【Q&A Question 068】2016.06.27
Thread Content
【Q&A Question No. 068】June 27, 2016: Methods for dealing with inaccurate remote liquid level indication. The answer key will be available after responding; scoring is based on identifying the key points. 1. Contact the instruments. 2. Issue a work order to bypass the relevant interlocks. 3. Calibrate the instruments. 4. After completion, observe for a while before activating the relevant interlocks.
If the remote liquid level indication is inaccurate, first check whether there are any blockages or leaks in the pressure guiding tubes of the transmitter unit, whether the power supply voltage is stable, and whether the transmitter, the display instrument, and the transmission wires are properly grounded...
The discrepancy between the on-site instrument display and the remote transmission is usually due to the incorrect setting of the value corresponding to 4-20mA. For example, 4 milliamps on the field instrument corresponds to 0 ； 20 milliamps corresponds to 5 meters, while on the digital display instruments or DCS systems at the far end, 20 mA corresponds to 7 meters. There is also the issue of lag.
Check the migration amount of remote meters; check whether the remote meters are faulty
1. Contact the instruments. 2. Issue a work order to bypass the relevant interlocks. 3. Calibrate the instruments. 4. After completion, observe for a while before activating the relevant interlocks.
Knowing which type of remote sensing sensor is being used, if there isn’t a significant discrepancy in the 4–20mA signals transmitted, it indicates that the float does not correspond to the actual liquid level; this could be due to the float being stuck or not moving properly； If the data shown on the visual gauge corresponds to the actual liquid level, but the electrical signal does not reflect the correct value, then there is a problem with the sensor or its installation ； If you think the precision is not sufficient, you can replace it with a transmitter based on the magnetostrictive principle, which can be attached to the outer wall of the flap cylinder; its precision can reach 1 mm.
The discrepancy between the on-site instrument display and the remote transmission is usually due to the incorrect setting of the value corresponding to 4-20mA. For example, 4 milliamps on the field instrument corresponds to 0 ； 20 milliamps corresponds to 5 meters, while on the digital display instruments or DCS systems at the far end, 20 mA corresponds to 7 meters. There is also the issue of lag.
1. The glass panel is equipped with an on-site level gauge for reference; contact the instrumentation team to handle it.