The installation tips of orifice plate flow meter
Author:vacorda Source:vacorda.com Date: 2018-05-03 15:33:00
Orifice flowmeter is a high-range differential pressure flow device which is composed of standard orifice plate and multi-parameter differential pressure transmitter (or differential pressure transmitter, temperature transmitter and pressure transmitter). It can measure gas and steam. The flow of liquids and natural gas. Orifice flowmeter throttling devices include annular chamber orifices, nozzles, and the like. The throttling device (orifice flowmeter) is a combination of flow, temperature, and pressure detection functions. It has strong functions, compact structure, simple operation, and easy use. The orifice flowmeter throttling device produced by Sichuan Vacorda Instrument Co., Ltd. is used in conjunction with a differential pressure transmitter to measure the flow of liquids, vapors, and gases. The orifice flowmeter is widely used in petroleum, chemical, metallurgy, electric power, and light industry and so on.
(1) Straight sections before and after the throttle must be straight and must not be bent by the naked eye.
(2) The straight section of the throttle device should be lubricated. If it is not lubricated, the flow coefficient should be multiplied by the roughness correction sparse.
(3) In order to ensure that the fluid movement in the 1D before the throttling component constitutes a well-developed turbulent velocity dispersion, and this dispersion is made into an average axisymmetric shape, so:
1) The straight section must be circular, and the circularity of the front 2D range of the throttle must be very strict and have a certain degree of roundness. Detailed trade-offs:
(A) At the front of OD, D/2, D, and 2D orifices of the throttling piece, the maximum measured value of the four pipe inner diameters is measured at the largest and equal angular intervals, and the average value D is taken. The difference between the single measured value and the uniform value should not exceed ±0. 3%
(B) After the throttling piece, the 8 id single-diameter values are measured by the above method in the OD and 2D positions. If the single measured value is comparable to D, the maximum yaw must not exceed ±2%.
2) A sufficiently long straight pipe section is required before and after the throttling piece. The length of the long straight pipe piece and the part of the drag piece before the throttling piece are related to the diameter ratio β, see Table 1 (β=d/D, d is Hole plate opening diameter, D is the inner diameter of the pipe).
(4) The length of the straight section between the first resistance part and the second resistance part on the downstream side of the throttling element may be in the manner of the second resistance element and β = 0.7 (regardless of the actual beta value). 1/2 of the value
(5) When the downstream side of the throttling element is a closed space or a large vessel with a diameter ≥ 2D, the closed space between the closed space or the large vessel and the throttling element shall not be less than 30D (15D) if the throttling element and the closed space are large When there are other parts of the resistance element between the containers, except for the minimum length of the straight tube section 1 which is attached to the rules in Table 1 between the throttling element and the part of the resistance element, the space between the closed space and the throttling element is straight. The total length of the pipe segment must not be less than 30D (15D). The minimum straight pipe length on the upstream and downstream side of the throttle table Table 1 The negative force way and minimum straight pipe length on the downstream side of the throttle piece
1. The above table only for the standard throttling installation, the special throttling installation for reference;
2. The number of columns is the multiple of the inner diameter D of the tube;
3. The figure outside the parenthesis in the above table is the value with “additional absolute limit error is zero”, and the figure in parentheses is the value with “additional absolute limit error of ±0.5%”. That is, when there is a bracketed value in the straight pipe length, the absolute limit error τQ/Q of the flow measurement is used. Should add arithmetic again 0.5% or (τQ/Q+0.5)%;
4. If the length of the straight section of the practice is greater than the value in parentheses and less than the value outside the parentheses, the “absolute error of the additional limit is 0.5%”.
1) In the pipeline, the direct current device must be perpendicular to the pipe axis and the maximum non-perpendicularity allowed must not exceed ±1°.
2) After the throttling device is in the pipeline, its opening must be concentric with the pipe, and its maximum allowable misalignment ε must not exceed the following formula to calculate the consequence: ε ≤ 0.015D (1/β-1).
3) All gaskets cannot use too thick data. It is better not to exceed 0.5mm. The gasket cannot protrude inside the pipe wall or it can cause a large measurement error.
4) Valves for regulating flow should be installed outside the minimum length of the pipe after the throttle
5) Devices that are throttled on the process piping must be stopped after the pipe cleaning purge.
6) Check the pressure in the throttle or installation of the gradient or tilting piping device.
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