Why Target Flow Meters Endure

Target flowmeters and electromagnetic flowmeters are old-fashioned flowmeters. Why do they have always been favored by people?

Target flowmeter is a kind of differential pressure flowmeter. It has been developed and applied in industry for decades. China developed electric and pneumatic target flow transmitters in the 1970s. It is a combination meter for electric and pneumatic units. Since force converters directly use the force balance mechanism of the differential pressure transmitter, such flow meters cannot avoid the disadvantages caused by the force balance mechanism itself, such as zero drift, low measurement accuracy, and reliable lever mechanism. Poor sex and so on. Due to the poor performance of the force balance mechanism, many advantages of the target flowmeter itself have not been effectively exerted, and the user's unfavorable impression on the old target flowmeter has not yet been eliminated.

The force transducer of the new target flowmeter adopts a strain-type force converter, which completely eliminates the disadvantages of the aforementioned force balance mechanism. The new target flowmeter also applies microelectronic technology and computer technology to the signal converter and the display part, and the flow rate The meter has a series of advantages and is believed to play an important role in many flow meters in the future.

Principle and structure 1. Working principle Place a circular shaped target plate coaxially at the center of the measuring tube (instrument body). When the fluid impinges on the target plate, the target plate is subjected to a force F, which is related to the flow velocity V, the medium density ρ and the target. Plate force area A relationship. (1) Formula F - force on the target plate, N; CD - drag coefficient; ρ - fluid density, kg/m3; V - fluid velocity, m/s; A - target force Area, m2. After derivation and conversion, the flow rate is calculated as follows: where qm, qv - mass flow and volume flow, respectively, kg/h, m3/h; α - flow coefficient; D - inner diameter of the measuring tube, mm; β - Diameter ratio, β = d/D; d - diameter of the target plate, mm. The rest of the symbols are the same as above. The force and force of the target plate are converted into electrical signals. After pre-amplification, AD conversion and computer processing, the corresponding flow and total amount can be obtained.

2, the structure of the structure of the target flow meter structure diagram shown in Figure 2, which consists of detection devices, force converters, signal processing and display instrument composed of several parts. The detection device includes a measuring tube and a target plate, the force transducer is a strain gauge type sensor, and the signal processing and display device can directly read the display on the spot or remotely transmit the standard signal. The structure of the target flowmeter can be divided into pipe type, clip type and insert type, and various types of structure can be divided into one type and two types. The integrated type is direct reading on the site, while the separate type separates the digital display from the detection device (usually no more than 100m).

The main characteristics of the flow meter 1, the sensing part is no moving parts, the structure is simple and solid;

2, the scope of application and adaptability is very wide, the general industrial process of fluid media, including liquid, gas and steam, diameter range (DN15 or more), a variety of working conditions (high, low temperature, pressure, high pressure) can be applied, It can be said that its application range can be compared with the orifice flowmeter.

3, high accuracy, total measurement up to 0.2% R;

4. The range is wide, from 4:1 to 15:1 to 30:1;

5, can solve the problem of difficult flow measurement, such as the measurement of dirty fluids containing impurities (fine particles); crude oil, sewage, high-temperature residue, slurry, caustic soda, asphalt, etc.;

6, high sensitivity, can measure small flow, the flow rate can be as low as 0.08m / s;

7. With bore diameter (DN15 ~ DN50), low Reynolds number (Red = 103 ~ 5 x 103) fluid, it can make up for the difficult application of standard throttling devices, such as small-caliber steam flow measurement;

8, can adapt to the measurement of high-parameter fluid, pressure up to tens of MPa, temperature up to 450 °C

9, can be used for the measurement of two-way flow of fluid;

10, the pressure loss is low, about half of the standard orifice plate;

11, anti-blocking upstream block strong ability, the upstream side of the straight pipe length is generally 5 ~ 10D; 12, you can take the dry (rolling weight method) check, to the user cycle checking convenience;

12. Direct-reading instruments need no external energy, clear, simple, and can output standard signals (pulse frequency or current signal);

13, the instrument performance and price ratio is high, as an economical flow meter;

14, the installation is simple and easy to maintain.