The accuracy level of the flowmeter is specified within a certain flow range. If it is used under a certain condition or a narrow flow range, for example, only in a small range, the measurement accuracy will be Higher than the specified accuracy level. If the turbine meter is used to measure the oil and the barrel is distributed, when the valve is fully opened, the flow rate is basically constant, and the accuracy may be increased from 0.5 to 0.25.
For trade accounting, storage and transportation handover and material balance, if the measurement accuracy is required to be high, the durability of the accuracy measurement should be considered. It is generally used for the flowmeter under the above conditions, and the accuracy level requirement is 0.2. In such a workplace, it is generally equipped with on-site measurement standard equipment (such as volumetric tubes) to perform on-line inspection of the flowmeter used.
The accuracy level is generally determined based on the maximum allowable error of the flow meter. It will be given in the flowmeter instructions provided by each manufacturer. It is important to note that the percentage of error is the relative error or the reference error. The relative error is the percentage of the measured value and is usually expressed as "% R". The reference error is the percentage of the upper limit or range measured, commonly used as “% FS”. Not stated in many manufacturer's instructions. For example, float flowmeters generally use reference errors, and some models of electromagnetic flowmeters also use reference errors.
A further problem is that the accuracy level specified for the flowmeter in the verification protocol or manufacturer's instructions refers to the maximum allowable error of the flowmeter. However, due to changes in environmental conditions, fluid flow conditions, and dynamic conditions when the flowmeter is used in the field, additional errors will occur. Therefore, the flowmeter used in the field should be the synthesis of the maximum allowable error and additional error of the instrument itself. The problem must be fully considered. Sometimes the error within the operating environment of the field may exceed the maximum allowable error of the flowmeter.