Thread Content
The diameter of electromagnetic flowmeters can reach 3000 mm. Installing electromagnetic flowmeters with such large diameters is much more complicated than installing those with smaller diameters. To ensure that the flowmeter functions correctly, instrumentation technicians provide users with guidelines on the precautions to take during the installation of large-diameter electromagnetic flowmeters for their reference. I. Key control points in the installation process of large-diameter electromagnetic flowmeters During on-site installation, in order to avoid affecting the measurement accuracy of the system, it is necessary to strictly comply with the following process requirements. 1. Keep the electrode axis horizontal. When installing the sensor of an electromagnetic flowmeter, the axes of the two electrodes must be horizontal. 2. The medium under test fills the measuring tube. The measuring tube must be completely filled with water; it should not be partially filled or contain any air bubbles. 3. Meet the requirements regarding the flow direction and straight pipe sections. The direction indicated by the arrow on the sensor is the positive direction of fluid flow; ultra-large diameter electromagnetic flowmeters (with the sensor and converter installed separately) are designed to be placed within the flowmeter well of the pipeline. To ensure accurate measurement, it is necessary to maintain a straight pipe section of 10D in front of and 2D behind the flow meter (where D is the nominal diameter). II. Process quality during the installation of large-diameter electromagnetic flowmeters 1. Assembly of the sensor and expansion joint: Install the grounding ring and expansion joint on the downstream side of the flowmeter, following the arrows indicated on the sensor, and pre-adjust the expansion joint to a shortened position. 2. Break in the flow meter well: The steps for handling a break in the flow meter well are as follows: (1) Identify the location where the sensor is installed, and accurately measure the dimensions of the broken pipe (based on the dimensions after the expansion joint has expanded). (2) Create skylights in the pipe fracture area and insert cross-shaped steel supports inside the pipe to ensure its roundness and prevent deformation of the pipe ends after the fracture, which could affect flange installation. (3) After cutting, the grooves at both tube ends are mechanically prepared to meet the requirements for welding flanges. 3. Lifting: The assembled sensor, along with the expansion joint, has a total weight of around 6 tons; a 25-ton truck crane is used on site to lift it into place. After it is lifted into place, adjust and release the expansion joint; install grounding rings and gaskets between the upstream flange and the sensor, insert bolts for alignment and tighten them; similarly, install gaskets between the downstream flange and the expansion joint, insert bolts and tighten them as well. 4. Flange welding: Adjust the positions of the upstream and downstream flanges, grounding rings, and gaskets of the pipeline, tighten the bolts, and secure them with spot welding. Remove the pre-tightening bolts of the upstream and downstream flanges, adjust the expansion joint, so that the upstream and downstream flanges are separated from the flow meter and the expansion joint, leaving space on the inside of the flanges for welding. The two flanges at the upstream and downstream ends are welded together using fillet welds on the inside and outside of the flange. 5. Non-destructive testing and anti-corrosion treatment of welds: (1) Testing standards and acceptable quality levels – All fillet welds at flange joints must undergo non-destructive testing, using electromagnetic testing methods, with a specified inspection ratio. The quality shall meet the requirements of Grade 2 as specified in standard JB4730-2005. If defects exceeding the specified limits are found in the welds of the pipe flanges, they must be addressed promptly to ensure successful re-inspection. Any weld can only be repaired once. (2) Outside the inner anti-corrosion flange weld: The internal and external anti-corrosion treatment of the steel pipe fittings on the flange is the same as that applied to the steel pipe itself. An modified chlorosulfonated polyethylene anti-corrosion coating is applied outside the flange weld; the internal anti-corrosion coating on the flange is a non-toxic epoxy coating suitable for drinking water use. All inner sides are coated with two layers of bottom coating and two layers of top coating. 6. Overall tight fixation of the electromagnetic flowmeter sensor expansion joint: After the welds on the upstream and downstream flanges pass the flaw detection, the process of overall tight fixation of the sensor expansion joint is carried out. (1) Adjust the release expansion joint; install a grounding ring and seal gasket between the upstream flange and the sensor, insert bolts, and tighten them. (2) Install a gasket between the downstream flange and the expansion joint, insert bolts, and tighten them. (3) In a symmetrical manner, tighten all flange bolts and install the position sensor and expansion joint. 7. System hydrostatic test: After the sensors and expansion joints have been installed as a whole, a hydrostatic test should be carried out on them along with the water delivery pipes. The test pressure is 1.5 times the working pressure. After passing the hydrostatic test, it can be put into operation. For more information, please visit the company’s official website at http://www.yb1518.com/. Please retain this link when reproducing the content! http://www.yb1518.com/UploadFiles/2012717174126829.jpg