fully open or fully closed position. And control valves with the implementing agency can go to any precise location of the valve. Although most of the implementing agencies are used to switch the valve, but the design of today's executive body far beyond a simple switching function, which contains the location of sensors, torque sensors, the electrode protection device, logic control devices, digital communication module and PID Top Entry Ball Valvescontrol module, etc., but all of these devices installed in a compact enclosure. Because more and more use of an automated factory control, manual operation has been replaced by machinery or automation equipment, it is requested that the Executive agencies can play a control system and valve interface between the role of mechanical movement, but also require implementing agencies to improve work safety performance and environmental performance. In some dangerous situations, automated devices can reduce the executing agency personnel injury. Some special valve requirements in exceptional circumstances of emergency open or closed, the valve can be the executing agency at the same time to prevent the further spread of dangerous plant damage to a minimum. For some large-diameter high-pressure valves, the required torque output of the executing agency is very large, then the necessary implementing agencies need to improve the mechanical efficiency and the use of high-output motor, so that smooth operation of large-diameter valves. 2, valves and automation In order to successfully realize the process automation, the most important thing is to ensure that the valve itself to meet the process and the special requirements of medium inside the tubes. Production processes and process media are usually able to determine the valve type, the type of spool valves and valves within the pieces of the structure and materials. Next, select the right valve is necessary to consider the following requirements for automating the choice of implementing agencies. Can be a simple operation of the valve according to two basic types to consider implementing agencies. . Rotary valve (single rotary valve) Such valves include: plug valves, ball valves, butterfly valves, and damper or baffle. Such valves have been required torque needed to conduct a 90-degree rotation of the implementing agencies 2. Multi-turn valves Such valves may be non-rotating valve stem or rotary hoist the non-upgrade-style bar, or say that they need to be transferred operations to drive the valve to open or closed position. Such valves include: straight-through valve (stop valve), gate valves, knife gate valve and so on. As an alternative, linear output pneumatic or hydraulic cylinder or film executive agencies to drive the valve open. There are currently four types of implementing agencies, they can use different drivers of energy, able to operate various types of valves. 1. Electric multi-turn actuator Power-driven rotary multi-executing agency is the most common and most reliable type of one of the implementing agencies. The use of single-phase or three-phase motor drives the final drive gear or the worm stem nut, stem nut so that there is movement to the valve stem to open or close. Multi-rotary actuator can quickly drive large-sized valves. In order to protect the valve from damage to the valve installed on the endpoint of the trip limit switch will cut off electrical power at the same time when the security of torque is exceeded, the torque sensor will cut off electrical power, position switch used to indicate the valve switch status, install handwheel clutch deviceFour-Way Ball Valves which could power failure manual valves. This type of executive body of the main advantage is that all components are installed in a shell inside, in this waterproof, dust-proof, explosion-proof shell and integrates all the basic and advanced features. The main drawback is that when the power fails, the valve can only remain in place, only the use of standby power systems, valves in order to achieve the fail-safe position (open or failure fault off) 2. Electric single rotary implementing agencies This electric multi-turn similar to the executing agency implementing agency, the main difference is the executive body the final output is 1 / 4 turn 90 degrees recorded movement. A new generation of rotary electric single executive body with most of the complexity of multi-turn the executing agency functions, such as: use of non-entry-style user-friendly interface to achieve parameter settings and diagnostic features. Rotary compact single executive body to small size of the valve can be installed, usually the output torque of up to 800 kg m, while the power required should be small, they can install the battery to achieve fail-safe operation. 3. Fluid-driven rotary or linear output over the implementing agencies Executing agency of this type often used for operations through valve (stop valve), and gate valves, which use pneumatic or hydraulic mode of operation. Simple structure, reliable operation, it is easy to implement fail-safe mode of operation. Usually people use electric multi-turn valve and the implementing agencies to drive the cut-off valve, and only in the absence of power supply before considering the use of hydraulic or pneumatic actuator. 4. Fluid-driven rotary single executive body Pneumatic, hydraulic single executive body rotation is very common, they do not need power supply, and simple structure, reliable performance. They use a wide range of areas. Usually the output from a few kilograms of rice to the tens of thousands of kilograms of rice. Cylinder and the gear they use the linear motion is converted to right-angle output, transmission devices typically include: fork, rack and pinion, lever. Rack and pinion in the whole trip within the same output torque, they are very suitable for small size valve, Fork in the itinerary with a high efficiency with high torque output from very suitable for large-diameter valves. Pneumatic actuator solenoid valve typical installation, location or the location of switches and other accessories to achieve the right of the valve control and monitoring. Executing agency of this type is very easy to achieve fail-safe mode of operation. 3, the executing agency selection factors Choose a suitable valve type and specifications of the implementing agencies must consider the following elements: 1. Driven energy The most common power supply or a fluid-driven energy source, if you select the power-driven energy, the valve is generally used for large-size three-phase power, for small size valve can choose single-phase power. General Electric implementing agencies may have a variety of power types available. Sometimes also an optional DC power supply, this time can be achieved by installing the battery power supply fail-safe operation. Are many kinds of fluid sources, first of all could be different media such as: compressed air, nitrogen, natural gas, hydraulic fluid, etc., then they can have a variety of pressures, the third executive body with a variety of sizes in order to provide the output power of the living moment. 2. Valve type When you choose the valve with the executing agencies, need to know the types of valves, so that we can choose the correct type of implementing agency. Some valves require multi-turn drive, some need a single rotary drive, some need to reciprocating drive, they affect the choice of the type of the implementing agencies. Usually multi-turn of the pneumatic actuator electric multi-turn than the more expensive the implementing agencies, but the straight reciprocating stroke of the pneumatic actuator output prices cheap electric multi-turn the executing agency. 3. Moment the size of For the 90-degree rotary valves such as: ball valve, butterfly valve, plug valves, preferably through the valve manufacturer to obtain the corresponding moment of the size of the valve, most valve manufacturers through the test valve at rated pressure valve needed operating torque, they will be available to customers in this moment. For the multi-turn valves situation is different, these valves can be divided into: reciprocating (Lift) Sports - stem does not rotate, reciprocating motion - stem rotation, non-reciprocating - stem rotation, required to measure the valve rod diameter, stem connecting thread size of the executing agency has decided to specifications. 4. Selection of the implementing agencies Once the executive body type and the required driving torque valve set, you can use the data provided by the executing agency vendor table or selection software selection. Sometimes need to take into account the speed and frequency of valve operation. Executive body of fluid-driven adjustable stroke rate, but the three-phase power supply of electric actuators that only a fixed traveling time. Part of the small size of the DC electric single-turn adjustable travel speed of the implementing agencies. Switch Control The greatest advantage of automatic control valves can be remote operation of valves, which means sit in the control room operator can control the production process without the need to visit the scene to manual operation of the valve on and off. Some people are just laying pipelines to connect the control room and executive bodies, driving the energy through pipelines directly inspired electric or pneumatic actuator, usually a 4-20mA signals to feedback from the valve position. Continuous control If the implementing Cast Steel Floating Ball Valvesagencies are required to process system used to control the liquid level, flow or pressure and other parameters, it is a frequent movements of the work of the implementing agencies, you can use 4-20mA signal as control signal, however, and process the signal may be as frequent change. If you need a very high-frequency action enforcement agency can only choose a special regulation of frequent start-stop-based executive body. When a process needs to more than one implementing agency, you can through the use of digital communications system will link the various implementing agencies, which can greatly reduce the installation costs. Digital communication loop can quickly and efficiently transfer instructions and information gathering. There are many means of communication, such as: FOUNDATIONFIELDBUS, PROFIBUS, DEVICENET, HART, and the executing agency for the design PAKSCAN valves, etc.. Digital communication system is not only can reduce investment costs, they can also collect a large number of valves of information, the information for predictive valve maintenance program is extremely valuable. 4, predictive maintenance The operator can make use of the built-in data memory to record the action when the valve torque sensing devices each time the measured data, which can be used to monitor the status of the valve operation, you can prompt the need for valve repair, you can also use these data to diagnose the valve. The valve can be diagnosed for the following data: 1. Valve seal or packing friction 2. Valve stem, valve bearing friction torque 3. Seat friction 4. Valve operation friction 5. Spool of the dynamic forces suffered 6. Stem thread friction 7. Stem position Most of these data exist in all types of valves, but with different emphasis, for example: for the butterfly valve, valve operation friction is negligible, but for plug valves are a great value of this force. Different valves have different torque curve of, for example: for wedge gate rice, opening and closing moments are very large, the other visit, only the packing friction and thread friction, is turned off, the liquid static pressure acting on the gate increase in seat friction, tight end wedge effect so that torque increases rapidly until it closed in place. Therefore, according to the changes in torque curve can predict the failure will occur, you can provide valuable predictive maintenance information. Intelligent Variable Frequency Control In the course of implementing agencies, due to frequent motor starts, leading to changes in the work of rated frequency, through the intelligent inverter control allows the frequency of rating For example: As the resistance or external reasons, the motor started slow, leading to stroke the control of the executing agency error, the use of intelligent inverter control, you can change the input speed, thus allowing the body work more reliable and stable.