The vortex flow meter accuracy has always been one of the topics we are more concerned about. The measurement accuracy determines whether the flowmeter can obtain the mass flow of the medium more accurately during work. First of all, let's classify the vortex flowmeter according to the following principles; the vortex flowmeter can be divided into flange type and clamping type according to the connection mode of the sensor, and can be divided into heat-sensitive type, stress type, capacitive type, and ultrasonic type according to the detection method , Vibration type, photoelectric type and fiber optic type, etc. According to the purpose, it can be divided into ordinary type, explosion-proof type, high temperature type, corrosion resistance, low temperature type, plug-in type, etc. According to the composition of sensors and converters, it is divided into two types: integrated type and split type, and according to the measurement principle, it is divided into volume flowmeter and mass flowmeter.
Speaking of which, the accuracy and vortex flowmeters maintenance efficiency is basically ±0.5%R~±2%R for measuring liquids, ±1%R~±2%R for gases, and the repeatability is generally 0.2%~0.5%. Since the instrument coefficient of the vortex flowmeter is relatively low and the frequency resolution is low, the instrument diameter should not be too large, usually below DN300.
1. Vibration of pipeline and flowmeter
As pipeline vibration acceleration increases, so too does the error of the instrument coefficient of the vortex flowmeter. The overall shock resistance to this is relatively low. But as the flow rate rises, despite any changes in vibration frequency, this error tends to decrease. The instrument coefficient of the vortex flowmeter will also be reduced if there is an increase in pipeline vibration frequency. Poor reinforcement of the pipe and flowmeter or placing them close to a motor can result in vibrational interference with a vortex flowmeter's measurements, leading to values that are too high or even causing miscalculations of flow.
2. Changes in pressure
The heating network pipeline includes multiple valves and pressure-reducing valves, which all have the ability to alter the line's pressure. The vortex flowmeter is not an accurate indicator of mass flow, because its measurement largely depends on two factors: the flow rate of the pipeline and the density of steam. This density is determined by pressure; thus, when a valve is opened, it can lead to an alteration in pressure that subsequently changes the steam’s density and produces a potentially inaccurate reading. Consequently, such occurrences can cause measurement inaccuracies.
3. Dryness change
In order to measure saturated steam with a vortex flowmeter, the saturated steam must have a dryness of not less than 85%, but the actual situation on site is that the saturated steam's dryness is less than 100% in the boiler, and the saturated steam's dryness will be less than 85% of the time, resulting in a drop in measurement vortex flow meter accuracy.
4. The outlet side of the flowmeter leads to the atmosphere
Since the vortex flowmeter has an open outlet to the atmosphere, excessive front and rear errors will cause the flow rate to exceed its upper limit, so the change in flow rate cannot be accurately reflected. Zero point drift and unreasonable pressure induction pipe arrangement are mainly responsible for this situation.
5. The installation of straight pipe sections before and after the flowmeter does not meet the requirements
If certain requirements are not met during the installation of the vortex flowmeter, the correct formation of the Karman vortex street principle will be affected, resulting in an inaccurate measurement of saturated steam.
As can be seen here, the accuracy of the vortex flowmeter determines the accuracy of the measurement medium. Consequently, you should read the instrument manual thoroughly after purchasing the vortex flowmeter before installing it to prevent unnecessary unknown factors from affecting the measurement accuracy after installation.
Beijing Sincerity, a professional vortex flow meter supplier & manufactuer, has developed over years to manufacture the Coriolis Mass Flow Meters industries. Through continuous research, development and transformation, we have become the leader of the Coriolis Mass Flow Meters industries in China.Beijing Sincerity has powerful technology knowledge over the flow meter industries. The Coriolis Mass Flow Meter are suitable for different kinds of industries--- high requirements testing experiments of universities, research institutes; and also the petroleum, medicine, metallurgy, electricities industries.