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    Home > Active Ingredient News > Drugs Articles > Application and maintenance of dsc86 electric valve actuator in power plant

    Application and maintenance of dsc86 electric valve actuator in power plant

    • Last Update: 2017-11-28
    • Source: Internet
    • Author: User
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    The electronic electric actuator has the basic functions of stroke control, torque protection, manual and electric switching and manual operation, remote and local control, etc it can control the upper control equipment and system (regulator, PLC or DCS )The command signal of electric quantity is transformed into corresponding displacement to drive the final control part of Zui (such as control valve, baffle, etc.) to the required position of the system, and then adjust and control the flow, temperature, pressure and other process parameters to achieve the process control of the system At present, the electric actuator is widely used in large-scale thermal power plants in China, but there are many problems In this paper, the application and maintenance of the electric actuator in thermal power plants will be described from the following aspects At present, DKJ (zkj), DKZ (ZKZ) and other series of domestic electric actuators are widely used in thermal power plants below 300MW, and advanced integrated intelligent electric actuators are generally used in new units above 300MW, represented by rotorkiq series actuators DKJ (zkj), DKZ (ZKZ) and other series of domestic electric actuators have the advantages of simple structure, low price, easy maintenance, etc.; their disadvantages are mainly to realize control by hard wiring, self inspection is not allowed for faults, reliability of motor protection is not high, and faults are easy to occur In general, the intelligent electric actuator adopts the fully closed and integrated structure, and adopts the advanced microprocessor control such as single chip microcomputer to realize the intellectualization of the actuator It not only has a simple structure, but also has a low failure rate Even if there is a failure, it can be found by self inspection, and the error code can be displayed to the engineer, so as to solve the problem as soon as possible It has the advantages of intelligent control, high protection level, high control accuracy, light weight and good stability In addition, it also solves many problems of traditional electric actuator, such as the realization of flexible control of motor speed In view of the above advantages, more and more new thermal power plants adopt integrated intelligent actuators 2 In order to make the electric actuator have stable performance in use, the appropriate electric actuator must be selected The selection of electric actuator should pay attention to the following aspects: (1) select the appropriate brand according to the importance of actuator in the system If the actuator that plays an important role in the system process, such as the moving blade regulating control device of the forced draft fan, Zui chooses the recognized mature brand well, the mean time between failures (MTBF) must be greater than one maintenance cycle (2) Select the specific model according to the specific situation of the site Each brand of actuator has a detailed description of its model Users should carefully select the model according to their needs For example, determine whether to use switch type or adjustment type, angle stroke or straight stroke, with position feedback or without position feedback; determine the enclosure protection level and explosion-proof level according to the environmental conditions at the installation site The shell protection grade refers to the shell anti foreign matter and waterproof grade of the electric actuator, which is indicated by the letter IP followed by two digits, * digit represents the anti foreign matter grade by 1-6, and the second digit represents the waterproof grade by 1-8 The model or split type that can adapt to high temperature shall be selected for high temperature, and IP68 shall be selected for heavy dust or underwater It is very important to choose the model suitable for the environment Generally, this factor is easy to be ignored Zui can easily cause actuator failure or reduce the life of the actuator (3) According to the requirements of the valve, it is important to choose the appropriate torque When the electric actuator is applied in the thermal power plant, it is always found that the valve is stuck, but the locomotive inspection is not This is because the actuator torque selection is too small; sometimes the valve selection is too large, and the valve stem is always pulled out, which is due to the selection torque is too large Selecting the electric actuator with proper torque is good for protecting the motor and valve When selecting, there should be a considerable margin, which should be verified according to the specific situation In addition, the appropriate electrical parameters should be selected according to the number of actions per unit time when the valve is working The appropriate electric actuator model should be selected according to the voltage level used 3 Problems and solutions in application although the manufacturing process and control mode of electric actuator are very advanced, but due to the frequent action of electric actuator, there will be various failures such as aging of control components 3.1 common faults and solutions of DKJ (zkj), DKZ (ZKZ) and other domestic electric actuators are in 300MW units and 300MW units Many domestic electric actuators of the above series are used in the following thermal power generating units, which are characterized by simple structure, and the basic functions of the electric actuator are mainly realized by hardwiring The circuit uses hardwiring to connect some electronic components directly It protects the motor through the insurance, thermocouple and torque switch, and the switch circuit is realized by interlocking Switch single operation The main problems of this type of electric actuator are as follows: (1) poor sealing The connection port of this series of electric actuator is installed together with travel switch, torque switch, motor, etc The environment of thermal power plant is relatively poor Due to careless installation or long use time, the protective sleeve is damaged, which leads to rainwater and dust entering the terminal box, then flowing into the control switch and motor from the terminal box, causing short circuit or damage to the control switch If the connection cable inlet is higher than the cable outlet pipe, only the protective sleeve needs to be wrapped; if the connection cable inlet is lower than the cable outlet pipe, in addition to wrapping the protective sleeve, holes need to be made at the Zui low part of the cable protection sleeve to prevent the water from flowing down the outlet pipe into the actuator Our company once had the situation that the actuator was damaged because the protective sleeve at the cable outlet pipe was broken and rainwater was poured into the actuator; after the hole was made at the lower part of the protective sleeve Zui, this situation did not occur again Therefore, the maintenance personnel should check frequently, so as to find out the bad sealing situation as early as possible, and try to eliminate the fault in the bud (2) Circuit components aging the series of electric actuator, its circuit components are mainly mechanical action, thermal relay, travel switch, counter prone to failure Many electric actuators of our company are damaged due to the failure of thermal relay With the increase of operation time, the protection function of the torque protection switch is gradually lost In addition, the thermal relay is damaged, and the environment of the thermal power plant is poor The actuator installed on some pipelines is easy to jam, which results in a large output of the motor and damage of the motor When the maintenance personnel find that the motor fails due to overload, they must replace the thermocouple in time Our company has found several times that the newly replaced actuator is damaged soon after use The maintenance personnel found that this kind of situation is caused by the large torque set during commissioning and the loss of protection function of the thermal relay Therefore, for components, it is necessary to replace them in time if they are found to be aged or lose their functions (3) Due to the long running time and large vibration of the power plant, the control parts of the electric actuators of this series are connected by hardwired components Therefore, some control circuits are prone to loose wiring, which leads to the actuator's operation in good time and bad Therefore, it is necessary to tighten the wiring of control circuit and power circuit regularly, so as to eliminate the problem before it occurs as soon as possible 3.2 common faults and solutions of integrated intelligent electric actuator control principle and DKZ of integrated intelligent electric actuator The model is similar, but its implementation method is different, the protection function is more powerful, the online fault diagnosis ability is stronger, the control mode is more, and the fault rate is lower; but there are also some problems, including the problems of the equipment itself, the selection problem, and the problems of the equipment module failure, the aging of electronic components, the damage of vulnerable parts, etc (1) The control device crashed in a technical transformation of our company, we selected an imported brand split type electric device for the auxiliary air damper control actuator, the installation and commissioning were very smooth, but after the unit was started, many electric actuators could not operate, and the operation was normal after the power was cut off and the power was transmitted again After sales report is the problem of original model selection Because the temperature of the auxiliary air baffle of the boiler is sometimes higher than 60 ℃, the actuator control device crashes After changing the model, the previous crash problem has been basically solved Some intelligent electric devices have watchdog program After the electric actuator control device crashes, it can reset and restart automatically; while others don't, after discovering the crash, it needs to restart manually (2) After the signal is cut off, the electric actuator fails to act in the correct position The intelligent electric actuator is selected for the control device of the induced draft fan moving blade of a 600MW unit Due to the loose wiring of the command line, the electric device loses the control signal, resulting in the full closing of the induced draft fan moving blade and the great change of furnace pressure During the fault analysis, the engineer relearned the equipment manual and reconfigured the equipment as follows: when the electric device loses the signal, the actuator does not act The main reason for the above problems is that the field engineer did not fully understand the function of the new control device, and made a wrong configuration of the device, resulting in the device not acting correctly when losing the signal The integrated intelligent electric actuator has many functions Only when we use it reasonably can it bring convenience to our work Otherwise, it will bring a lot of troubles (3) This phenomenon occurs in intelligent electric actuator with large deviation between command and feedback, mainly because the feedback resistor element loses linearity due to wear, or the feedback drive part is loose, or the command amplification module has problems The maintenance engineer shall analyze according to the actual problems In a word, the troubleshooting of electric actuator should start from the phenomenon analysis, firmly grasp the basic principle, and use various scientific means for analysis and processing In addition, it is necessary to carry out preventive maintenance for the electric actuator to avoid the occurrence of equipment failure For the intelligent electric actuator, it is necessary to make full use of its functions, so as to find problems as early as possible and predict problems as early as possible.
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