Plate orifice flowmeter

This post was last edited by zdl1966 on 2018-10-28 at 20:02. When using a standard throttling device, the properties and state of the fluid must meet the following conditions: (1) The fluid must fill the pipes and the throttling device and flow continuously through them; (2) The fluid flow rate does not change over time or changes very slowly; (3) No phase separation occurs as the fluid passes through the throttling element; (4) The fluid must be a Newtonian fluid, that is, it must be homogeneous and single-phase from a physical and thermodynamic perspective, or can be considered single-phase, including mixed gases, solutions, and colloids with dispersed particles smaller than 0.1 μm. Fluids containing no more than 2% (by mass) of uniformly dispersed solid particles in a gas, or no more than 5% (by volume) of uniformly dispersed bubbles in a liquid, can also be considered single-phase fluids, but their density should be taken as the average density; (5) Before flowing through the throttling element, the fluid stream must be a irrotational flow parallel to the axis of the pipe. Key points for installing orifice plate flow meters: 1. Before installation, check whether the number and size of the throttling device meet the requirements of the pipeline installation location. 2. For a newly installed piping system, the orifice plate must be installed after the pipes have been flushed and cleaned. 3. Pay attention to the installation direction of the orifice plate: the “+” sign should face the flow direction. 4. The center of the orifice plate should coincide with the centerline of the pipeline, and the concentricity error must not exceed the value of 0.015(1/β-1). 5. When installing the orifice plate in the pipeline, it is necessary to ensure that its end face is perpendicular to the pipeline axis, with the perpendicularity error not exceeding ±1°. 6. To avoid distortion in the transmission of differential pressure signals, the positive and negative pressure pipes should be laid as close to each other as possible; in extremely cold areas, anti-freezing measures should also be taken. Electric heating or steam heating can be used for insulation; however, it is necessary to prevent the medium being measured from overheating and vaporizing, as well as the formation of gases in the pressure guiding pipes, which could cause false differential pressure. 7. The installation site of the orifice plate flow meter must be airtight; no leaks are allowed. Therefore, the installation work must be carried out before pipeline pressure testing. 8. The pressure guiding pipe should be installed vertically or at an inclination, with the slope not being less than 1:12. For fluids with higher viscosity, the inclination should also be increased. When the distance over which the differential pressure signal is transmitted exceeds 3 meters, the pressure guide pipe should be inclined in sections, with gas collectors and settlers installed at each highest and lowest point. 9. The pressure guiding tube shall be made of materials resistant to pressure and corrosion, selected according to the properties of the medium being measured; its inner diameter must not be less than 6 millimeters, and its length should preferably be within 16 meters. 10. When the orifice plate is installed on a vertical main pipeline, the location of the pressure tapping port can be chosen arbitrarily within the plane of the pressure tapping device. The orifice plate is installed in a horizontal or inclined main pipeline.

Refer to GB2624.2; GB50093; HG 21581

1. For newly installed piping systems, it is necessary to perform line cleaning (i.e., pipe purging) before installing standard orifice plates or nozzles, in order to prevent impurities in the pipes from causing blockages or damage to the throttling devices. 2. Before installation, it is necessary to carefully verify that the numbers, identifiers, and specifications of the standard orifice plates or nozzles match the parameters such as pipeline conditions and flow range. The end marked with “+” near the pressure tapping point on the orifice plate or nozzle should be connected to the pipeline upstream of the medium, while the end marked with “–” should be connected to the pipeline downstream of the medium. The center line of the throttling device should be coaxial with the center line of the pipeline. 3. Installation position of the pressure tapping ports on standard orifice plates or nozzles in the pipeline: yunrun.com.cn/product/174.html ① When the medium being measured is gas, it is necessary to prevent water or contaminants from entering the pressure guiding tube. When a standard orifice plate or nozzle is installed in a horizontal or inclined pipeline, the position of the pressure tapping port should be above the horizontal line, with an angle A greater than 45 degrees, as shown in the figure: http://yunrun.com.cn/upload/201707/20/201707200021082542.png ② When the medium being measured is a liquid, it is necessary to prevent gas from entering the pressure guiding tube. When a standard orifice plate (standard nozzle) is installed in a horizontal or inclined pipeline, the position of the pressure tapping port should be below the horizontal line, with an angle A less than 45 degrees, as shown in the figure: http://yunrun.com.cn/upload/201707/20/201707200045501136.png ③ When the medium being measured is steam, it is necessary to prevent high-temperature steam from entering the pressure guiding tube directly; at the same time, it is important to ensure that condensate water is formed within the pressure guiding tube to isolate the high-temperature steam. When a standard orifice plate (standard nozzle) is installed in a horizontal or inclined pipeline, the position of the pressure tapping port should be above the horizontal line, with an angle A less than 10 degrees, as shown in the figure: http://yunrun.com.cn/upload/201707/20/201707200037395667.png ④ When a standard orifice plate or nozzle is installed in a vertical main pipeline, the position of the pressure tapping port can be chosen arbitrarily, as long as it is within the plane of the pressure tapping device. Actually, all of these are listed on the self-control installation diagram