Orifice flowmeter installation conditions introduction

(1) The straight pipe sections before and after the throttle piece must be straight and must not be visible to the naked eye.
(2) The straight pipe section used for installing the throttle piece should be smooth. If it is not smooth, the flow coefficient should be multiplied by the roughness correction sparse.
(3) In order to ensure the flow of the fluid, a fully developed turbulent velocity distribution is formed in the 1D before the throttle, and the distribution is made into a uniform axisymmetric shape, so
1) The straight pipe section must be round, and the roundness of the 2D range of the throttle is very strict and has a certain roundness index. Specific measurement method:
(A) On the OD, D/2, D, and 2D vertical tube sections of the throttle, the measured values of the inner diameters of the four pipes are measured at least equal angular distances, and the average value D is taken. The difference between the measured value of any internal diameter and the average value shall not exceed ±0.3%.
(B) After the throttle, 8 internal diameter single measurements are measured at the OD and 2D positions by the above method. The maximum single deviation is not more than ±2% compared with D.
2) Before and after the throttle, a straight pipe section of sufficient length is required. The length of the straight pipe section and the local resistance part before the throttle are related to the diameter ratio β, see Table 1 (β=d/D, d is Orifice opening diameter, D is the inner diameter of the pipe).
(4) The length of the straight pipe between the first resistance member and the second resistance member on the upstream side of the throttle member may be in the form of the second resistance member and β = 0.7 (regardless of the actual β value), as listed in Table 1. 1/2 of the value
(5) When the upstream side of the throttle member is an open space or a large container with a diameter ≥ 2D, the open space or the straight pipe length between the large container and the throttle member shall not be less than 30D (15D). If there are other local resistance members between the throttle member and the open space or the large container, the opening is provided between the throttle member and the partial resistance member, except that the minimum straight pipe length specified in Table 1 is attached. The total length of the straight pipe between the space and the throttle shall not be less than 30D (15D).
Minimum straight pipe length on the upstream and downstream sides of the throttle piece Table 1
The local thrust member form on the upstream side of the throttle member and the minimum straight pipe length L.