Sewage electromagnetic flowmeter

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Sewage electromagnetic flowmeter measurement tube has no moving parts and resistance parts, no press…

Products overview:
ZW - LDE seriesSewage electromagnetic flowmeterAdopting the new technology.Using the constant current low-frequency rectangular wave three values or double frequency rectangular wave excitation, the advantages of both the rectangular wave magnetic field, and overcomes the drawback of sinusoidal magnetic field;Can also eliminate the power supply voltage fluctuation, power frequency and the excitation coil impedance changes caused by the error;And has excellent stability of zero point and is not affected by fluid noise interference.Which has the characteristics of high stability, high reliability.In addition to measuring general conductive liquid, according to user's special needs, can also be measured conductive liquid solid two phase flow, high viscosity liquids and salts, such as strong acid, strong alkali liquid flow. 
Second, the working principle:
ZW - LDE seriesSewage electromagnetic flowmeter based on Faraday electromagnetic induction principle, with the measuring pipe axis and the magnetic field lines in the vertical tube wall installed on a pair of detecting electrodes, when conducting liquid along the measuring tube axis movement, conductive liquid cutting lines of magnetic force induced electric potential, the induction electric potential by two detection electrodes detection, numerical size and flow into a direct ratio, its value is: E = KBVD type:
E - induction electric potential;
K - factor related to the magnetic field distribution and the axial length;
B - magnetic induction intensity;
V - conductive liquid average flow velocity;
D - electrode gap;(the measuring tube diameter)
Sensor will be induced potential E as traffic signal, sent to the converter, amplifying, transform filter with a series of digital processing, USES dot matrix LCD display with backlight instantaneous flow and cumulative flow.Converter has 4 ~ 20 ma output, alarm output and frequency output, and is equipped with RS - 485 communication interface, and supports HART and MODBUS protocol.
Applications:
ZW - LDE seriesSewage electromagnetic flowmeter is mainly used to measure volume flow of conducting liquid and slurry in the closed pipeline.Such as water, sewage, slurry, pulp, all kinds of acid, alkali, salt solution, food slurry, etc., widely used in petroleum, chemical, metallurgical, textile, food, pharmaceutical, paper making industries and environmental protection, municipal administration, water conservancy construction and other fields.
Four, the main features:
1, instrument structure is simple, reliable, have no moving parts, working life is long;
2, no closure choke parts, there is no loss of pressure and fluid blocking phenomenon;
3, no mechanical inertia, fast response and good stability, can be applied to automatic testing, adjusting and SPC system;
4, the measurement precision is not affected by the type of measured medium and its temperature, viscosity, density, the influence of physical parameters such as pressure;
5, adopt ptfe or rubber lining material and Hc, Hb, 316 l, the different combination of electrode materials such as Ti can meet the needs of the different media;
6, with pipeline, plug-in, such as a variety of flow meter type;
Block 7, using EEPROM memory, measuring operation safe and reliable data storage protection;
8, integration and separation of two types;
9, high-definition LCD backlit display.
Five,Technical parameters:
1, precision instrument: pipeline magnitude 0.5, 1.0;Plug in 2.5 on the Richter scale are unlikely.
2, measuring medium: conductivity is greater than 5 mu S/cm of various liquid and liquid-solid two-phase fluid.
3, velocity range: 0.2 ~ 8 m/s.
4, work pressure: 1.6 MPa.
5, environmental temperature: - 40 ℃ ~ + 50 ℃.
6, medium temperature: ptfe lining 180 ℃ or less;Rubber lining material 65 ℃ or less.
7, explosion-proof marks: Exmibd Ⅱ BT4.
8, explosion-proof number: GYB01349.
9, outside magnetic interference: 400 a/m or less.
10, shell protection: integration type: IP65;
In mold: sensor IP68 (5 meters underwater, rubber lining only);Converter IP65.
11, the output signal: 4 ~ 20 ma DC, load resistance Ω 0 ~ 750.
12, communication output: RS485 and CAN bus.
13, electrical connections: M20 x 1.5 internal thread, phi 10 cable hole.
14, power supply voltage: 90 ~ 220 v AC, 24 + / - 10% V.D C.
15, power consumption: 10 or less va.

Six, according to excitation methods of classification:
To produce a uniform constant magnetic field, it needs to choose a suitable way of excitation.Such as divided according to the field current mode, have a dc field, ac (or other frequency) power frequency excitation, low-frequency rectangular wave excitation and dual-band rectangular wave excitation.
1, the dc excitation
Dc excitation method with direct current (dc) or by * magnet produces a constant homogeneous magnetic field.The dc excitation zui big advantage of the transmitter is affected by the ac electromagnetic interference is very small, so can ignore the influence of self-induction phenomenon of liquid.But using dc magnetic field is easy to make by measuring the electrolyte fluid of the pipe is polarized, the electrolyte by electrolysis in the electric field, produce positive and negative ions, in under the action of electric field force, ran to the anode, anion cation ran to the cathode, which will result in positive and negative electrodes were surrounded by ions of opposite polarity, seriously affect the normal work of the instrument.So, dc excitation only commonly used for measuring the liquid electrolyte, such as the liquid metal flow of mercury (room temperature and high temperature of liquid steel, lithium, potassium), etc.
2, ac excitation
Industrial use of electromagnetic, most used (50 hz) power supply power frequency ac excitation method to produce alternating magnetic field, to avoid the dc excitation on the surface of the electrode polarization interference.But the use of ac excitation will bring a series of electromagnetic interference problem, such as orthogonal interference, in-phase interference, zero drift, etc.).Ac excitation is now replaced by low frequency square wave excitation.
3, low frequency square wave excitation
Low frequency square wave excitation waveform has two values (positive - negative) and three values (positive - zero - negative - zero) two kinds, the frequency of power frequency usually 1/2 ~ 1/32.Low frequency square wave excitation can avoid orthogonal electromagnetic interference of ac magnetic field, power frequency interference caused by distributed capacitance, inhibition of ac magnetic field within the tube wall and fluid caused by eddy current, dc excitation polarization phenomenon.

Seven, the structure form:
1, the sensor:
Sensor is mainly composed of measuring tube and electrode, excitation coils, iron core, magnetic yoke and shell.
A, measuring catheter: by stainless steel tube, the lining and the connecting flange, as the carrier of measured liquid measurement working conditions on site.
B, measuring electrode: installed in the measuring tube inside wall, and the axial direction perpendicular to a pair of electrodes to measure liquid signal generation.
: c, excitation coil in a magnetic field measurement of intraductal two excitation coil.
D, iron core and magnetic yoke: the excitation coil of the magnetic field generated import liquid, and the magnetic circuit.
E, shell: instrument packaging.
2, the converter:
Is the smart secondary table, it will flow signal amplification processing??Single chip microcomputer after the operation, can display flow, total amount, and can output pulse and analog current signal, used in the measurement or control of fluid flow.
3, product assembly form:
It into a shape and size in two forms.
A, a shape: mounted sensors and switches.
B, size: separation installation sensor and converter, through the connecting cable form flow metering system.
C, in order to adapt to the measurement demands of the different medium, the lining of sensor and electrode materials can have many choices.
Eight, installation requirements:
1, the flowmeter should be installed in the lower part of the horizontal and vertical place, avoid installed in the pipeline zui highs and vertical section;
2, flow meter should be installed in the line up;
3, flowmeter in open discharge pipe installation, the lower part of the should be installed in the pipeline;
4, if the pipe head more than 5 m, downstream of the electromagnetic flowmeter installation exhaust valve;
5, control valve should be installed on the downstream side of the sensor and the cut-off valve, and should not be installed in the upstream of the electromagnetic flowmeter;
6, electromagnetic import and export, and must not be installed in the pump should be installed in the pump outlet;
7, when measuring well flow meter installed in the way.
Nine, installation considerations.
1, the axis of the measuring electrode must be similar to horizontal direction;
2, measuring the pipe must be completely filled with liquid.
3, less flowmeter zui ahead to have 5 * D for flow meter diameter (D) the length of the straight pipe, the rear zui to have less 3 * D for flow meter diameter (D) the length of the straight pipe;
4, the direction of fluid flow and the direction of arrow flowmeter;
Five should have can be damaged by vacuum meter, the pipe lining, special attention should be paid;
6, near the flow meter should be no strong electromagnetic field;
7, shall have plenty of space, near the flowmeter to installation and maintenance;
8, if measuring pipeline vibration, the flowmeter should be fixed on both sides of bearing when measuring the mixed liquid of different medium hybrid point and the distance between the flowmeter zui to have less 30 x D for flow meter diameter (D) the length of the cleaning and maintenance for the convenience of the flowmeter, should install bypass pipe.
Ten, earthing protection, must pay attention to the following:
1, sensor, converter should be separate grounding, never even on the motor, process piping, grounding resistance should be less than 10 ohms.
2, sensor measurement of tube and shell, shielded wire, converter and secondary instrument must be grounded.
3, sensors, converters, grounding on the scene, to the shield in the control room side of the secondary instrument grounding, not multiterminal grounding, lest introduced due to different potential interference.
4, sensors installed in a metal tube, the sensor can be grounding wire connected to the pipe flange according to the requirement of the factory, the formation of reliable grounding instrument ground should be an independent site, can not share other electrical equipment grounding.

11, the main technical data:

1, the whole machine and the technology of sensor data:

2, converter technology data:

3, the choice of the lining:

4, import protection flange and the choice of grounding flange ring (or ground) :

5, the choice of electrode:

Twelve, correct selection:

Instrument selection is very important work in instrumentation, relevant data show that the instrument in two-thirds of faults in the practical application is instrument error caused by selection or wrong installation, please pay special attention to.

1, collect data:

By measurement of body composition;
Large flow, small flow;
Z high work pressure;
, z z high temperature low temperature;

2, range scope confirmation:

General industrial use measured medium velocity of electromagnetic flowmeter with 2 ~ 4 m/s advisable, under special circumstances, z low velocity should not be less than 0.2 m/s, high z should be not more than 8 m/s.If the medium containing solid particles, commonly used flow rate should be less than 3 m/s, prevent excessive friction lining and electrode;For viscous flow, the velocity can choose more than 2 m/s, larger velocity help eliminate electrode automatic on the effect of viscous material, to improve accuracy of measurement.

Under the condition of the range of Q have been identified, according to the velocity V can be decided to the size of the flow meter diameter D, the range of the values calculated by the next type:

Q = PI D2V / 4
Q: flow (㎡ / h) D: pipe diameter V: velocity (m/h)

Electromagnetic flow meter range of Q zui flow value should be greater than expected, the flow of the normal value in a full scale slightly greater than the flowmeter calibration 50 is advisable.

3And the reference flow range:

4, selection of code:

13, design selection and ordering information:

1, the measured medium: name, composition, status, electrical conductivity and electrical conductivity;

2, working temperature (℃);

3, work pressure (Mpa);

4, the pipe diameter (DN), the smallest, normal, scope of quantity (m3 / h);

5, corrosion resistance, wear resistance, whether there is a negative pressure;

6, installation requirements and the environment: a body or fission, signal output, communications, power supply;

7, installation environment: protection grade and explosion-proof requirements.

After-sales service commitment:

1, from the date of signing of the contract, I in the way provided for products of the company offers free maintenance and maintenance service, commitment to lifelong maintenance service;

2, jiangsu wei measurement and control instrument co., LTD. Sales manager will be in regular contact with customers, understand the usage of products, and solve the problems of the customers to use in the process of produce, free of charge to provide technical support;

3 the man-made damage is found, the warranty period, our company is responsible for the maintenance, and the resulting maintenance fee;

4, product quality problems or are not satisfied with product, the user can choose unconditional return, wei tt&c don't charge any fees, appear quality problem, bear the freight back and forth.