外文翻譯---液位檢測(cè)

1、.附錄CLiquid Level MeasurementChemical industry with the progress of science and technology got rapid development, in order to make the equipment safe and reliable operation, and can be utmost to improve product quantity and quality, to effectively operate automatically and process adjustment, realize

2、 the scientific management for the enterprise to provide the necessary material and energy of accurate data, must be in production in the process of pressure, flow, level, temperature, chemical composition of various parameters such as timely, accurate measurement.Generally the process of containers

3、, tanks, towers, tank of liquid surface position level, slot bucket, cans, and warehouse ChuFa solid block, the accumulation of particles, powder height and surface position is called a material level; Two not fluid boundary between the height and the liquid and solid separation height is called int

4、erface position, the position of assembly level, material level, liquid level interface.Material level measurement to correctly measure the container storage capacity or quality, know container level of high and low and adjust at any time, in the material level to maintain the required height.Materi

5、al level measurement in chemical process, not only under normal temperature, atmospheric pressure and ordinary medium, material level, liquid level measurement of the interface, but also often meet high temperature, low temperature, high pressure, inflammable and explosive (negative temperature). Vi

6、scosity and foam, boiling dielectric material level measurement problems.In order to adapt to the characteristics of chemical objects, to meet the requirements of the chemical process material level measurement, there are many material level measurement and instrumentation.1. Ultrasonic liquid level

7、 meter and radar material level meter(1) ultrasonic liquid level meterMaterial level measurement process, the ultrasonic signal, issued by the ultrasonic probe, the liquid or solid material surface after launch back, by the same sensor receiving, ultrasonic measurement of the whole running time, so

8、as to realize the measurement of material level, acoustic velocity transmission of the ultrasonic pulse, from transmitting to receiving to ultrasonic pulse need time interval and the transducer to the surface of the measured medium is proportional to the distance.Emit ultrasonic level meter pulse, n

9、ot the echo of detection at the same time. Due to the launch of the ultrasonic pulse width has a certain time, and after launch the ultrasonic sensor and aftershocks, during cannot detect the echo, so from the start down the surface of the probe a short distance can't normal inspection, this dis

10、tance is called blind spots. Was the highest level such as into the blind area, detect instrument will not be able to correctly, there will be error, if necessary, heightened level meter can be installed.Ultrasonic liquid level meter also has shortcomings, the ultrasonic transmission by gas interfer

11、ence, level surface bubbles, corrugated, etc, the ultrasonic transmission by gas interference, level surface bubbles, corrugated, etc., the ultrasonic reflection effect. Material is volatile, liquid gas entrapment, the container by vibration (e.g., motors) are installed on the container can't us

12、e ultrasonic liquid level meter.(2) radar material level meterRadar level gauge USES launch - reflection - receive work mode. Radar level meter antenna emit electromagnetic wave, the wave reflected by the measured object surface, again by the antenna, the electromagnetic wave from transmitting to re

13、ceiving time is proportional to the distance to the liquid surface. In practice, there are two kinds of radar level gauge means the frequency modulation continuous wave and pulse wave. Liquid level meter adopts frequency modulation wave technology, power consumption is big, the four wire system, sho

14、uld be used in electronic circuit is complicated. And the radar pulse wave technology level gauge, low power consumption, easy to implement essential safety, high precision, wider application scope.Radar level gauge measuring the electromagnetic waves can pass through a vacuum, don't need a tran

15、smission medium, is not affected by air, steam, groove volatile fog effect, can be used for such as coarse benzene volatile medium level measurement.Radar level meter can be used for almost all of the liquid level measurement. Electromagnetic wave on the surface level when firing, signal attenuation

16、, when the signal attenuation through the hours, can lead to radar level meter cannot detect enough electromagnetic wave signal, the conductive medium can be a very good reflection of electromagnetic wave, the dielectric constant is greater than 1.5 non conductive medium dielectric constant was 1.0

17、(air) will also be able to guarantee sufficient reflection wave, dielectric constant, the greater the reflection signal. In practice, almost all medium can reflect enough of reflection wave.(3) radar level gauge, ultrasonic liquid level meterUltrasound and radar is the main measuring principle is di

18、fferent, lead to their different application occasions, radar is given that the dielectric constant of the measured substance, which is given that the density of the material being measured, so the low dielectric constant material radar measurements will be effect to sell at a discount greatly, the

19、solid matter in general, push harder, another wave of different means of transmission components, such as ultrasonic wave was launched by the vibration of the piezoelectric material, so it is can be used in higher pressure or negative pressure of the situation, usually only in the atmospheric pressu

20、re containers. The radar can be used in the process of high pressure tank. Radar emission Angle is bigger than ultrasound, small containers or elongated don't recommend using non-contact radar, generally recommend a director radar. Finally is the temperature on the accuracy, of course, must be h

21、igher than the ultrasonic, radar must use high resolution radar in the tank, without ultrasonic. As for the price, usually ultrasonic, lower than the radar in a wide range of course some ultrasonic price is also high. Such as the range of 6-70 meters, the preferred ultrasonic liquid level meter. Pay

22、 attention to the stirring groove, groove wall adhesion can produce interference of the reflected wave, level measurement, the installation is to choose the appropriate installation position, so as to avoid the interference of these factors.Level two categories, including liquid level and material l

23、evel. Liquid level and liquid level indicator and two continuous level measurement. Liquid level indicator is the level of several fixed position measuring, used in liquid level of upper and lower limit alarm, etc. Continuous level measurement is to measure liquid level continuously, it is widely us

24、ed in many fields such as petroleum, chemical industry, food processing, have very important significance. For more than 20 kinds of continuous level measurement method for comparative analysis. Glass tube, glass plate, double color water method.Manual gauging glass tube method: this method is using

25、 the principle of communicating vessels, level scale read directly from the instructions. Glass plate method: glass which can be installed through connectors can also be installed in the container wall openings, and series a few piece of glass to increase the range. Numerical scale read directly fro

26、m the glass plate level.Double color gauge method: this method using the optical principle, make water shows green, and make the water vapor shows red, which indicate the water level.Artificial gauging method: the method is used for measuring oil tank liquid level. When measuring, the surveyor gauge

27、 Surveyor to volume of the oil dipstick into oil, and filed when feet lead contact with the tank bottom oil dipstick. According to the quantity of oil traces on the oil dipstick, read out the oil level height; End according to the quantity of oil dipstick test cream color change to determine the hei

28、ght of the water cushion layer, to determine high oil and high water above 4 methods are artificial measurement method, measurement is simple, the advantages of high reliability, intuitive, and low cost.Blowing method, differential method, HTG blowing method: because of the blow pipe approximation i

29、s equal to the fluid column pressure in the static pressure, thus P = rho gH type of rho - liquid density; H - level. So the liquid level is measured by the static pressure P can be H. Strong method suitable for measuring the corrosive gas blowing, have suspended material content in the liquid, and

30、is mainly used in the measurement accuracy is not high.Differential pressure method: the open container or atmospheric vessels, valves and gas phase pressure pipeline saves. Based on the relationship between differential pressure and liquid level P = P2 - P1 = rho gH type: P - positive and negative

31、pressure chamber pressure transmitter; P2 and P1 - led tube pressure; H - level. Differential pressure transmitter will pressure difference transformation for 4 20 mA dc signal. If the pressure in the measuring range lower limit of the corresponding output signal is greater than or less than 4 mA, a

32、re all need to adjust the migration zero migration technology such as spring, is equal to 4 mA. HTG method: this method is applied to differential pressure oil tank liquid level measurement.Buoy method: this method USES the middle maglev barrel with holes as liquid level sensor. Stainless steel casi

33、ng from buoy hole through the middle, between fixed to the roof and bottom. Liquid level change driven maglev hollow tube (permanent magnet) hides inside can move up and down the casing, and attract the casing of magnet can move up and down the casing wall, secondary instrument | instrument accordin

34、g to the moving magnet volume to calculate the liquid level.Floating ball method: this method is using the lever principle of work. Floating ball with liquid level change and around the axis of rotation, the pointer on the drive shaft rotation, and at the other end of the lever balance weight balanc

35、e, at the same time indicates the level value on the dial. Floating ball method have ball float within and outside the floating ball type two kinds. Floating ball method is mainly used for high temperature measurement, the viscosity of the liquid level, but the range is smaller.Servo method: this me

36、thod USES volatile integral circuit, eliminate jitter, prolong life, improve the precision of level measurement. The modern servo liquid meter measuring accuracy is higher, has 40 m range less than the accuracy of 1 mm, and generally has the function of measuring density distribution and average den

37、sity.Sinking method: the location of the sinking as the change of liquid level change, but the variation is not equal and level variation. Torque tube sinking method: the torque tube core shaft torsional Angle changes, secondary instrument according to the torsional Angle variation to calculate the

38、liquid level above five kinds of methods are using the buoyancy principle to work.Such as R, R, l, is a fixed value, as long as the use of epsilon 1, epsilon 2, CH can calculate the liquid level H. Measurement of conductive liquid capacitance method principle, the formula is slightly. Capacitive liq

39、uid level meter price is low, easy to install and can be applied to occasions of high temperature and high pressure. Capacitive liquid level instrument measurements but repetitive accuracy is low, need regular maintenance and calibration again, working life is not very long.This method is especially

40、 suitable for the measurement of conductive liquid, sensitive device resistance characteristics, its resistance along with the change of liquid level change, so the resistance value is transmitted to the secondary circuit level. Electrical parameters of the liquid level sensor method to measure the

41、liquid level changes.Magnetostrictive method, ultrasonic method, modulating optical method, microwave method Magnetostrictive method: the method is used for measuring oil tank liquid level has two float, respectively used to detect oil and gas and oil/water interface. Each float in possession of a s

42、et of permanent magnets, used to generate a fixed magnetic field. Measurement, level gauge head emit low "enquiry" pulse current, the magnetic field generated from the current conduction down the waveguide. When electric current magnetic field is met, and float a "return" impulse

43、 (also called "waveguide distortion" pulse). Ask pulse and the back pulse time lag between the corresponding to the height of the oil-water interface and the interface of oil and gas. Easy to install, magnetostrictive liquid level meter measuring accuracy is high, but the liquid density an

44、d temperature changes can lead to a measurement error, float along the outside of the waveguide tube move up and down, are easy to be jammed.Ultrasonic method: antenna (mostly aperture antenna, also has a planar antenna) radiation, after liquid surface reflection is the antenna, and then calculated

45、by the secondary circuit, transmitting and receiving signals of liquid level difference. The liquid level meter adopts triangle wave form of frequency modulation, and through to the transmitting and receiving signal mixing after get the difference between the signal analysis, microwave transmission

46、time, thus calculate the liquid level. Microwave speed by the transmission medium, the influence of temperature, pressure, liquid dielectric constant is small, but the liquid interface fluctuations, on the surface of the dielectric constant of bubbles, liquid medium has a great influence on the micr

47、owave reflection signal strength. When the pressure in excess of the prescribed value, the pressure will have a significant impact on level measurement accuracy. For liquid dielectric constant is less than the stipulated value, most of the radar level gauge need to adopt waveguide, but rust, bend wa

48、veguide and tilt will affect the accuracy of measurement. Sky high h, for example, to 20 m, guided wave tube and vertical direction Angle alpha just over 0.573 °, is caused by the liquid level h will be more than 1 mm error, thus proved that the tilted Angle alpha (in degrees) is small, h meet:

49、Radar level gauge is particularly suited to high pollution and high viscosity of the product, such as asphalt, etc. Repeat accuracy of radar level gauge measuring is higher, need regular maintenance and calibration, measurement accuracy is higher, but the price is higher, difficult measurement of oi

50、l-water interface.Modulating optical method and microwave method is similar, only by phase or frequency modulation of optical signal instead of microwave signal. But light signals are greatly influenced by steam, oil, steam, and the liquid level fluctuation is very sensitive。All three methods above

51、is through testing to determine the level of the signal propagation time. Sets the time of transmitting and receiving signals to t, h = n / 2 is empty, v for wave propagation speed.6 magnetic flap method, the vibration method, radiation method, optical fiber sensors methodMagnetic flap method princi

52、ple: float is equipped with a set of permanent magnets, with the liquid level change and move up and down, flip through magnetic coupling driving magnetic flap components. When the liquid level goes up, the magnetic flap of red face outwards; When liquid level drops, white facing out. Therefore, acc

53、ording to the color of the magnetic flap determined level. Within the float magnet with magnetic flap magnetic structure is 10 mm, the distance between each frame. Adopt several magnetic flap device series can increase range.Servo control vibration hammer to climb up and down motion and vibration, v

54、ibration free vibration after vibration sensor detection, the detection signal after FET transform to get the frequency of the maximum power point, finally by the empty cans inherent frequency/liquid level of the liquid level relation. This method of level measurement need to shock hammer, servo mec

55、hanical moving parts, such as its working life is not too long, should be regular maintenance and calibration, installation is more complex.Radiation method: radioactive isotope in the process of decay radiation, common rays are alpha, beta, and gamma rays. Among them, the gamma rays of the strong p

56、enetrating power, range far, therefore, widely used in the radiation level measurement. Gamma-ray intensity before and after the experiment, through the material change.液位檢測(cè)化學(xué)工業(yè)隨著科學(xué)技術(shù)的進(jìn)步得到了迅速發(fā)展，為了能使設(shè)備安全可靠的運(yùn)行，并能最大限度的提高產(chǎn)品的數(shù)量和質(zhì)量，對(duì)生產(chǎn)過(guò)程有效的進(jìn)行操作會(huì)和自動(dòng)調(diào)節(jié)，為企業(yè)實(shí)現(xiàn)科學(xué)管理提供必要的物料和能量的準(zhǔn)確數(shù)據(jù)，就必須對(duì)生產(chǎn)過(guò)程中的壓力、流量、物位、溫度、化學(xué)成分得等各種

57、參數(shù)進(jìn)行及時(shí)、準(zhǔn)確的測(cè)量。一般把工藝過(guò)程中的罐、塔、槽等容器存在的液體表面位置叫液位，槽斗、罐、倉(cāng)庫(kù)等所儲(chǔ)發(fā)固體塊、顆粒、粉料的堆積高度和表面位置叫做料位；二種不容液體的分界高度以及液體與固體間的分界高度叫做界面位置，液位、料位、界面位置總成物位。物位測(cè)量的目的在于正確地測(cè)知容器中儲(chǔ)藏物質(zhì)的容量或質(zhì)量，隨時(shí)知道容器物位的高低和調(diào)節(jié)，在物位保持在所要求的高度。在化工過(guò)程的物位測(cè)量中，不僅有常溫、常壓，一般性介質(zhì)的液位、料位、界面的測(cè)量，而且還常常會(huì)遇到高溫、低溫（負(fù)溫）、高壓、易燃易爆。粘性及多泡沫、沸騰狀介質(zhì)的物位測(cè)量問(wèn)題。為適應(yīng)化工對(duì)象的特點(diǎn)，滿足化工過(guò)程物位測(cè)量的要求，目前已有許多測(cè)量物位

58、的方法和儀表。超聲波液位計(jì)、雷達(dá)物位計(jì)超聲波液位計(jì)物位測(cè)量過(guò)程中，超聲波信號(hào)，由超聲波探頭發(fā)出，經(jīng)液體或固體物料表面發(fā)射后折回，由同一個(gè)探頭接收，測(cè)量超聲波的整個(gè)運(yùn)行時(shí)間，從而實(shí)現(xiàn)物位的測(cè)量，超聲波脈沖以聲波速度傳播，從發(fā)射到接收到超聲波脈沖所需要時(shí)間間隔與換能器到被測(cè)介質(zhì)表面的距離成正比。物位計(jì)發(fā)射超聲波脈沖時(shí)，不能同時(shí)檢測(cè)反射回波。由于發(fā)射的超聲波脈沖具有一定的時(shí)間寬度，同時(shí)發(fā)射完超聲波后傳感器還有余震，期間不能檢測(cè)反射回波，因此從探頭表面向下開始的一小段距離無(wú)法正常檢測(cè)，這段距離稱為盲區(qū)。被測(cè)的最高物位如進(jìn)入盲區(qū)，儀表將不能正確檢測(cè)，會(huì)出現(xiàn)誤差，如有需要，可以將物位計(jì)加高安裝。超聲波液位

59、計(jì)也有不足之處，超聲波的傳輸受氣體干擾，物位表面有氣泡，波紋等不平，超聲波的傳輸受氣體干擾，物位表面有氣泡、波紋等不平，超聲波的反射效果大打折扣。物料有揮發(fā)、液夾氣時(shí)，容器上由震動(dòng)（如容器上安裝有電機(jī)）不能選用超聲波液位計(jì)。雷達(dá)物位計(jì)雷達(dá)液位計(jì)采用發(fā)射-反射-接收的工作模式。雷達(dá)液位計(jì)的天線發(fā)射出電磁波，這些波經(jīng)被測(cè)對(duì)象表面反射后，再被天線接收，電磁波從發(fā)射到接收的時(shí)間與到液面的距離成正比。在實(shí)際運(yùn)用中，雷達(dá)液位計(jì)有兩種方式即調(diào)頻連續(xù)波式和脈沖波式。采用調(diào)頻波技術(shù)的液位計(jì)，功耗大，須采用四線制，電子電路復(fù)雜。而采用雷達(dá)脈沖波技術(shù)的液位計(jì)，功耗低，容易實(shí)現(xiàn)本質(zhì)安全，精確度高，適用范圍更廣。雷達(dá)液位計(jì)測(cè)量時(shí)發(fā)出的電磁波能夠穿過(guò)真空，不需要傳輸媒介，具有不受大氣，蒸汽、槽內(nèi)揮發(fā)霧影響的特點(diǎn)，能用于揮發(fā)的介質(zhì)如粗苯的液位測(cè)量。雷達(dá)液位計(jì)幾乎能用于所有的液體的液位測(cè)量。電磁波在液位表面發(fā)射時(shí)，信號(hào)會(huì)衰減，當(dāng)信號(hào)衰減過(guò)小時(shí)，會(huì)導(dǎo)致雷達(dá)液位計(jì)無(wú)法測(cè)到足夠的電磁波信號(hào)，導(dǎo)電介質(zhì)能很好的反射電磁波，介電常數(shù)大于1.5的非導(dǎo)電介質(zhì)（空氣的介電常數(shù)為1.0）也能夠保證足夠的反射波，介電常數(shù)越大，反射信