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Flow Meter

The Main Reasons of the Error Produced by the Mag Meter I

Mag meter possesses a lot of advantages but if it is chosen the wrong model、incorrectly installed and used improperly, it will cause the increased error and unstable indicated value even the damages of the body. However, this text is going to analyze from the aspect of the medium:

(1)The pipe is not full of liquid

Because of the insufficient back pressure and bad installation site of the flow sensor, the pipe is not able to be filled with fluid. And the phenomena of breakdown have different performances as the degree of fullness and the diffusion of flow. If there is a few cases represent stratified flow and wavy flow in the water pipe, the phenomenon of breakdown will have a larger error, which means the measured value of the flow is not matched with the actual one. If the flow is bubble or slug, the phenomenon of breakdown includes not only the measured value does not agree with the actual one but its output will shake due to the gaseous phase covers the surface of the electrode. If the gaseous phase of the circulating sectional area in the laminated flow of horizontal pipeline, which means the degree that liquid is not filled with the pipe increases. And it will cause the output to shake. What’s worse, when the situation where the liquid is under filled with the pipe is rather serious which causes the liquid level is below the electrode, it will appear the phenomenon that the output is over.

(2)The liquid contains the solid phase

The liquid includes the solids such as powder、particles or fiber. And the faults that are likely to be produced will be listed as follows:

①Slurry noises;

②The surface of electrode is stained;

③The electric settled layers or isolated settled layers cover the electrode or liner;

④The liner is worn out or covered by the settled layers, making the circulating sectional area shrink.

(3)The liquid that is possible to crystallize should be considered carefully before used for the mag meter

Some readily crystallized chemical material can be used to measure commonly under the circumstances that the temperature is normal. Because the conductor of conveyance fluid has good thermal insulation and it will not crystallize during the heat insulation work. But the measuring pipe of mag flow sensor is hard to realize the thermal insulation. As a result, when the fluid passes through the pipe, it will lay a solid layer in the wall easily because of dropping in the temperature. As the flow meter which applies other principles will come across the same crystallized problems, we can choose to use a oring mag meter sensor which has a relatively short measuring tube. Then, we can put the upstream pipe of the flow meter to have thermal insulation in order to strengthen it. On the method of attachment of the pipes, providing that to discharge the flow meter sensor is convenient, we can choose it once crystallized as to disassemble and have maintenance handily. The Example 3 is not very common in which mag meter can not work regularly thanks to the liquid crystallization.

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