How to choose a flowmeter when measuring small flow

Small flow measurement is divided into two situations, one is to measure the gas or liquid flowing through the small pipe with high accuracy; the other is to measure the flow of the fluid with very slow flow. There are many kinds of common gas flowmeters suitable for measuring small flow, such as differential pressure type, float type, vortex type, thermal type, etc. Some of these gas flowmeters are suitable for measuring medium and large flow, as well as small flow, while Others are specifically designed to measure tiny flows. The following are some of the more common flowmeters for reference.
1. Differential pressure flowmeter: The differential pressure flowmeter suitable for measuring small flow is mainly a built-in orifice differential pressure flowmeter. This type of flowmeter is different from the flowmeter that is sensored by a standard throttling device. The first is the difference in structure. The built-in orifice plate is the integration of the sensor and the transmitter. The second is the difference in the pipe diameter. The pipe diameters suitable for the built-in orifice plate are all less than 50mm, and the typical inner diameter of the pipe is 10mm and 20mm. The third is the difference in measurement accuracy. The built-in orifice plate can be calibrated by real flow to ensure the measurement accuracy. If the working conditions allow, the measurement accuracy of 1.5 can be achieved by real flow calibration.
2. Float flowmeter: The rotameter can also be called a rotameter. According to the material classification, there are mainly glass tube rotameter and metal tube rotameter. Because of its advantages of small pressure loss and relatively large measurement range, the rotameter has become a commonly used flow measurement instrument in industrial control. In addition, the rotameter also has the advantages of convenient use and strong compatibility. It is especially suitable for medium flow measurement with low flow rate and small flow. The structure of the float flowmeter is relatively simple, the reading is intuitive, the pressure loss is small, and the maintenance is convenient. The float flowmeter is suitable for measuring the small flow through the pipe diameter D<100mm, and can also measure the flow of corrosive medium after special treatment.
3. Thermal gas mass flowmeter: The main feature of thermal gas mass flowmeter is that it directly measures mass flow without temperature and pressure compensation. No moving parts, low pressure loss and high reliability. It can measure the flow of small gas at low flow rate. The gas medium is required to be dry and clean, free of impurities such as moisture and oil. The plug-in thermal gas mass flowmeter is also suitable for the measurement of medium and large diameter gas flow. The thermal gas mass flowmeter has a range ratio of 500:1, which can be expanded according to the actual needs of users. It can realize the measurement of large diameter and small flow, and the lower limit of small flow can be measured as low as 0.5Nm/s.

Post time: 05-09-22