Principle and structure of metal tube float flow meter

Abstract: The principle and structure information of the metal tube float flow meter are provided by the excellent flow meter and flow meter manufacturers and quotation manufacturers. The rotameter is a volumetric flow meter in which the float rises and falls with the flow change in the vertical conical tube, and the flow area between them is changed to measure the volume flow meter, also known as the rotameter. At the beginning of the 20th century, this type of meter was named Rota meter in Germany, ie. For more flowmeter manufacturers to select models and price quotations, you are welcome to inquire. The following is the details of the principle and structure of the metal tube float flowmeter. The rotameter is a volumetric flow meter in which the float rises and falls with the flow change in the vertical conical tube, and the flow area between them is changed to measure the volume flow meter, also known as the rotameter. At the beginning of the 20th century, this type of meter was named Rota meter in Germany, which was popular in Europe, but in the United States and Japan, it was often called Variable Area Flowmeter or Area Flowmeter; A variety of variable area flowmeters, but because the float flow accounts for the vast majority of variable area flowmeters, it is customary to call them variable area flowmeters. The principle of rotameter was conceived in the 1860s, and commercial products appeared in the early 20th century. In the late 1930s, the carbon mandrel method created conditions for mass production of glass conical tubes, which laid the foundation for the industrial application of rotameters. In the 1940s and 1950s, Europe and the United States carried out development and performance research. In particular, Fischer and Porier companies in the United States made contributions to improving performance and expanding varieties, such as reducing the influence of liquid viscosity and having output signals, which greatly expanded the application field. In the late 1950s, Shenyang Glass Instrument Factory first provided glass tube rotameters in China, and in the mid-1960s Shanghai Guanghua Instrument Factory was the first to provide metal conical tube rotameters with output signals. From 1985 to 1987, the sales amount of rotameters in Japan, Western Europe and the United States accounted for 11% to 17% of the flow meters, and my country accounted for about 14% in 1990. From the perspective of the proportion of the number of applications, in 1985, the rotameter accounted for 19.2% of the 17,000 flow meters of 72 companies in the UK sample survey. In 1996, the output of rotameters in my country was estimated to be between 150,000 and 170,000 units, of which about 95% were glass tube rotameters. The principle and structure of metal tube rotameter The flow detection element of the rotameter is composed of a vertical tapered tube expanding from bottom to top and a float group moving up and down along the axis of the tapered tube. The working principle is shown in Figure 6.1. When the measured fluid passes through the annular gap 3 formed by the conical tube 1 and the float 2 from the bottom to the top, the upper and lower ends of the float generate differential pressure to form the lift force of the float. When the weight of the float is medium, the float will rise, the area of ​​the annulus will increase, the fluid velocity at the annulus will drop immediately, the differential pressure between the upper and lower ends of the float will decrease, and the lifting force acting on the float will also decrease, until the lifting force is equal to the immersion in the float. When the weight of the float in the fluid, the float is stabilized at a certain height. There is a corresponding relationship between the height of the float in the cone tube and the flow through it. The basic equation of volume flow Q is a—the flow coefficient of the instrument, which varies with the shape of the float; ε—the gas expansion coefficient when the measured fluid is gas, which is usually ignored because the correction amount of this coefficient is small, and it has been It is included in the flow coefficient, ε=1 for liquids•F - circulation annular area, m2g - local acceleration of gravity, m/s2; Vf - float volume, if there is an extension, it should also be included, m3ρf-float material density, kg/m3;ρ- The density of the fluid to be measured, such as the density of the gas on the upstream cross section of the float, kg/m3; Ff is the cross-sectional area m2 at the working diameter (maximum diameter) of the float; G is the mass of the float, kg. The relationship between the circulation annular area and the height of the float is shown in formula (6.3). When the structural design has been determined, d,βis a constant. There is a quadratic term of h in the formula. Generally, this nonlinear relationship cannot be ignored. Only when the cone angle is very small can it be regarded as approximately linear. In the formula, d—the maximum diameter of the float (that is, the working diameter), m; h—the rising height of the float from the point where the inner diameter of the conical tube is equal to the maximum diameter of the float, mβ- the cone angle of the tapered tube; a, b - constants. The typical structure of the 15-40 caliber transparent conical tube rotameter is shown in Figure 6.2. The most commonly used transparent conical tube 4 is made of borosilicate glass, and is customarily referred to as a glass tube float flowmeter. The flow indexing is directly engraved on the outer wall of the conical tube 4, and an indexing scale is also installed next to the conical tube. The inner cavity of the conical tube has two kinds of cone smooth surface and guide ribs (or plane). The float moves freely in the conical tube, or moves under the guidance of the ribs of the conical tube, and the instrument with the inner wall of the larger mouth smooth surface is also guided by a guide rod, as shown in Figure 6.4(a). 6.3 is a typical structure of a right-angle installation metal tube rotameter, which is usually suitable for instruments with a diameter of 15 to 40 or more. The conical tube 5 and the float 4 constitute a flow detection element, and the detection element is also composed of an orifice plate and a conical floating plug, as shown in Figure 6.4(f). The sleeve (not shown in Figure 6.3) has an extension of the guide rod 3, which transmits the displacement of the float to the conversion part outside the sleeve by means of magnetic steel coupling. The conversion part has two types of local indication and remote signal output. In addition to the right-angle installation structure, there is also a straight-through structure in which the center line of the inlet and outlet is concentric with the tapered tube, which is usually used for instruments with a diameter of less than 10 to 15 mm. Figure 6.4 shows examples of various structures of a transparent tapered tube (or transparent straight tube) rotameter and a metal tube rotameter. The above is the whole content of this article. You are welcome to inquire about the flowmeter selection and quotation of our factory. 'The principle and structure of metal tube float flow meter'

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