Pipe and Valve Knowledge: [Weekly Topic] What are the commonly used throttling devices in the chemical industry? (12.13---12.20)
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This post was last edited by WQC on 2010-12-12 at 18:47. What are the commonly used throttling devices in the chemical industry? What are the disadvantages and advantages of the throttling devices in each of these devices, and how can they be utilized to their fullest potential?
1. Valve 2. Venturi tube 3. Orifice plate 4. Nozzle. Your question is too broad; for throttling in ordinary pipelines, a valve is sufficient. As for flow meters, venturi tubes, orifice plates, and nozzles are used as throttling elements to control the flow rate. The minimum cross-sectional areas at the inlet and outlet after throttling, along with the corresponding pressures, are used to calculate the flow rate. Don’t ask questions like this in the future; I don’t know how to answer them.
Reply to 3# —Lantian— has covered it quite comprehensively; these are generally the ones that are used
1. Standard orifice plates feature high measurement accuracy, a wide range of applications, and low cost； Pressure tapping method: corner tapping, flange tapping, pitch tapping ； 2. Long-diameter nozzles are primarily used in the power industry in high-pressure or high-temperature and high-pressure applications. This typical design is employed for main steam, main feedwater, or desuperheated water systems with a capacity of 50MW or more; it features low pressure loss and a long service life ； 3. Venturi tube ； A flow detection element that uses a specially shaped tube to change the velocity of the fluid flowing through it, thereby creating a pressure difference. The axial cross-section consists of an inlet contraction section, a cylindrical throat, and a conical diffusion section. It has achieved good results in the measurement of combustion air, cooling air, and gas flow rates in hot blast stoves in steel mills (blast furnace gas, coke oven gas, converter gas), as well as in the measurement of large-diameter, low-flow pipelines for primary and secondary air in thermal power plant boilers. Solves the problem of accurate measurement of gas flow rates in current industrial plants for low to medium pressure, large diameter pipes, and low flow velocities. A fluid measurement device with a wide measurement range and easy installation. 4. Various types of valves ； 5. Throttle rod ；
Throttling devices come in two types: standard throttling devices and non-standard throttling devices. Standard throttling devices include angle-connected pressure tapping orifice plates, flange-connected pressure tapping orifice plates, and standard nozzles. Standard throttling devices have a wide range of applications, simple structures, and their display instruments are available in various series, offering a high degree of versatility. It can be used without individual calibration, has a relatively low cost, and is therefore widely used. According to statistics, it is currently used in over 70% of flow measurement applications in China. Standard throttling devices can be used for measuring the flow rate of general fluids (gases, liquids, vapors). The following are some of the more commonly used types of non-standard throttling devices. (1) Venturi tube, suitable for measuring the flow rate of low-pressure fluids in large pipes ； (2) Double orifice plate, suitable for measuring the flow rate of fluids with a Reynolds number Re greater than 3000 and less than 300000 ； (3) 1/4 circle nozzle, suitable for measuring the flow rate of fluids with a Reynolds number Re greater than 200 and less than 100000 ； (4) Annular orifice plates, suitable for measuring the flow rate of fluids that may contain precipitates or contaminants before and after the orifice plate.
Venturi tubes, nozzles, and orifice plates are generally used to restrict flow while measuring pressure differences, whereas valves serve solely to restrict flow
Orifice plates, nozzles, and Venturi tubes are all standard throttling devices that can be used without calibration. Under the same pressure difference, orifice plates have the greatest pressure loss, while Venturi tubes have the smallest pressure loss
1. Valves serve solely as flow restrictors; in refrigeration, they are throttling expansion valves. 2. Devices such as venturi tubes, nozzles, and orifice plates are used to restrict flow and simultaneously measure pressure differences. 3. Orifice plates function as flow restrictors, allowing valves to control the flow rate
Expansion units in large air separation plants.