Orifice plate flow meter, inaccurate measurement
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Steam outlet flow rate, measured using an orifice meter. Exit flow rate: 4.1 t/h; pressure: 2.6 Mpa; temperature: 410°C. The pipeline has a diameter of 65, and the distance from the exit to the installation is approximately 2.2 kilometers. Insulation measures have been applied along the entire length of the pipeline. The flow rate reaching the device passes through an orifice flow meter; the flow rate measured by this meter is 2.1 t/h, the pressure is 2.0 Mpa, and the temperature is 200°C. The flow rates measured by the orifice flow meters at both ends do not match each other. Both transmitters have been tested and pressure-tested. The current output is fine, and the DCS calculation formulas are also correct. I don’t know where the problem lies now; the flow rates at both ends do not match. After review by the design institute, it was stated that the design pressure and temperature drops are within reasonable ranges. Is there anyone who can help analyze what the problem is?
There is significant energy loss in the pipeline; does the calculation sheet for the flow meter on the unit side correspond to the current actual temperature and pressure? Is it also 2.6 Mpa in pressure and 410°C in temperature? It should be calculated using a pressure of 2.0 Mpa and a temperature of 200°C.
There are many sources of error in the measurement using orifice plate flowmeters; factors such as installation, compensation for temperature and pressure, the amount of water present in the steam, and whether there are leaks in the pressure guiding pipelines all need to be carefully checked.
Try swapping the positions of the two flow meters to see what happens
How do I know the DCS calculation is correct? At least you didn’t make it clear whether temperature and pressure compensation is included for all of them. With such a large drop in temperature, the insulation won’t be very good. You can also provide elbow valve data to calculate the pressure drop, thereby determining which flow rate is reasonable.
The temperature has dropped by more than half. If the temperature readings are accurate, it’s recommended to check the insulation first rather than the flow rate.
It is recommended to first check whether the actual operating conditions match those measured, especially the temperature and pressure at the device. If there is indeed such a significant decrease, it is advised to calibrate the flow coefficient of the orifice plate under the actually measured temperature and pressure conditions before proceeding with measurements. Moreover, thermal and pressure compensation should be added to make the data more accurate.
This post was last edited by Pandora on 2017-11-15 at 13:50. Steam flow measurement relies mainly on temperature and pressure compensation. Otherwise, it cannot be measured with precision. It’s not just a gauge issue. The cause must be analyzed from the entire steam system. Also, are the operating parameters of the two meters consistent with the actual values? I need to check the calculation sheet for the flow meter.
Measurement using orifice plate flowmeters results in large errors.
This is a common comprehensive requirement: good thermal insulation is necessary, temperature and pressure must be compensated for, and the flow resistance should be low – there are too many factors to consider.