Electric valves must be considered questions How to use electric valves accurately

Electric valves must be considered questions How to use electric valves accurately

 
In the pipeline engineering design of various industries, the accurate selection of electric valves is one of the prerequisites to meet the requirements of working conditions. If the selection of the electric valve used is not appropriate, it will not affect the use of, but also bring adverse consequences or severe losses, therefore, electric valves should be accurately selected in the design of pipeline engineering.

First, the working environment of electric series valves

In addition to the parameters of the pipeline, the electric valve should pay special attention to the working environment of the pipeline. Because the electric device in the electric valve is a mechanical and electrical equipment, its working condition is greatly affected by its working environment. Under normal circumstances, the electric valve in the working environment has the following 11 kinds:

1. Indoor installation or outdoor use with protective measures;

2, outdoor installation, wind, sand, rain, sunshine and other corrosion;

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℃ or above;

6, the ambient temperature is below -20℃;

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, wet);

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, for the electric valve, its control function is completed by the electric device (switch type, regulator type). The purpose of using electric valve is to open, close and adjust the valve linkage to achieve non-artificial electrical control or computer control. At present, the use of electric devices is not only to save manpower, because the function and quality of different manufacturers of products are different, therefore, the choice of electric devices and the choice of valve is important to the engineering equality.

Three, electric control of electric valve

Higher requirements for industrial automation in our country, one side is facing more and more usage of the electric valve, the other side is facing the electric valve control requirements are also higher and more complex. So the design of electric valve in electrical control is also constantly updated. With the improvement of science and technology, new and diverse electrical control methods will continue to emerge. 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 the centralized control mode, is still a single control mode, whether to link with other equipment, program control is still the application of computer program control, and so on, its control principle is different. The sample given by the valve electric device manufacturer is the scale electrical control principle, so the use part should be 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, the controller is purchased separately. In most cases, when using a single control, it is necessary to buy a controller, because the purchase of a controller is easier and cheaper than the user’s own design and manufacture. When the electrical control function can not meet the engineering design requirements, should be put forward to the production plant to modify 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, therefore, the accurate selection of the valve electric device is crucial to prevent the overload phenomenon (working torque is higher than the control torque). Usually, the accurate selection of valve electric device based on the following:

Operating torque The 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 the torque of the valve operating tripod.

There are two kinds of main machine structure to control the 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.

Output shaft rolling ring number valve electric device output shaft rolling ring number and the nominal diameter of the valve stem pitch, thread number, according to M=H/ZS calculation (M for the electric device should be satisfied with the total number of rolling rings, H for the valve opening height, S for the valve stem drive thread pitch, Z for the valve stem thread number).

Stem diameter for multi-turn open-rod valves, if the large stem diameter agreed by the electric device can not pass through the valve stem, it can not 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 the dark rod valves in the department rotary valves and multi-rotary valves, although it is not necessary to consider the diameter of the valve stem, the diameter of the valve stem and the size of the key way should also be fully considered in the selection, so that the assembly can work normally.

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 use conditions.

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 such as the following circumstances may lead to overload: first, the power supply is low, can not get the required torque, so that the motor stop rolling; Second, the torque limiting mechanism is incorrectly adjusted to make it greater than the rest of the torque, resulting in continuous excessive torque, so that the motor rest rolling; Third, intermittent use, generated heat savings, more than the motor temperature appreciation; Fourth, the circuit of the torque limiting mechanism fails for some reason, so that the torque is too large; Fifth, the use of ambient temperature is too high, so that the heat capacity of the motor decreases relatively. The previous methods to protect the motor are to use fuses, overcurrent relays, thermal relays, thermostats, etc., but these methods have advantages and disadvantages. There is no reliable protection method for electric device with variable load. Therefore, it is necessary to take a variety of combination methods, summed up in two kinds: one is to determine the increase or decrease of the motor input current; The second is to determine the fever of the motor itself. These two ways, regardless of the kind of motor heat capacity to consider the given time margin.

In addition, the basic protection method of overload is: the overload protection of continuous operation or 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.

How to use electric valve accurately

Electrical control of electric valve because of the continuous progress of the level of industrial automation requirements, one side is facing the use of more and more electric valves, the other side is facing 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 improvement of science and technology and the popularization of computer, the new and various electrical control methods will continue to rise. 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 the centralized control mode, is still a single control mode, whether to link with other equipment, program control is still the application of computer program control, and so on, its control principle is different. The sample given by the valve electric device manufacturer is the scale electrical control principle, so the use part should be 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, the controller is purchased separately. In most cases, when using a single control, it is necessary to buy a controller, because the purchase of a controller is easier and cheaper than the user’s own design and manufacture. When the electrical control function can not meet the engineering design requirements, should be put forward to the production plant to modify or redesign.

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 is important to the engineering equality.

In pipeline engineering, the accurate selection of electric valves is one of the prerequisites to meet the requirements of use. If the electric valve used is not selected properly, it will not affect the use, but also bring adverse consequences or severe loss. Therefore, the electric valve should be accurately selected in the design of pipeline engineering. In addition to the pipeline parameters, the electric valve should pay special attention to the environmental premise of its work. Because the electric device in the electric valve is a mechanical and electrical equipment, 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 corrosion;

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℃ or above;

6, the ambient temperature is below -20℃;

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, wet);

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.