product details

1、 Characteristics of flow meters

From the previous discussion, it can be seen that a turbine flowmeter is a flow meter with many advantages. In summary, it has the following characteristics
1. High accuracy
The accuracy of the flowmeter is between 0.5-0 About 1%. Within the linear flow range, even if the flow rate changes, the accuracy of cumulative flow will not decrease. And in a short period of time, the reproducibility of the turbine flowmeter can reach 0.05%
2. Range width ratio
The range ratio of the flowmeter can reach 8-10. Under the same caliber, the maximum flow value of the turbine flowmeter is greater than many other flowmeters
3. Strong adaptability
The flow meter can be made into a closed structure, and its speed signal is non-contact measurement, so it is easy to achieve high pressure resistance design.
If the turbine and bearings of the flowmeter are made of materials with high temperature resistance and low thermal expansion coefficient, they can be used over a wide temperature range. At this time, attention should be paid to correcting its instrument coefficient mainly due to changes in its flow cross-section:
K＝K 0 [1－ R ＋2 H t－to] 3－23
In the formula, K, K 0- instrument coefficients during use and calibration;
t. T 0- Fluid temperature during use and calibration;
R. H represents the material expansion coefficients of the turbine and the casing, respectively
4. Digital signal output
The output of the flowmeter is a pulse digital signal proportional to the flow rate. It has the advantages of accuracy not decreasing during transmission, easy accumulation, and easy input into the computer system

II Installation and use of flow meters
To fully utilize the characteristics of turbine flow meters, it is necessary to pay full attention to the installation and use of flow meters. Below is a brief discussion on this issue
1. Tested medium
The liquid measured by the flowmeter is generally a low viscosity liquid with a viscosity of less than 15 × 10-6 m2/s and low corrosiveness. Although turbine flowmeters are currently used for measuring various media, the measurement of high-temperature, high viscosity, and strongly corrosive media still needs to be carefully considered and corresponding measures taken. When the viscosity v of the medium is greater than 15 × 10-6 m2/s, the instrument coefficient of the flowmeter must be calibrated with real liquid, otherwise significant errors will occur
Gas liquid two-phase flow, gas-solid two-phase flow, and concentrated solid two-phase flow cannot be measured using flow meters

III Installation piping requirements
The installation of flow meters has a significant impact on their measurement accuracy
① Uneven flow velocity distribution and the presence of secondary flow inside the pipe are important factors affecting the measurement accuracy of turbine flow meters. Therefore, flow meters have certain requirements for upstream and downstream straight pipe sections. For industrial measurement, a straight pipe length of 20D upstream and 5D downstream is generally required. To eliminate secondary flow, it is best to install a rectifier at the upstream end. If there is a straight pipe section of about 20D at the upstream end and a rectifier is installed, the measurement accuracy of the flow meter can reach the accuracy level of calibration
② Flow meters have high requirements for fluid cleanliness, and a filter must be installed before the flow meter to ensure the cleanliness of the fluid. The filter can be funnel-shaped, and its cleanliness can be measured by measuring the differential pressure changes at both ends
③ To ensure that the liquid passing through the flowmeter is single-phase, that is, air or vapor cannot enter the flowmeter, a deaerator should be installed upstream if necessary. For liquids that are prone to gasification, a certain back pressure must be ensured downstream of the flowmeter. The size of this back pressure can be twice the pressure drop of the flow sensor at the maximum flow rate plus 1.2 times the vapor pressure of the measured liquid at the highest temperature