Working Principle and Characteristics of Metal Tube Float Flowmeter

product description

The metal tube float flowmeter is a variable area flow measurement instrument commonly used in industrial automation process control. It has the characteristics of small size, large detection range and easy use.

It can be used to measure the flow of liquid, gas and steam, and is particularly suitable for measuring the flow of media with low flow rate and small flow rate.

It has intelligent local display type and intelligent remote transmission type, with pointer display instantaneous/accumulated flow LCD display, upper and lower limit alarm output, cumulative pulse output, batch control, standard two-wire 4-20mA current output and other forms. It provides users with a very wide range of choices. In addition, the instrument uses advanced micro-processing central chips and high-quality industrial components.

According to the different structures of the measuring tube, Jiangsu Xianxing Instrument Technology Co., Ltd.'s metal tube float flowmeter can choose different measuring tube forms according to different user requirements, and has further improvements in maintenance and cleaning. On this basis, with the intelligent metal tube float flowmeter indicator, an intelligent metal tube float flowmeter can be formed.

Over the years, the various excellent performances and reliability of metal tube float flowmeters, as well as the good performance-price ratio, have been widely favored by petrochemical, steel, electric power, metallurgy, light industry, food, pharmaceuticals, and water treatment.

Structural principle

1. Structure

HLZ series metal tube float flowmeter mainly consists of two parts: measuring tube HR-F indicator. The measuring tube includes cone tube or orifice plate, guide, stopper, float and other parts, and the indicator includes magnetic follow-up system, pointer, disc, circuit and other components.

2. Working Principle

The measured medium flows from bottom to top through the upper and lower ends of the float of the measuring tube, generating a differential pressure to form a lifting force. When the lifting force on the float is greater than the weight of the float immersed in the fluid, the float rises, the annular gap area increases accordingly, the fluid flow rate in the annular gap drops rapidly, the differential pressure between the upper and lower ends of the float decreases, and the lifting force on the float decreases until the lifting force is balanced with the weight of the float immersed in the fluid. The float then stabilizes at a certain position, and the height of the float position immediately corresponds to the flow rate of the measured medium.

The float has a built-in magnet. When the float moves up and down with the medium, the magnetic field changes with the movement of the float.

a. For the local type, the follower magnet in the local indicator is coupled with the magnet in the float to rotate, and at the same time drive the pointer to indicate the flow rate at that time through the dial.

b. For the intelligent type, the follower magnet in the intelligent indicator is coupled with the magnet in the float, causing rotation, and driving the sensing magnet and pointer at the same time. The magnetic field change is converted into an electrical signal through a magnetic sensor, and then the instantaneous flow and cumulative flow are displayed through A/D conversion, digital filtering, temperature compensation, microprocessor processing, D/A output, and LCD display.

Suitable for measuring the flow of small-caliber and low-velocity gases, liquids and steam.

2. Magnetic coupling principle, no leakage and high pressure resistance.

3. High temperature resistance, up to 450℃.

4. Affected by a certain viscosity, it is not suitable for measuring high viscosity media.

5. When the flow rate exceeds 100m3/h water flow, the pressure loss is large.

6. Mostly used for process control instruments, with the best accuracy of 1%, generally 1.5%, and a range ratio of 10:1.

7. Both intrinsically safe explosion-proof and flameproof types are available, suitable for dangerous occasions.

8. There are many types to choose from, including local pointer type, battery type, two-wire type, 220V AC power supply type, etc.

9. The most suitable installation method is vertical installation with the machine in from the bottom and out from the top.

10. When measuring high temperature or low temperature (below -30 ℃) media, it is best to use a jacket type.

11. Not suitable for measuring media with large density changes.

12. Not suitable for measuring pulsating medium flow (such as metering pump outlet).

13. This meter has no temperature and pressure compensation for gas, which needs to be considered separately.

14. When multiple instruments are densely installed or carbon steel process pipelines pass near instruments, keep a distance of more than 100mm from the instruments to avoid magnetic field interference.

15. When measuring the flow of media containing a large amount of ferromagnetic particles, a magnetic filter should be installed in front of the meter and purged regularly.

16. The metal tube float flowmeter does not have high requirements for the straight pipe section, generally 5D in front and 250mm in the back.

17. If the instrument is used in explosion-proof environments, the round shell M4 indicator should be selected.

18. The high and low alarms of the flow meter are generally open collector OC gate mode, which requires an external relay for current amplification. Relay output type can also be selected, with a contact capacity of 1A@30VDC or 0.2@250VAC or 0.@125VAC.