Throttling flowmeter is a typical differential pressure flowmeter. It is the most common instrument used to accurately measure the total flow of gas, liquid and steam in the current industrial production. In all industrial production industries, the throttle meter also accounts for about half of the number of instruments and instruments, so the throttle meter is widely used in the industrial production industry. Both liquid and gaseous vapors can be accurately measured, and some mixed-phase flows such as gas-solid, vapor-liquid, and liquid-solid can also be used. Pipe diameters, working attitudes (working pressure and temperature) in general processing are available.
The throttling device is the most important branch of the flowmeter. It is divided into two types: standard throttling device and non-standard throttling device. Standard throttling devices are: standard orifice plate, ISA standard nozzle, long neck nozzle, classic venturi tube and venturi nozzle; non-standard throttling devices are: annular orifice plate, quarter round nozzle, quarter Round orifice plate, cone-shaped orifice plate, round orifice plate, axial force orifice plate, two-way orifice plate, bottom pressure loss total flow tube, rectangular frame venturi tube, V-shaped cone flowmeter, tapered flowmeter, hidden hole Plate, number of perforated plates, etc.
At the present stage, throttle type and dynamic head type are the most widely used among various types, and there are dozens of types of throttle type inspection pieces. Excellent varieties continue to appear, and the development trend towards the basic type is relatively complete. The dynamic pressure head type uses a uniform velocity tube flowmeter as a sign that there has been a rapid development trend in recent years, which is the key type of plug-in flowmeter. The basic throttling device can be put into use without actual flow correction, and is the only one in the flow meter. The category degree is narrow because the differential pressure data signal is related to the total flow by a quadratic power, generally 3: 1 or 4: 1. The impulse pipeline between the test piece and the differential pressure digital display instrument is a weak point, which is likely to cause common failures such as leakage, blockage, freezing and data frame loss.
The repeatability and accuracy of accurate measurement are in the middle of the flowmeter. Because of the harm of many factors, it is difficult to improve the accuracy. In order to fill the defects of the differential pressure flowmeter, some countermeasures are adopted, such as widening the scope, reducing the pressure loss, and improving the accuracy of accurate measurement. On-site installation standards have high requirements. If a longer distance between the pipe sections (such as orifice plate \ nozzle, etc.) is required, it is generally difficult to consider.
Throttling flowmeter has simple structure, convenient installation, reliable operation, low cost, and certain accuracy. It is necessary to be able to consider construction engineering survey. There is also a long history of application, with colorful and reliable test data, and the production and processing of design schemes have long been standardized. If the throttling flowmeter produced and processed according to the design standard does not need to carry out specific calibration, it can also carry out the total flow within the range of known uncertainty.