Orifice flowmeter installation pipeline conditions:
1. The straight pipe sections before and after the throttle must be straight, and there must be no visible bends.
2. The straight pipe section used to install the throttle should be smooth. If it is not smooth, the flow coefficient should be multiplied by the roughness to correct the sparseness.
3. In order to ensure that the fluid flow is 1D in front of the throttle, a fully developed turbulent velocity distribution is formed, and this distribution is uniformly axisymmetric, so:
1) The straight pipe section must be round, and for the 2D range in front of the throttle , its roundness requirements are very strict, and there is a certain roundness index. Specific measurement method:
(A) OD, D / 2, D, 2D 4 vertical pipe sections in front of the throttle , measure at least 4 single diameters of the inner diameter of the pipe at an equal angular distance, and take the average value D The difference between the single measured value of any inner diameter and the average value must not exceed ± 0.3%
(B) After the throttling part, the 8 inner diameter single measurement values are measured at the OD and 2D positions by the above method. When comparing any single measurement value with D, the maximum deviation must not exceed ± 2%.
2) A long straight pipe section is required before and after the throttle . This long straight pipe section is related to the form of the local resistance member in front of the throttle and the diameter ratio β.
3) The length of the straight pipe section between the first resistance member and the second resistance member on the upstream side of the throttling member can be 1/2 of the listed value according to the form of the second resistance member and β = 0.7 (regardless of the actual β value)
4. When the upstream side of the throttle is an open space or a large container with a diameter ≥ 2D, the length of the straight pipe between the open space or the large container and the throttle shall not be less than 30D (15D). If there are other local resistance parts between the throttle and the open space or the large container, in addition to the minimum straight pipe length 1 that meets the requirements between the throttle and the local resistance parts, from the open space to the The total length of the straight pipe sections between the flow pieces must not be less than 30D (15D).