Suspending Type Air Cooler,Air Cooler Evaporative,Air Water Cooler,Air Separation Cooler TAIZHOU NANFENG COLD-CHAIN CO., LTD , https://www.windpolar.com
Key words: electric drive; mechanical electromagnetic; domestic intelligent transformation; feasibility 1 Introduction Electric drive is an important execution unit of the process control system, mainly to automatically control and adjust the opening and action of some equipment and devices. The electric drive is mainly composed of a motor, a deceleration part, a manual operation and a switching part, a position detection, a torque protection and the like, wherein the position detection and the torque protection part are the core parts of the electric drive.
The different standard electric drives used in the position detection and torque protection control sections can be divided into: mechanical electromagnetic control type, electronic control type, intelligent control type (with HART, FF protocol), and the like. Mechanical electromagnetically controlled electric drives are old-fashioned products. After decades of technological development, electric drives have been modified from the original mechanical electromagnetic to electronically controlled, and then upgraded to the now widely used intelligent control. At present, the imported drives used in long-distance natural gas pipelines in Sichuan and Chongqing have two types: mechanical electromagnetic and intelligent control.
2 Structural characteristics and use status of mechanical electromagnetic electric drive 2.1 Working principle and internal structure Mechanical electromagnetic electric drive drives the deceleration worm turbine to rotate through three-phase motor, which drives the valve spool to do 90° switching action or drive the valve stem up and down. Linear motion enables automatic control of the device. The mechanical electromagnetic electric drive receives the mechanical dry contact signal, and the internal control circuit uses the dry contact signal as the on/off signal of the circuit to realize the control of the start and stop of the motor. When the mechanical cam of the internal position detecting control mechanism of the drive hits the valve position limit switch, the control circuit is disconnected and the motor stops. When the valve has a super-torque condition, the torque spring of the torque detection control mechanism abuts the cam, the control loop is disconnected, the motor stops, and the torque protection is achieved [1].
2.1.1 Position Detection Control The mechanical electromagnetic type electric drive adopts the bearing and the transmission rod to drive the cam to hit the valve position limit switch to realize the positioning of the valve position. When the equipment is first commissioned, the drive needs to be disassembled to manually adjust the position of the valve positioning cam.
2.1.2 Torque detection control The torque is adjusted by adjusting the cam position (ie, the torque spring) to tighten and loosen the control circuit. The torque spring has an adjustable gear (one for each opening and closing) for adjustment. Cam position. For initial commissioning, the drive housing needs to be removed and manually adjusted to find the optimum cam position based on valve operation.
2.1.3 Control Interface The five status buttons of the on-site operation interface are closed and disconnected by the mechanical dry contact and the internal circuit to realize the switching of different control loops to achieve the purpose of selecting the operating state of the equipment.
2.2 Characteristics of mechanical electromagnetic electric drive The mechanical electromagnetic electric drive has the following four characteristics:
1 Torque detection: The torque value cannot be calculated, the torque transmission speed is delayed, and the adjustment accuracy is poor. As the use time increases, the spring is prone to fatigue fracture [2];
2 Position detection: There is no position sensor, the valve position has no resolution, it can only be set manually, and the position of the valve position during valve operation cannot be displayed in real time. The valve position pointer has only two states of 50% and 100%, that is, when the valve starts to move, the pointer immediately points to 50%, and then remains unchanged. When the valve is in position, the pointer immediately points to 100%. The pointer indicates that the valve position cannot be displayed truthfully, which may cause misjudgment of whether the valve is in place or not, which is not conducive to safe operation on site;
3 control loop: the internal control loop has no self-test function, can not promptly prompt the fault information, increasing the difficulty of troubleshooting [2];
4 Appearance aspect of the device: no LCD display, no user window, can not directly observe the running status of the device, and can not obtain fault information.
2.3 Using the current mechanical electromagnetic electric drive As the use time increases, the gears, cams and torque springs on the device position torque detection control mechanism will wear and fatigue due to repeated use, and the control interface state selection contact and internal control circuit are also It will gradually age, resulting in the current mechanical electromagnetic electric drive often has problems such as inaccurate positioning, broken torque spring, poor button contact, and inability to motor. Since foreign manufacturers of such electric drives have already stopped production, domestic manufacturers have little knowledge of them and cannot purchase professional accessories required for equipment maintenance. Once a fault occurs, it can only be temporarily and temporarily handled, and the problem cannot be solved fundamentally. To a certain extent, it also affects the safe production of the gas station.
3 Intelligent transformation of mechanical electromagnetic electric drive to solve the problems of aging, fault and maintenance difficulties of mechanical electromagnetic electric drive, improve equipment control precision and operational stability, without changing the original motor, gear box, reduction worm and On the basis of the transmission, the ROTORK mechanical electromagnetic electric drive is intelligently modified.
3.1 Technical transformation measures Considering the differences between the new and old drive control parts, the four characteristics of the mechanical electromagnetic electric drive are modified by targeted technical measures:
1 The spring-type torque control is transformed into the speed sensor and the motor current transformer for torque detection, which improves the accuracy of the torque detection control. Because the torque data is collected in the non-contact mode, the service life of the component is extended [3];
2 The cam type valve position control was modified to use the multi-turn absolute encoder for valve position detection. The imported electric drive adopts the Hall effect sensor for position detection. When the electric drive encounters strong magnetic interference (such as intelligent detection) or the power supply loses power for a long time, the Hall effect sensor fails, and the electric drive loses the valve position in the field. Magnetic interference may also cause the reed switch to cause abnormal valve switching. In response to this situation, a multi-turn absolute encoder based on the photoelectric conversion and grating principle is selected as the valve position detecting element. The component is immune to strong magnetic interference and power loss (low power consumption, 5 years of backup battery), and can maintain the valve position for a long time. During the transformation, the original cam and the travel switch gear mechanism are all removed, and the multi-turn encoder is fixed to the original pinion on the device, and then the AC contactor is matched;
3 Transform the internal control loop into a domestic integrated circuit board with circuit self-test function. When the circuit is faulty, it can prompt the fault information actively. 4 Add the LCD screen to the operation interface to display the switch position, torque value, alarm and fault code. And other information; the shell adds a window bar to facilitate viewing of the LCD screen information;
5 Connect the temperature protection switch line in the original motor to the new circuit board motor protection interface to maintain the protection of the original motor [4].
3.2 The transformation results were implemented on site and successfully realized the intelligent transformation of a ROTORK fault mechanical electromagnetic electric drive. After repeated on-site verification, the position feedback of the electric drive agrees well with the actual stroke position of the valve. The equipment is in good condition after the transformation, and the electric drive after the transformation has the following advantages:
1 By directly measuring the motor speed and motor current, the high-precision detection torque value is realized, and the torque protection is accurately reached 1%;
2 The multi-turn absolute encoder is used to measure and control the position of the valve position, and the position detection resolution reaches 0.1%;
3 All internal sensors are non-contact, extending service life and control accuracy;
4 The use of integrated circuit board control with self-checking function reduces the number of internal mechanical parts, improves the reliability of the equipment, and enhances the automatic judgment function of fault information, which is convenient for maintenance personnel to find fault areas;
5 Enhanced on-site operation interface, which is convenient for operators to operate and monitor equipment operation. In the initial commissioning, the parameters are set through the on-site operation interface and the self-contained remote control board. The debugging can be completed without disassembling the electric drive housing. It has non-intrusive features in hazardous places, which greatly shortens the debugging time and improves the equipment. reliability;
6 The performance parameters of the circuit board are stable, which is basically consistent with the imported electric drive circuit board;
7 Comparing the cost of the retrofit with the replacement of the new imported electric drive of the same model, it can be seen that the retrofit scheme has better economics.
4 Conclusions and recommendations 4.1 Conclusions Based on the structural principle analysis of mechanical electromagnetic electric drives, this paper draws on the advantages of intelligent electric drives, comprehensively considers the structural differences between old and new equipment, and controls the torque position detection mechanism of mechanical electromagnetic electric drives. The key parts such as the control loop and the user interface were modified by means of speed and motor current sensor, multi-turn absolute encoder and integrated circuit board, and successfully realized the domestic intelligent transformation of a mechanical electromagnetic electric drive. The technical feasibility and economic feasibility of the transformation provide technical ideas for reducing the dependence of the transmission and distribution station on the imported drive and improving the management level of the station equipment.
4.2 It is recommended that only one mechanical electromagnetic electric drive should be implemented with domestic intelligent transformation. The type and quantity of mechanical electromagnetic electric drive should be appropriately increased to further test the performance of the modified equipment and improve the function of the equipment.
references:
[1] E170C2.ROTORK Electric Actuator Installation and Maintenance Manual [S]. UK: ROTORK, 2002.
[2] ROTORK failure phenomenon analysis manual [S]. Chengdu: Chengdu Zhonghao Electromechanical Co., Ltd., 2012.
[3] ZTYPE. Intelligent Multi-turn Actuator User Manual [S]. Changzhou: Changzhou Guoli Valve Control Co., Ltd., 2014.
[4] GB/T28270-2012. Intelligent valve electric device [S]. Beijing: Biaoxin (Beijing) Technology Co., Ltd. 2012.
About the Author:
Li Jin (1982- ), male, Han nationality, Chengdu, Sichuan, senior engineer, mainly engaged in long-distance natural gas pipelines, production operation management and related technical research work.
Talking about the Domestic Intelligent Transformation of the Imported Mechanical Electromagnetic Valve Electric Drive
Abstract: Mechanical electromagnetic electric drives have been used in Sichuan and Chongqing for nearly 30 years, and faults have generally occurred. Due to the long history, foreign manufacturers have already stopped producing mechanical electromagnetic electric drives. Domestic manufacturers also lack corresponding understanding of the equipment, and the maintenance of equipment and the procurement of accessories are difficult. Based on the analysis of the structural principle of the mechanical electromagnetic electric drive, this paper adopts the speed sensor and the motor current sensor, and the multi-turn absolute, respectively, through the key position detection control part of the mechanical electromagnetic electric drive, the internal control loop and the user operation interface. The technical means such as encoder and integrated circuit board were transformed, and the domestic intelligent transformation of a mechanical electromagnetic electric drive was successfully realized, which confirmed the technical feasibility and economic feasibility of the transformation, and reduced the transmission and distribution station field in the future. The dependence of imported drives and the improvement of station equipment management level provide technical ideas.