Problems in the use of Variable area flow meter

Posted by tinaxu on October 9th, 2018

Variable area flow meters are widely used in flow measurement, it can measure liquid, gas , or steam . and can manufacture the flow meter according to different requirement from the customers, such as only local display , or with any output , hygienic process connection or flange connection; the best part of the variable area flow meter is that it can measure small flow which some flow meters cannot handle.

We list some problems which are common when used the digital rotameter.

1.Pointer jitter:

(1).Slight pointer jitter: generally due to medium fluctuation. It can be overcome by increasing damping of metal tube variable area flow meter.

(2). Moderate pointer jitter: generally due to the state of medium flow. For gases generally due to medium operating pressure instability caused. Pressure or flow stabilizer can be used to overcome or increase the air damping of float meter.

(3). Violent pointer jitter: it is mainly caused by the medium pulsation, unstable air pressure or the pressure, temperature and flow of the gas operating state given by the user, which are not in accordance with the actual state of the float flow meter, and there is a large difference in the float flow meter's over-range.

2.The main reason why the pointer of metal tube rotameter stops at a certain position is that the float of the float meter is stuck.

Generally, the valve is opened too fast when the metal tube rotor flowmeter is used, which causes the float to strike up the stop quickly, causing the stop to deform and trapping the float. However, it is not ruled out that the float is stuck because the float guide rod and the stop ring are different from each other. Processing instrument can be removed, the deformation of plastic surgery to stop off, and check whether with guide bar work, such as different heart can be calibrated, then float installed, push float, feeling float up and down unimpeded card can, in addition, the flow meter must be vertical or horizontal installation, when installation cannot tilt, otherwise easy to cause the card table, and also brings to the measurement error.

3. Large measurement error

(1). If the installation is not in conformity with the requirements, the rotor flowmeter of metal tube should be kept vertical for vertical installation. If the inclination Angle is no more than 20 degrees, the float flowmeter should be kept horizontal for horizontal installation. The installation position should be far away from valve diameter change port, pump outlet, process pipeline turn port, etc. The requirements for the first 5 days and 3D straight pipe sections should be maintained.

(2). The variation of density of liquid medium is also a cause of large error. Before the calibration of the instrument, the medium is converted according to the density given by the user, and the water flow in the standard calibration state is calibrated. Therefore, if the density of the medium changes greatly, a large error will be caused to the measurement. The solution is to take the density of the changed medium into the formula, convert it into the error correction coefficient, and then replace the measured flow times the coefficient with the real flow rate.

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