Installation and maintenance adjustment and maintenance stone pneumatic actuator special fault handling two routines Fuhong Hubei Province Huangmailing Phosphorus Chemical Group Corporation nitrogen fertilizer plant. Cause analysis and treatment measures for the vibration of the control valve of Dawu 4328001 in Hubei 1.I asked the origin of the nitrogen fertilizer plant of Huangmailing Phosphorus Chemical Group Co., Ltd. 40 1 When the decarburization section of the new ammonia synthesis system is fully loaded, the gas flow is not about full load, and carbon The liquid is sent to the decarbonization tower to absorb the carbon oxides in the gas. The decarbonization tower liquid level is automatically controlled by the instrument. The pressure before the control valve is 265 cut, and the rear pressure is 0.49 river 3. Because the pneumatic diaphragm sleeve of the automatic control system is damaged by the falling edge, it cannot meet the production requirements. During the major overhaul in early 1999, the rated flow coefficient of the pneumatic diaphragm control valve using the idle spoon was 400. The flow characteristic was the line, and the rated flow coefficient of the original pneumatic diaphragm sleeve was 155, and the flow characteristic was logarithm. When the control valve is put into use, the vibration is large, especially when the ammonia system starts driving, and the lower gas flow is about. ! When a decarburization pump is turned on, the control valve vibrates greatly and has strong noise. The process pipe connected to the equipment is vibrated and the feedback rod connected to the valve positioner and the control valve is vibrated, so that the valve positioner cannot be reduced. The small vibrating body caused the control system to be unable to work normally, was forced to stop the operation, and switched to the manual control operation of the near-way valve to control the decarbonization tower liquid level, which brought serious reasons for the safety production to analyze the phenomenon from the vibration phenomenon. The author believes that the vibration is caused. There are three reasons. 3 External vibration source, that is, the inherent vibration of the equipment pipeline. 1 control valve is improperly selected, the control valve does not meet the design calculation and selection requirements, such as the spring stiffness difference flow characteristics are not suitable for the valve core and valve structure is not suitable for the valve diameter is too large in a small opening state, etc. 1. Especially control When the valve is opened at a small opening, there is a sudden change in flow velocity and pressure. It brings about the following effects on the service life of the control valve. 2 A sharp flow velocity changes, the slope will change, and the valve stability will exceed the control valve stiffness. Change, a total of production and strict, know the unbalanced force of the heart opening, the jump opens, the control valve can not be adjusted within this opening; 4 from the control valve structure, the two-seat valve has two Spool ball 1 Han University computer software major, now working in Huangmailing Phosphorus Chemical Group Corporation nitrogen fertilizer plant, Ren, workshop director, engaged in automation technology and computer applications, engineers, 5 papers. 508 milk thistle, 8 å©, the modification is basically the same as 81 hunger. Also need to delete, 131. After the modification of the contents of the lamp is completed, the application is completed and the original 3 is modified, and the effect of the positive, 1; private, the widening is changed, and the color of the target is enlarged. 3 in the original, the news, 1 module removed, saving space. The item in the magic operation mode is removed. The factory does not define the mode, and the other modes are enlarged for easy operation. The 60 input box input box is enlarged, and the household, 5, 0 clicks are set on fire. Each box is assigned to 038 with different color changes, and the effect is better. 4 The ending language is widely used. You can refer to the method of wooden text to pay for the position of 0, and the squat and foot wood are deleted and modified, and only the required parameters are retained. It is modified into the style that the operator likes, one is in the flow, the other is in the flow, and the stability is small at the small opening, which is easy to oscillate. Further, when the control of the linear flow rate characteristic is the same as the change in the relative opening degree, the relative change value of the flow rate small flow rate is large, and when the flow rate is large, the flow rate relative change value is small. Therefore, the linear flow characteristic control valve has poor regulation performance at a small opening degree. It often produces oscillations. Therefore, the linear flow characteristics control valve should not be used for small opening conditions, nor should it be used for large load changes. Fluid cavitation produces vibration. Carbon-propylene liquid absorption, carbon is a physical change, when the carbon-acrylic liquid is added in 265, the heart speed flows to control the menstrual valve core to reduce the pressure to 49. The carbon-propylene liquid produces flash cavitation. It is absorbed by the carbon-acrylic liquid. 3 treatment measures According to the above analysis, the author believes that the cause of the vibration of the control valve in the valve itself, but not in the equipment pipeline, decided to use the orifice plate to absorb part of the pressure drop. Reduce the throttle speed, overcome the valve vibration and the surface restriction orifice plate to change the frequency of the system, and avoid the resonance of the natural frequency of the control valve close to or equal to the natural frequency of the system. The specific method is to install a restrictor orifice plate in front of the control valve to reduce the pressure before the valve, so that the pressure difference between the front and the back of the control valve is reduced, the flow rate of the carbon-acrylic liquid is stabilized, the control valve is protected from cavitation, and the service life of the valve is prolonged. The restrictor orifice plate is considered to be calculated by reducing the front pressure by 49 cubits. such. The 2.651 carbon-propylene fluid from the decarbonization tower is depressurized by the restrictor orifice plate by 49 æ™·, after 3, it becomes 216 and then depressurized to 49 cubits through the control valve. After 3, the flash tank is removed, and the pressure difference between the valve and the valve is The 2.16 is reduced to 1.67 as 1. The current parameters of the current limiting orifice plate are calculated. The front and rear pressure of the orifice plate is selected. The orifice orifice plate is selected from the 7 orifice plate. The diameter of the single hole is calculated according to the number of openings of the mass concentration type 1 restrictor plate. Production is safe and stable for long-term operation. Two years later, the lower limit orifice plate was inspected and found that the restricted orifice plate was severely cavitation, but it could continue to be used for two years, which proved that cavitation did exist, and the previous analysis was correct. If the 7-hole restrictor orifice plate is made of stainless steel, it can greatly extend the service life. 2 The air distribution control system butterfly valve failure inspection and treatment 2 System composition The blow air gas heat recovery device requires that the blow air and air entering the combustion furnace be simultaneously added and cut at the same time. The control of the air volume of the blower gas waste heat recovery device of the plant is completed by a self-control instrument consisting of a manual operator, an electric valve positioner, a pneumatic membrane butterfly valve, etc. The instrument control principle is 1. 75 processing, after the current-limiting orifice plate is installed 12 system working principle The working principle of the system 4 When a gas generator is in the residual heat, the oil pressure control machine outputs 24 signals, and sends it to the relay box to reduce mutual interference. The gas generator in the Taiwanese furnace only installs relays. The relay works, the normally open contacts are closed, the manual operator is turned on, and the given output is 4 2, 1. Letter 1. The electric valve positioner converts the output 20 10013 gas signal to the pneumatic The butterfly valve works to complete the control of the air distribution. When there is no residual heat recovery signal, no air distribution is required, and the relay has no power supply. At this time, the normally closed contact is closed and the manual operator 658 is fixed to output 2, the signal is converted by the electric valve positioner to output 100, 3 signals, and the pneumatic butterfly valve is controlled. Closed to ensure that the air entering the furnace is cut off simultaneously with the blow air. 23 Fault phenomenon and inspection The pneumatic butterfly valve does not reset after the valve is closed in use. During the inspection, when the gas generator is in the waste heat recovery stage, the hydraulic control machine output 240 relay normally open contact closes the manual operator, enters the 8 input signal at this time, the electric valve positioner outputs 50 signal positioner input Does not correspond to the output, the pneumatic butterfly valve stops at the closed position, instead of closing the corresponding 17.5 position of 25. Check the pneumatic butterfly valve and disconnect the butterfly valve connecting rod from the crank. Remove the gas signal tube of the membrane head, the actuator will not reset when there is no gas signal, and the push rod can be moved by hand, which is very visual, thereby judging the actuator; shrinking, damaging, disassembling the actuator The membrane cover, remove the diaphragm and push rod, the spring has been broken into 3 sections, replace the spring of the same model, and then put the pneumatic butterfly valve grid into operation. After less than two months of use, the butterfly valve will not reset after being closed again. According to the previous experience, after the inspection, the compression spring has been broken into two sections, and the bakelite spring seat is also damaged and broken, and the same type of bakelite spring seat and compression spring are replaced. Reassemble the actuator to ensure that the length of the push rod and crank connection is the same, that is, the original stroke is unchanged. 2.4 Cause Analysis and Processing In order to avoid similar faults from happening again, find out the cause and completely eliminate the hidden troubles. With the signal generator, add 4, 2, 1 current signal at the input of the valve positioner, check the valve positioner and the pneumatic butterfly valve. When the 4 signal is added, the valve positioner outputs 40 kPa signal, the butterfly valve closes close to 20; when the 12 mA signal is added, the valve positioner outputs 85 kPa air signal, the butterfly valve closes at about 55; when the 20 signal is added, the valve positioner outputs 130 kPa. The signal obviously does not correspond to the input and output of the positioner. The butterfly valve closes more than 70 at about 95. From the inspection situation, the main reason for the butterfly valve spring damage is that the butterfly valve input gas signal is too large, close to the air source pressure, and the butterfly valve closes beyond the corner. 70 and the butterfly valve input gas signal is too large, which is caused by the valve positioner input and output do not correspond. After the valve positioner uses the zero time and the range change, the positioner output exceeds 100 mA corresponding to the input signal of 20 mA. The valve positioner and the pneumatic butterfly valve are adjusted again according to the requirements, so that the input signal of the positioner corresponds to the output signal. And adjust the butterfly valve stroke to ensure the input of 20,100kPa gas signal, the butterfly valve opening degree is not limited within the range of 0,70. In order to prevent it, two bolts 4, 25 are welded symmetrically on the inner wall of the valve body to ensure that the butterfly valve is closed and the spring is damaged. After the above treatment, the pneumatic butterfly valve no longer has a spring damage failure. 1 Ming Cidong. Control valve calculation and selection use 1. Chengdu Chengdu University of Science and Technology 2 Lu Demin, Zhang Zhenji, Huang Buyu. The first edition of the petrochemical automation control design manual. Beijing Chemical Industry Press, 1993.495306309. 3 Teng Yunshen. Install the restrictor plate to extend the life of the regulator. Chemical automation and 4 Cheng Fuhong. Air distribution control of the air-conditioning waste heat recovery device. Small nitrogen fertilizer, the length of the insulator connected to the 71st page should be shorter than the contact span of the sliding brush on the copper ring, and the junction of the 3 thermocouples and the copper ring divides the whole ring into 6 60 angles. Thus, when the kiln body rotates, there is always a measuring end of the thermocouple inserted under the material in the material. If at the position of 2, the sliding brush is in contact with the insulation, since the length of the insulation is shorter than the contact span of the sliding brush on the copper ring, the thermoelectricity measured by the following two thermocouples will be measured at this time. Potential average. The two thermocouples are now located on the tangent plane just to the point of symmetry. The thermoelectric potentials should be basically the same, and their average value should be their respective instantaneous measurements. Therefore, it can be said that the instantaneous temperature value of the material passing through the cut surface can be measured. This measurement is called transient temperature measurement. This output signal can be sent to the display and control unit for monitoring and control. The results of its measurement and control are ideal. If the length of the insulation is longer than the contact span of the sliding brush on the copper ring, then the sliding brush will all be output at the insulation and the measured temperature signal will be interrupted. This eliminates the need for a continuous temperature signal output. This signal can be displayed, but not as a control signal. The above is measured by using three thermocouples. It can be inferred that when the quantity is increased, the material rate of filling can be lower. The number of specific temperature measuring elements should be determined according to the actual diameter of the rotary kiln and the filling rate of the material. 4 Conclusion From the above analysis, we can know the purpose of process inspection and the characteristics of materials in the design process, so that we can choose the most ideal detection method to achieve the best purpose of the process.
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