LD series electromagnetic flowmeter

The LD electromagnetic flowmeter consists of two parts: a sensor and a converter. It works based on Faraday's law of electromagnetic induction and is used to measure the volumetric flow rate of conductive liquids with a conductivity greater than 5 μ S/cm. It is an inductive instrument for measuring the volumetric flow rate of conductive media. In addition to measuring the volumetric flow rate of general conductive liquids, it can also be used to measure the volumetric flow rate of strongly corrosive liquids such as strong acids and alkalis, as well as homogeneous liquid-solid two-phase suspensions such as mud, slurry, and pulp. Widely used in industrial sectors such as petroleum, chemical, metallurgical, textile, papermaking, environmental protection, food, as well as municipal management, water conservancy construction, river dredging and other fields for flow measurement.
Principle and Structure

According to Faraday's principle of electromagnetic induction, a pair of detection electrodes are installed on the tube wall perpendicular to the axis of the measuring tube and the magnetic field lines. When the conductive liquid moves along the axis of the measuring tube, it cuts the magnetic field lines and generates an induced potential. This induced potential is detected by the two detection electrodes, and the value is proportional to the flow rate. Its value is:
In the formula: E=KBVD
E-induced potential;
K - Coefficient related to magnetic field distribution and axial length.
B-Magnetic induction intensity;
V-average flow velocity of conductive liquid;
D-electrode spacing; (Measuring the inner diameter of the tube)
The sensor uses the induced potential E as a flow signal, which is transmitted to the converter. After amplification, transformation filtering, and a series of digital processing, the instantaneous and cumulative flow rates are displayed on a backlit dot matrix LCD. The converter has 4-20mA output, alarm output, and frequency output, and is equipped with communication interfaces such as RS-485.  

Characteristics of LD series electromagnetic flowmeter

There is no obstruction in the measuring tube, and the pressure loss is zero, making it less prone to blockage.
As long as the electrode and lining materials are selected reasonably, the requirements for corrosion resistance and wear resistance can be achieved.
The measurement results are basically independent of physical parameters such as pressure, temperature, density, viscosity, and conductivity (not less than the minimum conductivity) of the liquid, and are not affected by the environment, so the measurement accuracy is high, the work is stable, and reliable.
By adopting modern analog signal conversion technology and high-performance ultra large scale integrated chips, signals are isolated, filtered, amplified, and digitally processed. Accurately display measurement results.
It has the functions of power-off protection and over range alarm for measurement values, and can set the flow direction of the fluid inside the sensor. Therefore, the installation of the sensor is not limited by the direction of liquid flow and can achieve bidirectional flow measurement.
Adopting a backlit dot matrix dual row flow display, it can simultaneously display instantaneous flow, cumulative flow, and display working status, parameters, measurement units, etc.
The range of electromagnetic flowmeter is wide (maximum flow/minimum flow), with a normal application range of 20:1 and generally 30:1 or larger.
The instrument configuration has multiple output functions and can be matched with computers and unit combination instruments to meet the requirements of printing, communication, and networking.

Technical parameters
Main technical indicators

Flow Selection Table (Reference Curve Chart)

Model selection and description

Selection of electrode materials and lining materials

Selection of electrode materials
The user is responsible for selecting the electrode material based on the corrosiveness of the tested medium. For general media, relevant anti-corrosion manuals can be consulted to select the electrode material,
For media with complex components such as mixed acids, a hanging test should be conducted.
Corrosion resistance of electrode materials (for reference only, see Appendix 1 and Appendix 2 for details)
Corrosion resistance of electrode materials

Molybdenum containing stainless steel
00Cr17Ni14Mo2
(316L) For nitric acid, sulfuric acid, boiling phosphoric acid, formic acid, alkaline solutions at room temperature with a concentration less than 5%, and sulfurous acid under certain pressure
Acetic acid and other media have strong corrosion resistance and can be widely used in industries such as petrochemicals, urea, and vinylon. Suitable for weak acids
weak alkali.

Hastelloy B (HB) is suitable for almost all acid, alkali, and salt solutions (including fuming sulfuric acid and fuming nitric acid), and is not suitable for aqua regia and ammonium salts


Hastelloy C (HC) is resistant to corrosion by oxidizing acids such as nitric acid, mixed acids, or mixtures of chromic acid and sulfuric acid, as well as oxidizing salts such as Fe+++,
Corrosion caused by Cu++ak or other oxidants. Corrosion of seawater by solutions of hypoargon salts above room temperature.

Titanium (Ti) can withstand corrosion from seawater, various chlorides and hypochlorites, oxidizing acids (including fuming nitric acid), organic acids, alkalis, etc.
Not resistant to the corrosion of relatively pure reducing acids (such as sulfuric acid, hydrochloric acid), but if the acid contains fluorinating agents, the corrosion is greatly reduced.

Tantalum (Ta) has excellent corrosion resistance, similar to glass. Except for hydrofluoric acid, fuming sulfuric acid, and alkali, it can withstand almost all chemical media corrosion.


Selection of lining materials
The selection should be based on the corrosiveness, wear resistance, and temperature of the tested medium. Chloroprene rubber, resistant to general weak acid and weak alkali corrosion, temperature resistant to 65 ℃, chlorine
Rubber has abrasion resistance. Polytetrafluoroethylene can almost withstand strong acid and alkali corrosion except for hot phosphoric acid, and the medium temperature can reach 180 ℃, but it is not resistant to wear. gather
Amine ester rubber has good wear resistance, but poor acid and alkali resistance.

Performance and applicability of commonly used lining materials
Main performance and applicable scope of lining materials

Polytetrafluoroethylene
PTFE 1. It is the most chemically stable material among plastics, capable of withstanding boiling hydrochloric acid
Sulfuric acid, nitric acid, aqua regia, as well as strong alkali and various organic solvents
2. Poor wear resistance and adhesion performance.
1.-40℃-+180℃
2. Strong corrosive media such as acid and alkali
3. Sanitary media 4. Not suitable for negative pressure pipelines

neoprene
Polychloroprene 1 has excellent elasticity, high tensile strength, and good wear resistance
2. Resistant to corrosion in general low concentration acid, alkali, and salt media, not resistant to corrosion in oxidizing media. 1. ＜ 65 ℃
2. Measure general water, sewage, mud, and slurry

Polyurethane rubber
Polyurethane has excellent elasticity, high tensile strength, and good wear resistance
2. Resistant to corrosion in general low concentration acid, alkali, and salt media, not resistant to corrosion in oxidizing media. 1. Has excellent wear resistance (equivalent to ten times that of natural rubber)
2. Poor acid and alkali resistance