Common faults analysis of marine electric regulating valve during operation

Control valve, including the actuator and valve 2 parts, is an important part of the process control system. Process control system consists of the control object, measuring transmission device, regulator and regulating valve. The role of regulating valve is to receive the control signal sent by the regulator to regulate the flow of media in the pipeline, in order to achieve process automation. If the measurement transmitter is the eye, the regulator (or other control device) is the brain, then the regulator is the hands and feet of the process automation. Regulating valve performance directly affects the reliable operation of the control system and adjust the quality. Control valve according to their energy can be divided into pneumatic, hydraulic and electric and other 3 categories. They have their own advantages and disadvantages and use occasions. Because of the electric valve does not need to increase the gas pump, no laying of pipe, easy commissioning, simple structure, etc., are widely used in marine power plant, but there are also some problems in operation. This article will discuss the operation of marine electric control valve for your colleagues for reference. 1 Marine Control Valve Introduction According to the needs of ship power plant control object, the control valve sleeve valve, gear selection Rotork IQ intelligent electric actuator. IQ intelligent electric actuator is based on multi-turn electric actuator, through the installation of microprocessors, peripheral chip circuits, running software, intelligent control of the transmission. This type of electric actuator adopts the infrared setter to set the actuator parameters to achieve without open-lid debugging; the valve position is obtained through the non-contact measuring system, the torque is obtained by measuring the motor current and the magnetic field, the valve parameters such as the valve position and the torque, Screen real-time display; can fault self-diagnosis, and the LCD screen gives the appropriate alarm signal. Electric actuator base includes flange and drive shaft 2 parts, the base is fully sealed and life-long lubrication. Electric actuators are connected to the valve via standard flanges. The electric actuator drive sleeve has a simple structure and is detachable. After machining the internal thread according to the size of the valve stem, it is assembled with the valve. Such control valve has the advantages of simple structure, less transmission parts, high reliability, easy maintenance and good automatic control performance. Electric actuator and valve assembly shown in Figure 1. 2 common faults in operation 2.1 can not be electrically operated 2.1.1 phenomenon The electric actuator control mode selector switch placed in the teleoperation position, the control valve on the console manually remote control and automatic control valve opening indicator Will not change; the electric actuator control mode selector switch placed in the local electric position, toggle the electric actuator local electric switch, the electric actuator does not move; However, the control mode selector switch is placed in hand Manipulation position, through the manual / electric switching handle and operating hand wheel, to achieve manual control valve. 2.1.2 Analysis 1) dry battery power loss. In the power of electricity, dry batteries for electric actuator data records and liquid crystal display valve position display. When the dry battery is out of power, if the power was cut off, then the electric power to the electric actuator will be prohibited after the power is supplied again. Must be replaced dry batteries, electric control valve can be restored. 2) lack of phase. When the required three-phase electric actuator electric power phase, the electric control valve can not be implemented. 3) The main control board failure. Local electric control valve, manual remote control and automatic control, are required by the main actuator of the electric actuator to achieve, so when the main control panel failure damage, the electric control valve will malfunction. 4) motor temperature protection trip. The motor of the electric actuator adopts the intermittent cycle working system which is started, that is, the S4 working system of the International Electrotechnical Commission IEC341. Motor with temperature protection, if the motor overheating, the temperature protection switch will trip, the electric actuator will stop the electric operation. After the motor temperature is lowered, the temperature protection switch will reset automatically, and the electric actuator can continue running. 2.1.3 Handling Suggestion 1) Replace the battery. Dry batteries recommended lithium batteries or long-life alkaline batteries. After the replacement of dry batteries, you need to set the electric control valve fully open, fully closed limit, in order to ensure the correctness of the control valve. 2) Open the electric actuator junction box, check the reason for the lack of phase, to confirm the external power supply is caused by the internal terminals off, and do the appropriate disposal. 3) Replace the main control board. After the replacement is completed, set the controller to re-set the electric valve opening torque, valve closing torque, fully open limit, full close limit, sensitivity and other control parameters. 4) check the operating torque through the LCD screen, if impurities in the pipeline remain in the valve, valve stem movement resistance and electric actuator output torque increases, coupled with long-term operation of the marine control valve, easily lead to motor temperature and The occurrence of protective trip; Another possible reason is that the ambient temperature control valve is too high. No matter what kind of reason, it is necessary to disconnect the regulating valve power, the motor cooling. 2.2 Card Valve 2.2.1 Phenomenon Electric actuator stops shortly after the electric motor, the more common situation is: the control valve can only be within a certain degree of opening within the electric operation, close to fully open or fully closed position, the electric actuator can not Continue to move, or only the opposite direction, or even the opposite direction can not move. However, the operation of the hand wheel to restore the original electric opening, the valve can still be opened within a certain range of electric operation. 2.2.2 Analysis of reasons 1) mechanical reasons. If there is electric actuator shaft and valve stem poor neutrality, the valve stem bending, stem seal packing too tight and so on, the electric actuator output set the maximum torque is still not enough to overcome the resistance, electric control valve that appears Card valve phenomenon. 2) impurities in the pipeline. When larger impurities in the pipeline remain in the valve, poor valve operation, can also lead to the electric control valve card valve. 3) On and off valve torque setting is not suitable. If the control valve opening and closing valve torque lower set point in the pipe when the fluid resistance is large, the valve will be a failure. 2.2.3 Processing Suggestions 1) Improve the parts processing, control valve assembly and shipyard installation quality. Regulating valve stem seal packing not only to ensure its sealing performance, but also should not be too tight. 2) Remove the impurities trapped in the valve. From the system point of view, to ensure clean pipeline. 3) According to the characteristics of different piping systems and each regulating valve, set the electric actuator to open and close the valve torque value. Electric actuators open, close the valve torque value can be 40% of the rated value to choose between arbitrary, and 1% increments. 2.3 Electric actuator idling, the valve does not move 2.3.1 The phenomenon Whether it is electric operation, or hand wheel operation, the electric actuator LCD screen and the control valve opening instructions can be changed, but the valve does not change the mechanical instructions , The valve control object parameters do not change. That is, the electric actuator runs in idling, the valve does not move. 2.3.2 Analysis of the causes The bearing components on the driving sleeve come off, resulting in the key slot on the driving sleeve being separated from the key on the hollow output shaft of the electric actuator, resulting in the electric actuator unable to drive the valve rod through the driving sleeve. 2.3.3 Handling Recommendations The design of the drive sleeve has a retaining ring and a retaining screw hole around it. There is a captive screw to prevent the bearing components from falling off. Due to the vibration of the piping system of the ship and other reasons, the looseness of the screw can cause the bearing components to fall off. The handling method is, the drive shaft sleeve removed, the screws will be tightened off. 2.4 oscillation 2.4.1 phenomenon When the electric control valve into automatic control, the electric actuator can not be stable at a certain degree of opening, always back and forth in the vicinity of an opening and closing action. 2.4.2 Analysis of the reasons set sensitivity is not reasonable. Can not increase the control accuracy, the sensitivity of the electric control valve is set to 10 or less. 2.4.3 Handling Recommendations Set the sensitivity of the electric control valve between 10 and 12 through the setter. This will not only ensure the accuracy of control, but will not make the valve oscillation phenomenon. 3 Conclusion In this paper, marine electric control valve in the operation of the common fault, for example, were analyzed for the reasons, and gives treatment recommendations. On the one hand, I hope the regulator valve users and users have some lessons and inspiration; the other hand, hope to play a role in throwing jade, hope you experts and colleagues, for marine control valve design and operation need to pay attention to Problems, essays, essay comments, a wide range of exchanges and discussions to enhance the design and application of the level of control valve, try to avoid or reduce the occurrence of the problem.