Electric valve fault treatment method electric valve should be considered
The reasons for the electric valve are:
(1) Control channel is blocked by debris (small channel, easy to block);
(2) The piston is stuck in the position due to rust; Although the upper part of the force, but can not move down, can not open the main channel. Therefore, the piston pressure reducing valve must be installed before the filter; For newly installed or long-term disuse of pressure reducing valves, be sure to open inspection and cleaning.
The second fault, the valve straight, can not reduce pressure.
The reasons are:
à The piston is stuck in a certain position (not position);
¢à The stem of the main valve is stuck at a certain position (not the tight position) in the guide hole of the cylinder disc;
¢à The spring under the valve disc of the main valve is broken or failed;
(4) The handle of the pulse valve is stuck at a certain position in the hole of the valve seat (not the close position), so that the piston is always under pressure;
(5) Between the sealing surface of the main valve disc and the main seat, there is dirt stuck or notched;
Diaphragm failure due to fatigue or damage. For pressure relief valves, regular inspection should be emphasized. If found dirt, rust stains should be removed in time; Piston ring damage should be updated; Spring failure should be replaced with usable; If the sealing surface is not close, it should be ground again; Diaphragm is not working to replace; After use, if it is confirmed that the valve handle is thick, use sandpaper to polish it.
Three, the pressure after the valve can not be adjusted. In addition to the above reasons,
And:
¢à Regulating spring failure;
(2) Cap seam leakage, can not maintain pressure. Imported metering pump
This also depends on timely inspection and treatment to prevent. In addition, there is a phenomenon, is the valve behind the pressure pulse fluctuation, extremely unstable. This is the difference between the input medium and the output medium is too large, so the valve diameter should be selected again. There is also a reason for the instability of the pressure after the valve is that the adjustment spring is not selected properly; A nominal pressure reducing valve, regulating spring has several, such as nominal pressure is 16 kg/cm2, regulating spring there are 1-3 kg/cm2, 2-8 kg/cm2, 7-11 kg/cm2 three, if the valve after pressure only 1-3 kg/cm2, and the spring is 7-11 kg/cm2 of that, The pressure behind the valve is not adjusted correctly.
2, one of the spring type safety valve failures, sealing surface leakage.
The reasons are:
(1) There are sundries between the sealing surface;
¢à The sealing surface is damaged. This kind of failure should be prevented by regular maintenance.
Fault two, the sensitivity is not high.
The reasons are:
¢à spring fatigue;
¢à Improper use of spring. The spring is tired and should undoubtedly be replaced. Improper use of spring, is the user does not pay attention to a nominal pressure of the spring type safety valve, there are several pressure sections, each pressure section has a corresponding spring. Such as nominal pressure for 16 kg/cm2 safety valve, the use of pressure is 2.5-4 kg/cm2 pressure segment, installation of 10-16 kg/cm2 spring, although it can also make do with open, but high and low, very insensitive.
6.2.3 Common faults of check valve or check valve include:
¢à disc break;
¢à Medium backflow. The cause of disc breakage is that the medium pressure before and after the check valve is in a balanced and mutual âsawâ state, disc often beats with the seat, and some brittle materials (such as cast iron, brass, etc.) made of disc will be broken. The way to prevent is to use the disc as a ductile material of the check valve.
The causes of dielectric backflow are as follows:
¢à Damage of sealing surface;
¢à Clamp the impurities. Repair the sealing surface and clean impurities to prevent backflow. The above description of common faults and prevention methods can only play an inspirational role. In actual use, there will be other faults. In order to prevent the occurrence of valve faults actively and flexibly, the fundamental one is to be familiar with its structure, material and operation principle.
Electric valve should be considered
In pipeline engineering, the correct selection of electric valve is one of the guarantee conditions to meet the use requirements. If the electric valve used is not selected properly, it will not affect the use, but also bring adverse consequences or serious losses, therefore, the electric valve should be correctly selected in the design of pipeline engineering.
First, the working environment of electric valve
In addition to the pipeline parameters, special attention should be paid to the environmental conditions of the electric valve, because the electric device in the electric valve is a mechanical and electrical equipment, and its working condition is greatly affected by its working environment. Normally, the electric valve is in the following working environment:
1. Indoor installation or outdoor use with protective measures;
2, outdoor installation, wind, sand, rain, sunshine and other erosion;
3, with flammable, explosive gas or dust environment;
4, hot and humid zone, dry tropical environment;
5, the temperature of the pipeline medium is as high as 480¡æ or above;
6, the ambient temperature is below -20¡æ;
7. Easy to be flooded or immersed in water;
8, with radioactive material (nuclear power plants and radioactive material test equipment) environment;
9. The environment on the ship or dock (with salt spray, mold, moisture);
10, with violent vibration occasions;
11, prone to fire occasions; For the electric valve in the above environment, its electric device structure, materials and protective measures are different. Therefore, the corresponding valve electric device should be selected according to the above working environment.
Two, electric valve function requirements
According to the engineering control requirements, the control function of the electric valve is completed by the electric device. The purpose of using electric valve is to open, close and adjust the valve linkage to achieve non-artificial electrical control or computer control. The current use of electric devices is not just to save manpower. Because the function and quality of the products of different manufacturers are different, therefore, the selection of electric devices and the selection of valves are equally important to the project.
Three, electric control of electric valve
Due to the continuous improvement of the level of industrial automation requirements, on the one hand, the use of more and more electric valves, on the other hand, the control requirements of electric valves are becoming higher and higher, more and more complex. So the electric valve in the electrical control side of the design is also constantly updated. With the development of science and technology and the popularization of computer, new and diverse electrical control methods will appear constantly. For the consideration of the overall control of the electric valve, attention should be paid to the choice of the control mode of the electric valve. For example, according to the needs of the project, whether to use centralized control mode, or single control mode, whether to link with other equipment, program control or application computer program control, and so on, its control principle is different. The * given by the valve electric device manufacturer is the standard electrical control principle, so the user department should make technical disclosure with the electric device manufacturer to clarify the technical requirements. In addition, when choosing electric valves, we should consider whether to purchase additional electric valve controller. In general, controllers are purchased separately. In most cases, when a single control is used, it is necessary to buy a controller, because buying a controller is more convenient and cheaper than the userâs own design and manufacture. When the electrical control performance cannot meet the engineering design requirements, it should be proposed to the manufacturer for modification or redesign.
Valve electric device is an indispensable equipment to realize valve program control, automatic control and remote control. Its motion process can be controlled by stroke, torque or the size of axial thrust. Because the working characteristics and utilization rate of the valve electric device depend on the type of valve, the working specification of the device and the position of the valve in the pipeline or equipment, the correct selection of the valve electric device is of great importance to prevent overload (the working torque is higher than the control torque). Usually, the correct selection of valve electric device based on the following:
Operating torque Operating torque is the main parameter for selecting the valve electric device. The output torque of the electric device should be 1.21.5 times of the large operating torque of the valve.
There are two main structure of operating thrust valve electric device: one is not configured with thrust disc, direct output torque; The other is the configuration of thrust disc, the output torque through the thrust disc stem nut into the output thrust.
The number of turning turns of the output shaft of the valve electric device is related to the nominal diameter of the valve stem pitch and the number of threads. It is calculated according to M=H/ZS (M is the total number of turning turns that the electric device should meet, H is the opening height of the valve stem drive thread, S is the pitch of the valve stem thread, Z is the number of valve stem thread).
Stem diameter For multi-turn open-stem valves, if the large stem diameter allowed by the electric device cannot pass through the valve stem, it cannot be assembled into an electric valve. Therefore, the inner diameter of the hollow output shaft of the electric device must be greater than the outer diameter of the stem of the open-rod valve. For some rotary valves and dark rod valves in multi-rotary valves, although it is not necessary to consider the problem of the passage of the valve stem diameter, the valve stem diameter and the size of the key way should be fully considered in the selection, so that the valve can work normally after assembly.
If the opening and closing speed of the output speed valve is too fast, it is easy to produce water percussion phenomenon. Therefore, the appropriate opening and closing speed should be selected according to different conditions of use.
Valve electric device has its special requirements, that is, must be able to limit torque or axial force. Generally, the valve electric device uses a torque-limiting coupling. When the specification of the electric device is determined, its control torque is determined. Generally in the pre-determined time of operation, the motor will not overload. But if the following circumstances may lead to overload: first, the power supply is low, can not get the required torque, so that the motor stops rotating; Second, the torque limiting mechanism is incorrectly adjusted to make it greater than the stopping torque, resulting in continuous excessive torque, so that the motor stops rotating; Third, intermittent use, heat savings, more than the motor allowed temperature appreciation; Fourth, the circuit of the torque limiting mechanism fails for some reason, so that the torque is too large; Fifth, the ambient temperature is too high, so that the heat capacity of the motor decreases relatively.
In the past, the protection method of motor is to use fuse, overcurrent relay, thermal relay, thermostat, etc., but these methods have advantages and disadvantages. There is no reliable protection method for electric device with variable load. Therefore, various combination methods must be adopted, which can be summed up into two kinds: one is to judge the increase or decrease of the motor input current; The second is to judge the heating situation of the motor itself. Either way, the motor heat capacity should be considered for a given time allowance.
Usually, the basic protection method of overload is: for the overload protection of continuous running or point-and-point operation of the motor, the thermostat is used; Thermal relay is used for the protection of motor blocking; For short circuit accidents, fuse or overcurrent relay is used.
Post time: Nov-28-2022
