(1) The straight pipe section before and after the throttle member must be straight, and there must be no visible bend.
(2) The straight pipe segment used for installing throttling parts should be smooth. If it is not smooth, the flow coefficient should be multiplied by roughness to correct sparsity.
(3) In order to ensure that the flow of the fluid forms a fully developed turbulent velocity distribution 1D before the throttle, and makes this distribution into a uniform axisymmetric shape, so:
1)The straight pipe section must be round, and its roundness is strictly required for the 2D range before the throttling parts, and there is a certain roundness index.Specific measurement methods:
(A) On OD, D/2, D and 2D4 vertical pipe sections before throttling parts, single measurement values of inner diameters of at least 4 pipes were measured at an angular distance large to the same, and the average value D was taken.The difference between the measured values of any single inner diameter and the mean value shall not exceed plus or minus 0.3%
(B) After throttling parts, 8 single measurement values of inner diameter were measured by the above method at OD and 2D positions, and the maximum deviation between any single measurement value and D could not exceed plus or minus 2%
2) A long enough straight pipe section is required before and after the restrictor, which is related to the form of local resistance member before the restrictor and the diameter ratio, as shown in table 1 (d/ d, d is the hole opening diameter of the orifice plate, d is the inner diameter of the pipe).
(4) The length of the straight pipe segment between the first resistance member and the second resistance member on the upstream side of the throttle member may be 1/2 of the values listed in table 1 in the form of the second resistance member and beta =0.7 (regardless of the actual value)
(5) The throttling upstream side to open space or a diameter of 2 d large container, or open space or a large container with throttling a long straight tube shall not be less than 30 d (d) 15 if throttling and open space or there are other local resistance between large container, except in throttling and local resistance parts with adhesion between specified minimum straight tube long, from the open space to the throttling parts between the straight pipe section chief, also should not be less than 30 d (d).
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(1)DC is installed in the pipeline, the front end must be perpendicular to the pipe axis, to allow maximum not verticality shall not exceed + 1 °.
(2) When the throttle is installed on a pipe, its opening must be on the condition that the maximum allowable difference is not more than 0.015d (1/ beta-1) for the conditions calculated by the formula.
(3) All gaskets shall not be made of too thick material, preferably no more than 0.5mm. Gaskets shall not be protruded into the wall of the pipe, or it may cause great measurement error.
(4) The valve used for regulating flow shall be installed beyond the minimum length of pipe section after throttling
(5) The installation of throttling device on the process pipeline must be carried out after the pipeline is cleaned and purged.
(6) Pressure extraction method of throttle device installed in horizontal or inclined pipeline.
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