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Flowmeter related knowledge& B- v9 t' t- Y : a# B* W: l5 b ( g5 a" l2 q# G& w, J' t * r一. + e: t. y9 c( W) A% xIntroduction content: Flowmeters are classified according to the measurement principle; focusing on the orifice plate and pitot tube in differential pressure flowmeters; electromagnetic flowmeter, vortex flowmeter, mass flowmeter. Each flowmeter will be introduced from its principle, general structure, applicability, advantages and disadvantages. 6 Q6 @4 P, c2 l3 X$ f& O1 l 1. - ] " B# o6 @; |1 \! ~) t, j1 oChemical Technology Forum Gift Rose Hand with Remaining Fragrance Flowmeters are generally classified according to the measurement principle: - V4 N r2 _0 @: c7 B * fChemical Technology Forum Gifts Rose Hands with Remaining Fragrance Principles of differential pressure: orifice plate, pitot tube, wedge, V cone, venturi tube, flow nozzle, etc. 7 @7 q( N0 m4 O5 X' s3 J+ h% N6 i * B - k# K- b3 @5 v: K speed principle: electromagnetic flowmeter, vortex flowmeter, turbine flowmeter, ultrasonic flowmeter Chemical Technology Forum presents roses with lingering fragrance; o# P) _8 e7 p+ J Mass flow meter: Coriolis mass flow meter, thermal mass flow meter # V( ^5 S3 `" F0 Y; u5 M * v7 z Volumetric flowmeter: Volumetric flowmeter (h4 _; U" @8 o+ 2. Z6 P2 k/ A. o9 B% j% h; vChemical Technology Forum presented a rose hand with lingering fragrance orifice flow meter i4 u) p# V! w% `& ?8 n: ] , Y! G8 Z * M4 p 2.1 Orifice plate flow meter principle: Place a thin disc with sharp-edged openings in the fluid pipe. When the fluid passes through the orifice plate, the fluid speed increases and the pressure decreases, a pressure difference will occur. Through the measured pressure difference, the flow rate % is converted from the formula z9 G1 J2 l0 T2.2 Advantages and disadvantages: : x; H# }& w4 e! t& Z7 Y/ z$ x% S Advantages: Firm, stable and reliable performance, long service life, low price. It has strong applicability. All one-way fluids, including liquid, steam, and steam, can be measured, and some gas-solid, gas-liquid, liquid-solid, etc. can also be applied. 5 m: \- w6 `0 O; ?, m Disadvantages: The edge of the orifice must be kept clean and sharp to obtain the best instrument performance, so the maintenance cost will increase. In addition, the orifice plate may cause high pressure loss. The orifice plate needs to be connected to the pressure guide pipeline, the three-valve group and the pipe bracket, so the installation cost is relatively high. The repeatability and accuracy of measurement are at a medium level among flowmeters. Due to the complex influence of many factors, the accuracy is difficult to improve. The range is narrow... z& s9 K% W; }7 Q3 S The requirements for on-site installation conditions are high, and if a longer straight pipe section is required, it is generally difficult to meet it. - e" X/ ] ' `8 a1 d' r8 v3. : ?: n; F" f; K( w) C6 M Chemical Technology Forum Gift Rose Hands with Remaining Fragrance Average Pitot Tube' }/ I: U5 ~9 F, O3 rbbs. * * .net3.1 Principle 1 p8 m- x4 _& Q1 ^ * `3 I3.2 Advantages and Disadvantages: Average pitot tubes have excellent long-term accuracy (1-3%), in part because they have no front-end wear problems. However, fluids containing impurities can clog the measurement holes, thus reducing accuracy. Compared with other differential pressure flowmeters, pitot tubes produce relatively low differential pressures, making the measurement of pressure differences difficult and limiting the adjustable range or turndown ratio. In addition, the permanent pressure loss of pitot tubes is very low. 3 |& d8 _7 c- ^& K Q9 I# C3.3 Applicability: It is very suitable for pipes with large diameters. Pitot tubes are easy to install and inexpensive, and can measure fluid flow in any direction. Like orifice plates, they are not suitable for measuring environments containing solid particles that will cause device wear and deformation. In addition, when installing Annubar, the installation length of Annubar should not be less than two-thirds of the pipe diameter. If the pipe diameter is very large, Annubar needs to be inserted through the entire pipeline and fixed with a flange at the other end to prevent deformation. " \ g3 X, g( j) _6 p. A% Zbbs. * * .net4.Electromagnetic flowmeter (8700 series) / e1 D& H$ ^- n1 ^0 S6 Obbs. * * .net4.1 Principle: Faraday electromagnetic induction principle: H9 h I2 4.3 Advantages and Disadvantages: It is not constrained by Reynolds number and flow velocity distribution, has high accuracy, has a high adjustable range, and does not cause pressure loss. Because it is not easy to block, it is suitable for measuring liquid-solid two-phase fluids containing solid particles or fibers, such as pulp, coal-water slurry, ore slurry, etc. The disadvantage is that it cannot measure liquids with very low conductivity, such as petroleum products and organic solvents. ! D c% n M2 ~4 T- B8 q) U6 `bbs. * * .net5. Vortex flowmeter (8800C) ) Z' M4 q# Y; u) Z G& k# DE" H 5.2 Structure: 3 z" ^+ n8 W( K$ ] . c5 B vortex generator detection element ------ generally installed on the generator, or directly opening a hole in the generator, and installing the detection element in the pressure guide hole to detect the differential pressure on both sides of the generator. 6 w, S * |$ l% t4 S5 ^. d 5.3 Advantages: simple and firm, easy to install and maintain, suitable for many fluids, such as liquids, gases, steam and partially miscible fluids, with high precision and small pressure loss. The chemical technology forum gave the rose hand a lingering fragrance 4 G$ N/ e: X- j0 L% | Disadvantages: Not suitable for use with high viscosity, low flow velocity, and small diameter. Stability is affected by changes in flow velocity distribution and rotating flow. Not suitable for locations with strong earthquakes. 0 b; D1 t: ] 1 I9 K; x1 H * B 6 Coriolis mass flow meter (Micro Motion F series, Micro Motion T series) 8 d( P8 ^4 v6 D, v * G S6 x- A! h * I! S. Y6.1 Principle: An unobstructed, curved tube is used as a sensor, and Newton's second law of motion is used to determine the flow rate. An electromagnetic drive coil is positioned at the bend center of the tube, causing the tube to vibrate like a tuning fork. That is, there is a thin-walled measuring tube with both ends fixed. It is excited at the resonance or close to resonance frequency of the measuring tube at the midpoint. The fluid flowing in the tube generates Coriolis force, causing the two halves of the measuring tube before and after the midpoint to twist in opposite directions. The amount of distortion is measured using optical or electromagnetic methods to obtain the mass flow rate. 4 K+ ?3 p$ S+ I, Q5 s4 i' Y * l# E8 C4 V0 E- x% X, D * q 6.28 f) K% G7 x5 b Advantages: High measurement accuracy. A wide range of measurable fluids, including various liquids with high viscosity, slurries containing solids, liquids containing trace amounts of gas, and high and medium pressure gases with sufficient density. ) w3 X# T+ S" n; V( Q% T6 X Chemical Technology Forum’s gift of a rose hand has a lingering fragrance is not sensitive to the incoming flow velocity distribution, so there is no upstream and downstream straight pipe section requirement. Chemical Technology Forum’s gift of a rose hand has a lingering fragrance, p3 t0 n# q$ C$ D" t L 9 m, L0 W# B% ?# R% z8 \bbs. * * .net6.3 Disadvantages: It is easy to form zero point drift and affect the accuracy; bbs. * * .net+ t3 N4 B j& c- t) cannot measure low-density media such as low-pressure gas. If the gas content in the liquid exceeds a certain value, it will significantly affect the measured value.bbs. * * .net+ r' e$ C * \7 W! l, Q! y are more sensitive to external interference. In order to prevent the influence of pipeline vibration, the installation requirements are relatively high. The chemical technology forum gives people rose hands with lingering fragrance. p$ p. O9 t7 s' `! c, f. b The wear, corrosion or sedimentation of the inner wall of the measuring tube will affect the measurement accuracy. 0 _( }" z" z4 u5 C. Z is expensive, about 2-5 times that of the electromagnetic flowmeter of the same caliber. 6 E# n5 e% g" g$ f0 N. @