Factors affecting the differential pressure of orifice plate flow meters
Thread Content
Dear experts, what are the factors that affect the differential pressure of orifice plate flow meters?
Please refer to the \"Design Manual for Flow Measurement Throttling Devices\". There are many factors that affect the differential pressure across an orifice plate; changes in the fluid’s temperature and pressure, scaling in the pipes over time due to prolonged use, which leads to changes in the pipe diameter, etc., can all influence the value of the differential pressure.
If the density of the gas being measured changes, how will the differential pressure change? For example, the moisture content in the gas changes, and if there is moisture present in the gas, will the measured flow rate be higher or lower?
Reply to 3# hongzi111: It applies specifically to gases. If the gas contains water, its density increases, and as a result the range of the differential pressure transmitter will increase. For example, if it was originally 1.5 KPA, it might now be 1.7 KPA; hence, the measured flow rate is higher than the actual value
Reply to 4# yangmin029: At the moment, the measured flow rate is much higher than the actual flow rate being used, so we are trying to find out the reason. It seems that neither the transmitter nor the orifice plate has any problems; we’re quite puzzled ……
Reply to 5# hongzi111: In this case, it is necessary to change the range of the transmitter. The range needs to be increased – but to what extent? It is important to determine the amount of moisture present in the gas. It can also be assumed that the orifice plate is installed correctly; the transmitter’s current value should then be adjusted based on the actual flow rate (in other words, the upper limit of the range needs to be determined through repeated testing)
Personally, I think it’s necessary to recalculate based on the components of the current operating conditions
Reply to 6# yangmin029: Can changing the range of the transmitter alter the measurement results? The differential pressure doesn’t change
In fact, the differential pressure remains unchanged; it is the range value that has changed, which in turn causes the current value corresponding to the differential pressure to change. A differential pressure transmitter essentially converts pressure signals into electrical signals, and the signals sent to the control room are 4-20mA electrical signals. However, the mathematical model in your PLC or DCS needs to be adjusted (or the upper limit for differential pressure must be modified)