The choice of electromagnetic flowmeter is mainly the correct choice of the transmitter, and the converter only needs to be matched with it.
Choice of caliber and range
The diameter of the transmitter is usually the same as that of the piping system. If the piping system is to be designed, the diameter can be selected according to the flow range and flow rate. For electromagnetic flowmeters, the flow rate is suitable for 2 - 4m / s. In special cases, such as solid particles in the liquid, in consideration of wear, the optional flow rate is ≤ 3m / s, for easy to manage the fluid. Available flow rate ≥ 2m / s. After the flow rate is determined, the transmitter diameter can be determined according to qv= D2.
The range of the transmitter can be selected according to two principles: one is that the full scale of the meter is greater than the expected maximum flow value; the other is that the normal flow is greater than 50% of the full scale of the meter to ensure a certain measurement accuracy.
Temperature and pressure selection
There are certain restrictions on the fluid pressure and temperature that the electromagnetic flowmeter can measure. When used, the pressure used must be lower than the working pressure specified by the flowmeter. At present, the working pressure specifications of domestically produced electromagnetic flowmeters are:
Less than 50mm caliber, working pressure is 1.6MPa; 900 mm caliber, working pressure is 1 MPa;More than 1000mm caliber, working pressure is 0.6MPa.
If there are special requirements on the pressure resistance of the transmitter, you can negotiate with the manufacturer.
The operating temperature of the electromagnetic flowmeter depends on the lining material used, which is generally 5 - 70 ° C. Such as special treatment, can exceed the above range, such as the wear-resistant corrosion-resistant electromagnetic flowmeter produced by Tianjin Automation Instrument No.3. The transmitter allows the measured medium temperature to be -40 to 130 °C.
Selection of lining material and electrode tree material
The lining material and electrode material of the transmitter must be correctly selected according to the physical and chemical properties of the medium. Otherwise, the instrument will be damaged quickly due to the corrosion of the lining and the electrode, and the corrosive medium will easily cause an accident if it leaks. Therefore, the electrode and the lining material must be carefully selected according to the specific measurement medium in the production process.
General principles for electromagnetic flowmeter selection
(1) Whether the medium to be tested is a conductive liquid or slurry, thereby determining whether an electromagnetic flow meter is selected;
(2) The conductivity of the measured medium determines the type of electromagnetic flowmeter—whether it is high conductivity or low conductivity;
(3) The nominal diameter of the large, small and common flow process pipelines required by the process, determine whether the flow rate of the medium is at a more economical flow point, whether the pipeline needs to be reduced, and then determine the diameter of the flowmeter;
(4) Determine whether to use an integrated or split flowmeter, and the degree of protection of the flowmeter, etc., based on the layout of the process piping.
(5) Selecting the electrode type according to whether the measured medium is easy to crystallize or crusting;
(6) selecting an electrode material according to the corrosiveness of the measured medium;
(7) The corrosiveness, wear and temperature of the measured medium determine the lining material to be used;
(8) The high working pressure of the measured medium determines the nominal pressure of the flow meter;
(9) The insulation of the process piping determines the type of grounding ring.
Flowmeter challenges
Traditional mechanical flowmeters, such as differential pressure flowmeters, positive displacement flowmeters, and variable area flowmeters, are already in the stage of popularization, with fierce price competition, decreasing profit margins, less technological innovation, and relatively mature markets. . Frost & Sullivan believes that achieving product differentiation and customized production is an important breakthrough for manufacturers in the fierce competition in mature markets. Based on Frost & Sullivan's analysis of the needs of industry users, the user community expects manufacturers to provide automated equipment that will bring tangible benefits to the production process. Users will have specific requirements in the application process, such as: application in the special environment of the petrochemical industry, the need for rugged design and explosion-proof certification; user demand for Coriolis flowmeter designed for straight pipe. How to effectively obtain the actual needs of users and improve the traditional products is a challenge to the manufacturer's differentiated and customized production process.
Guiding users to accept and use new technology flow meters, such as ultrasonic flow meters, electromagnetic flow meters, and thermal mass flow meters, is another challenge for manufacturers to make the market bigger and stronger. In fact, the new technology flowmeter mentioned above has been developed and applied more than ten years ago. How to make customers realize that using the new technology flowmeter can effectively improve the production efficiency is an important issue for manufacturers.
In addition, new technology flowmeters are constantly being introduced into various industries, and fast and efficient after-sales service is also crucial for manufacturers. In particular, the use of Flowfield based on Foundation Fieldbus and Profibus PA bus has certain requirements for software technology. Effective services can provide users with more suitable solutions and close to users.