Turbine flowmeter is a kind of economical speed instrument, which has been applied in many occasions. The accuracy of turbine flowmeter is determined under reference conditions (or standard working conditions). For turbine flowmeter, reference conditions generally include:

A. Environmental conditions (ambient temperature 15℃ ~ 35℃, relative humidity 45% ~ 75%, atmospheric pressure 86kPa, ~ 108kPa, no electric and magnetic field interference, no vibration);

B. Power source conditions (220V± 10% or 110V,50HZ±1, or 24VDC);

C. Fluid conditions (when calibrating with fluid, the calibration pipe is industrial circular pipe, single-phase Newtonian fluid, fully full pipe, fully developed turbulent velocity, axisymmetric distribution, no vortex, no disturbance, and steady flow.The fluid temperature is generally at room temperature, and the fluid pressure is generally below 0.25MPa.It is obvious that the actual operating conditions of the turbine flowmeters are usually different from the reference conditions, which may cause a change in the accuracy of the turbine flowmeters.

The accuracy of turbine flowmeter decreases during use, which may be due to the following reasons:

1, fluid temperature, pressure changes may make the escape of air or liquid in the pipe due to the pressure inside the pipeline is lower than the saturated vapor pressure of fluid, make part of the liquid and steam, is also likely to make out with medium pressure air is sucked into the pipe, the gas with the measured liquid, caused its indication value increase, there is error, adverse to the fluid of the buyer.

2. Fibrous or viscous impurities in the fluid are attached to the rotating part of the flowmeter, which will increase the rotational resistance and cause the indicating value of the meter to decrease, resulting in negative error, which is unfavorable to the fluid supplier.

3, there are some impurities in the medium, the bearing, the shaft to wear, so that the gap between the two increase, the dynamic balance of the moving parts is destroyed, rotational speed decline, or dirt into the clearance, so that the motion resistance increase, rotational speed decline.All these cause the decrease of instrument display value and negative error, which is unfavorable to the fluid supplier.

4. Poor working environment, such as electromagnetic interference, dust, high temperature, vibration, humidity, etc., may cause wrong operation or failure of turbine flow sensor, which directly leads to the indicating error of turbine flowmeter. The error may be positive or negative, which may not be obvious, or may be completely ineffective.For the above phenomenon, when it is more serious, problems can be found from the comparison of the working status of the process, and it is easy to take corresponding measures.But at the beginning of a problem, you can't find it without taking special measures.

According to the principle of turbine flowmeter and site construction work experience, it is suggested that in the early part of the turbine flowmeter installation, upstream and downstream of the flow meter on the 2 times the diameter of the tube wall add a pair of pressure, need with differential pressure gauge is linked together, in the working status, indicating value of the flowmeter and the contrast between the differential gauge indicating value relationship, if everything is in order, then put the contrast relationship as the basis of later check whether the flowmeter work normally.

For relatively dirty fluid or liquid that may produce gas, in the installation of flow timing, can be installed in its upstream filter or gas eliminator, gas collector, strengthen the daily maintenance work, regularly clean the filter, eliminate gas or debris in the gas collector, to ensure the normal operation of the flow meter.

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