Thread Content
Check of electromagnetic flowmeter output I. Causes of failure The fluctuations in the output can generally be attributed to 5 types of fault causes, which are: (1) The flow itself is fluctuating or pulsating; this is not actually a fault of the electromagnetic flowmeter, but rather a reflection of the actual flow conditions； (2) The pipe is not fully filled with liquid or the liquid contains bubbles ； (3) Electrical and magnetic interference from external stray currents, etc ； (4) Reasons related to liquid properties (such as uneven liquid conductivity or slurries containing a large number of variable particles/fibers, etc.) ； (5) The electrode material is not properly matched to the liquid. II. Inspection Procedure The procedure for checking the fluctuation in the output of the electromagnetic flowmeter. First, conduct a comprehensive initial investigation and assessment in accordance with the procedure, and then carry out detailed checks item by item to troubleshoot the issues. The principle governing the sequence of checks listed in the process is as follows: ① Those that can be determined through observation or questioning without requiring extensive procedures come first; in other words, the easier tasks are handled first ； ②Based on past on-site maintenance experience, those that occur frequently and are likely to happen again in the future are listed first ； ③Check the sequential requirements of the process itself. If the causes of these faults are confirmed through a preliminary investigation, a detailed inspection can also be carried out in advance. 1. Start – Check whether there are any sources of pulsating flow disturbances in the piping system of the electromagnetic flowmeter sensor – Determine whether the source of flow motion is a reciprocating pump or a diaphragm pump. If so: a. Install a gas chamber and flow restrictor to reduce pulsation; b. Increase the damping of the instrument. If not: Check whether hunting vibration occurs in the downstream pumps and valves Yes: Improve the control characteristics of the control valve. No: Check for other disturbance sources that may cause fluctuations If present: target the disturbance sources for elimination. If not, please see 2. 2. Check whether the liquid inside the tube is full? Does the liquid contain bubbles? --A gas collection tank and a manual exhaust valve are installed downstream of the sensor to facilitate inspection and verification. a. Check whether the liquid inside the tube is full? If it is not fully filled: Special attention should be paid when the electromagnetic flowmeter sensor is installed horizontally or in a vertical position with flow from top to bottom; it should be adjusted to a position where it can be completely filled, such as a vertical installation with flow from bottom to top. b. Does the liquid contain bubbles? If there are bubbles: Install another separator or automatic vent valve upstream of the sensor. If there are no bubbles, please see 3. 3. Check whether the sensor is properly grounded? In the absence of proper grounding: a) The sensor and adjacent pipes should be connected using a third type of grounding (with resistance below 100 ohms). b) When connecting to insulated pipes or pipes with anti-corrosion linings, grounding rings or grounding sleeves should be installed at both ends of the sensor. If the grounding is good, then check whether there are any interferences such as stray currents in the pipes. If there is interference, remove the source of interference. If there is no interference, check whether there are strong magnetic field sources such as large power transformers near the electromagnetic flowmeter sensor. If so, then change the installation location, based on the principle of a strong magnetic field source. 4. Check the physical properties of the liquid – whether it is a slurry – whether the liquid conductivity is uniform – and whether the liquid conductivity is too low. 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