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.
Flowmeter product features:
Frequency programmable low frequency rectangular wave excitation improves stability of flow measurement and low power loss;
The new 16-bit ultra-low power microprocessor with FLASH memory has high integration, fast calculation speed and high calculation accuracy.
Full digital processing, strong anti-interference ability and reliable measurement;
Ultra-low EMI switching power supply, suitable for power supply voltage variation range, high efficiency, small temperature rise; good EMC performance;
Chinese and English menu operation, easy to use, easy to operate, easy to learn and understand;
High definition backlight wide temperature LCD display;
It can perform bidirectional flow measurement and bidirectional total accumulation; it has automatic range switching function, which can effectively improve the measurement accuracy of analog current and frequency output, especially suitable for occasions where the diurnal flow range changes greatly and needs to send control signals; flow measurement range Up to 1500:1;
There are three totalizers inside, which record and display the forward cumulative amount, the reverse cumulative amount and the accumulated difference integrated amount, which are convenient for fluid metering and custody transfer;
Provide isolated or non-isolated RS485/RS232C digital communication interface, and support fieldbus communication modes such as MODBUS, PROFIBUS-DP and HART;
Constant current source fluid resistance measurement can accurately measure the internal resistance of the electrode signal in the case of long-line transmission. It can be used not only to determine whether the fluid in the sensor is empty or not, but also to identify abnormal phenomena such as contamination and coverage of the electrode, and to provide cleaning for the user. Fault processing information such as electrodes;
However, since the volume of condensed water in the wet steam is relatively small, the flow of excess water in the ascending pipe often appears as an annular flow structure, but when the amount of water is particularly large, it also appears as a ring with fibers. Flow structure. Among them, the fibrous fluid is actually a condensed water. Flow in a vertically descending pipe: In a vertically descending pipe, the structure of the gas-liquid two-phase flow is similar to that of a vertically ascending flow, but differs not only in the opposite flow direction but also in the case of the same average flow velocity. The flow rate of the liquid in the vertical drop pipe is much faster than the flow rate of the liquid in the vertical rise pipe.
Second, steam vortex flowmeter measurement considerations
Vortex flowmeters measure steam. Accurately arrange the steam traps accurately: People have long discovered that when the steam has more water, the vortex flowmeter will have a "leakage pulse" phenomenon, that is, in the case of a stable steam flow rate, the vortex flow It should have a stable pulse output proportional to the flow rate. But sometimes it is found that the output pulse of the meter is inexplicably less. The distribution of the output pulse recorded on the two-dimensional coordinates can also be clearly seen. The pulse that should be approximately evenly distributed is one less at a place. Pulses, in severe cases, are a lot less pulses, and in the worst case, there are no pulses at all. This may be related to the formation of a vortex column by impinging on a large volume of droplets having a non-uniform distribution on the vortex generator.