A throttling device is a type of flow device in which a fluid filled with a pipeline flows through the pipeline. The flow beam will form a local contraction at the throttling point, thereby increasing the flow velocity and reducing the static pressure, resulting in a static pressure difference (or throttling flowmeter) before and after the throttling element.
Category:
As the most important branch of flow meters, throttling devices are divided into two categories: standard throttling devices and non-standard throttling devices. Standard throttling devices include: standard orifice plate, ISA standard nozzle, long neck nozzle, classic Venturi tube, and Venturi nozzle; [1] Non standard throttling devices include: annular orifice plate, quarter round nozzle, quarter round orifice plate, conical inlet orifice plate, circular orifice plate, eccentric orifice plate, double orifice plate, low-pressure loss flow tube, rectangular Venturi tube, V-shaped cone flowmeter, wedge-shaped flowmeter, internal orifice plate, limiting orifice plate, etc
Basic principle:
During the movement of a continuous fluid medium in a pipeline, when it flows through the pre-set throttling device inside the pipeline, its flow stream will form a local reduced diameter state at the throttling device. As a result, the flow velocity of the fluid medium increases and the hydrostatic pressure relatively decreases. This situation will result in a pressure drop (pressure difference) upstream and downstream of the throttling device (orifice plate). The larger the flow rate of the flowing medium, the greater the pressure difference generated upstream and downstream of the throttling device.
Therefore, the pressure difference of the throttling measuring device can be converted to measure the relative flow rate of the fluid flowing through the throttling device. This is the basic principle of using the throttling device to specifically measure the continuous flow medium flow rate in the pipeline
Purpose:
Throttle flowmeter is a typical differential pressure flowmeter. It is the most commonly used flow meter for measuring gas, liquid, and vapor flow in industrial production. According to surveys and statistics, about 70-80% of the flow meters used in industrial production systems such as steel mills and refineries are throttling flowmeters. In the entire industrial production field, throttling flow meters also account for more than half of the total number of flow meters. The reason why throttling flow meters are widely used is mainly because they have two outstanding advantages:
① The structure is simple, easy to install, reliable in operation, low in cost, and has a certain degree of accuracy. It can meet the needs of engineering measurement.
② It has a long history of use, rich and reliable experimental data, and standardized design and processing. As long as the throttling flowmeter is designed and processed according to the standard, it does not require actual calibration and can perform flow within a known uncertainty range.
Measurement:
Especially the second advantage makes the throttling flowmeter very convenient to manufacture and use. Because for a flow meter, especially one used for high flow measurement, various difficulties will be encountered during calibration.
A throttling flowmeter typically consists of a throttling device that can convert fluid flow into a differential pressure signal, and a differential pressure gauge that measures differential pressure and displays flow rate. The throttling device installed in the circulation pipeline is also known as the "primary device", which includes a throttling element, a pressure measuring device, and front and rear straight pipe sections. The display device is also known as the "secondary device", which includes instruments required for differential pressure signal pipeline measurement.