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Analyze the common problems of electromagnetic flowmeter
In the past, the electromagnetic flowmeter calibration is necessary to send to the professional calibration machine equipment to carry out inspection.However, with the development trend of electromagnetic flowmeter production technology and the expansion of the application of manufacturing industry, the application of electromagnetic flowmeter is more and more, the specification is more and more large, sent to the calibration machine equipment to verify the difficulty factor is more and more.In particular, water supply and drainage manufacturing industry, because of the use of the advantages of the jingang class manufacturing industry, to ensure that the table takeout check, the actual operation is more difficult, both time and effort, and even can not unload.However, companies in accordance with the ISO9001 quality certification system, as a metrological verification instrument of the electromagnetic flowmeter, must carry out on time inspection.Therefore, the use of electromagnetic flowmeters and manufacturers have been struggling to find a free online electromagnetic flowmeter testing method to replace the traditional offline verification method.
Common problems with electromagnetic flowmeters
In recent years, the world common electromagnetic flowmeter free online terms of inspection: large size electromagnetic flow meter way of free online check 90 times in the new century, Shanghai water system began to search for free online regular inspection certification, they use special digital signal inspection converter and controller inspection is to detect electrode liquid resistor, check the excitation regulator contains electromagnetic coil excitation regulator connection cable grounding resistor of resistance and copper, and the inspection, the excitation current converter output mode of magnetic induction intensity for Jane.In the pipe with stop-flow standard, from the preset inlet hole around the controller to the pipe, check the electrode and the lining for dirt, accumulation and cleaning.
Shanghai water supply company and source water enterprise under the mutual cooperation of the electromagnetic flowmeter factory, explored and accumulated more than 300 large-scale electromagnetic flowmeter inspection experience, and in 1997 ~ 1998 formulated the "large-scale electromagnetic induction flowmeter free online calibration method", which was implemented under the company of Shanghai public utilities administration office.Now Shanghai water authority has basically formulated the "electromagnetic induction flow meter free online calibration standards" regional professional specifications of this document.The same definition is mentioned in some references, such as the Tokyo metropolitan waterways agency and Japan
Some of the common faults in the application of electromagnetic flowmeters are caused by the failure of the electronic components of the meter itself, and some are caused by the failure of improper use, improper installation, natural environment standards, fluid mechanics characteristics and other factors, such as the fluctuation of display information, precision reduction and even the failure of the meter.It can be generally divided into two types: the installation of the adjustment of the fault (fault adjustment period) and all the normal operation of the fault (fault operation period).
(a) fault adjustment during the adjustment period it is hoped that the fault generally appears in the adjustment link of instrument installation. Once it is cleared, it will not easily reappear under the same standard.Generally, the fault in adjusting period is caused by improper installation, natural environment and damage of hydrodynamics characteristics.
1) the installation level is generally the fault caused by the wrong installation position of the electromagnetic induction flow sensor. Generally, the controller is installed at the ** point of the piping system where the vapor body is easy to accumulate;Or installed on the vertical pipe from the top down, will appear exhaust;Or there is no back pressure behind the sensor, fluid mechanics immediately into the air to produce an accurate measurement of the tube is not full tube.
2) at the level of natural environment, the general key is the pipeline stray current dry torsion, indoor space strong radio wave dry torsion, large and medium-sized electric motor electromagnetic field dry torsion, etc.The line stray current dry torsion generally USES the good independent protection grounding can obtain the satisfactory result, but if meets the strong stray current (such as the electrolysis workshop pipeline, has?
Free online induction verification GS9 total number of the application of electromagnetic flowmeter in Europe * *, its free online inspection technical * * perfect, also some of the key way of electromagnetic flowmeter producers on the basis of the above development also designed the special electromagnetic flowmeter online testing instrument, such as KROHNE GS9 electromagnetic flowmeter verification online free of charge.The instruments and equipment as a set of comprehensive test verification of the converter controller and electromagnetic flowmeter, the test content includes electrode data signals, the precise measurement of the simulation traffic output, the current excitation regulator on the spot measurement, power flow and the precise measurement of the output frequency, the electromagnetic coil and electrode resistors, etc., and the database record in many aspects, can also be transmitted to a micro computer.
The GS9 instructions for the whole process of inspection are very simple. If the connection (plug and play) is carried out according to the logo of the cable and the steam flow meter, and then the automatic calibration is started, the database will be stored in the internal memory chip (70 meters), and then the database can be transferred to the electronic computer for solution.Tester automatic loading instrument GK, measuring range, specifications, excitation current, current and frequency of the output Settings, and has just started to do precise measurement, inspection of exciting current electromagnetic coil and electrode resistors or short-circuit fault (the way), test two accurate measurement data signal electrode and current, frequency of converter output test.The whole process of "Pass" or "fail" diagnosis and storage of all verifications is obtained for different components of the converter.The whole process of calibration is transmitted to the electronic computer by the automatic control system according to RS232 communication port.Traceability GS9 is immediately traceable to KROHNE's ** web-side calibrator (GS100) and (Spanish institute for metrology and verification NMI), with controller calibration uncertainty of 0.03% and measurement uncertainty of GS9 of 0.09%.The GS9 is connected to the PC on the spot or in the instrument room according to RS232 in such a way as to perform the free online inspection or special instrument equipment, although it is not necessary to stop the total flow of the pipeline and then conduct the inspection of the steam flowmeter
If the conductivity is higher than the hydrodynamic conductivity, the electrode control circuit will have a short circuit fault and the instrument will not work properly.Therefore, it is necessary to eliminate the adhesion scale layer in the precise measuring tube of electromagnetic flowmeter immediately.It is very easy to induce high working voltage and surge current in the instrument route by lightning, which will destroy the instrument.It is key according to the power plug or excitation regulator electromagnetic coil or sensor and converter between the total flow of the power line, especially in the main control room power plug import accounted for the majority.3) natural environment standard transition during the adjustment period because the natural environment standard is good (such as no interference source), the steam flow meter works normally, which is usually very easy to install the standard carelessly (such as the grounding device is not very good).In such a case, once the natural environment standard changes, there will be new interference sources in the operation period (when the steam flowmeter peripheral pipeline arc welding, installed on the surrounding large transformers, etc.), it will dry all the normal operation of the meter, the steam flowmeter output data signal will appear fluctuation.
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