The LJ series strong bar flowmeter analyzes the advantages and disadvantages of existing bar flow sensors such as Annubar, TORBAR, and Verabar in the market, and innovatively designs a new cross-sectional shape detection rod flowmeter. It is currently one of the more advanced flow meters.
The cross-sectional shape of the detection rod of the averaging tube flow sensor is the key to determining the performance of the sensor. The current cross-sectional shapes of detection rods on the market include square, gem shaped, wing shaped, shuttle shaped, diamond shaped, etc. The cross-section of the detection rod of this product is a polygon with a "pointed front and blunt back" shape. Its head (upstream face) is equipped with a "high-pressure tapping port", which can obtain the most complete "total pressure". The connection between its front and rear sides is angular, allowing the boundary layer to separate precisely and completely here, maintaining the outflow coefficient basically unchanged over a wide range of Reynolds numbers. There is a "low-pressure tapping port" on the rear side of the tail (backflow surface), and the measured pressure is lower than the static pressure of the fluid. The high-pressure tap and low-pressure tap are respectively connected to the high-pressure chamber and low-pressure chamber inside the detection rod, and after averaging, they are transmitted to the high-pressure chamber and low-pressure chamber of the differential pressure transmitter. The electrical signal output by the differential pressure transmitter can reflect the magnitude of the flow rate (flow rate).
It is currently one of the more advanced flow meters, and currently, Liqiangba has obtained national trademark registration with registration number 6982103.

Compared with other flow sensors, this product has essential differences in the shape of the detection rod. Not only in theoretical analysis, but also in practical verification, this product has the following advantages:
1. Strong differential pressure signal and high sensitivity
The "high-pressure tapping port" of this product is located at the concave prism head, which can obtain the most sufficient total fluid pressure, while the "low-pressure tapping port" is located on the "rear side" of the boundary layer that has completely separated from the rod body, and the pressure obtained is lower than the static pressure of the fluid. Therefore, the differential pressure signal transmitted from the "high-pressure tap" and "low-pressure tap" to the differential pressure transmitter is strong and sensitive, which is beneficial for expanding the flow measurement range and improving measurement accuracy. It has been validated in the flow testing laboratory and has a sensitivity about twice that of the shuttle shaped detection rod.
2. The detection rod is sturdy, durable, reliable in operation, and has a long lifespan
This detection rod has an integral structure, no slender pressure (suction) pipes, no welds, and a conical body with a flow blocking surface that ranges from thin to thick. The generated vortices are very small and the longitudinal (along the flow direction) size is larger than the transverse size. The rigidity and strength of the rod are high, and the detection rod does not vibrate or be damaged.
3. Stable differential pressure signal, high measurement accuracy, and wide flow range
Because this detection rod does not cause significant obstruction to the fluid, strong vortices, and unstable differential pressure signals like square, diamond, or gem shaped detection rods; Unlike wing shaped and shuttle shaped detection rods, where the separation point of the boundary layer moves along the side of the rod with changes in Reynolds number, the outflow coefficient remains basically unchanged over a wide range of Reynolds numbers (from 1 × 105 to 1 × 107, nearly 100 times). The flow range of this product is close to 100:1. Basically meets the user's requirements (using one detection rod can solve the flow detection problem of various fluids in the same diameter). The results of calibration in the flow testing laboratory indicate that. High accuracy of ± 0.5% for water calibration and ± 1% for gas calibration has been achieved over a wide range.

4. Low pressure loss and energy conservation
This product not only has lower pressure loss than orifice plate and nozzle sensors, but also has lower pressure loss than other averaging tube sensors, with a very significant energy-saving effect. Especially for long-distance transmission of large-diameter fluids and steam pipelines, the economic benefits are significant.
5. The product has a variety of structural types and is easy to install and use. It can solve some problems that other averaging tube sensors currently cannot solve
For example, a typical averaging tube sensor is a detection rod that can only sense flow velocity information near the central axis of the flow cross-section. Therefore, it is required that the flow field is a fully developed turbulent and axisymmetric flow field, otherwise significant measurement errors will occur. This requires a longer length of the straight pipe section, which is generally difficult to meet on site. The LJ-S type of this product uses two detection rods spaced 90 degrees apart. Inserting a measuring tube can detect the vast majority of flow velocity information, and the required length of the straight pipe section can be greatly reduced.
6. The cross-sectional shape of the detection rod is simple, and the dimensional processing accuracy is easy to improve, ensuring good interchangeability of detection rods of the same specification
This not only ensures the improvement of overall accuracy, but also benefits mass production and reduces the cost of detection rods.
7. Strong anti blocking ability, low maintenance workload, and reliable work. It is beneficial to replace the detection rods that need to be replaced on site
Due to the fact that the low-pressure tap of this detection rod is not located in the impurity accumulation area at the end of the rod, it is not easily blocked. The high-pressure tapping port is located at the front end of the detection rod, in the high-pressure zone of the fluid, and impurities will be washed away with the fluid. The distribution of "high-pressure tap" and "low-pressure tap" makes it difficult for dirt and impurities to enter, so there is generally no situation of tap blockage or loss of differential pressure signal. Even in case of blockage, maintenance is easy: by pulling out the detection rod with or without stopping the flow, it can be thoroughly cleaned or even replaced.
8. Can accurately measure the flow rate of industrial circular pipe flow
This product is also a type of plug-in flowmeter, which reflects the average flow velocity of the circular tube flow by the reasonable arrangement of the pressure ports on the detection rod. This detection rod adopts the internationally advanced "Chebyshev integral expansion method" to determine the opening position of the pressure tapping port. The average pressure difference in the pressure chamber accurately reflects the average flow velocity of the circular tube flow, thereby improving the measurement accuracy (precision) of this product.

This product does not belong to the throttling device and cannot use the basic equation of the throttling device. This product belongs to the fluid dynamic flowmeter, and the basic principle is as follows:
The pressure measured by the high-pressure tap and low-pressure tap are respectively transmitted to the high-pressure chamber and low-pressure chamber of the detection rod. After averaging, the "average total pressure" and "average back pressure" are obtained and transmitted to the high-pressure chamber and low-pressure chamber of the differential pressure transmitter, respectively. The differential pressure signals of the two are converted into current signals, which can be processed by the display instrument to obtain the fluid flow rate.
Neglecting some insignificant factors, derive the theoretical equation for the "Strong Bar Flow Meter" according to the speed formula:

The flow coefficient K needs to be experimentally obtained using fluid calibration methods. The structure of this product is simple, the shape is regular, and it is easy to achieve precise processing and accurate inspection, so the K value of the same specification is basically the same. We can develop 'real flow calibration for each unit' into 'sampling real flow calibration for the same batch and specification of inspection rods, and conducting size inspection for others', and apply the flow coefficients obtained from those real flow calibrations within the specified deviation range.
We have conducted experimental research on the relationship between the size of dozens of detection rods and the flow coefficient, and have proven that using real flow calibration one by one can achieve an accuracy (precision) of ± 0.5%; By using sampling real flow calibration, an accuracy (precision) of ± 1% can be obtained. Users can decide which method to choose based on their accuracy requirements (at different prices).

The LJ series strong bar flowmeter is mainly divided into six structural forms, which are used in different occasions. They can be widely used in various types of gas (such as blast furnace gas, converter gas, mixed gas, coke oven gas, coal water gas, semi water gas), industrial waste gas, flue gas, air, hot air, natural gas, city gas, superheated steam, saturated steam, industrial wastewater, cooling water, petrochemical gases, chemical fluids, etc., according to the structural characteristics and on-site use experience of this product.

3. Determination of installation orientation
Gas (horizontal), liquid, and water vapor (horizontal)

Gas (vertical) Water vapor (vertical)

Any flowmeter has its own optimal range of use and is not omnipotent. Use it in situations where its advantages can be fully utilized. The optimal range of use for this product is on medium to large caliber, medium to low pressure gas (including dirty gas), steam, and liquid pipelines. The commonly used gas flow rate is not less than 4m/s (to avoid differential pressure less than 50pa, as condensation in the gas can cause errors), and it is not required to be used in situations where high precision (accuracy) is not required. The key points for selection are as follows:
1. For newly laid pipelines, it is recommended to use LJ-B type; If the process flow can be stopped when needed, in order to reduce the initial investment in instruments, it is recommended to use the LJ-H type. Both of these come with a measuring short tube, which ensures the correct position of the detection rod in the measuring section and high measurement accuracy.
2. For situations where there are existing pipelines and installation work must be completed in a short period of time, such as installing the product during equipment overhaul, it is recommended to use LJ-Q type. In situations where flow maintenance is allowed, LJ-C type can be used.
3. For situations where fluid temperature and pressure may randomly change during flow measurement, it is recommended to use an intelligent strong bar flowmeter with automatic temperature and pressure compensation function, model LJ-HX or LJ-HM.
4. For situations where the length of the straight pipe section is insufficient. If the measurement accuracy cannot be reduced as a result, it is recommended to use the LJ-S type.