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Turbine flow meters, the main type of velocity flow meters,which are instruments that use multi-blade rotor (turbine) to sense the average flow velocity of fluid, and derive the flow or total amount.Generally it consists of two parts, the sensor and the display, and it can also be made into a whole. Turbine flow meters, volumetric flow meters and Coriolis mass flow meters are called the three types of flow meters with the best repeatability and accuracy. As one of the ten types of flow meters, their products have developed into the scale of mass production of multiple varieties and series.

Advantages:

(1)High accuracy. In all flow meters, it belongs to the most accurate flow meter.

(2)Good repeatability;

(3)No zero drift, good anti-interference ability;

(4)Wide range;

(5)Compact structure.

Disadvantages:

(1) The calibration characteristics cannot be maintained for a long time;

(2) Fluid properties have a great impact on flow characteristics.

Application overview:

Turbine flow meters are widely used in some of the following measurement objects: petroleum, organic liquids, inorganic fluids, liquefied gases, natural gas and cryogenic fluids.In Europe and the United States, turbine flow meters are second only to orifice plate flow meters for natural gas meters. In the Netherlands alone, more than 2,600 turbines of various sizes and pressures from 0.8 to 6.5 MPa are used on natural gas pipelines. They have become excellent natural gas meters.

1) The sensor structure of electromagnetic flow meter is simple, and there are no movable parts in the measuring tube, and there are no throttling parts which obstruct the flow of fluid. Therefore, when the fluid through the flow meter will not cause any additional pressure loss , and is one of the flow meters with the lowest energy consumption in the flow meter.

2) The flow rate of the dirty medium, corrosive medium and the suspended liquid-solid two-phase flow can be measured. This is because there are no obstructing parts in the inner part of the measuring tube，and only the inner lining and electrode of the measuring tube are contacted with the measured fluid.The material can be selected according to the nature of the measured fluid.For example,using PCTFE or PTFE as the lining can measure various corrosive media such as acid, alkali, salt, etc。Wear-resistant rubber as the lining is especially suitable for measuring liquid-solid two-phase flow with solid particles, wear larger slurry, cement slurry and various suspended liquids with fiber and paper pulp.

3) Electromagnetic flow meter is a volume flow measuring instrument.During the measurement process, it is not affected by the temperature, viscosity,density and conductivity of the measured medium (in a certain range).Therefore, the electromagnetic flow meter can be used to measure the flow rate of other conductive liquids only after being calibrated by water.

4) The output of the electromagnetic flow meter is only proportional to the average flow velocity of the measured medium, and is independent of the flow state (laminar or turbulent flow) under symmetrical distribution.Therefore, the electromagnetic flow meter has an extremely wide measuring range, and its measuring range can reach 100:1, and some even reach a running flow range of 1000:1.

5) The electromagnetic flow meter has no mechanical inertia and is sensitive to the reaction. It can measure the instantaneous pulsating flow rate and also measure the flow in both the positive and negative directions.

6）Industrial electromagnetic flow meters have a wide range of diameters from a few millimeters up to several meters,and there are already 3 meters of real-flow calibration equipment in China, which lays the foundation for the application and development of electromagnetic flow meters.

The main problems existing in the use of vortex flow meter are as follows:①indication long-term inaccuracy;②there is no indication at all;③the indication fluctuates in a large range,unable to read;④the indication does not return to zero;⑤there is no indication at small flow rate;⑥It is OK to indicate when there is a large flow, and inaccurate when there is a small flow;⑦when the flow changes, the indication change cannot keep up with;⑧The K coefficient of the instrument cannot be determined ,and many data are inconsistent.

The main reasons for these problems are summarized as follows:

1. Problems in the selection of vortex flow meter.Some vortex flow meters choose a large size due to the change of process conditions after caliber selection or design selection.The actual selection should be as small as possible to improve the measurement accuracy.The reasons in this aspect are mainly related to the problems of ①,③,⑥.For example, a vortex pipeline design is used by several equipments. Due to the process,some equipments are sometimes not used,the actual flow is reduced, the actual use causes the original design selection caliber to be too large, which is equivalent to raising the lower limit of the measurable flow.When the process pipe has a small flow rate, the indication cannot be guaranteed.When the flow rate is large, it can be used, because it is sometimes too difficult to remodel,the change of process conditions is only temporary. The accuracy of the indication can be improved by adjusting the parameters.

2. Problems in installation of vortex flow meter. The main reason is that the length of the straight pipe section in front of the sensor is not enough, which affects the measurement accuracy.The reason in this aspect is mainly related to the problem of ①.For example, the straight pipe section in front of the sensor is obviously insufficient. Since FIC203 is not used for measurement but only for control, so the current accuracy can be used, which is equivalent to downgrading.

3. Reasons for parameter setting direction.The instrument is incorrectly indicated due to a parameter error. Parameter error makes the calculation error of the full-scale frequency of the secondary instrument. The reasons in this aspect are mainly related to the problems of ①,③.The similar full-scale frequency makes the indication inaccurate for a long time. The actual full-scale frequency is greater than the calculated full-scale frequency, which makes the indication fluctuate in a wide range and cannot be read. The inconsistency of the parameters on the data affects the final determination of the parameters of the vortex flow meter.Finally, the parameters are determined through re-calibration and mutual comparison, and this problem is solved.

Which electrode and lining are selected for electroplating wastewater?

Electroplating wastewater is a very complex medium.How to choose the flow meter?The electromagnetic flow meter is preferred because of its conductivity, high accuracy and reliable performance.So how do I choose electrodes and linings?

First of all, we need to know what electroplating wastewater is. The composition of electroplating wastewater is very complex. Except for the wastewater containing cyanide (CN-) and acid-base wastewater, heavy metal wastewater is a potentially hazardous wastewater category in the electroplating industry.Classify them according to heavy metal elements contained in heavy metal wastewater, it can be generally divided into chromium (Cr) wastewater, nickel (Ni) wastewater, cadmium (Cd) wastewater, copper (Cu) wastewater, and zinc (Zn) wastewater. , gold (Au) wastewater, silver (Ag) wastewater, etc.In general, water is acidic and a small amount is alkaline,and the heavy metal content varies with surfactants, brighteners, and production processes.In other words, it is unstable.

First,we can choose polytetrafluoroethylene (PTFE) as the lining of the electromagnetic flow meter.Because of its excellent corrosion resistance and heat resistance,, it can resist almost all chemical media, including concentrated nitric acid and aqua regia.Secondly,for the choice of electrodes, tantalum (Ta) electrodes can be selected because of its strong corrosion resistance, which can withstand the corrosion of almost all chemical media except hydrofluoric acid.

The HHD electromagnetic flow meter developed by Huahai is a kind of inductive instrument that measures the volume flow of conductive medium in the pipe according to Faraday's law of electromagnetic induction. It adopts the embedded technology of single chip microcomputer to realize digital excitation,and adopts CAN field bus in electromagnetic flow meter. It is the first in China and its technology has reached the domestic leading level.