The electromagnetic flowmeter has a large measuring range, usually 20:1~50:1, and the optional flow range is wide; the diameter of the electromagnetic flowmeter is wider than other types of flowmeters, from a few millimeters to 3 meters; the positive and negative two-way flow can be measured. The pulsating flow rate can also be measured as long as the pulsation frequency is much lower than the excitation frequency; the meter output is linear in nature; it is easy to select the material type of the fluid contact member, and can be applied to corrosive fluids and the like. Since the electromagnetic flowmeter measures much more with suspended solids or dirt than other flow meters, the probability of failure of the inner wall adhesion layer is relatively high. If the electrical conductivity of the adhesion layer is close to the liquid conductivity, the instrument can output the signal normally, but only change the flow area to form a hidden fault of the measurement error; if it is a high conductivity adhesion layer, the electromotive force between the electrodes will be short-circuited; if it is an insulating adhesion layer The surface of the electrode is insulated to disconnect the measuring circuit. The latter two phenomena will make the meter inoperable.
Turbine flowmeter composition
Turbine flowmeters are speed flowmeters, also known as impeller flowmeters. The impeller type flowmeter utilizes the relationship between the rotational angular velocity of the impeller placed in the fluid and the fluid flow velocity. By measuring the rotational speed of the impeller to reflect the volumetric flow rate of the fluid passing through the pipeline, it is a relatively mature high-accuracy instrument in the flowmeter. One. Turbine flowmeters generally consist of the following five typical parts:
1. Body
The material of the body is generally steel or cast iron, and the ends are flanged. The small diameter gauge also has a threaded interface.
2. Measured component
The turbine has precision machined blades that together with a set of reduction gears and bearings form the measuring assembly. The two high-precision stainless steel permanent self-lubricating bearings that support the turbine ensure a long service life of the assembly. Turbine flowmeters can also be lubricated with an external lubricant pump, but be careful not to overdo it.
3. counter
The following important information is available on the counter panel:
(1) Maximum working temperature and pressure:
(2) Metering and minimum and maximum flow levels
(3) Product model and number
(4) Explosion-proof grades and signs
(5) The equivalent of the fluid corresponding to the low frequency or high frequency pulse and the wiring method.
4. Rectifier
The rectifier is used to keep the fluid flowing through the turbine flow meter in a regular state, thereby eliminating the disturbance and having an unaffected effect on the metering. High metering accuracy.
5. Magnetic coupling transmission device
The device separates the counter portion in the atmospheric environment from the gas being measured and transmits the rotation of the measuring assembly to the counter.
First, the gas turbine flowmeter installation requirements
1. When the gas flowmeter is installed, it is strictly forbidden to directly conduct electric welding at the inlet and outlet flanges to avoid burning the internal parts of the flowmeter;
2. For the newly installed or overhauled pipeline, it must be purged to remove the debris in the pipeline before installing the flowmeter;
3. The gas turbine flowmeter should be installed in a place that is easy to maintain, has no strong electromagnetic field interference, no mechanical vibration and thermal radiation;
4. Gas turbine flowmeters should not be used in places where flow is frequently interrupted and there is strong pulsating flow or pressure pulsation;
5, the gas turbine flowmeter should ensure that the pipeline is coaxial, and prevent the gasket from protruding into the pipeline, otherwise it will disturb the flow profile;
6. The flow direction of the gas turbine flowmeter should be consistent with the direction marked on the casing. The upper and lower pipelines of the flowmeter should be guaranteed with 2DN and 1DN straight pipe sections;
7. When using external power supply, the flowmeter must have reliable grounding, but it should not share the grounding wire with the high-power system; when the pipeline is installed or repaired, the grounding wire of the welding system should not be overlapped with the flowmeter.
8. Since the flowmeter needs to be repaired and calibrated, in order to ensure normal gas supply, bypass piping should be set. The bypass pipe valve must be closed during normal use;
9. When constructing pipelines, it is advisable to install telescopic tubes or bellows to avoid serious stretching and causing breakage of the flowmeter;
10. When the gas turbine flowmeter is installed outdoors, the upper part should be covered to prevent the rainwater from immersing and the sun exposure affecting the service life of the flowmeter;
11. When installing the gas turbine flowmeter, it is advisable to add a filter to the flowmeter (filtering accuracy is recommended ≤20μm).
Second, gas turbine flowmeter requirements
1. When the gas turbine flowmeter is put into operation, the upstream valve of the flowmeter should be slowly opened (not less than 15 seconds), and then the downstream valve of the flowmeter should be slowly opened to prevent the instantaneous airflow from rushing to the turbine;
2. When the flowmeter needs to have a long-distance signal, it should be connected to the external power supply (+12~+24VDC) strictly according to the electrical performance index of the gas turbine flowmeter. It is strictly forbidden to directly connect 220VAC (or 380VAC) power supply at the signal output.