What is a float flow meter?

The float flow meter is also called a rotameter. The float flow meter is a volumetric flow meter in which a float rises and falls in a vertical tapered tube as the flow changes, changing the flow area between them. It is often called Variable Area Flowmeter or Area Flowmeter in the United States and Japan. The float flow meter can be used to measure the flow of liquid, gas, and steam. It is especially suitable for medium flow measurement under low flow rates and small flow conditions.

Float Flow Meter Technology

How does a float flow meter work?

Float Flow Meter is also called rotor flow meter. It is mainly used for small and medium caliber flow measurement. It can measure liquid, gas, steam, etc. The product series have complete specifications and are widely used.

Float Flow Meter working principle

How does a float flow meter work?

Float Flow Meter consists of two parts. One of the rotameter is a tapered tube that gradually expands from bottom to top. The other is a rotor that is placed in the tapered tube and can move freely up and down along the centerline of the tube.

When measuring the flow of fluid, the measured fluid flows in from the lower end of the tapered tube. The flow of fluid impacts the rotor and produces a force on it. The magnitude of this force varies with the flow rate.

When the flow is large enough, the generated force will lift the rotor and raise it.

At the same time, the measured fluid flows through the annular section between the rotor and the tapered tube wall. At this time, there are three forces acting on the rotor. The dynamic pressure of the fluid on the rotor, the buoyancy of the rotor in the fluid, and the gravity of the rotor itself.

When the flowmeter is installed vertically, the center of gravity of the rotor coincides with the axis of the tapered tube. The three forces acting on the rotor are all along the direction parallel to the axis of the tube.

When these three forces reach a balance, the rotor floats smoothly on a certain position in the cone tube.

For a given rotameter, the size and shape of the rotor have been determined. Therefore, its buoyancy in the fluid and its own gravity is known to be constant. Only the dynamic pressure of the fluid on the float changes with the flow rate of the incoming flow.

Therefore, when the flow rate of the incoming flow becomes larger or smaller, the rotor will move up or down. The flow cross-sectional area of ​​the corresponding position also changes. Until the flow rate becomes the corresponding speed when the flow rate becomes balanced, the rotor is stable in the new position.

For a given rotameter, the position of the rotor in the cone tube is in one-to-one correspondence with the flow rate of the fluid flowing through the cone tube.

In order to prevent the rotor from touching the tube wall when moving up and down on the centerline of the tapered tube, two methods are usually used.

One is to install a guide mandrel in the center of the rotor to keep the rotor moving up and down on the centerline of the tapered tube.

The other is a chute on the edge of the rotor disc. When the fluid flows through the rotor from bottom to top, one side bypasses the rotor. At the same time, it passes through the chute to generate a reverse thrust. The rotor keeps rotating around the centerline. . It can keep the rotor from touching the pipe wall when working. The rotor material of the rotameter can be made of stainless steel, aluminum, bronze, etc.

Types of Float Flow Meter-variable area flowmeter

It can be divided into transparent material cone tubes and metal cone tubes.

  1. Transparent conical tube float flow meter

Transparent tapered tube materials include glass tubes, transparent engineering plastics such as polystyrene, polycarbonate, plexiglass, etc. Among them, glass pipes are most used, but they are easy to break. Engineering plastic pipes are not easy to break. Some are also resistant to corrosion by corrosive media such as acid and alkali.

The diameter of the transparent tapered tube float flow meter is 15~40mm, and the flow index is directly engraved on the outer wall of the tapered tube. Or an indexing scale is installed beside the tapered tube. The tapered tube has a cone smooth surface and a guiding rib (or flat surface). ) Two kinds.

The float moves freely in the tapered tube or moves under the guidance of the tapered tube ribs. The instrument on the inner wall of the large smooth surface is also guided by a guide rod.

  1. Metal Conical Tube Float Flow meter

The diameter of the metal tube conical tube float flow meter is 15~40mm, and the displacement of the float is transmitted to the conversion part outside the casing by means of magnetic steel coupling. Compared with transparent conical tube float flow meter. It can be used for higher medium temperature and pressure. And it is not easy to break.

There are several other structures of the transparent float flow meter. For example, the transparent straight tube float flowmeter is a deformed structure of the transparent conical tube float flow meter. The flow detection element is composed of an orifice plate and a cone floating plug.

There are other types of deformed structures of the metal tube conical tube float flowmeter. Among them, the direct indication type directly observes and reads the position of the float through the transparent straight pipe and the floating plug.

The horizontal installation type can be installed in the horizontal pipeline; the straight-through type has a different right-angle flow direction from the typical structure. It is not necessary to change the flow direction. It can be directly connected to the vertical pipeline. Easy to install.

The floating plug orifice plate type replaces the rotor tapered tube with a floating plug orifice plate. It is more convenient to change the flow specification as long as the floating plug with a different taper is changed.

It can be divided into on-site instructions, pneumatic remote signal output, electric remote signal output, alarm, etc. Transparent tube float flowmeters are all on-site indication types.

Sometimes a proximity switch is installed to output upper and lower limit alarm signals.

The conversion part of the remote signal output instrument converts the displacement of the float into an analog signal output of current or air pressure. Respectively become air remote transfer float flowmeter and electric remote transfer float flowmeter.

It can be divided into hose connection, flange connection, and threaded connection.

There are three connection methods for the transparent tube float flowmeter.

Among them, hose connection is often used for instruments with a diameter of less than 10mm and places with low working pressure.

The threaded connection is often used for instruments with a diameter below 40mm. The scope of application is not wide.

Flange connection is used for instruments with a diameter of 15~100mm, and the application is the most common.

Metal tube float flowmeters are usually flanged, and individual models are connected by a thread.

It can be divided into liquid, gas, and steam.

Most float flow meters can measure both liquid and gas in the same instrument.

Only specially designed metal tube float flowmeters can be used to measure steam. Or add additional components to the standard instrument. Such as adding liquid damping parts with fins. Install heat sinks at the junction with the indicating conversion part.

It can be divided into basic types, jacket insulation types, explosion-proof types, corrosion-resistant types, and blowing types. The basic type is the most widely used.

Jacket insulation type is used for occasions where the temperature in the pipeline is significantly higher (or lower) than the ambient temperature.

When used in explosive gas or dust, the electric remote float flowmeter adopts an explosion-proof type. At present, there are explosion-proof design structures and intrinsically safe explosion-proof design structures in China.

Corrosion-resistant float flowmeters are made of engineering plastics such as polytetrafluoroethylene, etc., for the structural parts and float in contact with the medium.

The flow rate of the blowing type is small, the air is 20~3000L/h, and the water is 0.3~100L/h, and the accuracy requirements are not high.

The blow-flow type float flowmeter is integrated with a small self-operated differential pressure regulator. The flow change is caused by the pressure fluctuation of the power source or the disturbance of the downstream parameter change. Self-adjustment to maintain a constant flow rate.

It can be divided into full flow type and split flow type.

The full-flow type refers to the instrument in which all the fluid to be measured flows through the float flowmeter.

The shunt type means that only part of the measured fluid flows through the flow detection part such as the float. The shunt-type float flowmeter is a combination of a standard orifice plate installed on the main pipe and a smaller diameter float flowmeter. It is used for larger flow rates with pipe diameters greater than 50mm. And as long as the place indicated on the spot.

Float type water flow meter

Rotameters can be used to measure the instantaneous flow of water. There are many flow meters for measuring water. Almost all flow meters that measure liquids can be used to measure water.

The original rotameter used to measure water is now used to measure the flow rate of gasoline. Is the reading correct?

Certainly not. Rotameter measuring liquid is most affected by liquid density and viscosity. It is recommended to find the manufacturer to tell them the parameters of your gasoline. It should be able to help you convert and tell you the true flow rate when the current scale is used to measure gasoline.

Rotameters measure different liquids. How to convert?

Rotameter display value correction. The fluid and state when the flowmeter is in use are generally different from the fluid and state when the flowmeter is scaled. Therefore, the value of the flow meter reading during use is not the real flow through the flow meter. The indicated value must be corrected according to the fluid and state in use. In order to get the correct flow.

The flow meter produced by Sino-Inst is calibrated with water for measuring liquid. The flowmeter for measuring gas is calibrated with air. The indicated value is scaled according to the volume flow rate of the standard state (water at 20°C; air at 20°C, 101.325KPa). Therefore, all corrections are based on the standard state index.

Extended reading: Beginner’s Guide: Variable area flow meter

More Featured Water Flow Meters:

Float air flow meter

Metal tube rotameter can be used to measure air. Because rotameter is a kind of variable area flow measuring instrument commonly used in industrial process automation control.

It has the characteristics of small size, large detection range, and convenient use.

It can be used to measure the flow of liquid, gas and steam. It is especially suitable for medium flow measurement with low flow rate and small flow, so there is no problem in measuring air.

However, it should be noted that the metal tube rotor flowmeter is only suitable for the flow measurement of small-diameter and low-velocity media within DN200.

More Featured air flow meters:

Frequently
Asked
Questions

Rotameter is a kind of variable area flowmeter. The working principle of the rotameter is in a vertical cone tube that expands from bottom to top. The gravity of the float of the circular cross-section is borne by the hydrodynamic force. The float can be in the cone The tube rises and falls freely. It moves up and down under the action of flow velocity and buoyancy. After being balanced with the weight of the float, it is transmitted to the dial to indicate the flow through the magnetic coupling.

The rotameter consists of two parts. One of the rotameter is a tapered tube that gradually expands from bottom to top. The other is a rotor that is placed in the tapered tube and can move freely up and down along the centerline of the tube.

When measuring the flow of fluid, the measured fluid flows in from the lower end of the conical tube. The flow of fluid impacts the rotor and produces a force on it. The magnitude of this force varies with the flow rate). When the flow rate is large enough At this time, the force generated will hold up the rotor and raise it.

The accuracy of the conventional model of the rotameter is 1.5. This accuracy is not the highest. But it has been able to meet the measurement needs of most users.

Sino-Inst offers over 30 Float Flow Meter products. About 50% of these are for liquids. 40% are for gas. At the best price.

A wide variety of Float Flow Meter options are available to you, such as free samples, paid samples.

Sino-Inst is a globally recognized supplier and manufacturer of Rotameter flow meters, located in China.

The top supplying country is China (Mainland), which supply 100% of the Float Flow Meter respectively.

Sino-Inst sells through a mature distribution network that reaches all 50 states and 30 countries worldwide. Float Flow Meter products are most popular in Domestic Market, Southeast Asia, and Mid East.

You can ensure product safety by selecting from certified suppliers, with ISO9001, ISO14001 certification.

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