In the pipeline engineering, the correct selection of electric brass valves is one of the guarantee conditions to meet the requirements of use. If the electric brass valve used is not properly selected, it will not only affect the use, but also bring about bad consequences or serious damage. Therefore, the electric brass valve should be correctly selected in the pipeline engineering design.
Working environment of electric brass valve
In addition to paying attention to the pipeline parameters, electric brass valves should pay special attention to the environmental conditions of their work, because the electric device in the electric brass valve is an electromechanical device, and its working condition is greatly affected by its working environment. Under normal circumstances, electric brass valves are used in the following working environments:
1. Indoor installation or protective measures for outdoor use;
2, outdoor open-air installation, wind, sand, rain, sun and other erosion;
3. It has a flammable, explosive gas or dust environment;
4. Wet tropical and dry tropical environment;
5, the pipeline medium temperature is up to 480 ° C or more;
6. The ambient temperature is below -20 °C;
7, vulnerable to flooding or immersion in water;
8. Environment with radioactive materials (nuclear power stations and radioactive material testing devices);
9. The environment on the ship or dock dock (with salt spray, mold, moisture);
10. Occasional vibrations;
11. Occasional fires;
For electric brass valves in the above environment, the structure, materials and protective measures of the electric device are different. Therefore, the corresponding valve electric device should be selected according to the above working environment.
Electric brass valve function requirements
According to the engineering control requirements, the control function of the electric brass valve is completed by the electric device. The purpose of using an electric brass valve is to achieve non-manual electrical or computer control of the opening, closing and adjustment of the valve. The current use of electric devices is not just to save manpower. Since the functions and quality of products from different manufacturers vary greatly, it is equally important to select the electric device and the valve to be selected.
Electrical control of electric brass valves
Due to the increasing requirements of the industrial automation level, on the one hand, the use of electric brass valves is increasing, and on the other hand, the control requirements for electric brass valves are becoming higher and more complex. Therefore, the design of electric brass valves in electrical control is constantly being updated. With the advancement of science and technology and the popularization and application of computers, new and diverse electrical control methods will continue to emerge. For the overall control of electric brass valves, attention should be paid to the choice of the control method of the electric valve. For example, depending on the needs of the project, whether to use centralized control mode, single control mode, linkage with other devices, program control or application computer program control, etc., the control principle is different. The valve electric device manufacturer sample only gives the standard electrical control principle, so the use department should make technical disclosure with the electric device manufacturer and clarify the technical requirements. In addition, when selecting an electric brass valve, consideration should be given to whether or not to purchase an electric brass valve controller. Because of the general situation, the controller needs to be purchased separately. In most cases, when using a single control, it is necessary to purchase the controller, because it is convenient and cheaper to purchase the controller than the user design and manufacture. When the electrical control performance does not meet the engineering design requirements, the manufacturer should propose modifications or redesigns.
The valve electric device is an indispensable device for realizing valve program control, automatic control and remote control. The movement process can be controlled by the stroke, torque or axial thrust. Since 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 on the pipeline or equipment, the correct selection of the valve electric device prevents overload phenomenon (operating torque is higher than control) Torque) is crucial. In general, the basis for the correct selection of valve electric devices is as follows:
Operating torque The operating torque is the most important parameter for selecting the electric device of the valve. The output torque of the electric device should be 1.2 to 1.5 times the maximum torque of the valve.
There are two types of mainframe structures for operating the thrust valve electric device: one is to configure the thrust disc without the thrust disc, and the other is to configure the thrust disc, and the output torque is converted into the output thrust through the stem nut in the thrust disc.
Output shaft rotation number The number of rotations of the output shaft of the valve electric device is related to the nominal diameter of the valve, the pitch of the valve stem and the number of threads. It should be calculated according to M=H/ZS (M is the total rotation circle that the electric device should meet). Number, H is the valve opening height, S is the stem drive thread pitch, and Z is the stem thread number).
Stem diameter for multi-turn type open-end valves. If the maximum stem diameter allowed by the electric device cannot pass through the valve stem of the valve, it cannot be assembled into an electric brass valve. Therefore, the inner diameter of the hollow shaft of the electric device must be larger than the outer diameter of the stem of the open rod valve. For the partial rotary valve and the dark rod valve in the multi-turn valve, although the problem of the diameter of the stem is not considered, the diameter of the stem and the size of the keyway should 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, water hammer is likely to occur. Therefore, the appropriate opening and closing speed should be selected according to different conditions of use.
Valve electric devices have special requirements that must be able to limit torque or axial forces. Usually the valve electric device uses a torque limiting coupling. When the specifications of the electric device are determined, the control torque is also determined. Generally running in a predetermined time, the motor will not be overloaded. However, if the following conditions occur, the overload may be caused: first, the power supply voltage is low, the required torque is not obtained, and the motor stops rotating; second, the torque limiting mechanism is set incorrectly to be greater than the stopped torque. Cause continuous excessive torque generation, so that the motor stops rotating; Third, intermittent use, the generated heat accumulation exceeds the allowable temperature rise value of the motor; Fourth, for some reason, the torque limiting mechanism circuit fails, causing the torque to pass Large; five is the use of ambient temperature is too high, relatively reducing the thermal capacity of the motor.
In the past, the protection of the motor was to use fuses, overcurrent relays, thermal relays, thermostats, etc., but these methods have their own advantages and disadvantages. For the variable load device of the electric device, there is no absolute and reliable protection method. Therefore, various combinations must be adopted, which can be summarized in two ways: one is to judge the increase and decrease of the input current of the motor; the other is to judge the heat of the motor itself. In either case, the time margin given by the thermal capacity of the motor must be considered.
Generally, the basic protection method of overload is: using a thermostat for overload protection of continuous or jog operation of the motor; using a thermal relay for the protection of the motor stall; and using a fuse or an overcurrent relay for a short circuit accident.
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NAFCO is a quality China brass valve manufacturer and supplier, with full line of brass valves China for your selection, such as brass ball valves, brass gate valves,brass radiator valves, brass angle valves, as well as relevant brass fittings. Please don't hesitate to contact us for any questions at support@acrofluid.com.
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