How to use and maintain the hottest electric contr

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How to use and maintain the electric control valve

precautions for installation and use

for the newly designed and installed control system, in order to ensure the normal operation of the regulating valve during startup and the safe operation of the system, before the installation of the new valve, first check whether the nameplate mark on the valve is consistent with the design requirements. The following items shall also be commissioned. Basic error limit; Full stroke deviation; Return difference; Dead zone; Leakage amount (in case of strict requirements)

if the control valve in the original system is overhauled, in addition to verifying the above items, the sealing of the stuffing box and the connection of the old valve shall also be checked

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

(1) the control valve is a field instrument, and it is required that 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 at high temperature, waterproof and cooling measures shall be taken. Keep away from the vibration source or add anti vibration measures where there is a source

(2) generally, the regulating valve shall 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 shall be added to protect the valve

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

(4) before the installation of regulating valve, the pipeline shall be cleaned to remove dirt and welding slag. After installation, in order to ensure that no impurities remain in the valve body, the valve shall be cleaned again, that is, all valves shall be opened when the medium is introduced to prevent impurities from getting stuck. After using the hand wheel mechanism, it shall be restored to the original neutral position

(5) in order to enable the production process to continue in case of failure or maintenance of the regulating valve, the regulating valve shall be equipped with a bypass pipeline

at the same time, special attention shall 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. Explosion proof products shall be installed according to the requirements of code for installation of electrical equipment in explosive hazardous areas. If the field conductor is SBH type or other six core or eight core, the outer diameter is Φ Install cables with about 11.3mm rubber. During use and maintenance, it is strictly prohibited to power on and open the cover for maintenance and pry the flameproof 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) the reducer of the actuator shall be lubricated after disassembly and repair. Generally, the low-speed motor shall not be disassembled, cleaned and lubricated. After assembly, check whether the valve position is consistent with the valve position opening indication

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 addition to eliminating these faults at any time during the production process, 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 control 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 general faults and maintenance methods of the electric control valve

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 μ A (100 for type II μ A)。

Hangzhou clothing wholesale (3) input signal > 240 μ A (150 for type II μ A) When, 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) the 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 disconnected

c, diode D105 ~ d108 is faulty or damaged

d, the offset current is abnormal

e. AC winding is asymmetric

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

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 the electrolytic capacitors C110 and c111 are damaged

c. short circuit of AC exciting winding

d. there is damage or faulty soldering in diodes D105 ~ d108

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

① there is no input signal (the magnetic preamplifier 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

let some people who have technology but don't want to start a business ② have input signals and no trigger pulse at the output end. It may be that:

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

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

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

③ the output trigger pulse is abnormal. There are the following phenomena:

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

b. the outputs on both sides of the start trigger are normal. After working for a period of time, the output pulse gradually disappears. There may be a problem with the single junction tube

c, positive and negative pulses appear in the output, which may be diode D207 D208 is broken down or the diameter of faulty soldering is less than or equal to "our high-performance materials and all-round customer service can speed up the marketing speed of innovative small lightweight and decelerated vehicles by 120mm.

(3) after the above inspection and maintenance, the servo amplifier should work normally when the control circuit is free of fault. Otherwise, there are the following two cases:

① when there is no input signal, there is an output voltage (the voltage is close to 220VAC) It may be that:

a, SCR 1 and SCR 2 are damaged

b, capacitors C301 and C302 are broken down

② when there is an input signal, there is no output signal or the output voltage is low, it may be that:

a, diodes D301 ~ d308 are broken down

b. SCR 1 and SCR 2 are damaged

control valve

when 4 ~ 20mA signal is input, the valve rod of the control valve can move up and down freely with the signal change within the rated stroke. If it cannot operate normally, there may be the following faults:

① the handwheel feels abnormal

a, the feeling is too light, and the handwheel detent may fall off or break

b. feeling too heavy or unable to rotate. There is foreign matter stuck in the reducer; The valve core is stuck with the bushing or the valve seat; The valve rod is severely bent

② input 4 ~ 20mA signal, and the regulating valve does not act

a. the system wiring is incorrect

b. the motor split phase capacitor CD is damaged

c. motor wiring is open circuit

d, valve core falls off or valve rod breaks (at this time, the actuator acts)

③ input 4 ~ 20mA signal, and the regulating valve cannot complete the rated stroke

a. the position of differential transformer is not adjusted properly

b, some diodes d701 ~ d712 are damaged

c, triode bg701 is damaged

(4) other faults during field use

① valve vibrates and sounds

a. the sensitivity is adjusted too high and the actuator vibrates

b. the fluid pressure changes too much and the actuator is not pushing forward. Both sides plan to develop a series of measures to stimulate the domestic consumption of polymer materials in the field of highway construction

c. the regulating valve is selected to be large, and the valve often works at a small opening

d. the medium flow direction is consistent with the valve closing direction

e, other nearby sources, unstable support

f, valve element and bushing are severely worn

② the valve is slow

a. the medium is too viscous, with blockage or coking

b. the filler is aged and pressed too tightly

③ large leakage

a. the valve element or valve seat is corroded or worn

b, the valve seat is loose or the thread is corroded

c. there are foreign matters on the valve seat and valve element

d. the start point (electrically open) or end point (electrically closed) of the valve is not adjusted properly

④ leakage at the joint of packing and upper and lower valve covers

a. the packing gland is not compacted

b, PTFE packing is aging and deteriorated

c. valve rod is damaged

d. the fastening nut is loose

e. the sealing gasket is damaged

the correct use and maintenance of electric control valve can not only improve the reliability of process control, but also increase the service life of electric control valve, which has considerable economic benefits for energy saving and consumption reduction of enterprises

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