﻿ Magnetic flow meter

# Magnetic flow meter

2019/9/22 7:46:00

## Magnetic flow meter

Choice of protection level
The protection level of the electromagnetic flowmeter should be selected according to the actual situation. If the sensor is required to be installed below the ground and is often flooded, IP68 should be selected. If the sensor is installed above the ground, IP65 and IP67 should be selected. In any case, the display area of ??the electromagnetic flowmeter cannot be used with water or enter the water, which may cause damage to the electromagnetic flowmeter. As a chemical company, the workshop produces high humidity, but IP65 (IP65 is a water-proof type. The electromagnetic flowmeter sensor housing allows the faucet to spray water from the sensor in any direction of the sensor of the electromagnetic flowmeter. The pressure of the water spray is 30Kpa, the water output It is 12.5L/S and the distance is 3 meters.) The electromagnetic flowmeter of the protection grade fully meets the requirements of on-site measurement.
Choice of connection method
Electromagnetic flowmeters have threaded connections, flanged connections, clamps, etc. In the chemical industry, flange-connected electromagnetic flowmeters are generally used. The selection must be consistent with the process-flange engineering pressure and standards.
Conclusion, with the maturity of the domestic instrument industry, chemical companies such as lithium carbonate, boric acid and potash will also enter the market in line with the domestic market. As an important industrial flow measuring instrument, electromagnetic flowmeter should play its role in DCS control. The right selection is especially important to provide accurate measurement data, reduce labor costs and increase production efficiency.

## Magnetic flow meter

Vortex flowmeter working principle
The working principle of the vortex flowmeter is to arrange a vortex generator in the fluid, so that the vortex is alternately generated on both sides of the body, and the vortex column is asymmetrically arranged downstream of the vortex generator to generate a certain frequency, by the formula f= St*v/(1-1.27d/D)*d, (St is the Strauhal number, which is a dimensionless number, related to the vortex generator and Reynolds number; v is the flow velocity; d is the incident head width; D is the nominal diameter) to get the flow rate.
In general, the vortex flowmeter output signal (frequency) is not affected by changes in fluid properties and composition, which means that the meter factor is only related to the shape and size of the vortex generator and the Reynolds number. Its advantages are: simple and firm structure, convenient installation and maintenance; suitable for a variety of fluids, liquid, gas, steam and some mixed phases are applicable; high precision, generally up to ± 1% R; flow range is wide, up to 10 : 1 or 20:1 or more; low head loss; no zero drift; relatively cheap price; disadvantage: not suitable for low Reynolds number Re <20000, limited use of high viscosity, low flow rate, small diameter The requirements for the environment are high, and places with vibration should be eliminated as much as possible, and the upstream side needs to have a long straight pipe section; the meter factor is lower, and the larger the diameter, the lower the diameter. The signal resolution is reduced, so the aperture should not be too large, generally used in DN15~DN300mm.

## Magnetic flow meter

Variable area flowmeter (equal pressure drop flowmeter)
The float placed in the upper and lower small tapered flow passages is moved by the force of the fluid flowing from the bottom to the top. When this force is balanced with the "display weight" of the float (the weight of the float itself minus the buoyancy of the fluid it receives), the capture is stationary. The height at which the float is stationary can be used as a measure of the flow rate. Since the cross-sectional area of ??the flowmeter varies with the height of the float, and the pressure difference between the upper and lower parts is equal when the float is stationary, the flowmeter is called a variable area flowmeter or an equal pressure dropmeter. A typical instrument of this type of flow meter is a rotor (float) flow meter.
Momentum flowmeter
A flowmeter weighing flowmeter that uses the momentum of a measuring fluid to reflect the flow rate. Since the momentum P of the flowing fluid is proportional to the density of the fluid and the square of the flow velocity v, i.e., p v2 , when the flow cross section is determined, v is proportional to the volumetric flow rate Q, so p Q2 . Set the proportional coefficient to A, then Q=A. Therefore, P is measured to reflect the flow rate Q. In this type of flowmeter, most of the flowmeters are used to convert momentum into pressure, displacement or force, and then the flow rate is measured. Typical meters for such flow meters are target and rotary wing flow meters.