Valve fault analysis and solution
Hardware Processing Equipment(Metal Processing Machinery) can be divided into: Spinning Machine ; Curling Machine ; Shearing Machine ;Edge Cutting Machine; Rolling Machine .
Hardware Processing Equipment,Metal Processing Machinery,Spinning Machine,Curling Machine,Shearing Machine Dongguan Rener Automation Technologies Co.,Ltd , https://www.rener-automation.com
Valve fault analysis
1. On-site water supply control valve failure: 1 valve oscillation, tweet, performance is adjusted too high, the actuator is oscillating; pressure changes too much, lack of actuator thrust; control valve selection is too large, the valve often work in a small opening The valve plug and bushing wear badly. 2 The valve is dull, showing a blockage; the packing is aging and the packing pressure is too tight. 3 Large amount of leakage, valve core or valve seat is corroded and worn; valve seat is loose or the thread is corroded; foreign material 4 packing on valve seat and valve core and connection between upper and lower bonnets are leaking, showing that packing gland is not covered. Pressing; stem damaged; Loose nut loosened; seal broken.
2. Boiler electric water supply control valve product selection is poor, mainly in the 1 boiler water supply pressure gauge pointer kept swinging, water supply pressure and water level fluctuations 2 regulating valve stem keep moving up and down, resulting in serious wear of the valve stem 3 The long adjustment time makes the adjusting valve rod bend 4 electric actuators, and the motor is easy to burn.
3 boiler electric water supply control valve and the system does not match the degree, mainly in a high temperature of the feed water is generally 102-104 °C, so that the water supply to regulate the valve body temperature is higher, not conducive to motor cooling, easy to burn the electric control valve motor 2 The pressure difference between the two ends of the electric water supply regulating valve is large, the outlet pressure is determined by the steam pressure, the pressure difference between the two ends of the electric water supply regulating valve is large, and the output torque of the electric actuator motor is large, so the water supply regulating valve will not close at a low load to cause a water level. Unsteady 3 boiler drum liquid level control parameters time constant small load changes, the adjustment process is prone to system oscillations, in particular the use of three impulse regulator control, select three parameters, time constants are small, high precision control and short cycle If you do not take effective anti-jamming measures, the water supply control valve stem will frequently move up and down, causing friction, wear too fast, and there will be serious water leakage at the seal.
4. The boiler electric control valve uses a single-phase AC motor as the servo motor, and the single-phase AC motor has two weaknesses. 1 The single motor is a capacitor-phase split type starter. The starting torque is relatively small, with the function of speed control. 2 The starting current of a single motor is very large. Frequent operation of nearly 7 times of the rated current will cause the motor to be in a state of high current, causing the motor to be burned when the motor is hot.
Valve malfunctions need to be taken
1. The selection of the electric water supply regulating valve, according to the boiler production system process requirements, the flow regulating ratio of the water supply valve should be selected to be larger. Boiler feedwater valve has a large range of pressure difference, which can reach 1-3.82Mpa. When the load is small, the valve opening is small, the pressure difference is large, and the pressure difference is small when the normal operation flow rate is large. The operation of the regulating valve is more frequent, and the two operating time of the frequency conversion electric regulating valve can be set longer and the soft start time is set longer.
2. The installation of electric control valve 1 Requirements Ambient temperature should be in the range of -25-60 °C, relative humidity ≤ 95%, such as installed in open air high temperature occasions, should take waterproof, cooling measures 2 regulating valve should generally be installed vertically, special circumstances You can tilt it down. If the angle of inclination is large or the valve itself is too heavy, increase the support protection. 3 The pipeline for installing the regulating valve should not be too high from the ground or the floor. When the pipeline height is greater than 2m, the platform should be set to facilitate the operation of the handwheel and facilitate maintenance. 4 Before the installation of the regulating valve, the pipeline shall be cleaned to remove dirt and welding slag. After installation, in order to ensure that no impurities are left in the valve body, the valve shall be cleaned again 5 in order to make the regulating valve in case of failure or maintenance. The production process can be continued, and the bypass valve should be added to the regulating valve.
3. The use of intelligent controller to control, to achieve the optimization of the control process, reduce the number of motor start and stop reduce valve wear, mainly in the built-in intelligent control module is an adaptive multi-function controller, that is, the action process always with the control signal and The valve position feedback is biased adaptively to ensure that the highest control accuracy is achieved with the minimum number of start-stops and thus the control process is optimized. It is also possible to reduce valve wear due to a reduction in the number of start-stops. In addition, setting the interval between forward and reverse actions can effectively avoid unnecessary vibration caused by the interference signal to the valve.
4. The use of three-phase AC asynchronous motor, power, reliability. Strong intelligent variable frequency electric water supply regulating valve servo motor is changed from one-way reversible alternating current motor to three-phase alternating current motor. Because the three-phase alternating current motor has simple structure and strong reliability, the power in the same volume is nearly 3 times larger, so the intelligent frequency conversion water supply Electric control valve uses three-phase AC asynchronous motor output power to increase reliability.
5. The soft start can avoid the impact on the valve. The valve opening degree can be gradually adjusted at the low speed of the maximum torque, and the flexible current can be used to reduce the starting current. Even if the load changes very frequently, the number of times of starting is not high. Will burn the motor. When approaching the set or limit position, the inverter starts to adjust the frequency and voltage of the motor supply, reduces the motor speed, and slowly reaches the position at the lowest speed, avoiding the electric brake function caused by excessive inertial valve overshoot and collision. So that the actuator output torque will never exceed the previously set off torque.
6. Improve the linear characteristics of the valve, use more simple valves, complete the complex control. According to the characteristics of the valve, the built-in intelligent control module automatically adjusts the running speed of the full stroke, divides the full stroke running time into 10 steps, and each file runs at a different speed. The parameter setting is used to complete the setting. At the same time, it also has the ability to improve the flow characteristics of the valve. The built-in intelligent control module can implement the conversion between linear and geometrical approximate fast opening flow characteristics through parameter setting to meet the water supply system control requirements.
7. Grasp the state of the valve, the long-term valve wear and corrosion will cause the valve to run is not flexible enough, built-in intelligent module includes self-diagnosis, self-accumulation function, automatically raise the lower limit frequency to increase the motor output power, to solve the valve is not flexible enough.