Four tips during the installation of the wedge flowmeter
Author:vacorda Source:vacorda.com Date: 2018-09-27 16:35:58
1. Install the wedge flowmeter by the direction marked
Although some articles and materials say that the wedge flowmeter installation has no direction requirements, it can be used for reverse flow measurement. From the measurement principle of the wedge flowmeter, if it is a standard V-shaped wedge, its throttling of the fluid is positive and negative. It’s the same. However, on the surface of the wedge flowmeter, the manufacturer has indicated the flow direction arrow of the wedge flowmeter fluid. The wedge is installed in the center of the wedge flowmeter, and the wedge is not installed in the center of the wedge flowmeter. We must install according to the direction of the wedge flowmeter to prevent the installation direction from increasing the measurement error.
2. Regarding the direction of the pressure tapping interface
According to the pressure gauge of the measuring instrument, when measuring the gas flow rate, the pressure tapping port is at the upper middle part of the throttling element, and when the liquid flow rate is measured, the pressure tapping port is at the lower middle side of the throttling element, and when the dirty medium is measured, the pressure tapping port is The middle position of the throttle element. However, the wedge flowmeter differs from the orifice flowmeter in that the throttle wedge is not evenly distributed in the body cavity, and the position of the pressure tap is fixedly prefabricated by the manufacturer, which is above and below the wedge weld.
If the pressure is specified strictly, when the liquid is measured, if the pressure port is installed in the middle and lower part of the pipeline, the wedge inside the wedge flowmeter is also in the middle and lower part of the pipeline, causing the fluid to flow from the top of the wedge flowmeter. However, this method will cause the precipitation of medium impurity particles in the fluid in the lower surface of the wedge flowmeter, which has the hidden danger of blocking the pressure port in front of the wedge, which may cause the flowmeter to malfunction, so it is necessary to the situation is treated differently.
3. Vertical pipe installation
Wedge flowmeters are recommended for horizontal installation to minimize vertical installation because the zero calibration of the wedge flowmeter cannot be performed during vertical installation.
When the wedge flowmeter zero calibration is required, the working medium is filled with the wedge flowmeter, and then the front and rear valves of the pipeline are closed, and the flowmeter is calibrated while ensuring that the fluid inside the wedge flowmeter is at a standstill. Since the flow meter of the throttling element generally does not design the secondary line cutting facility, there is generally no process cut-off valve before and after the throttling element, and it is more difficult to calibrate the wedge flow meter in this situation. If the wedge flowmeter is installed horizontally, we can think that the static fluid has no additional influence on the differential pressure detected by the wedge flowmeter. Therefore, we only need to close the front and rear pressure regulating valves of the wedge flowmeter and release the pressure to the atmosphere to realize the flowmeter. Zero calibration.
If the wedge flowmeter is installed vertically, the static medium will generate a static pressure in the inner cavity of the wedge flowmeter. This static pressure acts on the positive pressure chamber of the transmitter to increase the differential pressure of the differential pressure transmitter. The zero point differential pressure of the wedge flowmeter is not zero, and the static pressure accessory error is also generated in the negative pressure measuring pressure pipe. Therefore, calibration of the zero point becomes difficult at this time. Even with the double flange transmitter, we can calculate the static pressure of the negative pressure measurement, but the density of the measured medium can only be calculated by the ideal value at the time of design, and the static pressure in the measuring tube of the wedge flowmeter is roughly calculated. In the calibration revision, the reliability of the zero point of this method will be reduced.
The vertical installed wedge flow meter below makes it difficult to zero calibration.
Therefore, it is best not to install the wedge flowmeter vertically in the actual installation. If the process cannot meet the horizontal installation, in addition to ensuring the full flow of the wedge flowmeter during the vertical installation process, we must accurately correct the differential pressure of the wedge flowmeter zero point. For the conversion, it is not possible to perform the zero calibration only after the positive and negative pressure-receiving valves are closed.
4. Install the sewage pressure reducing valve
The flow detection mode of the wedge flowmeter + double flange transmitter shall be provided with a drain relief valve between the pressure regulating valve and the double flange connection component. This valve is very important. During the calibration of the flowmeter, it can ensure that the pressure between the positive and negative double flanges is consistent with atmospheric pressure to ensure reliable calibration and better maintenance personnel.
If the double flange transmitter needs to be replaced, the drain pressure relief valve can determine whether the valve is leaking once the pressure is taken. Only when the safety is ensured can the double flange transmitter be removed. In many engineering installations, the installation of the drain and pressure relief valve is omitted. This is not correct and must be rectified.
Wedge flowmeter with drain valve installed is more convenient for maintenance and repair work
Summary: No matter which type of flowmeter is installed and used, it needs to be written in accordance with the instructions and combined with its own characteristics.
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