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KH-LG saturated steam flowmeter
Brief description: The application of saturated steam flowmeter has certain limitations. It can only measure the liquid flow rate of conductive media
Product details
There are various reasons for the situation of saturated steam flow meters, such as unreasonable selection, inappropriate range, insufficient length of upstream and downstream straight pipe sections, incorrect installation, significant deviation of fluid properties from the design state, operating conditions exceeding allowable values, pulsating flow effects, and complex environmental conditions such as vibration. Therefore, flow measurement is a systematic problem, including detection devices, display devices, front and rear straight pipe sections, and auxiliary equipment. The accuracy of flow measurement refers to the precision obtained by the flow measurement system, which is different from the accuracy of the flow meter itself. Just because the steam flowmeter itself has good performance and high accuracy, it may not necessarily achieve high measurement accuracy. To ensure the accuracy of the flow measurement system, in addition to reasonable selection, correct installation and commissioning, timely maintenance and upkeep of the flow meter, considerations for the use of KH-LG saturated steam flow meter include:
(1) The scaling or wear of the water supply pipeline will change the inner diameter size, which will affect the original flow value and cause measurement errors. If the inner diameter of a 100mm diameter instrument changes by 1mm, it will result in an additional error of about 2%.
(2) The application of KH-LG has certain limitations, as it can only measure the liquid flow rate of conductive media and cannot measure the flow rate of non-conductive media, such as heating water with better gas and water treatment. In addition, its lining needs to be considered under high temperature conditions.
(3) It determines the volumetric flow rate under working conditions by measuring the velocity of conductive liquid. According to the measurement requirements, for liquid media, the mass flow rate should be measured, and the measurement of medium flow rate should involve the density of the fluid. Different fluid media have different densities and vary with temperature. If the converter does not consider fluid density and only provides volumetric flow rate at room temperature, it is not appropriate.
(4) When measuring viscous liquids with dirt, sticky substances or sediment adhere to the inner wall of the measuring tube or electrode, causing a change in the output potential of the transmitter and resulting in measurement errors. When the dirt on the electrode reaches a certain thickness, it may cause the instrument to fail to measure.
(5) The measurement signal of the transmitter is a very small millivolt level potential signal, which contains not only flow signals but also some signals unrelated to flow, such as phase voltage, orthogonal voltage, and common mode voltage. In order to accurately measure flow, it is necessary to eliminate various interference signals and effectively amplify the flow signal. The performance of the flow converter should be improved by using a microprocessor based converter to control the excitation voltage. The excitation mode and frequency should be selected according to the properties of the measured fluid. KH-LG can eliminate in-phase and quadrature interference.
Pipeline installation conditions:
The straight pipe section before and after the throttle element must be straight and there must be no visible bending.
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 to correct for sparsity.
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, therefore:
(1) The straight pipe section must be circular, and the roundness requirements for the 2D range 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 in front of the throttling element, and take the average value D. The difference between any single measurement value and the average value of the inner diameter shall not exceed ± 0.3% (B). After the throttling element, 8 single measurement values of the inner diameter shall be measured at the OD and 2D positions using the above method. The large deviation between any single measurement value and D shall not exceed ± 2%. (2) A sufficiently long straight pipe section is required before and after the throttling element, which is related to the form of the local resistance element in front of the throttling element and the diameter ratio β.
(3) The length of the straight pipe section between the upstream resistance element and the second resistance element of the throttling element can be taken as half of the listed value in the form of the second resistance element and β=0.7 (regardless of the actual β value).
Easy to be affected by vibration interference, the well-designed KH-LG can eliminate interference through hardware and digital signal processing, thereby obtaining stable signals. A long straight pipe section is required before and after installation, and some manufacturers can provide a design for reducing the diameter inside the flowmeter, greatly reducing the need for users to specifically equip straight pipe sections. If a valve is installed near the upstream of the installation point, constantly opening and closing the valve will have a great impact on the service life of the flowmeter, and it is very easy to cause * damage to the flowmeter. Try to avoid installing flow meters on very long overhead pipelines as much as possible. Over time, the sagging of the flow meter can easily cause seal leakage between the flow meter and the flange. If installation is necessary, pipe fastening devices must be installed at 2D positions upstream and downstream of the flow meter.
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