Vortex steam flowmeter, if the length of the straight pipe section is not enough, will there be a po

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First of all, we exclude the influence of the rear straight pipe section, because the impact is very small, and the front straight pipe section is not enough, we have to distinguish between the vertical elbow and the horizontal elbow, if it is a vertical elbow, it will only be larger and not smaller.

If it is a horizontal elbow, it depends on the distance from the elbow to the throttle, and the position of the throttle is probably the head.

Vertically down position, generally we think:

1. The length of the throttle to the elbow is more than 2d, which is too large.

2. The length of the throttle to the elbow is less than 2d, which is small.

This is a simulated data based on the gas flow field, which can be used as a reference for measuring gas and steam, and in the case of low flow velocity (flow rate of 10m s), the faster the flow rate, the more chaotic the flow field, which is difficult to analyze, and different gases will also have an impact on this 2D position.

Of course, if there is a valve in front, it is quite complicated... There are too many types of valves, and the back of the gate valve and butterfly valve will generally be larger, and the back half of the ball valve will be smaller.

Hope thank you.

If the front straight pipe section is not enough, the measured flow rate is generally larger than the real value.

The distance between the vertical vortex flowmeter and the valve is less than 10 times the pipe diameter, and the measurement result is small or large?

Hello friends, according to the vertical installation of the vortex flowmeter and the valve before the distance is less than 10 times the diameter of the tube, the measurement result will be smaller. This is because installing the flowmeter in front of the valve will be affected by the fact that the fluid in front of the valve is close enough to the flowmeter, so that the vortex in the flowmeter will be disturbed and the metering result will be smaller. In the actual measurement, it should be ensured that the distance between the valve and the flowmeter is not less than 10 times the pipe diameter, which can reduce the measurement error and improve the accuracy.

The knowledge of this problem extends to the influencing factors of the measurement error of the flowmeter. In addition to the installation location, factors such as changes in fluid parameters, roughness of the inner wall of the pipe, etc. are also included. Therefore, before the installation of the flowmeter, it is necessary to do a good job in the measurement and calculation of relevant parameters, and reasonably plan the installation location of the pipeline to ensure the accuracy of the measurement results.

First of all, it has nothing to do with the small flow, because the small flow is zero, there is no cut flow, if it is a small flow problem, it stands to reason that the number of steam will be larger than the actual value, but now the actual measurement of your side is 50% smaller than the water supplement

Second, if the range selection is calculated according to the amount of water replenished, the basic problem is not big, theoretically there is no loss, a ton of water is a ton of steam, unless the loss is particularly large, you can take a look at the loss yourself, that is, the steam becomes water discharged from the trap.

Third, whether it is equipped with temperature and pressure compensation, or whether the temperature and pressure compensation is normal, the change of density value and the change of flow rate is great, and whether the flow coefficient is consistent with the sensor, this aspect of the setting must be checked.

Fourth, open the large and small valve to observe the change of the instrument, and if the change can be based on the steam flow rate, the linearity of the flow sensor should be no problem, otherwise it is necessary to consider whether the circuit board and probe are broken.

You can check it out according to the above points, and if you have any questions, you can contact me.

1 The small flow cut cannot be set to 0, depending on your measurement range and the diameter of the pipe.

2. You should observe the possible reasons for the error, and first see whether the installation position is reasonable and whether it can achieve as much full pipe as possible. Then check whether the parameters of the flowmeter are correct, especially the diameter of the pipe and the characteristics of the medium.

3. It's not clear whether you're measuring water or steam or a mixture. What is the basis of your calculations, and if it is based on water to convert steam, then there is no problem with your calculations.

4. Another thing you should pay attention to is that if you calculate the amount of evaporation according to the amount of water supplemented, it is impossible to completely correspond, and this must be calculated comprehensively.

Is the actual flow rate you are using within the measurement range of the meter? Otherwise, there is an error, and it is time to change the meter, as well as the selected density. It has something to do with stress.

I don't know how much difference you have? Calculate the error. If the error is too large (more than 5%) and the meter replacement phenomenon is still the same, then do you usually put too high a small flow removal?

Also, is the temperature and pressure compensation of the steam calculated correctly?

Pour. What about big data. Have you tried to turn off the upstream and downstream valves to see the zero position? Is the pipeline vibrating a lot?

In fact, the domestic vortex street and the imported vortex street are not much different now, and if there are conditions, the imported vortex street is still used, such as rosemount, krohne, e+h, which will be a lot less troublesome.

It depends on what company you are.

cBecause the water in the impulse pipe needs to generate pressure, if the height of the two impulse pipes is the same, at the same temperature, the pressure generated is the same, and the pressure difference acting on the differential pressure transmitter is 0

If the heat mixing pipe is too close to the positive pressure side, the temperature in the conduit on the positive pressure side will be higher, and the higher the temperature, the smaller the pressure difference will be, resulting in the pressure on the positive pressure side being less than the pressure on the negative pressure side, resulting in a low instrument indication.

c. Because the heat mixing tube is too close to the positive pressure side, the temperature in the conduit on the positive pressure side will be higher, and the higher the temperature, the smaller the pressure difference will be, resulting in the pressure on the positive pressure side being less than the pressure on the negative pressure side, resulting in a low indication of the instrument.

and Shunda flow meter.

c。The condensate density in the impulse pipe decreases due to the positive pressure measurement of ** too close, and the water column pressure generated by the low density is also small (relative to the negative pressure side), which is finally reflected in the low indication of the decrease in differential pressure.

Hello, dear--

1. One-time compensation implementation method.

Firstly, the working parameters of the steam - temperature and pressure are determined, and the vortex flowmeter determines the density of the steam in the working state according to the working parameters, and the density is calculated as the density of the steam in the future flow measurement process. The actual change in steam is no longer compensated or corrected during operation, which is known as the one-time calculation compensation method.

The accuracy of the steam flow measurement can be guaranteed if the operating parameters of the steam are consistent with the set values at the time of design. If the parameters deviate from the actual operating conditions, or even by a large margin, the deviation of the measurement results can be significant.

The one-time compensation method, the measurement method used in the early stage of the development of automatic detection technology, has a large error in the measurement results, and can be used as a rough measurement. Such a design method is still used in the widely popular flow throttling device design manual.

The vortex flowmeter can realize integrated temperature and pressure compensation, and there is a strict one-to-one correspondence between the temperature and pressure of saturated steam. The density of saturated steam can be either its temperature or its pressure as a single function. According to the temperature value or pressure value of saturated steam, the real-time density value can be obtained by looking up the table method or the formula calculation method (IFC1967 or IAPW-1997).

In flow measurement, vortex flowmeters can be implemented with temperature-compensated or pressure-compensated flowmeters. To choose a flow meter with temperature compensation. Turn on the temperature sensor of the flowmeter to detect the measured steam temperature in real time, so as to obtain the corresponding density value.

Superheated steam is a type of steam with special qualities obtained by reheating saturated steam. It breaks the strict one-to-one correspondence between temperature and pressure inherent in saturated steam. Vortex flowmeters can treat superheated steam as a single medium during flow measurement.

The density of superheated steam is a composite function of its temperature and pressure. When ordering vortex flowmeters, you should choose the temperature and pressure compensation type. In actual use, the temperature and pressure sensors are turned on at the same time to measure the steam temperature and pressure value in real time, and the density value can be accurately calculated according to the superheated steam density table or density calculation formula.