Expansion of mature instrument applications
针对经典或新颖仪表在某一领域应用受到的限制，经局部适应性改进，且技术有上所突破而使得在该领域应用有迅速的发展。 The electromagnetic flowmeter is aimed at the limitation of the application of classic or novel instruments in a certain field, and has been locally adapted to improve, and the technology has made breakthroughs, which has led to rapid development of applications in this field. For example, the differential pressure flow meter is limited for viscous liquids with a low Reynolds number (below Re = 104) and high solids concentration slurry. After the wedge tube is equipped with a differential pressure transmitter with a sealed capillary tube, Pressure flow meters have been expanded in this application area. As another example, ultrasonic flow meters have not been accepted for a long time due to the measurement accuracy of natural gas custody transfer. Traditional electromagnetic flow meters cannot measure non-full pipe liquid flow. Coriolis mass flow meters have not been used in previous years. Medium pressure gas, only suitable for measuring high pressure gas and so on. In recent years, these meters have made breakthroughs in technology, and their applications in the field have developed rapidly. 1. Ultrasonic flowmeter suitable for custody transfer metering
在固体与气体界面上的传播效率低，管道外夹装超声换能器（探头）难以从管壁传送足够的声能，因此目前还没有外夹装式气体超声流量计。 Due to the low propagation efficiency of the electromagnetic flowmeter on the solid-gas interface, it is difficult for an ultrasonic transducer (probe) clamped outside the pipe to transmit sufficient acoustic energy from the pipe wall, so there is currently no externally clamped gas ultrasonic flowmeter. Gas ultrasonic flowmeter products began in the early 1980s, and most of them consisted of a measuring tube and a transducer inserted into the tube wall. Due to the low measurement accuracy (1.5% to 2% FS), the price was not able to be used in the past. The field of expensive natural gas trade settlement measurement has gained a place. In recent years, a variety of high-precision gas ultrasonic flowmeters have appeared. German Krohne company's ALTOSONIC GFM 700 is a parallel two-channel Z method (that is, one side of the transducer emits sound waves obliquely to the opposite side of the transducer to receive it) and is placed on the chord position. The range is 50 ～ 800mm. It has lower requirements for the length of the upstream straight pipe section. Z is about 1/2 ～ 1/4 of the mono. The USM type of German Elster Handel Company is a dual-acoustic V method reflection. Its characteristic is that the transmitting transducer emits the sound beam scattered to the opposite side of the transducer and receives it.) It is arranged at the chord position, the measurement error is ± 2% R, and the upstream straight pipe length is very low. It only needs 3 times the pipe diameter. It only takes 2 times downstream. In 1997, the Japanese company Obar had a Posonic-1 monophonic V method (that is, the transmitted sound wave was reflected by the opposite tube wall to another transducer on the same side to receive it) in Shanghai. The measurement error after Reynolds number correction is ≤ ± 1% R, and the caliber range is 50 ～ 250mm. RVG company demonstrated four-channel combined propagation sound waves at the 1995 INTERKAMA exhibition and the 1997 ACHEMA (Chemical Industry Equipment Exhibition). Two channels are the V method reflection arrangement, which are the basic signals for flow measurement; the other two sound signals The sound beam of one of the channels is propagated by a diameter path, and the sound beam of the other is propagated by a triangular reflection path as an auxiliary signal for correcting the velocity distribution. The minimum measurement error is ≤ ± 0.5% R, and the caliber range is 200 ～ 1000mm. According to the members of the gas flow measurement team who visited Europe in 1998, the mainstream flow meters used for natural gas measurement in Europe are: ① orifice plate differential pressure type; ② waist volume equal volume type; ③ turbine type; ④ vortex street type; ⑤ ultrasonic type. At present, German and Dutch experts think of these instruments: Orifice differential pressure is not recommended, but the high-pressure gas in the gas field is metered out. It is currently the only type selected; vortex and ultrasonic are recommended but not promoted. Application experience to be accumulated; turbine type and volumetric type are only suitable for medium and low pressure small pipe diameter places. The author believes that the ultrasonic flowmeter will have a tendency to compete with large-diameter high-pressure natural gas flow measurement and orifice plate differential pressure.
Non-full tube electromagnetic flowmeter
的问世，使非满管圆形管的测量误差从传统槽式流量仪表的3%~5%FS降低到1%～2%FS。 The advent of non-full-tube electromagnetic flowmeters has reduced the measurement error of non-full-tube circular tubes from 3% to 5% FS of traditional trough flow meters to 1% to 2% FS. Since the first Fischer + Porter company to show people non-full-tube electromagnetic flowmeters in 1992, four models from four manufacturers have been introduced to the market. The caliber range is 150 ~ 1000mm. The non-full-tube electromagnetic flowmeter still uses the Faraday's law of electromagnetic induction to measure the flow rate, and then measures the level of the cross-section liquid level to obtain the flow area, and the two are multiplied to obtain the flow. Two types of the above four types of meters use two sets of upper and lower excitation coils in series and single coil excitation (or forward and reverse series excitation) to generate two kinds of magnetic field distribution and intensity, and measure two flow rates. Signal, the ratio between the two has a certain functional relationship with the liquid level height, and the liquid level height is obtained indirectly. The third model of the two excitation line circular axis is horizontal, the magnetic field line is parallel to the horizon, one electrode is placed at the bottom of the measuring tube, and the flow signal takes the potential difference between the potential signal and the grounding ring at the end of the measuring tube. Both are proportional, and the flow rate can be obtained without the calculation of the liquid level height and flow velocity. The measurement principle of the fourth type of liquid level height is the same as that of the capacitive liquid level gauge. Since there is no non-full-tube electromagnetic flowmeter production in China, the asking price of foreign manufacturers and their agents is very high, which is more than two or three times that of traditional meters. In addition to the above-mentioned non-full-tube electromagnetic flowmeter, which has a similar shape to the traditional structure, there is also a flat sensor composed of an electromagnetic flow velocity detection element and a solid level detection element. It is placed on the bottom of the mounting ring. Measure flow in non-full pipe piping. The Suzhou River sewage treatment project in Shanghai has tried to measure sewage flow.