Case Study - Metal Tube Float Flowmeter

A metal tube float flowmeter (metal tube rotor flowmeter) is a variable area flowmeter commonly used in industrial automation process control. It features a compact size, wide detection range, and ease of use. It can be used to measure the flow of various liquids, gases, and other gases. It is particularly suitable for measuring low flow rates and small flow rates.

Custom Case Study

A customer from Singapore wanted to measure the flow of glycerol water, but the flow rate was relatively low. We recommended a metal tube float flowmeter with the following parameters:

Metal Tube Float Flowmeter
DN25mm
Medium: glycerol water
Flow range: 400-4000 L/h
Pressure: normal pressure
Temperature: normal temperature
Output: 4-20 mA + HART
DC24V
ANSI 1″ 150LB flange
Material: 304 stainless steel
Vertical installation, bottom inlet and top outlet
Pointer indicates instantaneous flow
LCD displays instantaneous flow and cumulative flow Total

Glycerol water is a mixture of glycerin and water. Its characteristics and applications stem from glycerin’s inherent physical and chemical properties: strong moisturizing, high viscosity and lubricity, antifreeze properties, broad solubility, and stability. Glycerol water has a wide range of applications, primarily in the cosmetics industry and personal care. It can also be used as an antifreeze in automotive cooling systems or aircraft wings. It can also be used in the medical and food industries.

Operating Principle

A metal tube float flowmeter consists of two main components: a sensor and an indicator. The sensor consists of a connecting flange, a measuring cone, a float, and upper and lower guides; the indicator consists of a housing, a magnetic drive system, a dial, and an electrical remote transmission system.

A float moves up and down within a vertical, tapered measuring tube. When the fluid As fluid flows upward through the annular gap formed by the conical tube and the float, the float is affected by the combined forces of buoyancy, gravity, and fluid dynamic pressure. When these three forces reach equilibrium, the float stabilizes at a certain height. At this point, the annular gap area is linearly related to the flow rate. Based on the Bernoulli equation in fluid dynamics, the principle of force balance, and the law of fluid continuity, the instantaneous fluid flow rate through the annular area can be calculated. Therefore, the metal tube float flowmeter utilizes the variable area flow measurement principle.

A high-performance permanent magnet is located inside the float. When the float is in equilibrium, it creates a uniform and stable magnetic field around the float. A magnetic sensor is mounted on the outside of the conical tube, which transmits the linear displacement of the float within the measuring tube to an indicator via a non-contact method. After detection and processing, the resulting displacement is displayed on the indicator scale or outputs a corresponding standard 4-20 mA current signal.

Features Of Float Flowmeter

Float flowmeters have low Reynolds number requirements. As long as a float shape is insensitive to viscosity, the flow coefficient remains stable even at Reynolds numbers above 40 or 500, unaffected by changes in fluid viscosity. This allows them to provide accurate measurements even at low Reynolds numbers.

Float flowmeters do not require strict straight pipe sections, increasing installation flexibility.

Float flowmeters have a wide flow range. The output of the flow sensing element is nearly linear, and pressure loss is relatively small, making them advantageous in a variety of applications.

Most float flowmeter structures can only be installed in vertical pipes from bottom to top.

Glass tube float flowmeters are popular for their simple structure and affordable price, but glass is fragile, especially when used with gases in unguided configurations. Metal tube float flowmeters eliminate the risk of cone tube rupture, offer a wider operating temperature and pressure range, and are more durable.

Float flowmeters are primarily suitable for small and medium-sized pipe diameters. Full-flow float flowmeters are not suitable for large pipe diameters. For larger pipe diameters, split-flow meters are a better choice. Furthermore, if the fluid used differs from the factory calibration fluid, such as if the fluid was calibrated with water but the actual fluid properties differ, flow indication correction may be necessary.

Applications

Chemical Industry: In polyethylene production, precise control of catalyst flow improves product yield. In chlor-alkali processes, titanium metal tube float flowmeters are resistant to chloride ion corrosion.

Oil and Gas: The explosion-proof design of metal tube float flowmeters ensures safe measurement of flammable gas flows.

Food and Beverage: In food filling lines, the hygienic design prevents bacterial growth. In fruit and vegetable filling lines, the hygienic design prevents bacterial growth. Low-flow rate flow measurement in juice concentration processes also ensures accuracy.

Water Treatment: In sewage treatment plants, its anti-clogging capabilities can filter particles as small as 2mm in diameter. In seawater desalination projects, titanium models resist chloride ion corrosion.

Pharmaceutical Industry: In vaccine production, its zero-dead-angle design meets GMP requirements. In solvent recovery systems, high-precision measurement reduces raw material waste.

Other Flow Meters For Liquid Measurement

Electromagnetic Flow Meters: Require a certain degree of conductivity for the measured liquid. They also need to avoid air bubbles and electromagnetic interference. They have no obstructing components and no pressure loss. They are corrosion-resistant and wear-resistant, require minimal maintenance, and have a long service life.

Ultrasonic Flow Meters: Suitable for clean, uniform, and uniform liquids. They utilize non-contact measurement, eliminate pressure loss, and can be installed with either clamp-on or plug-in mounting styles. They are suitable for large-diameter pipes.

Mass Flow Meters: Suitable for a variety of liquids. Highly accurate, it can directly measure mass flow and is unaffected by changes in temperature, viscosity, and density. However, it is relatively expensive.

Gear flowmeters: These include circular and oval gear flowmeters. They are particularly suitable for measuring the flow of high-viscosity, impurity-free liquids. They do not require a straight pipe section. Furthermore, our circular gear flowmeters can also measure the flow of cryogenic liquid ammonia.

Turbine flowmeters: Suitable for clean, low-viscosity liquids. Mechanical components are susceptible to wear and require regular maintenance and calibration.

Vortex flowmeters: Suitable for low-viscosity, clean liquids, or those containing fine particles.

Summary

Accurate flow measurement ensures stable production. Metal float flowmeters are most commonly used for flow measurement in small and medium-diameter pipes: their tapered tube rises and falls with flow, and their metal material can withstand high temperatures and high pressures. This Sino-Inst model allows you to select the pipe material based on the medium, select between pointer and remote transmission, and offer output options of 4-20 mA, RS485, and relay alarms. It can be used with both liquids and gases. Need to select a model? Contact our technical team directly to provide you with a tailored solution.

Case Study – Metal Tube Float Flowmeter