Summary of Common Problems with Rosemount Differential Pressure and Pressure Transmitters
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Summary of Common Problems with Rosemount Differential and Pressure Transmitters – Simple issues that often occur with these transmitters in the field:1. The operator panel is in English, so users generally don’t even look at it.
2. Users don’t know how to perform basic operations using the operator panel.
3. Poor wiring by users results in zero current in the circuit.
4. Communication problems.
5. For level transmitters, proper handling of the filling fluid in the pressure tap tubes.
6. Correct calibration of remote transmitters.
7. Use of valve assemblies.
8. On-site zeroing.
I. Regarding the English-language operator panel: Inform users of the first screen that appears after the panel enters communication mode.
II. What do the shortcut key codes mean? There’s an operation guide included with the instrument box, which outlines these codes; knowing how to use them is sufficient.
III. When users report no output or communication issues, ask for detailed information such as the current value; if there’s no current, check the circuit by measuring the voltage across the instrument.
IV. If the instrument cannot communicate, ask the user whether the supply voltage is normal, what the circuit current is, and whether a 250-ohm resistor has been installed in the circuit.
V. For level transmitters, since pressure tap tubes are installed at both the low-pressure and high-pressure ends, there must be no air in these tubes. There should also be no U-shaped section in the lower pressure tap tube. Reason: If the liquid level is below the pressure tap tube, the liquid will flow back, causing air to accumulate inside the tube. Changes in pressure within the tube will then cause changes in the liquid level displayed by the transmitter.
VI. For remote transmitters with dual capillaries, if users report inaccurate measurements, ask whether they have calibrated the transmitter according to the required specifications and whether they have adjusted the zero point. If calibration hasn’t been done, press the zero button for 5 seconds when the liquid level is at zero. The measurement range of the instrument is determined by adding the liquid level height multiplied by the specific gravity to the zero point value.
VII. When using a three-valve assembly, both valves on either side should be open while the middle valve is closed during operation. For a five-valve assembly, both valves on the sides are open while the others are closed. To zero the instrument, open the balance valve in the middle of the three-valve assembly and close the high-pressure valve. In the case of a five-valve assembly, close the topmost valve and the high-pressure valve, while keeping the two middle valves open.
VIII. Zeroing includes adjusting differential and gauge pressure transmitters with respect to atmospheric pressure, as well as adjusting the zero point and range when atmospheric pressure is not used as the reference point. The former can be done using the operator panel, for example, with the shortcut key 12331. The latter requires using the instrument’s built-in zeroing function; press Z for 5 seconds once it’s confirmed that the zero point is correct at the site.
This post was last edited by violetta on 2009-4-17 00:04