Orifice plate flowmeter is a high range ratio 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). It can measure the flow of gas, steam, liquid, and lead, and is widely used in process control and measurement in the fields of petroleum, chemical, metallurgy, power, heating, water supply, etc. The throttling device, also known as the differential pressure flowmeter, consists of a primary detection element (throttling element) and a secondary device (differential pressure transmitter and flow display instrument), which are widely used in gas applications. Flow measurement of steam and liquid. It has a simple structure, easy maintenance, and stable performance.
Verification and testing:
This flowmeter has a wide range of applications, and can measure all single-phase flow rates, as well as some mixed phase flows. Due to two-phase flow, accurate measurement may not be possible, and even water hammer phenomenon may occur, damaging the pipe fittings. If a circular orifice plate is used, condensed water can flow away from the edge of the annular orifice plate, and the minimum flow surface is the circular ring tightly attached to the inner wall of the pipe, while the minimum flow surface of a standard orifice plate is the concentric circle located at the center of the pipe. The impurity flow rate in the fluid is relatively low and generally flows closely along the pipe wall. With the continuous emergence and promotion of new types of throttling devices, differential pressure transmitters and display instruments that are compatible with throttling devices have developed rapidly in terms of performance and quality.
The orifice flowmeter, which should have had a sharp and right angled inlet edge, turned into a trumpet mouth, changing the outflow coefficient and causing significant errors, and had to be replaced. It can be seen that this product is the best choice for measuring the flow rate of high-temperature fluids.
Design Style:
The fluid flows through the throttling device inside the pipeline, causing local contraction near the throttling element, increasing the flow velocity, and creating a static pressure difference on both sides upstream and downstream.
The throttling device of the orifice flowmeter has a simple and sturdy structure, stable and reliable performance, long service life, and low price. It is a commonly used flow measurement instrument in industry. The entire processing process adopts international standards and undergoes strict calibration and testing.
The orifice flowmeter increases the flow velocity and lowers the static pressure, resulting in a pressure drop before and after the throttling element, known as the pressure difference. The larger the flow rate of the medium, the greater the pressure difference before and after the throttling element. Therefore, the orifice flowmeter can measure the magnitude of fluid flow by measuring the pressure difference. This measurement method is based on the laws of energy conservation and flow continuity.
Orifice flow meters can measure the flow rate of various fluids in pipelines, including liquids, gases, and steam. They are widely used in industrial sectors such as petroleum, chemical, metallurgical, light industry, and coal mining.
A static pressure difference is generated before and after the orifice flowmeter, which has a certain functional relationship with the flow rate. The larger the flow rate, the greater the pressure difference. The differential pressure signal is transmitted to the differential pressure transmitter and converted into a 4-20mA. DC analog signal output, which is transmitted far to the flow accumulator to achieve fluid flow measurement. Mass flow meters utilize intelligent differential pressure transmitters to automatically compensate for operating temperature/pressure, enabling measurement of fluid mass flow rate
The orifice flow meter needs to supply hot air, and the hot blast stove is generally close to the blast furnace with many bends. In the past, standard orifice plates were used, but the error was significant due to the insufficient length of the straight pipe section. This instrument requires a 2D long straight pipe section due to the presence of a pressure equalization ring and multiple pressure taps. After being installed on the air supply duct of the hot blast stove, the application situation is very satisfactory. More than thirty hot blast stoves have been equipped with annular orifice flow meters and have been running for more than three years without any faults
Scope of application:
1. Nominal diameter: 15 mm ≤ DN ≤ 1200mm
2. Nominal pressure: PN ≤ 40MPa
3. Working temperature: -50 ℃ ≤ t ≤ 550 ℃
4. Range ratio: 1:10, 1:15
5. Accuracy: Level 0.5, Level 1
Selection:
1. Pipeline conditions:
(1) The straight pipe section before and after the throttling element must be straight and there must be no visible bending.
(2) The straight pipe section used for installing throttling components should be smooth. If it is not smooth, the flow coefficient should be multiplied by the roughness correction factor.
(3) To ensure that the fluid flow forms a fully developed turbulent velocity distribution 1D in front of the throttling element, and to make this distribution uniformly axisymmetric, the straight pipe section must be circular, and the roundness requirements for the 2D range in front of the throttling element are very strict, with certain roundness indicators. Specific measurement method: (A) Measure the inner diameters of at least four pipes on four vertical pipe sections, OD, D/2, D, and 2D, at equal angular distances, and take the average value D. The difference between any single inner diameter measurement value and the average value shall not exceed ± 0. 3% (B) After the throttle element, 8 single inner diameter measurements were taken at OD and 2D positions using the above method. The maximum deviation between any single measurement and D should not exceed ± 2%. 2) A sufficiently long straight pipe section is required before and after the throttle element, which is related to the form of the local resistance element in front of the throttle element and the diameter ratio β, as shown in Table 1 (β=d/D, where d is the diameter of the orifice plate opening and D is the inner diameter of the pipeline).
(4) The length of the straight pipe section between the first resistance element and the second resistance element on the upstream side of the throttling element can be in the form of the second resistance element and β=0. 7 (regardless of the actual beta value) take 1/2 of the values listed in Table 1
(5) When the upstream side of the throttling element is an open space or a large container with a diameter ≥ 2D, the length of the straight pipe between the open space or large container and the throttling element shall not be less than 30D (15D). If there are other local resistance elements between the throttling element and the open space or large container, in addition to the minimum straight pipe length 1 specified in Appendix Table 1 between the throttling element and the local resistance element, the total length of the straight pipe section from the open space to the throttling element shall not be less than 30D (15D).
Table 1 Minimum straight pipe length on the upstream and downstream sides of the throttling element
The form of the local negative force component on the upstream side of the throttling element and the minimum length of the straight pipe section L
Note: 1. The above table is only for standard throttling devices and can be used as a reference for special throttling devices
2. The column number system is a multiple of the inner diameter D of the tube.
3. The number outside the parentheses in the table represents the value of "zero additional relative limit error", while the number inside the parentheses represents the value of "± 0.5% additional relative limit error". When there is a value in parentheses in the length of the straight pipe section, the limit relative error of flow measurement is τ Q/Q. The arithmetic addition should be 0.5%, which is (τ Q/Q+0.5)%
4. If the actual length of the straight pipe section is greater than the value in parentheses but less than the value outside parentheses, it should be treated as "additional limit relative error of 0.5%".
(1) The DC component installed in the pipeline must have its front end face perpendicular to the pipeline axis, and the maximum allowable non perpendicularity shall not exceed ± 1 °.
(2) After the throttle element is installed in the pipeline, its opening must be concentric with the pipeline, and the maximum allowable eccentricity ε shall not exceed the calculation result of the following formula: ε ≤ 0.015D (1/β -1).
(3) All gaskets should not be made of too thick material, preferably not exceeding 0.5mm. The gaskets should not protrude from the pipe wall, otherwise it may cause significant measurement errors.
(4) All valves used for regulating flow should be installed beyond the minimum length of the pipe section after the throttling element
(5) The installation of throttling devices on process pipelines must be carried out after pipeline cleaning and blowing.
(6) The pressure tapping method of throttling devices installed in horizontal or inclined pipelines.
1) When the fluid being tested is a liquid, in order to prevent bubbles from entering the process pipeline and entering the dental arch, the pressure tap should be located at a position below the centerline of the process pipeline, with a deviation of ≤ 45 °. The positive and negative values should be taken as α - α 1
Product Category:
Since its application in the industrial field, the range of application of orifice flow meters has continued to expand. The original product specifications and standards cannot better adapt to the rapidly changing development of industrial machinery. Therefore, researchers in the production of orifice flow meters have developed two types of orifice flow meters that can meet the needs of various industries, mainly including integrated orifice flow meters and intelligent orifice flow meters.
The difference between the two lies in:
1. The integrated orifice flowmeter is a differential pressure generating device for measuring flow, which can be used in conjunction with various differential pressure gauges or transmitters to measure the flow of various fluids in pipelines. The throttling device of the orifice flowmeter includes a ring chamber orifice plate, nozzles, etc.
2. The intelligent orifice plate flowmeter is a new generation flowmeter that integrates flow, temperature, and pressure detection functions, and can automatically compensate for temperature and pressure. This orifice plate flowmeter adopts advanced microcomputer technology and low-power new technology, with strong functions, compact structure, simple operation, and convenient use.