Describe the different methods for taking pressure readings using orifice plates What are their respective characteristics?

The error resulting from orifice plate throttling varies depending on the location where pressure is taken,; therefore, the method of taking pressure has a significant impact on the flow coefficient of the orifice plate. Currently, there are 5 methods for pressure tapping, each with its own characteristics as follows: 1. Corner tapping method: The distance from the center of the pressure tapping holes on the upstream and downstream sides to the front and rear surfaces of the orifice plate is equal to half the diameter of the pressure tapping hole (for single-hole tapping) ； When using a annular chamber for pressure measurement, it is generally equal to the width of the annular gap. 2. Flange pressure tapping method: The distance from the center of the pressure tapping holes on the upstream and downstream sides to the front and rear surfaces of the orifice plate is 25.4±0.8 mm, which is also known as the “1-inch flange pressure tapping method”. 3. Theoretical pressure tapping: The distance from the center of the pressure tap at the upstream side to the front surface of the orifice plate is equal to the ratio d/D of the inner diameter of the pipe. When d/D lies between 0.1 and 0.8, the position of the pressure tap varies within the range of 0.84D to 0.5D. 4. Radial distance pressure tapping method: The distance from the center of the upstream pressure tap hole to the front surface of the orifice plate is D, while the distance from the downstream pressure tap hole to the front surface is 0.5D. 5. Pipe pressure tapping method: The distance from the center of the upstream pressure tap hole to the front surface of the orifice plate is 2.5D, while the distance from the downstream umbrella-shaped pressure tap hole to the front surface is 8D.

1. Pressure tapping orifice plate for annular chambers: It belongs to the category of standard orifice plates. By enabling pressure sampling at the annular chamber, it improves measurement accuracy and reduces the minimum length of straight pipe required during installation, allowing for widespread use in various industries. 2. Elbow-type separately drilled pressure-taking standard orifice plate: It belongs to the category of standard orifice plates. This format is commonly used when the pipe diameter is 400 millimeters or more. The pressure tapping methods include drilling individual flange holes for pressure tapping, or using circular or square pressure equalizing rings for pressure tapping. The orifice plate format can include orifice plates with stems or non-standard elliptical orifice plates, etc. 3. Flanged pressure-taking orifice plate: It belongs to the standard orifice plate type. Regardless of the pipe diameter, the centers of the pressure tapping holes upstream and downstream are both located at a distance of 25.5 mm from the end faces on either side of the orifice plate; this design is commonly used in oil refining systems. 4. Orifice plate with radial distance pressure tapping: It belongs to the standard orifice plate type. The pressure measurement method is pipeline-based. The center of the upstream pressure tap is located at one diameter of the pipe in front of the orifice plate. The center of the downstream pressure tap is located at a distance of half the inner diameter of the tube from the rear end face of the orifice plate.