Process flow detection features
In order to ensure the material balance in on-line flow production, it is necessary to detect and control the flow of fluid in the pipeline. This process flow detection has some distinct characteristics, because the production is continuous, subject to the fluctuations of production required materials in a dynamic balance process, specific to a period of time stable in a flow range, and specific to a point in time every moment, can not ensure consistency. The material control of macro production is not the pursuit of absolute constancy of a point, but requires the relative stability of a range, so the error of this flow detection specific to a moment can be relaxed, but the change trend of the material should be characterized correctly. Therefore, the accuracy of this kind of process detection flow meter can be appropriately reduced, and two or even three flow monitoring meters can be selected.
Restrictions in the use of standard orifice plates
The above defects in the use of orifice flowmeters force engineers and users to look for instruments of other structures. With the long-term accumulation of use and the efforts of instrument developers, a large number of non-standard throttling components have been developed. Although these non-standard throttling components cannot be supported by perfect experimental data as standard holes, they cannot achieve standardized production, but after long-term use and continuous improvement by manufacturers, they can meet the requirements of process flow detection. Wedge flowmeter has been widely used in many non-standard throttling components in recent years.
Wedge flowmeter structure characteristics
From the appearance, the wedge flowmeter is a metal straight pipe with a connection flange welded at both ends, leaving two open interfaces in the middle of the metal pipe, and the interface has two ways of pipe mouth and flange, and the flange interface is mainly used in the industry. From the connection flange at both ends, it can be seen that there is a V-shaped protruding part that is fixed with the chamber in the body of the meter, which is the throttle element wedge block of the wedge flowmeter, and the pressure interface is opened on the front and back of the wedge block. From the appearance of the wedge flowmeter, it can be seen that the structure of the wedge flowmeter is greatly simplified, and the connector seals are reduced compared with the hole plate, and the installation and use are simpler and more convenient than the hole plate flowmeter.
Measuring principle of wedge flowmeter
Wedge flowmeter is a throttling element, the structure of the throttling element is based on the Bernoulli principle - the sudden reduction of the fluid flow area caused by the static pressure dynamic pressure energy mutual conversion manufacturing, so a common throttling element is the flow area of the fluid suddenly greatly changed.
The throttling element of the wedge flowmeter is a V-shaped wedge welded to the chamber of the meter body, through which the protruding wedge and the space formed by the chamber of the meter body realize the sudden change of the fluid flow area, so that the static pressure and dynamic pressure of the fluid can be converted to each other. The instantaneous flow rate of the fluid is measured by the differential pressure transmitter before and after the V-shaped wedge block, and the volume flow of the fluid flowing through the wedge flowmeter is converted.
Advantages of wedge flowmeter
1. eliminate impurities plugging
It can be seen from the structure of the wedge flowmeter that the wedge is installed on one side of the surface body, and the flow area is between the wedge and the cavity in the surface body. This structure can flow through the wedge flowmeter with the fluid for impurities, particles and even larger welding slag in the medium, and will not accumulate in the surface body, so it can be used in the fluid measurement of particulate impurities that the orifice flowmeter cannot use.
2. apply to more situations
The throttle wedge welded to one side of the instrument cavity produces a much smaller head (pressure) loss for the fluid passing through the body than the orifice plate with the middle opening, so the additional head loss for the hydrostatic dynamic pressure conversion process is much smaller than the orifice flowmeter. The wedge flowmeter is suitable for a wide range of fluid viscosity, which can be used for the measurement of crude oil, dirty oil, wax oil, fuel oil and even asphalt with high viscosity, and is widely used in the petroleum refining process.
3. the pressure mode change
The flange pressure taking mode of wedge flowmeter simplifies the construction of throttle element + differential pressure transmitter to measure fluid flow. By using the mode of double flange transmitter, it can not only save the laying of pressure tube and tracing wire, but also significantly improve the accuracy of the measurement process of throttle element because of the stability of filling silicone oil in the capillary tube of double flange transmitter. It overcomes the additional error introduced by the qualitative change of the static medium in the pressure tube of the throttle element, reduces the failure rate and maintenance frequency of the flow meter, and improves the measuring accuracy of the wedge flowmeter as a whole.
4. energy conservation and emission reduction
The head loss of wedge for overflowing fluid is less than that of orifice plate flowmeter, and the static pressure loss of wedge flowmeter and orifice plate flowmeter for the same medium should be reduced more. The detection method of wedge flowmeter + double flange transmitter eliminates the laying of pressure primer pipe, thus saving the laying of tracing heat source and the consumption of tracing steam. The pressure interface of wedge flowmeter can be insulated with the surface body and process pipeline as a whole, and the anti-freezing measures of wedge flowmeter in winter can be ensured through the heat source of the fluid itself, saving the steam energy consumption and condensate discharge of the device. The overall energy consumption of the device is reduced to a certain extent.
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