Tiankang metal float flowmeter

Tiankang metal float flowmeter

1、 Product Overview
Anhui Tiankang metal tube float flowmeter is a commonly used flow measurement instrument in industrial automation control. It has the characteristics of low pressure loss, large detection range (range ratio 10:1), and easy use. It can be used to measure the flow of gas and steam, especially suitable for measuring the flow rate of low flow rate and small flow medium. The HW50 series metal tube float flowmeter has both local display and intelligent remote transmission types, with pointer display, instantaneous flow rate, cumulative flow rate, LCD display, upper and lower limit output, cumulative pulse output, and a two-wire 4-20mA current output, providing users with a wide range of choices. In addition, the instrument adopts a high MCU microprocessor to ensure the excellent performance of the flowmeter in various application scenarios.

For many years, the excellent performance and reliability of metal tube flowmeters, as well as their cost-effectiveness, have been widely favored by industries such as petrochemicals, steel, power, metallurgy, and light industry.

2、 Structural principle
1. Structure
The series metal tube float flowmeter mainly consists of three parts
a、 Indicator (intelligent indicator, local indicator)
b、 float
c、 Cone shaped measuring room
2. Working principle
When the measured medium passes through the conical measuring tube from bottom to top, a differential pressure is generated at the upper and lower ends of the float, forming an upward force. When the upward force acting on the float is greater than the weight of the float immersed in the fluid, the float rises, and the annular gap area increases accordingly. The fluid flow velocity at the annular gap immediately decreases, and the differential pressure between the upper and lower ends of the float also acts on the upward force of the float. Until the upward force is equal to the weight of the float immersed in the fluid, the float is at a certain height. The height of the float position corresponds to the flow rate of the measured medium. The float is equipped with magnetic steel, and the magnetic field changes with the float as it moves up and down with the medium.
a、 For the in-situ type, the magnetic steel in the in-situ indicator is coupled with the magnetic steel inside the float, causing rotation and driving the pointer to indicate the current flow rate through the dial.

b、 For the intelligent type, a solid-state magnetic sensor in the intelligent indicator converts the changes in magnetic field into electricity, and through A/D conversion, microprocessor, D/A output, and LCD display, the flow rate and cumulative flow rate are displayed.

3、 Main features
1. Suitable for small diameters and low flow rates
2. Reliable work, small quantity, long lifespan
3. Low requirements for downstream straight pipe sections
4. Has a wide flow range of 10:1
5. Local pointer indication is close to linear
6. The intelligent indicator is equipped with an LCD display, which can display instantaneous and cumulative flow rates, as well as output pulses and outputs
7. Equipped with temperature compensation
8. There are various forms such as on-site type, remote transmission type, jacket type, explosion-proof, corrosion-resistant, etc

4、 Main technical parameters

1. Measurement range: Water 2.5-100000l/h (20 ℃)
2. Range ratio: 10:1
3. Accuracy level: 1.0, 1.5, 2.5
4. Work pressure: DN15, DN25, DN50 are PN4.0MPa, up to 10.0MPa, DN80, DN100 are PN1.6MPa, up to 6.4MPa
5. Medium temperature: -40 ℃~300 ℃
6. Medium viscosity: DN15: η<5mPa · s (F15.1~F15.3)
the <30mPa·s(F15.4~F15.8)
DN25：the <250mPa·s
DN50~DN150: the <300mPa·s
7. Temperature: LCD type: -40 ℃~85 ℃
Pointer type: -40 ℃~120 ℃
8. Connection type: flange (executed according to DIN2501 or manufactured according to the flange provided by the user)
9. Instrument height: 250mm
10. Cable interface: M20 * 1.5
11. Power supply: 24VDC two-wire system 4-20mA or 85-265VAC 50/60Hz (remote transmission type)
12. Output: Upper or lower limit instantaneous flow relay output (large contact capacity) 5A@250VAC ）Or open collector output (large) 100mA@30VDC Internal impedance of 100 Ω
13. Pulse output: Accumulated pulse output, with small intervals of one pulse every 10 seconds (AC type) or one pulse every 50 milliseconds.
14. LCD display: dual row LCD display, displaying instantaneous flow and cumulative flow.
15. Intrinsic safety explosion-proof: Exia II CT4

16. Material of measuring tube: 316 stainless steel (ordinary type) or lined with polytetrafluoroethylene (anti-corrosion type)

Tiankang metal float flowmeterProduct Selection

Measurement principle:

The metal tube float flowmeter is a variable area flowmeter, which means that in the vertical measuring tube of the flowmeter, when the fluid flows upward through the tube. The float moves upward, and at a certain position, the lift and gravity of the float reach equilibrium. At this point, the circulation gap area between the float and the orifice plate (or cone tube) remains constant. The annular gap area is proportional to the rising height of the float, that is, a certain height of the float represents the size of the flow rate. When the float moves up and down, the position is transmitted to the external indicator in the form of magnetic coupling, so that the pointer of the indicator follows the movement of the float, and with the help of the cam plate, the pointer linearly indicates the size of the flow value. [1]

The electric remote transmission type accurately converts the flow rate value into a standard signal of 0-10mA or 4-20mA through an angular displacement sensor and an electric transmission circuit while the pointer indicates the flow rate on site.

Structural principle:

The flow detection element of a metal float flowmeter consists of a vertically expanding conical tube and a float group that moves up and down along the axis of the conical tube. The working principle is shown in Figure 1. When the measured fluid passes through the annular gap 3 formed by the conical tube 1 and the float 2 from bottom to top, a differential pressure is generated at the upper and lower ends of the float, forming a force for the float to rise. When the upward lift force on the float is greater than the weight of the float immersed in the fluid, the float rises, and the annular gap area increases accordingly. The fluid flow velocity at the annular gap immediately decreases, and the differential pressure between the upper and lower ends of the float decreases. The upward force acting on the float also decreases until the upward lift force is equal to the weight of the float immersed in the fluid, and the float stabilizes at a certain height. The height of the float in the cone tube corresponds to the flow rate it passes through.

The basic equation for volumetric flow rate Q is

(1) When the float is a non solid hollow structure (load adjustment amount), then

(2) In the formula, α represents the flow coefficient of the instrument, which varies depending on the shape of the float;

ε - the coefficient of gas expansion when the measured fluid is a gas, which is usually ignored due to its small correction amount and has been included in the flow coefficient through verification. If it is a liquid, ε=1;

△ F - circulation annular area, m2；

G - local gravitational acceleration, m/s2；

Vf - Float volume, if there is an extension, it should also include, m3；

ρ f - density of float material, kg/m3；

ρ - the density of the fluid being measured, such as the density of gas on the upstream cross-section of the float, kg/m3；

Ff - cross-sectional area at the working diameter (maximum diameter) of the float, m2；

Gf - Float mass, kg。

The relationship between the circulating annular area and the float height is shown in equation (3). When the structural design is determined, d and β are constants. There is a quadratic term for h in the equation, and this nonlinear relationship cannot be ignored. It can only be considered approximately linear when the cone angle is very small.

m2

(3) In the formula, d represents the maximum diameter of the float (i.e. working diameter), m；

H - The float rises from the point where the inner diameter of the cone tube is equal to the maximum diameter of the float, m；

β - cone angle of the cone tube;

a. B - Constant.

The typical structure of a transparent conical tube float flowmeter with a diameter of 15-40mm is shown in Figure 2. The commonly used transparent conical tube 4 is made of borosilicate glass, commonly referred to as a glass tube float flowmeter. The flow index is directly engraved on the outer wall of cone tube 4, and there are also additional index scales installed next to the cone tube. The inner cavity of the cone tube has two types: a smooth conical surface and a guide rib (or plane). The float can move freely inside the cone tube or move under the guidance of the cone tube ribs. For instruments with larger smooth inner walls, guide rods are also used for guidance.

Figure 3 shows a typical structure of a metal tube float flowmeter with a right angle installation method, which is usually suitable for instruments with a diameter of 15-40mm or more. Cone tube 5 and float 4 form a flow detection element. There is an extension of the guide rod 3 inside the casing (not shown in Figure 3), which transmits the displacement of the float to the conversion part outside the casing through magnetic coupling and other methods. The conversion part has two types: local indication and remote signal output. In addition to the right angle installation method, there is also a straight through structure where the centerline of the inlet and outlet is concentric with the cone tube, which is usually used for instruments with a diameter less than 10-15mm.