Analysis of the four major factors affecting the accuracy of liquid flowmeter measurement

1. Mechanical wear and effect

Generally, the analysis of the new liquid flow meter is run-in after a period of time, the gap between the gears is suitable, and the leakage flow is relatively small. After the flowmeter is used for 2~3 years, the long-term mutual movement of the gear will cause the end of the gear to wear, the gap becomes larger, and the leakage flow becomes larger. Therefore, the frequently used flowmeter should be tested frequently, and the worn gears should be replaced in time to ensure the normal operation of the flowmeter.

2, temperature impact

When the temperature rises, the gap between the gears of the liquid flow meter becomes larger, and the leakage flow rate of the flow meter becomes larger, but it is also considered that the volume of the measurement space is also increased due to the temperature rise, and the medium is thermally expanded.

3, the pressure difference effect

When the pressure difference between the inlet and outlet of the liquid flow meter is small, the gear rotation speed is low, and the leakage flow rate at this time is relatively large. When the pressure between the inlet and outlet of the flowmeter is too large, the gear rotation torque is large, the rotation speed is too high, the leakage flow rate is also increased, and the error is also large, so only the inlet and outlet pressures are controlled within a suitable range, and the flow rate is The leakage flow of the meter can be controlled to be small.

4, the influence of medium viscosity

When the viscosity of the liquid flowmeter medium changes, the leakage flow rate also changes significantly. When the viscosity increases, the leakage flow rate is small, the error is small, and when the viscosity is decreased, the leakage flow rate is large and the error is large. Therefore, JJG667-1997 also stipulates that the medium used for the test and the flowmeter actually have the same viscosity. When using other media for inspection, be aware that the introduced error should not exceed one-third of the flowmeter error limit.