Use and maintenance 3. Vortex Flowmeter
Published on:2015-3-9 10:18:15 Hits:

Basic Information

222A water treatment stations and two cycles in Beijing Dongfang Chemical utility system plays a very important role, 222A water desalination station is to provide water for the boiler started to provide purified water for ethylene, ethylene oxide / ethylene drunk, through providing softening off for two alkaline; second cycle is to provide circulating cooling water for ethylene, ethylene oxide / ethylene drunk, started in the boiler, the water station.

In both devices, I used a total of 22 sets of plant LUGB vortex flow sensors and supporting secondary instrument FD910 type.

Vortex Flow sensor secondary instrument accept 12VDC power supply, the use of piezoelectric crystal element detection vortex separation frequency. Probe body mounted inside the cylinder vortices on both sides feel the pressure pulse generated by the rear cylinder, buried in the probe inside the body to feel the strain of the piezoelectric crystal element force of the alternating electric charge, the sensor output processing certain amplitude pulse signal to the secondary instrument. The pulse signal proportional to flow through the pipeline, which is determined by the ratio between the K-factor of the sensor, K coefficient is generally calibrated by the manufacturer, K factor represents the number of pulses flowing through the pipeline every one flow sensor units issued.

Secondary instrument is MCS51 series 8031 as the main flow meter showed that after the pulse signal is received, on the one hand by Analog ammeter display instantaneous flow, while total flow or the cumulative time from 8 digital display, another aspect can output 4 ~ 20 mA or 0 ~ 10 mA signal to the regulator or the logger to use. Second table based on the K-factor and flow range sensors to set the parameters.

The main problem

From 22 sets of vortex flowmeter is still in use, there have been a lot of problems. There are: ① indication of long-term allowed; ② always no indication; ③ indicate large-scale fluctuations, can not be read; ④ indicator does not return to zero; no indication ⑤ small flow; indication ⑧ large volume can also, when a small flow indication allowed ; when ⑦ change indicates a change to keep up with the flow; ⑧ meter K-factor can not be determined, many data are inconsistent.

Analyze and solve the main problem

Analyze and solve spent nearly six months, due to the complex issues, from design juice installation, parameter setting, routine maintenance, there are varying degrees of problems operating environment, many issues are entwined these issues, plus the need to solve some problems wait for some time for the process to run, so to solve the problems brought great difficulties. Some problems are caused by a common cause of several different reasons, some causes and several different issues are related.

Summarizes the main cause of these problems, mainly related to the following aspects:

(1) selection of issues. Some vortex sensor on the caliber of the selection or after the design and selection due to changes in process conditions, making a big choice - specifications, the actual selection should be chosen as small as possible caliber, in order to improve the measurement accuracy, the main reasons for this same problem ①, ③, ⑥ relevant. For example, a vortex line designed for the use of several devices, sometimes due to process some of the equipment is not used, resulting in the current actual flow rate decreases, the actual use of the original design Selection diameter is too large, equivalent to improve the flow can be measured limit, when the small craft pipeline flow indicators can not guarantee flow also can be used, because if you want to reinvent too difficult (sometimes. variation of process conditions is only temporary). Parameters can be combined with re-tuning to improve the accuracy of instructions.

(2) Installation of the problem. Mainly straight pipe length in front of the sensor is not enough, affect the measurement accuracy, the main reasons for this same issue ① related. For example: Two straight through the front FIC203 sensor segment is obviously insufficient, since FIC203 not used to measure, just for control, so you can use the current accuracy (equivalent to downgrade).

(3) the reasons given direction parameter tuning. Because of a parameter error, leading to incorrect instrument instruction. Parameter error makes full-scale secondary instrument frequency calculation error, the main reasons for this same problem ①, ③ related. Full-scale frequency makes almost the same instructions allowed long-term, the actual full-scale frequency big full-scale calculations indicate a wide range of frequencies so that fluctuations can not be read, and the data inconsistency parameters also affect the final to determine the parameters of the final pass recalibration combination compared with each other to determine the parameters, to solve this problem.

(4) secondary instrument failure. This part of the fault more, including: a dashboard disconnection of a circuit board, set a range of individual display bad, K factor set a bad individual display, making it impossible to determine the range of settings and set the K-factor, which Part of the reason is mainly the problem ①, ② related. By fixing the corresponding fault, the problem is resolved.

(5) four-line connection problems. On the surface portion of the loop line connection is very good, careful examination, and some have loose joints actual cause circuit interruption, although some joints connection is tight but the Vice-line problem securing screw tightening in the skin on the line, but also makes the circuit interruption, partly because it is mainly related to the same problem ②. The corresponding line problem solving, problems solved accordingly.

(6) and subsequent secondary instrument instrument connectivity issues. Because of the subsequent instrument problems or due to subsequent instrument maintenance, making secondary instrument mA output loop is interrupted, for this type of secondary instruments, this is partly because of major problems with ② related. Especially for subsequent logger, in the case of long-term damage to the recorder can not be repaired, we must pay attention to the output of two meters short.

(7) As the second axis meter cable fault circuit always caused no indication. Due to the long run, coupled affected by dust, causing the horizontal axis cable fault, clean or replace the horizontal axis through the wire, the problem is resolved.

(8) For the problem is mainly due to secondary instrument ⑦ display meter coil fixing screw is loose, causing subsidence header pointer friction with the case, moves failed, and re-fixed by adjusting the header, corresponding to resolve the problem.

(9) use of environmental problems. Especially the installation of sensors in some wells, due to environmental humidity, causing the board to damp, this part of the main reasons the same problem ②, ② related. Through the corresponding modification measures on the part of the environmental humidity sensor to a large part of the probe and the conversion of the separation process, instead of separate sensors, Gushan the working environment, before this part of the instrument is operating well.

(10) Because the field adjustment is not good, or due to changes after the re-adjustment of the actual situation. Because the field of vibration and noise sensitivity adjustment bad balance adjustment. Or due to run again after a period of time after the change of scene, creating, indicate a problem, the problem with this part of the main reasons ④, ⑤ related. Using an oscilloscope, plus the operation of the bonding process, re-adjust.

(11) The reason for the problem ⑧ singled out, based on the analysis of the impact of this issue for a long time to solve the problem, because the plants do not have the K-factor Oriental calibration conditions, the data can only provide the basis for the K-factor manufacturers, manufacturers themselves Some changes, resulting in the information provided on several K factor is not - caused by the impact of the problem is solved. By finding conditions recalibration, or by repeated changes contrast, they finally determine a unified instrument parameters.

Through careful analysis period summary, the vortex can be basically solved the problems, this instrument is currently running well, basically meet the needs of plant production processes.

To sum up

(1) Due to determine the K-factor in the whole part of the vortex of very heavy play, accurate or not K-factor directly affects the accuracy of the loop, instrument replacement parts as well as wear and tear process piping, etc., are likely to affect the K-factor . The calibration of the East and the lack of chemical means and capabilities, can send calibration, the affected process is running, remove the vortex sent calibration to be 5 or 6 days time, it is difficult to meet the technological aspects from the pipeline, which can not be determined K-factor. This year, through the transformation between the flow meter, although already has a smaller diameter vortex calibration conditions, but for larger diameter vortex still powerless, the future should be noted that the use of vortex field calibration method using standard frequency and portable ultrasonic meter, measure the instantaneous flow in the pipeline as well as pulse output frequency of the sensor, on-site K-factor calculation.

(2) should be cleaned regularly vortex flowmeter probe, the inspection had found that detection of individual probe hole is clogged with dirt, or even wrapped in plastic sheeting, affecting the normal measurements.

(3) regularly check the grounding and shielding cases, eliminate outside interference. Sometimes the problem is due to interference indicating actions.

Moisture probe (4) installation environment. Drying should be regularly once or for moisture treatment. Because at the end of the probe itself and for moisture treatment, after moisture affect operation.

Management (5) meter data should be taken seriously enough to facilitate future work.

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