Common causes of failures in various parts of electric control valves

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The last edit to this post was made by yuchenchf on 2017-3-16 at 15:28. Causes of common faults in electric control valves: The performance of electric control valves directly affects the quality of operation of the entire control system. Since control valves are in direct contact with the medium being regulated on-site and operate in extremely harsh conditions, they are prone to various failures. During the production process, in addition to promptly resolving these faults, regular maintenance and periodic inspections are also necessary. Especially for control valves used in particularly harsh environments, greater attention should be paid to maintenance and regular inspections. Different types of control valves have different faults and causes for those faults. Taking the straight-stroke electric control valve as an example, the common causes of failures in electric control valves are as follows: 1. Servo amplifier: When the servo amplifier is operating properly: (1) there should be no output voltage when there is no input signal. (2) Open-loop dead zone current ≤ 160 μA (100 μA for Type II). (3) When the input signal is >240μA (150μA for Type II), the output load voltage is 205–220VAC. (4) The output voltages are basically symmetric. 2. If the servo amplifier is not functioning properly, the following situations may occur in its various components: (1) Pre-amplifier: ① When there is no signal input, the output of the dual-pulse amplifier can be adjusted to zero using potentiometer W101. If zeroing is not possible, it may be due to: A. The transformer W101 being desoldered or damaged. B. Resistors R110 and R111, as well as electrolytic capacitors C101 and C102, are poorly soldered or have loose solder connections. C. Diodes D105～D108 are poorly soldered or damaged. D. The offset current is abnormal. E. Asymmetry of the alternating current winding. ②There is an input signal, but no output or an asymmetric output; this may be due to: A, an asymmetric voltage at the secondary side of transformer B301 that supplies current to the AC windings. B. The resistance values of resistors R110 and R111 have changed, and the electrolytic capacitors C110 and C111 are damaged. C. Short circuit in the AC excitation winding. D. One or more of the diodes D105–D108 are damaged or have poor soldering. (2) When there is an input to the flip-flops, a pulse signal should appear on the oscilloscope screen for one of the flip-flops; changing the polarity of the input signal will result in a pulse signal appearing on the other flip-flop. The number and amplitude of the trigger pulses in the two groups should be essentially the same. Everyone, please continue to add explanations for the incorrect or incomplete parts, so that those who read it next will learn more. What you know is exactly what everyone needs.