Insertion electromagnetic flowmeter inaccurate measurement of the reasons

Project Overview

• （1）Insertion type electromagnetic flowmeter for the pipeline is a requirement exists, for the pipeline straight section of the high requirements in the design of the new water plant can try to meet, and for the old water plant renovation and retrofitting, want to meet the above conditions has become a little difficult, it will affect the stability of the equipment. The solution is to add a rectifier to improve the flow characteristics.
• （2）For the measured water flow rate is too low, also will affect the accuracy of the measurement, especially in some districts and cities in the boundary installation of the flowmeter, due to the regional company in the end of the pipeline network, the pressure difference is small and caused by the flow rate is too low. And for the solution can try to open the valves on both sides of the border to improve.
• （3）When there is gas in the pipeline, it will cause measurement fluctuations and instability, want to solve the problem we must find out the source of the gas, and to be solved, if necessary, can be installed in the pipeline exhaust valve.
• （4）Installed in the raw water pipeline flow meter sensor electrode surface contaminated by silt deposits, shape impact measurement. The solution is to choose the scraper electrode, wells regularly maintained and cleaned.

Insertion type electromagnetic flowmeter field installation, insertion type electromagnetic flowmeter is not allowed to error calibration.

• （1）Liquid in the pipeline is not full, error due to insufficient back pressure or flowmeter installation position is poor, resulting in the measurement of the liquid in the pipe is not full of pipe. Produced by the failure phenomenon due to the degree of unfilled and flow conditions have different performance. If a small amount of gas in the water pipe pipeline as a layered flow or undulating flow, the fault manifests itself as an increase in error, the measured value is significantly larger than the actual value; if the flow is a bubble flow or plug flow, the fault phenomenon in addition to the measured value and the actual value does not match the surface of the electrode because the gas phase momentarily covered the output shaking; if the horizontal pipeline layered flow in the circulation of the cross-sectional area of the gas part of the increase in the degree of liquid is not full of the pipeline increases, there will also be output Swaying. If the liquid is not full of pipe situation is serious, so that the liquid surface in the electrode below, the output will appear super full of pipe phenomenon. Solenoid in order to avoid such phenomena, in the engineering design and construction, should be designed to install the shut-off valve in the flowmeter downstream.
• （2）The liquid contains solids. The liquid contains solids such as powdery particles or fibres. Possible errors or malfunctions are: 1. Slurry noise 2. Electrode surface staining 3. Conductive deposits or insulating deposits covering the electrode murai 4. Lining is worn or covered by deposits, reducing the flow area. For the flow meter, where the normal operation at the beginning, with the passage of time, the flow rate display is getting smaller and smaller, it should be considered whether there are impurities caused by deposits.
• （3）There is a possibility of crystallisation of the liquid, should be used with caution some easy to crystallise chemical materials, electromagnetic in the case of normal temperature can be measured normally, due to the conduit for transporting liquids are accompanied by thermal insulation facilities, but the flow of the measuring element can not be implemented electric insulation, fluid flow through the measuring tube, easy to crystallise due to cooling, so that it can not be used.
• （4）Liquid conductivity exceeds the permissible range and cannot be measured Liquid conductivity may also be made to wobble if it is close to the lower limit value. Usually considered stable measurement of the conductivity of the lower limit value to be 1 to 2 orders of magnitude higher. Insertion type electromagnetic flowmeter containing particles or fibre fluid generated by the slurry noise, take the method of increasing the excitation frequency can effectively improve the output shaking phenomenon. In the measurement of hydrochloric acid, the use of tantalum electrodes are not affected by the concentration of hydrochloric acid, can be stable measurement.