Features, use and maintenance of the hottest elect

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With the rapid development of China's industry, electric control valves are more and more widely used in metallurgy, petrochemical and other fields. Its stability, please re tension the tensioning wheel, and its reliability is becoming more and more important. Its working state will directly affect the automatic control process. This paper will elaborate on the use and maintenance of electric control valves

1 Notes on installation and use

for the newly designed and installed control system, in order to ensure that the regulating valve can work normally during startup and make the system operate safely, before installing the new valve, first check whether the nameplate mark on the valve is consistent with the design requirements. At the same time, the following items should also be debugged

basic error limit; Full stroke deviation; Return difference; Dead zone; Leakage volume (when the requirements are strict)

if the regulating valve in the original system is overhauled, in addition to verifying the above items, the sealing inspection of the stuffing box and joints of the old valve should also be carried out

in field use, many of the regulating valves are not caused by the quality of the regulating valve itself, but by improper installation and use of the regulating valve, such as improper installation environment, installation position and direction, or unclean pipelines. Therefore, the following aspects should be paid attention to when installing and using the electric control valve:

(1) the control valve is a field instrument, and the ambient temperature should be in the range of -25 ~ 60 ℃ and the relative humidity should be 95%. If it is installed in the open air or high temperature, waterproof and cooling measures should be taken. Keep away from the vibration source or add anti vibration measures where there is a source

(2) generally, the regulating valve should be installed vertically, and it can be tilted under special circumstances. If the tilt angle is large or the self weight of the valve is too large, the supporting parts should be added to protect the valve

(3) generally, the pipeline installing the regulating valve should not be too high from the ground or floor. When the pipeline height is greater than 2m, a platform should be set as far as possible to facilitate the operation of the handwheel and maintenance

(4) before the installation of the regulating valve, the pipeline should be cleaned to remove dirt and welding slag. After installation, in order to ensure that impurities do not remain in the valve body, the valve should also be cleaned again, that is, when the medium is introduced, all valves should be opened to prevent impurities from getting stuck. After using the handwheel mechanism, it should be restored to the original neutral position

(5) in order to make the production process continue in case of failure or maintenance of the regulating valve, the regulating valve should be added with a bypass pipeline

at the same time, special attention should be paid to whether the installation position of the regulating valve meets the requirements of the process

(6) the electrical part of the electric control valve shall be installed according to the construction requirements of relevant electrical equipment. If it is an explosion-proof product, it should be installed in accordance with the requirements of the code for installation of electrical equipment in explosive hazardous areas. For example, SBH type or other six core or eight core rubber cables with an outer diameter of about 11.3

mm are used as field conductors. During the use and maintenance, it is strictly forbidden to power on, open the cover for maintenance and pry the explosion-proof surface in explosive places. At the same time, do not knock or scratch the flameproof surface during disassembly and assembly, and return to the original flameproof required state after maintenance

(7) pay attention to oil lubrication after the disassembly and repair of the reducer of the actuator. Generally, do not disassemble, wash and add oil for the low-speed motor. After assembly, check whether the valve position is consistent with the valve position opening indication

2 common fault location and cause analysis

the working performance of the regulating valve will directly affect the working quality of the whole regulating system. Because the regulating valve is in direct contact with the regulated medium on site, the working environment is very bad, so it is easy to produce various faults. In the production process, in addition to eliminating these faults at any time, regular maintenance and regular overhaul must also be carried out. Especially for the regulating valve with particularly harsh service environment, more attention should be paid to maintenance and regular overhaul

different types of regulating valves have different faults and their causes. Taking the straight stroke electric control valve produced by Sichuan general instrument factory as an example, this paper explains the common faults and maintenance methods of the electric control valve co organized by Hebei Jintian Plastic Co., Ltd

2.1 servo amplifier

when the servo amplifier is in normal working state:

(1) when there is no input signal, there should be no output voltage

(2) open loop dead time current 160 a (100 a for type II)

(3) when the input signal is> 240 a (150 a for type II), the output load voltage is? 205~220V? AC。

(4) the output voltage is basically symmetrical

if the servo amplifier does not work normally, there may be the following conditions in each part:

(1) pre magnetic amplifier

① when there is no signal input, the output of the double beat magnetic amplifier can be adjusted to zero through potentiometer w101. If zero cannot be adjusted, it may be:

a, transformer w101 is desoldered or damaged

b, resistance R110, R111 and electrolytic capacitor C101, C102 are faulty or desoldered

c, diode D105 ~ d108 is faulty or damaged

d, the offset current is abnormal

e, the AC winding is asymmetric

② there is an input signal, but there is no output or the output is asymmetric, which may be:

a, the voltage at the secondary end of the AC winding current supplied by transformer B301 is asymmetric

b, the resistance values of resistors R110 and R111 change, and electrolytic capacitors C110 and c111 are damaged

c, short circuit of AC exciting winding

d, one tube in diodes D105 ~ d108 is damaged or soldered

(2) when the trigger has input, the trigger on one side should have pulse signal on the oscilloscope screen. If the polarity of the input signal is changed, the trigger on the other side has pulse signal. The number and amplitude of the two groups of trigger pulses should be basically the same. Otherwise, there are the following situations

① there is no input signal (the pre magnetic amplifier is in normal working state), and there is a trigger pulse at the output end, which may be:

a, the triode on the output side of the trigger pulse is damaged, or the C and e poles are soldered

b, the resistance values of r204, r205, r208 and r209 change

② there is an input signal, and there is no trigger pulse at the output end, which may be:

a, the triode and single junction tube on the side without output pulse are damaged

b, the primary or secondary circuit of the pulse transformer on the side without output pulse is open or short circuited

c, the diode (D207 or d208) on the side without output pulse is short circuited

③ abnormal output trigger pulse has the following phenomena:

a, when there is no signal, the two sets of triggers have pulse output, and after adding the signal, they are normal, which may be the faulty welding of electrolytic capacitor C202 or C203

b, the output of both sides of the trigger is normal. After working for a period of time, the output pulse gradually disappears, and there may be a problem with the single junction tube

c, positive and negative pulses appear in the output, which may be the breakdown or faulty soldering of diodes D207 and d208

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