Application of the hottest DWM2000L electromagneti

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Application of DWM2000L electromagnetic flowmeter in circulating water system

Abstract: This paper introduces the performance specifications and technical indicators of DWM2000L electromagnetic flowmeter, and summarizes the actual application of the instrument in the circulating water system of petrochemical and chemical plants, as well as the application comparison with other types of flow instruments

key words: accuracy of circulating water system of electromagnetic flowmeter DWM2000L


in petrochemical and chemical plants, the circulating water system, as the utility system of the plant, is not only an important link in environmental protection, but also a key component of petrochemical and chemical plants. Therefore, selecting and using the flow instrument of circulating water is also one of the key tasks of chemical plants in the start-up stage. This paper introduces the application of DWM2000L electromagnetic flowmeter used in the circulating water system of solution SBR plant in Shanghai Caojing Chemical Industry Zone

1 circulating water system of solution styrene butadiene rubber plant

the solution styrene butadiene rubber plant in Shanghai Caojing Chemical Industry Zone, with the process package technology provided by Asahi Chemical Co., Ltd., was completed and started up in July 2006, and can produce 15 brands of solution styrene butadiene rubber and low CIS rubber. The normal amount of circulating cooling water in the unit is 4000t/h, which is used for cooling the materials in the main process unit. Part of the circulating cooling water enters the cooler to reduce the temperature of the materials, and part of the circulating cooling water enters the condenser to cool the materials in the gas phase into the liquid phase. The unit is equipped with two cooling towers with the same capacity, with a diameter of 7000mm, a power of 75kW and a capacity of 2000m3/h; Three high-power circulating water pumps are set to supply circulating cooling water to the main process unit. Sewage pipelines are set in the circulating water system to regularly discharge polluted wastewater; A make-up water pipeline is set up for replenishment after regular discharge; And dosing pipeline, which is used to inhibit the breeding of bacteria in circulating water and prevent the attachment and corrosion of heat exchange equipment

the electromagnetic flowmeter of Cologne company that cannot move up and down is used on the above pipelines, among which optiflux 4300c ex/ifc300c ex is selected on the sewage and make-up pipelines, and DWM2000L plug-in electromagnetic flow is selected on the circulating water supply pipeline. The process flow diagram of circulating water system is shown in Figure 1

Figure 1 process flow diagram of circulating water system

2 DWM2000L electromagnetic flowmeter

2.1 measurement principle

according to Faraday's law of electromagnetic induction, the movement of the conductor in the magnetic field can produce induced voltage U0. The measured liquid water is a kind of conductor, whose movement direction is perpendicular to the magnetic induction intensity B, and the induced voltage between two electrodes (platinum electrode and grounding electrode):

u = k × B × V × D

where: K is a constant; B is the magnetic induction intensity; V is the medium flow rate; D is the electrode spacing

voltage U is converted into 4~20ma electrical signal output which is proportional to the flow rate and independent of the load through the transmitter. The measurement schematic diagram is shown in Figure 2

Figure 2 measurement schematic diagram

2.2 technical parameters

dwm2000l plug-in electromagnetic flowmeter is applicable to the flow measurement of conductive liquid and slurry suspension. It has ordinary type, with the protection grade of IP66, which is equivalent to NEMA 4; It has submersible type, and the protection grade is IP68. It can be used in open pipelines and flooded occasions. DWM2000L is an extended sensor with a length of more than 3m. Technical parameters are shown in Table 1. Table 1 table of technical parameters

2.3 installation

when selecting the installation position, first of all, it is necessary to meet the length of the upstream and downstream straight pipe section of the instrument. Secondly, it is necessary to avoid large motors and equipment prone to generate magnetic fields to prevent interference. It is also necessary to select a position convenient for installation and maintenance. The installation diagram is shown in Figure 3. In Figure 3, (a) is the correct installation method, and (b) is wrong. In addition, when installing the extended type, be sure to mark the insertion depth first. Generally, the insertion depth is 1/8 of the pipe diameter. After the insertion depth is satisfied, rotate the whole sensor to make the flow direction mark consistent with the fluid direction. Finally, lock the locking parts and tighten the safety chain. For the submersible type, users should pay special attention that the cable interface of IP68 cannot be opened, and the manufacturer has made special sealing treatment for the cable connector before leaving the factory

Figure 3 installation diagram

2.4 set

① determine the position of electronic components. Open the converter housing so that the arrow direction on the electronic component is consistent with the medium flow direction, and then tighten the locking piece. If the arrow direction is inconsistent with the medium flow direction, wrong measurement results will be produced

② set the reference speed. Set the reference speed through two dial switches (1m/s and 0.1m/s). The speed can be calculated according to the formula v= 354 × (Q/D × D) Where v=m/s, q=m3/h, d= inner diameter of pipeline mm

③ set the time constant. Select the time constant of 5, 8 or 10s through the dial switch

④ set the alarm state. Normally closed contact no means that when the speed is greater than the reference speed, the circuit is disconnected; Normally open contact NC indicates that when the speed is greater than the reference speed, the circuit is closed; When the circuit is disconnected, the LED is illuminated

after setting, pay special attention to the installation of the rubber sealing ring when connecting the IP68 shell. The sealing ring must not be damaged, and the inner surface of the sealing ring must not be damaged at all, so as to prevent water from entering the IP68 shell, such as the thermoformed food packaging box and the cover from damaging the instrument

3 practical application of DWM2000L electromagnetic flowmeter

in April 2006, the on-site installation engineer installed it under the guidance of the manual, and conducted linkage commissioning with the device in June. With the device started up, the meter was put into normal operation. So far, there is no maintenance workload and deviation, and the circulating water volume reflects the production and operation status of the device in a very timely manner

differential pressure flow measuring instruments are also used in the circulating water system, including Weiba flowmeter. Weiba flowmeter uses the principle of differential pressure for flow measurement, and adopts the non shrinking throttling design to reduce the pressure loss. It can measure various media such as gas, liquid and steam. The range ratio is greater than 10:1, and the installation is simple. It only needs to open a small hole on the pipeline and then weld a base, without cutting off the pipeline; The measurement system has very high requirements for the accuracy of relevant parameters of the measured medium. Compared with the electromagnetic flowmeter used in the circulating water system, the measurement principle is not specific to the conductivity of water, the range ratio is not large enough, and the installation cannot meet the diving requirements of IP68. The impulse pipe is easy to plug, and the changes of differential pressure, maximum flow and working temperature are easy to cause measurement errors

4 conclusion

dwm2000l electromagnetic flowmeter is characterized by a wide range of measurable caliber, which can be widely used in the treatment of sewage, cold water and tap water. It can replace electronic units without interrupting work, with low power consumption. The wetted part is of stainless steel or ceramic structure, without moving parts and maintenance free. Practice has proved that it is appropriate to adopt electromagnetic flowmeter in the industrial water system of developing precision seamless steel pipe and ductile iron pipe in Shuiye and Linzhou


1 Liang Guowei's use in cars is also on the rise, caiwuchang Flow measurement technology and instruments [m] Beijing: China Machine Press, 2002

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