Precautions for installing orifice plate flow meters
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Precautions for installing orifice plate flow meters: 1. The pressure tapping for gases should be located at the upper part of the pipeline； The liquid pressure tapping point should be below the side surface but not directly below it, as sediment particles can block the tapping point ； For steam, the pressure tap is located on the side of the pipe ； 2. Be careful not to get the direction of the orifice plate wrong; the side marked with “+” indicates the positive direction, while “-” indicates the negative direction. “+” corresponds to the direction in which the fluid is flowing. 3. The pressure guide tubes leading from the positive and negative pressure taps must remain parallel under all circumstances ； 4. Orifice plates are generally used in conjunction with differential pressure transmitters; when connecting the pressure guide tubes to the differential pressure transmitter, care must be taken to ensure that the positive and negative sides are not connected incorrectly, with “H” representing the positive side and “L” representing the negative side ； 5. For measuring gases, it is recommended to place the differential pressure device above the pipeline; for liquids, it should be placed below the pipeline. When measuring steam and a condenser is available, the condenser must be at the same horizontal level. 6. Requirements for straight pipe sections: The lengths of the straight pipe sections required in front of and behind the orifice plate are determined based on calculations; typically, 20D in front and 10D behind is required (D refers to the diameter of the orifice plate)
This post was last edited by Yunmu on 2019-4-4 at 13:48. Installation method of the flow meter: 1. Correct installation direction: The flow direction of the fluid should be consistent with the direction of the arrow on the flow meter. 2. Installation location: The installation site should be kept away from strong electrical equipment, high-frequency devices, and powerful switching power supplies. It should also be free from high-temperature heat sources, corrosive gases, and high-temperature environments, with installation pipes that experience minimal vibration being selected. 3. Piping: a: The inner diameter of the piping is the same as that of the flow meter. b: The piping should be concentric with the transmitter, and the deviation of the pipe axis should not exceed 0.05D (where D denotes the inner diameter of the pipe). c: The gasket must not protrude into the pipe. d: When welding flanges together, it is necessary to ensure that the flange holes are aligned, and the two flange surfaces should be parallel to each other ； The end face of the pipe should be slightly lower than the flange sealing surface; it must not protrude, as this could affect the sealing performance, nor should it be significantly recessed, as this could impact fluid flow. 4. Switches of the three-valve assembly: Before completion of installation, the valves on both sides of the three-valve assembly should be closed, while the balance valve in the middle should be opened ； After installation is complete, open the valves on both sides of the three-valve assembly, and finally close the balance valve in the middle ； When it is necessary to close the valves on both sides, the balance valve should be opened first. 5. Usage of the condenser: A condenser is required whenever the fluid temperature is >100°C ； Before allowing fluid to flow through, the condenser must be filled with condensate (water); otherwise, the differential pressure transmitter will be damaged. 6. Installation of the differential pressure transmitter: The positive terminal (H terminal) of the differential pressure transmitter should be installed at the positive pressure lead tube end of the flow meter, while the negative terminal (L terminal) should be installed at the negative pressure lead tube end of the flow meter. The flow direction is from the H end to the L end. 7. Installation with a liquid medium: When the medium is a liquid, the pipeline must be filled with fluid. In horizontal pipes, the flow meter should be installed at a lower position along the pipe ； In a vertical pipe, the fluid must flow from bottom to top.
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