Abstract: The composition and classification of the diaphragm pump , as well as the selection principle and method of the type, actuator, mode of action and flow characteristics of the diaphragm are mainly described . The methods and principles of adjusting the enthalpy are analyzed.
Key words: control valve; diaphragm pump ; classification; selection; analysis
The role of the diaphragm pump in process control is to accept the control signal of the regulator or computer, change the flow of the medium to be adjusted, and maintain the adjusted parameters within the required range to achieve automation of the production process. If the automatic adjustment system is compared with the manual adjustment process, the detection unit is the human eye, and the adjustment control unit is the human brain, then the execution unit- diaphragm pump is the human hand and foot. To achieve the control of certain parameters of the process such as temperature, pressure, flow, liquid level, etc., the diaphragm pump is inseparable . Therefore, the correct choice of diaphragm pump is of great significance in process automation. 1 diaphragm pump composition and classification
Diaphragm pumps, also known as control pumps, are the main type of actuators that change the flow of fluids by means of power control by accepting control signals from the output of the control unit. Diaphragm pumps typically consist of actuators and valves. If by using it with the actuator, a diaphragm pump can be divided into pneumatic, electric, hydraulic three kinds, i.e., a pneumatic diaphragm pump compressed air power source, electrically powered diaphragm pump electric source to the liquid medium (such as oil) pressure-powered electro-hydraulic diaphragm pump, in addition to its function and characteristics, there are solenoid valves, electronic, intelligent, fieldbus diaphragm pumps. Diaphragm pumps come in many different types and structures, and are constantly being updated and changed. Valves are generally versatile and can be matched to pneumatic actuators or to electric actuators or other actuators.
2 diaphragm pump type selection
2.1 Valve body type selection of diaphragm pump The choice of valve body is an important part of diaphragm pump selection. There are many types of diaphragm pump bodies. There are 10 types of single-seat, straight-through two-seat, angle, diaphragm, small flow, three-way, eccentric rotation, butterfly, sleeve, and spherical. Before selecting the valve, carefully analyze the media, process conditions and parameters of the control process, collect sufficient data, understand the system requirements for the diaphragm pump , and determine the type of valve to be used based on the collected data. In the specific choice, you can consider the following aspects:
(1) The shape of the spool is mainly based on factors such as the selected flow characteristics and unbalanced forces.
(2) Abrasion resistance When the fluid medium is a suspension containing a high concentration of abrasive particles, the valve core and the valve seat joint face are severely rubbed each time they are closed. Therefore, the flow path of the valve should be smooth and the internal material of the valve should be hard.
(3) Corrosion resistance Because the medium is corrosive, in the case of meeting the adjustment function, try to choose a simple valve.
(4) Temperature and pressure of the medium When the temperature and pressure of the medium are high and the change is large, the valve and the material of the valve seat should be selected to be small in temperature and pressure.
(5) Prevention of flashing and cavitation Flashing and cavitation are only produced in liquid media. In the actual production process, flashing and cavitation not only affect the calculation of the flow coefficient, but also generate vibration and noise, so that the service life of the valve is shortened, so the valve should be prevented from flashing and cavitation when selecting the valve.
2.2 Diaphragm pump actuator selection
2.2.1 Consideration of output force Regardless of the type of actuator, its output force is the effective force for overcoming the load (mainly refers to unbalanced force and unbalanced torque plus friction, sealing force, gravity, etc.) Role). Therefore, in order for the diaphragm pump to work properly, the actuator used should generate sufficient output force to overcome various resistances, ensuring high sealing and opening of the valve.
For double-acting pneumatic, hydraulic, and electric actuators, there is generally no return spring. The magnitude of the force is independent of its direction of travel. Therefore, the key to selecting an actuator is to clarify the large output force of the Zui and the rotational torque of the motor. For single-acting pneumatic actuators, the output force is related to the opening of the valve, and the forces appearing on the diaphragm pump will also affect the motion characteristics, thus requiring a force balance across the diaphragm pump 's opening range.
2.2.2 Determination of the type of actuator After determining the output force of the actuator, select the appropriate actuator according to the requirements of the process environment. For explosion-proof requirements on site, pneumatic actuators should be used, and the junction box is explosion-proof, and electric actuators cannot be selected. If there is no explosion-proof requirement, pneumatic and electric actuators can be used, but in terms of energy saving, electric actuators should be selected as much as possible. For hydraulic actuators, the use is not as extensive as pneumatic and electric actuators, but it has the characteristics of high adjustment precision, fast and stable movement. Therefore, in some cases, in order to achieve better adjustment effect, hydraulic actuation must be selected. Institutions, such as speed regulation of power plant transparent machines, temperature regulation control of refinery catalytic converters, etc.
3 diaphragm pump function mode selection
The mode of action of the diaphragm pump is only when the pneumatic actuator is selected, and its action mode is formed by the combination of the positive and negative action of the actuator and the positive and negative action of the valve. There are 4 types of combination, namely positive (air-closed), positive and negative (air-open), reverse (air-open), and reverse (air-closed). The diaphragm pump formed by these four combinations has a gas function. Both open and closed. For the choice of diaphragm pump mode of action, mainly consider three aspects: a) process production safety; b) medium characteristics; c) to ensure product quality, economic loss.
4 diaphragm pump flow, selection of characteristics
The flow characteristic of the diaphragm pump refers to the relationship between the relative flow rate of the medium flowing through the valve and the displacement (relative opening of the valve). The ideal flow characteristics mainly include four types: straight line, equal percentage (logarithm), parabola and quick opening. The curve and spool shape are shown in Figures 1 and 2. The commonly used ideal flow characteristics are only straight lines, equal percentages (logarithmic), and quick opening. Parabolic flow characteristics are between straight and equal percentages, generally can be replaced by equal percentage characteristics, while fast open characteristics are mainly used in two-position adjustment and program control, so the choice of diaphragm pump characteristics is actually linear and equal percentage flow characteristics. s Choice.
The choice of diaphragm pump flow characteristics can be calculated theoretically, but the methods and equations used are complex. At present, the experience criteria are often used, and the following aspects are considered: 1 from the adjustment quality of the adjustment system and selected; 2 from the process piping; 3 from the load change analysis.
By selecting the flow characteristics of the diaphragm pump , the shape and structure of the valve spool can be determined according to the flow characteristics. However, for diaphragm valves, butterfly valves, etc., due to their structural characteristics, it is impossible to change the shape of the valve core to achieve the desired shape. The required flow characteristics can be achieved by changing the shape of the feedback cam of the valve positioner.
5 diaphragm pump diameter selection
The choice and determination of the diaphragm pump diameter is mainly based on the valve's flow capacity, Cv. In the design and selection of instruments for various projects, the diaphragm pump must be Cv calculated and the diaphragm pump design specification provided. From the calculation of the Cv of the diaphragm pump to the determination of the diameter of the valve, the following steps are generally required:
1) Calculate the calculation of the flow. The existing production capacity, equipment load and the condition of the medium determine the Qmax and Qmin of the calculated flow.
2) Determination of the differential pressure before and after the valve. S (resistance coefficient) is selected according to the selected valve flow characteristics and system characteristics, and then the calculated differential pressure is determined.
3) Calculate Cv. Select the appropriate calculation formula and graph according to the adjusted medium to find Cmax and Cmin.
4) Select Cv. According to Cmax, select >Cmax in the selected product standard series and the level C is close to its zui.
5) Diaphragm pump opening degree check. Generally, the opening degree of Zui's large calculation flow rate is ≯90%, and the opening degree of Zui's small calculation flow rate is ≮10%.
6) Check the actual adjustable ratio of the diaphragm pump . Generally, the actual adjustable ratio ≮10 is required.
7) Determination of seat diameter and nominal diameter. After verification is appropriate, it is determined according to C.
6 Conclusion
The choice of diaphragm pump is very meticulous work, not only has a solid professional theoretical knowledge, but also has a wealth of practical experience. Choosing well is not only conducive to adjusting the tuning of the PID parameters of the control loop, so that the adjusted parameters get better control effect, and the service life of the diaphragm pump is greatly increased. The choice of diaphragm pump should be adapted to local conditions, not constant, and must be summarized and innovated in the process of practice. Especially with the application of mechatronics technology, computer and digital information technology, the structural function of diaphragm pump becomes better and more comprehensive. Great convenience for choosing a diaphragm pump .
QBY pneumatic diaphragm pump , DBY electric diaphragm pump <br> Product Overview:
QBY series pneumatic diaphragm pump uses compressed air, steam and industrial waste gas as the power source. It can exhaust all kinds of corrosive liquids, liquid with particles, high viscosity, volatile, flammable and highly toxic liquid. It has many advantages of self-priming pumps , submersible pumps , shielded pumps , mud pumps and impurity pumps . It is widely used in petroleum, chemical, electronics, ceramics, textile and other industries.
The pumps are placed in a variety of special occasions to pump a variety of media that can not be pumped by conventional pumps, and have achieved satisfactory results.
Suction medium range:
- Diaphragm pump peanut butter, kimchi, mashed potatoes, small red sausage, jam apple pulp, chocolate, etc.
- Diaphragm pump paint, gum, pigment.
- Adhesives and glues, all types can be pumped with a diaphragm .
- Various tile, porcelain, brick and pottery glaze.
- After the oil well is drilled, use the diaphragm pump to deposit and grout.
- Diaphragm pumps for various emulsifiers and fillers.
- Diaphragm pumps for all types of sewage.
- Use the pump as the tanker, and the barge clears the tank to absorb the sewage.
- Hops and baking powder slurry, syrup, molasses.
- Diaphragm pump water in mines, tunnels, tunnels, beneficiation, slag.
- Diaphragm pump cement grouting and mortar, various rubber slurries.
- Various abrasives, corrosives, oil and mud, cleaning grease and general containers.
- A variety of highly toxic, flammable, volatile liquids.
- A variety of strong acids, strong bases, strong corrosive liquids.
Diaphragm pump ordering instructions:
One, one diaphragm pump product name and model 2 diaphragm pump diameter 3 diaphragm pump head (m) 4 diaphragm pump flow 5 diaphragm pump motor power (KW) 6 diaphragm pump speed (r / min) 7 diaphragm pump pressure [V] 8 diaphragm Pump suction (m) 9 diaphragm pump with accessories so that we can choose the right one for you.
2. If the diaphragm pump model of our company has been selected by the design unit , please order directly from the sales department of Yangzijiang Pump Co., Ltd. according to the diaphragm pump model.
Third, when the occasion of use is very important or the environment is more complicated, please provide the design drawings and detailed parameters as much as possible, and our technical experts from Yangzijiang Pump Industry will check and check for you.
Thank you for visiting our Yangzijiang Pump Industry. 】, if you have any questions, you can call us, we will do our best to provide you with quality service.
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