If the electromagnetic flowmeter installation can guarantee the length of the straight pipe section, the accuracy of the flowmeter measurement can be ensured. The requirements of the electromagnetic flowmeter installation on the straight pipe section:
The installation position of the electromagnetic flowmeter is too strict, and the straight pipe section at the installation position is also strict. One section needs to be installed with 5 times the pipe diameter in the front section and 3 times the pipe diameter in the rear section to make the flowmeter measurement accuracy normal. The electromagnetic flow sensor Upstream also has a certain length of straight pipe section, but its requirements are lower than other instruments. After 90 degree elbow, T-shaped tube, concentric reducer, and fully open gate valve, it is generally considered that as long as the straight pipe section is 5 times the diameter (5D) length from the centerline of the electrode of the electromagnetic flowmeter, the valve with different openings needs 10D; the downstream straight The pipe section is (2 ~ 3) D or no requirement; but to prevent the butterfly valve, the valve piece extends into the measuring tube of the sensor. The length of the upstream and downstream straight pipe sections proposed by various standards or verification regulations is also inconsistent, and the requirements are higher than usual. This is because in order to ensure that the current requirements of 0.5-level precision instruments are met.
2. The requirements of electromagnetic flowmeter installation on straight pipe section
Incorrect installation methods and installation points will not only affect the accuracy of the electromagnetic flowmeter, the life of the electromagnetic flowmeter, but even damage the electromagnetic flowmeter.
3. Requirements for straight pipe section
In order to ensure the accuracy of the electromagnetic flowmeter, the inner wall of the upstream and downstream straight pipe sections where the instrument is located should be clean, without obvious dents, scale and peeling. The upstream and downstream straight pipe sections of the electromagnetic flowmeter installation location generally follow the first ten to five principles. The front straight pipe section is not less than 10D and the rear straight pipe section is not less than 5D; if other chemical substances are injected at the upstream pipe section, it is easy to cause uneven conductivity Therefore, the flowmeter should be at least 20D away from the main inlet as far as possible; if the reducer is used upstream and downstream of the electromagnetic flowmeter, the central cone angle α of the reducer should be less than 15°.
In order to ensure the accurate measurement of the electromagnetic flowmeter, the installation location must be selected correctly.
(1) The requirements of the electromagnetic flowmeter on the straight pipe section:
The electromagnetic flowmeter must be installed horizontally on the pipeline (the pipeline is inclined within 50). When installing, the flowmeter shaft Verabar flowmeter line should be concentric with the pipeline axis and the flow direction should also be the same.
The length of the upstream pipeline of the electromagnetic flowmeter should have a straight pipe section of not less than 2D. If the installation site permits, it is recommended that the upstream straight pipe section is 20D and the downstream pipe is 5D.
(2) Requirements of electromagnetic flowmeter for piping:
The inner diameter of the upstream and downstream piping at the installation point of the flowmeter is the same as the inner diameter of the flowmeter.
(3) The electromagnetic flowmeter's requirements for the bypass pipe:
In order to ensure that the flowmeter does not affect the medium during the maintenance, shut-off valves (shut-off valves) should be installed on the front and rear pipes of the flowmeter, and bypass pipes should be installed. The flow control valve should be installed downstream of the flowmeter. When the flowmeter is used, the shut-off valve installed upstream must be fully open to avoid unstable flow of the upstream part of the fluid.
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