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technical article
Rotameter flow measurement and selection
2011-5-25 16:33:32

Rotameter flow measurement and selection

Float flowmeter , also known as rotor flowmeter , is a type of variable area flowmeter.In a vertical cone tube that expands from bottom to top, the gravity of the circular cross section of the float is supported by the liquid power. The float can Freely rise and fall inside the cone. It moves up and down under the action of flow velocity and buoyancy, and after balancing with the weight of the float, it is transmitted to the dial to indicate the flow through magnetic coupling. Generally divided into glass and metal rotor flowmeters. Metal rotor flowmeters are the most commonly used in the industry. For corrosive mediums with small diameters, glass materials are usually used. Due to the fragility of glass materials, the key control point is also available with all titanium and other precious metals.
Working principle of metal tube float flowmeter
When the measured medium flows from the bottom to the top of the measuring tube, a differential pressure is generated at the upper and lower ends of the float to form a rising force. When the rising force of the float is greater than the weight of the float immersed in the fluid, the float rises, and the ring gap area increases. The flow velocity of the fluid drops rapidly, the differential pressure at the upper and lower ends of the float decreases, and the lifting force acting on the float decreases, until the lift force is in equilibrium with the weight of the float immersed in the fluid, the float is stabilized in the first position, the height of the float position is Corresponds to the size of the measured medium flow. The float has a built-in magnetic steel. When the float moves up and down with the medium, the magnetic field changes with the movement of the float. A magnetic sensor converts the change of the magnetic field into an electrical signal, and displays the instantaneous flow rate and accumulated flow rate through analog-to-digital conversion, digital filtering, temperature compensation, microprocessor processing, digital-to-analog conversion, liquid crystal display, and switch control output. control.
Rotor flowmeter features:
Rotameters are the most commonly used flowmeters in industry and laboratories. It has the characteristics of simple structure, intuitive, small pressure loss, convenient maintenance and so on. Rotary flowmeter is suitable for measuring small flow through pipe diameter D <150mm, and can also measure the flow of corrosive media. In use, the flow meter must be installed on a pipe section that runs vertically, and the fluid medium passes through the rotor flow meter from bottom to top.
Rotor flowmeter works :
The rotor flowmeter consists of two parts. One of the rotor flowmeter is a tapered tube that gradually expands from bottom to top; the other is a rotor that is placed in a tapered tube and can move freely along the centerline of the tube. . Rotary flowmeter When measuring the flow of fluid, the measured fluid flows in from the lower end of the conical tube. The flow of the fluid impacts the rotor and generates a force on it (the magnitude of this force varies with the flow); when the flow is large enough At this time, the generated force lifts the rotor and raises it. At the same time, the measured fluid flows through the annular section between the rotor and the conical tube wall, and flows out from the upper end. When the force of the measured fluid on the rotor is exactly equal to the weight of the rotor in the fluid (called the display weight), the force of the rotor is in equilibrium and stays at a certain height. Analysis shows that the position height of the rotor in the conical tube has a corresponding relationship with the flow rate. Therefore, by observing the position height of the rotor in the conical tube, the corresponding flow value can be obtained.
In order to prevent the rotor from hitting the wall of the tube when moving on and down the centerline of the conical tube, two methods are usually used: one is to install a guide core rod in the center of the rotor to keep the rotor at the centerline of the conical tube. Up and down movement, the other is a chute on the edge of the rotor disc. When the fluid flows from the bottom to the rotor, it bypasses the rotor on one side, and at the same time generates a reverse thrust through the chute, so that the rotor does not move around the centerline. Stopping rotation can keep the rotor from hitting the wall of the pipe during work. Rotor flowmeter rotor material can be made of stainless steel, aluminum, bronze and so on.