Flowmeter calibration procedure

Meters need to be calibrated or verified regularly; adjusting them arbitrarily cannot ensure the accuracy of measurements.

1. Affected by the installation method and operating conditions on site, many types of flowmeters exhibit a certain discrepancy between their measured values and the true values during use; this is what users often refer to as readings that are too low or too high. Of course, installation errors and malfunctions of the instrument are excluded from this scenario； 2. Given the actual conditions of ordinary users, it is difficult to accurately calibrate flow meters at their respective locations; after all, once the flow meters are installed, it is not feasible to spend time and money removing them repeatedly for calibration at specialized institutions ； 3. If high precision is not required, the flow meter readings can be adjusted to values closer to the true value based on experience from actual use or relatively accurate data obtained through other means (data that is often provided by the department using the equipment rather than by the instrument technicians) ； 4. Although the true value exists objectively, all that instruments can do is to use every possible means to obtain a measurement value as close as possible to that true value.

Which flow meter to check: The differential pressure flow meter must be isolated, so that the pressure tap lines are empty; then check whether the gauge reads zero under that pressure. Alternatively, ensure that both pressure tap lines are filled with the medium, close the valve once, and verify that the reading returns to zero without any external influences. For mass flow meters and vortex flow meters, the pipeline must be filled with the medium and left stationary in order to return to zero. To be able to adjust it using the zeroing screw, the rotameter must ensure that no medium is attached to the rotor.

A pressure-reducing flow meter? If so, it’s likely that most of the instruments in factories have been subjected to such treatment. I would say that the pressure reduction value and flow rate value during design are fixed. If you think the measured flow rate is incorrect, and you believe it should be some other value, that’s fine; it can be changed. But this essentially alters the original relationship between differential pressure and flow rate. This point might match, but all the other points don’t. Also, the process suggests there are so many of them – is the number he came up with reliable? Although some of the on-site personnel have extensive experience, which is a valuable asset, if you think the numbers are reliable, then why need so many modern instruments?