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The characteristics of the vortex flowmeter and the applicable working conditions
Characteristics of vortex flowmeter and applicable working conditions Main problem The vortex flowmeter has been widely used for more than ten years, and the use effect is not satisfactory. The main reasons are summarized as follows. 1) Product quality problems, design principles or design solutions have serious defects, product materials, process quality is not good. Especially in recent years, some production plants have pursued profits unilaterally, and the products have been shoddy, which has tarnished the reputation of vortex flowmeters. 2) The selection and use of the instrument, the user-specified process parameters are inaccurate, resulting in improper selection; there is a problem with the installation location, and the installation does not meet the requirements. 3) On-site adjustment problems, lack of adjustment or improper adjustment of on-site operation, correct adjustment is the key to use. 2. Applicable conditions Vortex flowmeters are not suitable for measuring low Reynolds number (ReD ≤ 2 × 104) fluids. When the Reynolds number is low, the Strauhal number changes with the Reynolds number, the linearity of the instrument becomes worse, and the high viscosity of the fluid will significantly affect or even hinder the generation of the vortex. A limitation of the selection is that it cannot be used under the limit Reynolds number. . Vortex flowmeters are suitable for a wide range of fluids, but care should be taken with regard to the dirty nature of the fluid. The turbidity of the vortex generator caused by the fluid containing solid particles generates noise and wears the vortex generator. If the short fibers contained are wound on the vortex generator, the meter factor will be changed. Vortex flowmeter has little experience in the application of mixed-phase fluids. It can generally be used for dispersing and uniform micro-bubbles, but the volumetric gas-bearing rate should be less than 7%-10% of gas-liquid two-phase flow. If it exceeds 2% The meter factor should be corrected. It can be used in gas-solid and liquid-solid two-phase flow with dispersed and uniform solid particles and content of not more than 2%. It can be used for two-component flow of liquid and liquid (such as oil and water) which are insoluble in each other. Pulsating and rotating flows can have a severe impact on VSF. If the pulsation frequency coincides with the vortex frequency band, it may cause resonance to destroy normal operation and equipment, causing the vortex signal to produce a "lock-in" phenomenon, at which time the signal is fixed at a certain frequency. "Locking" is related to the pulsation amplitude, the shape of the vortex generator, and the clogging ratio. The pulsation threshold for the normal operation of the vortex flowmeter has yet to be determined experimentally. Since the 1980s, flow measurement workers at home and abroad have carried out many experimental studies on the application of VSF in mixed-phase flow and pulsating flow. The technical report issued by the International Organization for Standardization (ISO) also pays attention to this aspect. 3. Economics Among the numerous flow meters, the vortex flowmeter is economical and is an economical flow meter. The basic performance of the vortex flowmeter is at a medium-to-high level. The purchase cost is lower than that of mass, electromagnetic, and volumetric. The installation, operation, and maintenance costs are lower than the throttle type, volumetric type, and turbine type. The control system test instrument can use the dry calibration method to save the cycle check cost.