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technical article
How to ensure the measurement accuracy of the orifice flowmeter
2011-5-30 9:58:14

    When the orifice plate flowmeter is measured on the spot, the measurement results often have large errors due to some objective factors. Here are the main measures to ensure the accuracy of the orifice plate flowmeter :

1. Orifice flowmeters are calibrated one by one. Everyone knows that standard orifice plates can be used directly as long as they are designed and manufactured in accordance with relevant standards, without the need for actual flow calibration. Because the outflow coefficient can be calculated directly by software, but the computer calculation is ideal after all, and there is still a certain difference from the field environment. Therefore, in order to ensure the measurement accuracy, it is recommended to perform a real-flow calibration on each flowmeter to calibrate the outflow. The coefficient is compared with the calculation result, and the difference is calculated and corrected.

2. Reynolds number correction. There is a definite relationship between the flow coefficient of the orifice flowmeter and the Reynolds number. When the mass flow rate changes, the Reynolds number changes in proportion to the change in the flow coefficient.

3, the effect of temperature on the orifice plate flowmeter and its correction, changes in the density of the fluid caused by the temperature change of the fluid, resulting in changes in the relationship between differential pressure and flow, and secondly, the change in temperature caused changes in the inner diameter of the pipe, the orifice opening The correction of temperature change is to use a temperature meter to measure the temperature on the spot and then input it to the secondary meter to correct the error caused by the temperature change.

4. Calculation of steam mass flow rate. When the orifice flowmeter measures steam, the flow rate value is obtained from the differential pressure signal, and then the density is calculated from the steam temperature and pressure value check table to calculate the steam flow mass.

5. Swellability correction. When measuring the flow of steam and gas with an orifice flowmeter , the fluid's expandability must be corrected. For specific correction coefficients, refer to the throttle device design manual.

In fact, the orifice plate flowmeter to find the flow is very widely used by us, and it is also a representative of the differential pressure flowmeter. You can promote other differential pressure flow meters through appropriate inference.



Article Keywords:

Orifice flowmeter