Industrial Research on the performance of the hott

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Industrial Research on the performance of ultrasonic flowmeter

Abstract: the mono channel and multi-channel ultrasonic flowmeter were tested on the flowmeter research device of the gas Research Institute in San Antonio, Texas, to establish the benchmark conditions and evaluate the performance under the benchmark installation conditions and other pipeline installation conditions. The purpose of the test is to determine the performance of 8in mono channel and multi-channel flow meters under different pipeline installation conditions and when used with a beam rectifier. Compare the test results with the data under the benchmark conditions to make an in-depth evaluation. The test results of 8in multi-channel flowmeter show that the rectifier has the function of improving its measurement accuracy, which depends on the type of flowmeter and the position relative to the interference source. The experiment of mono channel flowmeter shows that the accuracy better than 0.5% can be obtained under good flow field conditions. The sensitivity of the flowmeter to simple turbulence is illustrated by a 90 ° elbow installed upstream. In these tests, the error range of installed flow measurement is 1% - 4% compared with the reference test

I. preface

ultrasonic flowmeter derives gas volume flow by measuring the propagation time of ultrasonic pulse in fluid. For an ultrasonic flowmeter, since the determination of flow accuracy is a function of the flowmeter design and calculation method and the requirements of the upstream pipeline, it is different from many traditional measurement methods

for example, when the orifice flowmeter measures the flow, the accuracy of the determined outflow coefficient requires symmetry and no swirling vortex. In order to obtain the published performance of flow measurement, AGA Report No. 3 recommended the minimum length of straight pipe, the change of pipe diameter, and the installation requirements upstream of orifice flowmeter. Specification of orifice flowmeter( β As the flow blockage is reduced, the shaping effect of the orifice plate on the velocity profile is also reduced, and its sensitivity to fluid interference is also increased

the turbine flowmeter also improves the flow profile due to the effect of fluid on the rotor. Due to the improvement of the inlet flow profile, the performance of the turbine flowmeter has also been improved. Because the turbine flowmeter is sensitive to the asymmetry of the velocity profile, aga7 report requires the turbine flowmeter to use a rectifier to eliminate the flow vortex at the inlet with petroleum asphalt glass fiber tire waterproof membrane gb/t14686 ⑵ 008

since the ultrasonic flowmeter basically has no obstacles that affect population flow, the flowmeter will not change the flow profile. This flowmeter accurately determines the flow according to the flow sample obtained by the flowmeter and reliable calculation method

in the design of multi-channel ultrasonic flowmeter, manufacturers try to optimize the flowmeter to reduce their sensitivity to flow interference. If the flowmeter can correct and compensate all flow interferences, then the rectifier can not be used. However, due to a small amount of published data on how the rectifier affects the performance of multi-channel ultrasonic flowmeter, there is still interest in the joint application of rectifier and ultrasonic flowmeter. According to the application experience of other types of flowmeter, rectifier means potential benefits

as a cost-effective alternative to multi-channel flowmeter, it is also meaningful to use rectifier together with cheap mono channel ultrasonic flowmeter. In addition, there are a few reliable test data to confirm the performance of the mono channel flowmeter using rectifier

these results are derived from the first part of the test, which attempts to determine the practical experience of installing 8in mono channel and multi-channel ultrasonic flowmeter with different piping and when used in combination with a rectifier. This test is to set one elbow or two elbows upstream of the test flowmeter, and operate when the flowmeter is equipped with or without rectifier

the further test is intended to evaluate the measurement performance of the bidirectional flowmeter and the flow measurement accuracy when the flow is less than 1% of the flowmeter capacity. In places where the fluid can flow in two directions, such as underground gas storage facilities, people who plan to install ultrasonic flowmeter are concerned about the performance of two-way measurement

for the installation of a metering station, it is necessary to determine the number and diameter of flow meters. Because of the range ratio, the measurement performance of low flow should also be paid attention to

II. Test method

the flowmeter is installed on the test pipe section of the high pressure loop (HPL), and the test medium is natural gas at the transmission stage. At the same time, collect the data on the critical flow nozzle group on the ultrasonic flowmeter and HPL as the flow standard

under different pressures, five double weighted sonic nozzles are calibrated on site relative to the HPL weighing tank system. For all calibrations, the gas properties are determined by a gas chromatograph and AGA Report No. 8 equation of state

the static pressure related to the reference pressure of HPL is measured at twice the pipe diameter downstream of 1 flowmeter. The gas temperature is measured at three times the pipe diameter downstream of each flowmeter. The measured temperature and pressure, together with the measured gas components and the gas volume measured by the ultrasonic flowmeter, are used to calculate the mass flow of the ultrasonic flowmeter, which is then used to compare with the flow determined by the critical flow nozzle

according to the scheme selected by the manufacturer, ultrasonic flowmeter can obtain volume flow in different ways. The internal calibration method of flow meters m3 and M4 is used to calculate the total gas volume and the time during operation. Then calculate the average flow according to the total volume

flow meters M1 and M2 report (measure) the actual flow, provide the flow value once per second, and determine the average volume flow. The status, speed and sound speed data of a single channel are also recorded

a typical test system is composed of recyclable gas passing through the flow loop, and the gas temperature and pressure are stable. Select and switch different sonic nozzle combinations to determine the stable flow. A test point consists of the average value of the flow and other measurements calculated during the 90s period. A test point should be repeated 6 times to calculate the average value and standard deviation. The measurement data are also collected by two turbine flow meters. The data of turbine flowmeter confirm the consistency of the experiment

the four flow meters used in this test are provided by the manufacturer, and they are all commercializable. There is no flow calibration before the test of this project. Four flow meters have two multi-channel and two mono channels. Table 1 shows the sound channel layout of the flowmeter. Table 1 test the geometric parameters of flow meter

all flow meters are manufactured into a unified flange to flange size (31.5in length) and inner diameter (within 0.005in) to facilitate the exchange of flow meters at different installation positions. The manufacturer provides parameters for mechanical, electronic and other measured flow meters according to special procedures. During the test, the profile correction parameters with the flowmeter shall be checked by the manufacturer. The special parameters related to the test conditions (the fluid properties of the electronics used in the flowmeter) are adjusted each time as needed

III. Basic test installation

the pipeline installation of basic test is shown in Figure 1. All piping is made of 40 carbon steel pipe (7.981in inner diameter) with an 8in inner diameter, and the internal weld is polished. The flowmeter tested is installed at 40d (d = 8in), 59D and 97d downstream of the 90 ° long-diameter elbow. Install a 12in upstream of the elbow × 16in × 10In Sprenkle beam rectifier, followed by a 10In rectifier × The mechanical properties of 8in concentric reducer and 4 are almost the same as those of injection molded parts, and the 3D 8in straight pipe section is up to the elbow. Each flowmeter can be tested in two of the four axial positions (see Table 2). Table 2 test position of flowmeter under reference conditions

Table 2 test position of flowmeter under reference conditions

the complete test plan for each flowmeter requires testing at four positions. When the flowmeter is moved from one axial installation position to another, the upstream and downstream straight pipe sections (10d and 5D respectively) should be disassembled together with the flowmeter to align the flanges connecting the upstream and downstream of the flowmeter. The pressure and temperature transmitters related to each flowmeter shall also be retained on the original straight pipe section when the flowmeter position is changed, so as to reduce additional errors

IV. Basic test results

the test performance of two multi-channel flow meters (M1 and M3) under the benchmark installation conditions is shown in Figure 2 and figure 3. The results are expressed in percentage error (relative to the mrfhpl critical flow nozzle) as a function of the average flow rate through the flowmeter. One point represents the average value of 6 repeated measurements under each flow, and the error band represents the 95% confidence level

for flowmeter M1, when the speed is greater than 10ft/s, all data fall within the range of 0.4%, which is independent of the speed (see Figure 2). When the flow velocity is lower than 10 ft/s, the error curve deflects upward, which may be caused by a positive zero deviation or the deviation of the correction algorithm. This cannot be completely attributed to the different velocity profiles under low flow, or the combination of the two effects

check the zero flow of the flowmeter, indicating that the zero drift is 0.01ft/s. If zero drift is removed, the upward deflection will be flattened, because the minimum velocity point (2.8ft/s) drift is 0.35% and the drift at 5.6ft/s is 0.18%. In any case, this shows that the upward deflection of the curve cannot be considered to be entirely caused by zero drift

Fig. 2 basic flow measurement results of multi-channel flowmeter M1 Fig. 2 basic flow measurement results of multi-channel flowmeter M1

check the flow calibration curve, which shows that there is about 0.2% difference between the measurement error when the flowmeter is installed at 97d and 59D. 4. Debugging in the direction. The error at 97d is larger (more negative) than that at 59D. Similar measurement errors also exist in the test conditions of 400 lb/in2 (a) and 900lb/in2 (a)

the measurement error of flowmeter m3 is related to the speed flowing through the flowmeter, as shown in Figure 3. The nonlinear characteristics of the measurement error of this flowmeter are different from the results observed in similar experiments of the 12 inch flowmeter previously done in MRF (grimly) and elsewhere (completed by van Bloemendaal and van der Kam). Only when the flowmeter is installed at 59D and the data is collected under the pressure of 400 lb/in2 (a), when the average flow rate is still above 10ft/s, the error falls within the range of 0.3%. When the speed increases, the error curve inclines downward

in the 59D, 400 lb/in2 (a) data set, individual channel status information indicates that this is because the measured propagation time cannot pass the internal consistency check. This may be the reason for the deviation from other data groups

data, including suspicious data sets, remained within 0.5% error at speeds above 10 ft/s. These data also showed that the flow measurement difference was 0.2% when the pressure increased from 400 lb/in2 (a) to 900 lb/in2 (a). When the flowmeter is compared at 59D and 97d, the difference between the current volume results at 900 lb/in2 (a) is 0.1%

the possible explanation for this difference is that the velocity profile continues to develop after 59D. Through the comparison of the velocity ratio of a single channel, it can be seen that the shape of the velocity profile is improved. Table 3 shows the ratio of the central channel velocity (the ultrasonic channel is at the centerline of the pipeline axis) to the external channel velocity at the maximum flow point of flowmeter M1. Similar calculated values of flowmeter m3 are shown in Table 4. Since the flowmeter has a unique sound channel position, different flowmeter types should not be compared

however, there is a consistent difference between the test results of the two flowmeters at 59D and 97d. The smaller ratio of 59D test data indicates that the velocity profile at this location is faster than that at 97d

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