General principles for electromagnetic flowmeter selection
(1) Whether the medium to be tested is a conductive liquid or slurry, thereby determining whether an electromagnetic flow meter is selected;
(2) The conductivity of the measured medium determines the type of electromagnetic flowmeter—whether it is high conductivity or low conductivity;
(3) The nominal diameter of the large, small and common flow process pipelines required by the process, determine whether the flow rate of the medium is at a more economical flow point, whether the pipeline needs to be reduced, and then determine the diameter of the flowmeter;
(4) Determine whether to use an integrated or split flowmeter, and the degree of protection of the flowmeter, etc., based on the layout of the process piping.
(5) Selecting the electrode type according to whether the measured medium is easy to crystallize or crusting;
(6) selecting an electrode material according to the corrosiveness of the measured medium;
(7) The corrosiveness, wear and temperature of the measured medium determine the lining material to be used;
(8) The high working pressure of the measured medium determines the nominal pressure of the flow meter;
(9) The insulation of the process piping determines the type of grounding ring.
According to different output signals, these products can be divided into LWGY-□N type and LWGY-□A type.
LWGY-□N type sensor: 12～24VDC power supply, three-wire pulse output, high level ≥8V, low level ≤0.8V; signal transmission distance ≤1000m;
LWGY-□A type transmitter: 24VDC power supply, 2-wire 4-20mA output, signal transmission distance ≤1000.
This type of turbine flow products are divided into basic type and explosion-proof type (ExdIIBT6).
2, intelligent integrated turbine flowmeter
Intelligent integrated turbine flowmeter adopts advanced ultra-low-power single-chip microcomputer technology to develop a new intelligent instrument integrating turbine flow sensor and display integration. It adopts double-row liquid crystal field display, with compact structure, intuitive reading and reliability. High, free from external power interference, lightning strike, low cost and other obvious advantages. The instrument has three-point correction of the meter coefficient, the intelligent compensation meter coefficient is nonlinear, and field correction can be performed. The high-definition LCD displays both instantaneous flow (4 significant digits) and cumulative flow (8 significant digits with clear function). All valid data is not lost after 10 years of power failure. These turbine flowmeters are explosion-proof products with an explosion-proof rating of ExdIIBT6.
Selection of measurement types for special industrial and commercial users
2. Case 2: A heavy machine tool factory
The main gas plant of the heavy-duty machine tool factory is 13 production kiln, and there is also a machine repair workshop and 63 mobile burners. The total gas load of all gas facilities is 1837m3/h. See Table 1 for details. The customer promised that all gas facilities could not be fully activated at the same time, the maximum gas consumption required was 1200m3/h, and the minimum pressure required before the furnace was 0.055MPa. The pressure regulator used in the on-site pressure regulating metering box is opened and ready, and the flow meter is in the form of a G1600 turbine table plus bypass.
When debugging the kiln, it was found that the flowmeter in the pressure regulating metering box had a stop-and-go phenomenon. If only some of the kiln was opened or only some of the kiln was used, there would be a phenomenon that the flowmeter did not measure or the measurement error was large.