Selection of flow meter for vacuum distillation tower

The process has changed and the rotor needs to be recalculated.

The balance pipe of the reflux tank and the distillation tower is not connected. Check whether the balance pipe of the vacuum system is smooth.

This is the process flow chart, the same as on site

This is the process flow chart, which is more intuitive. I hope you can give me some advice.

I don’t know if the rotor of the flow meter is too small.

1. The rotor flowmeter has large measurement error: 1. Since the gas medium is greatly affected by temperature and pressure, it is recommended to use temperature and pressure compensation to obtain the true flow rate. 2. Due to long-term use and pipeline vibration and other factors, the float flowmeter's sensing magnet, pointer, counterweight, rotating magnet and other moving parts are loose, resulting in large errors. Solution: You can verify it by pushing the pointer first. First, press the pointer at the RP position to see if the output is 4mA and the flow rate display is 0%, and then verify according to the scale. If discrepancies are found, the position of the parts can be adjusted. Generally, professionals are required to adjust, otherwise the position will be lost and it will need to be returned to the manufacturer for correction. 3. The installation does not meet the requirements: For vertical installation, the rotameter must be kept vertical, with an inclination angle of no more than 20 degrees; for horizontally installed rotameters, it must be kept horizontal, with an inclination angle of no more than 20 degrees; there must be no ferromagnetic objects in the 100mm space around the rotameter. The installation location should be far away from the valve reducing port, pump outlet, process pipeline turning port, etc. It is necessary to maintain the requirement of 250mm straight pipe section at the front and rear. 4. Large changes in the density of the liquid medium are also a cause of large errors. Since the meter converts the medium according to the density given by the user before calibration, and converts it into the flow rate of water in the calibration state for calibration, so if the density of the medium changes greatly, it will cause a large error in the measurement. The solution can be to bring the changed medium density into the formula, convert it into an error correction coefficient, and then multiply the flow rate measured by the flow meter by the coefficient to change it to the real flow rate. 2. Rotameter pointer jitters: 1. Slight pointer jitter: Generally caused by medium fluctuations. This can be overcome by increasing damping. 2. Moderate pointer jitter: Generally caused by the flow state of the medium. For gases, it is generally caused by unstable operating pressure of the medium. Pressure stabilizing or flow stabilizing devices can be used to overcome or increase the gas damping of the rotameter. 3. Violent pointer shaking: Mainly due to medium pulsation, unstable air pressure or the pressure, temperature, and flow rate of the gas operating state given by the user do not match the actual state of the rotameter, and there is a large difference causing the rotameter to be over-range. 3. The pointer of the rotameter stops at a certain position.: The main reason is that the rotor of the rotameter is stuck. Generally, when the rotameter is used, the valve is opened too quickly, causing the rotor to quickly impact the stopper upwards, causing the stopper to deform and jam the rotor. However, it is not ruled out that the rotor is stuck because the rotor guide rod and the stop ring are not concentric. During processing, you can remove the instrument, remove the deformed stopper and reshape it, and check whether it is concentric with the guide rod. If it is not concentric, you can correct it. Then install the rotor and push the rotor by hand until you feel that the rotor is smooth up and down without any obstruction. In addition, when installing the rotameter, it must be installed vertically or horizontally and cannot be tilted, otherwise it will easily cause the meter to jam and bring errors to the measurement.

The rotameter is a manually adjusted flowmeter. After the vacuum pump is turned on, the rotor of the flowmeter is adsorbed and the reflux ratio cannot be adjusted. I checked the literature and other people's vacuum distillation also did this, but this did not happen to me.

It is recommended to disassemble the rotameter and see if the float inside can move normally and whether it is stuck. Sometimes the upper and lower positioners may get stuck on the float.