First, the orifice flowmeter overview
The orifice flowmeter is a high-range differential pressure flow device composed of a standard orifice plate and a multi-parameter differential pressure transmitter (or differential pressure transmitter, temperature transmitter and pressure transmitter), which can measure gas, The flow of steam, liquid and natural gas is widely used in process control and measurement in the fields of petroleum, chemical, metallurgy, electric power, heating, water supply and so on.

Second, the orifice plate flowmeter installation requirements
1. Pipeline conditions:
(1) The straight pipe sections before and after the orifice flowmeter must be straight and must not be visible to the naked eye.
(2) The straight pipe section of the device throttle 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 activity is spread in the 1D front of the throttle to form a sufficient turbulent velocity, and this is spread into an average axisymmetric shape,
1) The straight pipe section must be round, and for the front 2D range of the throttle, its roundness is required to be severe and has a certain roundness target. Detailed trade-offs:
(A) On the OD, D/2, D, 2D and 4 vertical pipe sections of the throttle, the measured values ​​of the inner diameters of the four pipes are measured at most equal angular intervals, and the uniform value D is taken. The difference between the measured value and the uniform value of the free inner diameter shall not exceed ±0.3%.
(B) After the throttle, in the OD and 2D position, 8 internal diameter single measurements are measured by the above method, and the single measured value is compared with D, and the maximum deviation must not exceed ±2%.
2) Before and after the throttle, a straight pipe section of sufficient length is required. The length of the straight pipe section and the part of the 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 section between the first resistance member and the second resistance member on the downstream side of the throttle member may be in the form of the second resistance member and β = 0.7 (regardless of the practice β value), as listed in Table 1. 1/2 of the value
(5) When the downstream side of the throttle piece is a closed space or a large container with a diameter ≥ 2D, the closed space between the closed space or the large container and the throttle piece shall not be less than 30D (15D) if the throttle piece and the closed space or large When there are other partial resistance members between the containers, the straight line between the closing space and the throttle member is provided, except that the minimum straight pipe length 1 attached to the rule on Table 1 is provided between the throttle member and the partial resistance member. The total length of the pipe section shall not be less than 30D (15D).
2. The number of columns is a multiple of the inner diameter D of the tube.
3. The number outside the parentheses in the above table is the value of “additional absolute limit error is zero”, and the number in parentheses is the value of “additional absolute limit error is ±0.5%”. That is, when there is a value in the brackets in the length of the straight pipe, the limit absolute error τQ/Q of the flow measurement. The arithmetic should be added by 0.5%, which is (τQ/Q+0.5)%.
4. If the length of the straight pipe is more than the value in parentheses and less than the value outside the brackets, it should be disposed according to the “additional limit absolute error of 0.5%”.
(1) The DC component device shall have a front end face perpendicular to the pipe axis in the pipe, and the maximum allowable non-perpendicularity shall not exceed ±1°.
(2) After the throttle device is installed in the pipeline, its opening must be concentric with the pipeline, and the maximum allowable centripetal ε allowed must not exceed the following formula to calculate the consequence: ε ≤ 0.015D (1/β-1).
(3) All the gaskets can't use too thick data, the Zui does not exceed 0.5mm, the gasket can not protrude inside the pipe wall or it can cause a large measurement error.
(4) Where the valve for regulating flow rate is to be installed outside the minimum length of the pipe section after the throttle
(5) Throttling devices installed on the process piping must be stopped after the pipe cleaning purge.
(6) The pressure-receiving method for the throttling installation of the degree or inclination of the pipe device.

For details, please refer to: Jinling Instrument

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