The Annubar flow sensor is developed based on the pitot tube velocity measurement principle. It determines the flow rate by multiplying the average flow velocity of the pipeline and the effective cross-sectional area of ??the pipeline. Generally, the flow velocity distribution in pipelines is uneven. If it is a fully developed fluid, its velocity distribution is exponential. In order to accurately measure, the entire circular cross section is divided into multiple semicircles and multiple half rings with equal unit areas. The detection rod of the sensor is composed of a hollow metal tube, and multiple pairs of total pressure holes are drilled on the flow-facing surface. They are located in the center of each unit area and respectively reflect the flow velocity in each unit area. Since all the total pressure holes are connected, the total pressure values ??transmitted to each point in the detection rod are averaged and then led from the total pressure outlet pipe to the high-pressure joint and sent to the positive pressure chamber of the sensor. When the sensor is correctly installed on a process pipeline with a long enough straight section, there should be no vortex on the flow section, and the static pressure of the entire section can be considered a constant. There is a detection hole on the back or side of the sensor, which represents the pressure of the entire section. static pressure. The static pressure lead-out pipe is led from the low-pressure connector to the negative pressure chamber of the sensor. The square of the pressure difference between the positive and negative pressure chambers is proportional to the average flow velocity of the flow section, and the relationship between the differential pressure and the flow rate is obtained. On the basis of this relationship, the flow calculation formula of the velocity equalizing tube flowmeter can be derived from the Bernoulli equation and the continuity equation Qv=α﹒ ε﹒ (π/4)﹒ D2﹒ (2?P/ρ1)0.5 Qm=α﹒ ε﹒ (π/4)﹒ D2﹒ (2?P﹒ρ1)0.5 Among them: Qv: Volume flow Qm: Mass flow α: Sensor structure coefficient △P: Differential pressure value ε: Fluid expansion coefficient ρ: Density under fluid conditions ε: Fluid expansion coefficient for incompressible For a compressible fluid ε=1, for a compressible body ε﹤1, if D, △P, and ρ1 in the formula all use SI units, the unit of QV is M3∕S and the unit of Qm is ㎏∕S. The flow coefficient α and expandability coefficient ε of the sensor are known from the calibration on the standard device and are noted on the certificate of conformity when leaving the factory.
A brief installation guide for Annubar flowmeter: A brief installation guide for Annubar flowmeter Step 1: Determine the correct installation direction and straight pipe section requirements for Annubar flowmeter Step 2: Drill holes in the pipeline Note: The pipeline must be drilled. If acetylene gas or other ablation methods are used to drill holes, the maximum flow error after installation can reach 10. 1. Depressurize the pipeline and drain the accumulated liquid. 2. Select the location where you will drill. For vertical pipelines, you can drill holes at any position in the circumferential direction. For horizontal pipelines, the location of the holes is based on the Annubar measurement of the fluid. Applications. · To measure liquids: Make a hole at the bottom of the pipeline · To measure gases: Make a hole at the top of the pipeline · To measure steam: Make a hole at the bottom of the pipeline.
3. Determine the size of the opening based on the table above. 4. After opening the hole, remove the burrs in the hole. 5. If you also need to install a counter support, drill a second hole in the direction opposite to the first opening, and then Remove burrs from the hole. Step 3: Weld the welding connector to the pipeline. 1. Assemble Annubar with the welding connector provided by the factory, and then insert it into the drilled hole. 2. Use Annubar’s mounting head Position the upper plane (or transmitter---if it is an integrated instrument) so that it is parallel to the pipeline. 3. Spot weld, fix the welded connection to the pipeline, and then remove the Annubar sensor. 4. Weld Before, in order to prevent the welding slag splash from damaging the threads of the connecting parts, wrap the threaded part with the thick aluminum foil provided by the factory. Or screw on a protective nut. Weld evenly to prevent the welding parts from deforming and complete the welding. Step 4: Insert and install the Annubar flow 1. After the installation connector has completely cooled, install the connector. 2. Install the first sealing ring (packing) between the sealing compression ring and the pre-welded locking ring; be careful not to damage the sealing ring. 3. Press the sealing ring into the interior of the connector to the pre-welded locking ring. Repeat the above steps to install the remaining two sealing rings. Adjust the position of the sealing ring opening so that the position of each opening is staggered to 180 degrees. 4. Adjust Annubar direction, point the arrow mark on the head of the Annubar to the fluid direction of the pipeline, and tighten the Pak-Lok compression nut and the connector by hand until it cannot be tightened by hand. 5. Use a wrench to lock the nut and tighten evenly Nut, the nut can be tightened to avoid leakage. Do not tighten the compression nut with excessive force, otherwise the installation components will be damaged.