In many industries such as petroleum, chemical industry, metallurgy, electric power, light industry, food, etc., throttling devices have been widely used. They have the advantages of simple structure, reliable operation, stable performance, moderate accuracy and long service life. A common throttling device for orifice flowmeters is a high turndown differential pressure flow device composed of a standard orifice plate and a multi-parameter differential pressure transmitter, which can measure the flow of gas, steam, liquid, and partial mixed-phase flows.

There are three commonly used methods of pressure taking for throttling devices: corner joint pressure, flange pressure, and radial distance pressure.

Corner connection pressure: two pressure ports are located at the angle between the upper and lower end faces of the orifice plate and the pipe wall, and the distance between the pressure center of the upstream and downstream sides and the front and rear ends of the orifice is equal to half of the pressure diameter (single hole pressure ); When the annular chamber takes pressure, it is equal to half the width of the annular gap. There are two types of corner joint pressure taking, the annular chamber taking pressure, and the direct drilling pressure taking. The ring chamber needs to consider accuracy, which has a voltage stabilizing effect, and is suitable for cleaning media. Among them, the GD structure is suitable for flow measurement under high temperature and high pressure conditions. When selecting the annular chamber, the medium and pipe diameter should be considered. If the diameter is too small, the annular chamber is not easy to achieve. If the diameter is too large, the airflow edge effect will be relatively small. Therefore, if the diameter is too large, the flange can be used for pressure.

Flange pressure: The distance between the upstream and downstream pressure ports is 25.4mm from the upstream and downstream end faces to the front and rear ends of the orifice plate. Used when the caliber is too large. The pressure-taking structure of the flange is relatively simple. The flange is a special orifice flange with a pressure rating of 300LB, and the cost will increase accordingly. It is easy to remove dirt and is suitable for various media.

Diameter pressure: the distance from the center of the upstream pressure hole to the front face of the orifice is D, and the distance from the center of the downstream pressure hole to the front face of the orifice is D/2. In general, in order to avoid on-site installation errors, the diameter pressure is taken by a complete set of throttling devices with straight pipe sections. It is easy to remove dirt and is suitable for various media.