Model selection formula of the hottest metal rotam

2022-08-15
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The selection formula of metal rotameter and attention to installation and use

as a primary detection element for small flow measurement, metal rotameter has been applied in argon measurement system of special steel plant, oxygen measurement system of medium-sized plant and oxygen measurement system of machinery plant successively. Among them, in the oxygen measurement system of medium-sized plant, metal rotameter has operated stably for several months and achieved good measurement results. The following is a brief description of the characteristics, type selection and use of metal rotameter

I. measurement principle and characteristics of metal rotameter

the measurement part of metal rotameter is composed of orifice plate and conical float. When the fluid flows upward through the pipe, the conical float moves upward and reaches balance at a certain position. At this time, the annular gap between the float and orifice plate remains certain, and the annular gap area is proportional to the rising height of the float, and a certain height of the float represents the flow. When the float moves up and down, It is transmitted to the external indicator in the form of magnetic coupling, so that the pointer of the indicator follows the displacement of the float, and with the help of the cam plate, the pointer linearly indicates the flow. Features: metal rotameter has simple structure, reliable operation, wide application range and high range ratio, generally 10b1

II. Selection of metal rotameter

when measuring liquid, metal rotameter is generally calibrated with water under standard conditions (20tnp series spring change fatigue testing machine is applicable to the fatigue performance testing and research of various springs (high strength, high stress, anisotropic parts, special materials), dynamic experiment of elastic components, normal temperature cycle life experiment, etc.); When measuring the gas, mark the scale with the air under the standard state (20E, absolute pressure 011013mpa). Therefore, when selecting an instrument for a certain measuring fluid, its flow range should be converted into the water or air flow in the standard state, and then the model should be selected according to the converted flow range and the standard scale of the metal rotameter. The following takes the oxygen consumption of riveting and welding workshop in the oxygen metering system of machinery factory as an example. The original data, such as (for example, the clamp clamping surface of the plastic film, fiber wire and other samples,):

pipe diameter: Ф 70@5 ; Maximum oxygen consumption: 110m3/h; Minimum oxygen consumption: 10m3/h; Working pressure: 113mpa; Working temperature: 30e; Local average atmospheric pressure: 011mpa

calculation:

(1) oxygen density

(3) flow correction formula under the actual fluid condition used by the metal rotameter:

where: ZS (zsn input in the setting of the experimental machine (force arm)) is the compression coefficient of the measured gas under the standard state (working state) (generally zsuzsn); QS is the actual flow of oxygen under working conditions; QN is the actual flow of air under standard conditions; QN is the density of air under standard conditions (11293kg/m3); PN is the standard atmospheric pressure; TN is the standard temperature 293115k; QSn is the density of oxygen under standard conditions (i.e. Q20); PS is the actual working pressure of oxygen (i.e. P1); TS is the actual working temperature of oxygen (i.e. T1)

according to the model selection instructions of metal rotameter products, lzdh-25 (315-35) is the most suitable

setting the upper limit of the flow of the tertiary and secondary meters

takes the oxygen consumption of the riveting workshop as an example. The secondary meter selected is the compensated intelligent flow integrator produced by Jinan Zhonghuan Automation Research Institute. The parameters to be set in the middle ring meter are: FH, pH, pH, PS, CH, CH, CS

the upper limit of flow FH should be the oxygen flow under the standard state corresponding to the upper limit of the scale of the metal rotameter. Because the scale of the metal rotameter is the air mark under the standard state, it must be converted to the oxygen flow under the standard state

q if necessary, n upper (QN lower): that is, the upper (lower) limit of the flow calibrated by the metal rotameter according to the air under the standard state

according to the selected model lzdh-25 (315-35) metal rotameter, the measurement range of oxygen is 121711m3/h - 127111m3/h. Basically meet the measurement requirements of 11m3-110m3

IV. precautions in the installation and use of metal rotameter

(1) the flowmeter must be installed vertically. The measured fluid flows through the flowmeter from bottom to top, and the inlet and outlet shall be guaranteed to have a straight pipe section with 5 times the diameter of the instrument. For the newly installed pipeline, the pipeline shall be washed clean before the installation of the flowmeter

(2) in order to facilitate the maintenance and replacement of the flowmeter, it is necessary to connect the bypass pipeline during the installation of the instrument

(3) a valve should be installed upstream of the flowmeter, and a flow regulating valve should be installed at 5-10 times the diameter of the instrument downstream. For small diameter instruments, filters should be installed upstream. If the measured medium contains magnetic substances, magnetic filters should be installed in front of the flowmeter

(4) when the measured medium is dirty, the pipe and float should be cleaned in time

(5) the measurement accuracy of metal rotameter is generally grade 215. When the measurement accuracy is required to be high, metal rotameter should not be selected

v. conclusion

the use of metal rotameter solves the problem that small flow cannot be accurately measured, makes the energy measurement work more perfect, and also provides more reliable settlement data for the cost accounting of secondary factories and mines

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