Common Issues and Solutions for Emerson Mass Flow Meters

Thread Content

I. No flow in the pipeline, but the flow meter shows a reading: The flow meter gives a stable reading; the zero point is incorrect; the cut-off for low flow values is too low (0.2–0.5% for continuous measurement, 0.5–1.0% for intermittent measurement). There is leakage in the valves; the pipeline is not fully filled (check the density reading); excessive installation stress; the flow meter gives unstable readings; the flow meter is not fully filled; there are deposits on the flow tube; damping is too low; external wiring issues (9-wire sensor, poor contact, or incorrect cable type).

II. No flow, but the instrument still shows a non-zero reading: The flow meter was zeroed during factory calibration. Zeroing on-site is not recommended in conditions of low temperature, high temperature, or two-phase flow. For calibration and trade handover purposes, follow the specified procedures.

III. Conditions and criteria for zeroing: Conditions for zeroing the flow meter: The process fluid should flow through the sensor for 20–30 minutes; the temperature of the sensor should be close to that of the fluid being measured; the sensor must be completely filled; the valves before and after the sensor should be closed. Methods to determine if the pipeline is fully filled: The density reading at the current temperature should match the density of the fluid; the drive gain should be within the normal range. – For flow meters with small diameters: – For flow meters with large diameters (>4”), the drive gain (Drive%) should not exceed 20%.

IV. Inability to connect the handheld device to the field instrument: · Check whether there is a current of 2–22 mA in the mA circuit. · Check if there is a resistor of 250–600 ohms connected in series in the mA circuit. · Check the safety barrier in the circuit; some models of safety barriers do not support Hart communication. · If a safety barrier is used, check whether its settings conflict with those of the transmitter’s output channel. · Check if the transmitter has an A101 alarm. This alarm occurs when the circuit current mode is disabled; the handheld device can also be disabled. The circuit current mode can be enabled through the transmitter’s offline menu. If the Hart address is not zero, this alarm will also be triggered. In normal applications, the Hart address must be set to zero. · Check whether the open-circuit voltage between transmitter output terminals 1-2 is 24VDC ； Otherwise, it is a fault in the output channel (not applicable to intrinsically safe output transmitters) ； · If 24VDC is available, disconnect the mA output wire and directly measure whether the current between terminals 1-2 is within the range of 2-22mA; if not, it indicates a fault in the output channel (this does not apply to intrinsically safe output transmitters). · If the current is within the range of 2-22mA, use a resistor of 250–600 ohms to connect terminals 1-2 directly, then hang the two hooks of the handheld controller on either side of the resistor, and try making the connection several times. For transmitters manufactured after 2013-01, check whether the Hart version setting of the transmitter is set to 5. Check the polling settings in the Hart application of the handheld device: utility > Polling setup; set it to polling by Address, that is, polling by address, and also set the polling address range to 0-15. V. Inaccurate flowmeter readings
Flowmeter-related factors – Check alarm messages – Verify that the flow coefficient set in the flowmeter matches the value indicated on its nameplate – Ensure that the coefficients for mass, volume, and density are set to 1.0000 – Check the zero point of the instrument – Verify the measurement units used by the instrument – Examine the damping settings for mass flow, density, and temperature – Calculate the rated accuracy at the current flow rate – Check whether there is any discrepancy between the cumulative values shown by the receiving device and those from the flowmeter.
Process-related factors – Check for leaks in the bypass pipelines and valves – Ensure that the pipeline where the flowmeter is located is always full; check for gas-liquid two-phase conditions – Verify that the volume in the pipeline where the flowmeter is located remains consistent – Consider whether there are significant changes in operating temperature and pressure – In situations where the flow rate is low and pressure changes significantly, metal pipes should be used.
Testing methods and reference devices – When comparing with weighing equipment, take into account the accuracy of the weighing device as well as its resolution’s impact on the measured quantities – When comparing with volumetric equipment, consider the accuracy of the container’s volume meter, as well as the accuracy of measurements for liquid level, temperature, and density, as well as the effect of air buoyancy – Containers and tanks (sealed or open) – Should have an accurate volume meter – For liquid level measurement, if an automatic level gauge is used, manual verification is still necessary – When comparing with a flowmeter, consider the rated accuracy of the reference flowmeter – When conducting comparisons for small batches, account for timing errors; when collecting data periodically, consider the differences in data collection times