Newbie seeks expert help to resolve drum level issue
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The boiler drum level transmitter is a Rosemount transmitter; the H side of the transmitter is connected to the liquid phase (–), while the L side is connected to the vapor phase (+). This installation method should be correct. The transmitter can be zeroed with respect to the gauge reading, and the negative drift ranges from –5.2 to 0. The level indicated by this transmitter differs significantly from that shown by the magnetic coupling level gauge nearby. Both the vapor and liquid sides of the valve at the bottom of the drum have been closed; however, there is still steam on the H side, and a small amount of water is flowing on the L side. The current level in the drum is 30 cm. The center distance between the transmitters is 670 mm. Under normal operating conditions, the saturated steam temperature is 350°C, and there is no blockage. Under normal condensation conditions, the gauge reading is slightly negative, around zero point several, indicating a level that is close to full. I’m not sure what the problem is at this point; I hope experts can provide some guidance and help resolve this issue
One is to connect a multimeter in series at the cabinet to measure current, and in parallel to measure voltage. Check whether the DCS can display the corresponding liquid level with a normal voltage and normal current signal; if it does not display, look for faults in the DCS. The voltage is normal but the current signal is abnormal; check the transmitter to locate the fault point.
The current and voltage are both normal; the DCS screen shows a yellow flashing indicator with a question mark, and reconnecting a gauge to the module channel also works fine, which indicates that the channel is in good condition. The transmitter can be zeroed out, but the DCS screen continues to show a yellow flashing indicator with a question mark and a numerical value
This score range is used for troubleshooting; it’s not necessary to replace a component as soon as it shows signs of failure. Whether the issue lies with the instruments on site, the wiring, or the system itself, troubleshooting can be carried out through measurement, observation, and replacement. By using the method of elimination—for example, by connecting that component to another point to see if it functions properly, or vice versa—one can identify the problem!
First, disconnect the field gauge and wires and use a 475 handheld controller to connect them, which ensures that the gauge is in good working condition. Second, disconnect the cable on the field side from the DCS side in order to check the continuity of the cable as well as its insulation properties. Third, add an analog signal at the channel to check whether the display is correct.
Is this a two-chamber balanced level gauge? Was the condensate drained?
As the gentleman upstairs said, first use the values available on site to disconnect one wire from the channel in the cabinet and measure the current with a multimeter to check whether it’s within the 4-20mA range. After that, determine if there are any issues with the channel card. Since you say there are no problems with the channel, it’s possible that there is a software or DCS program-related issue. It is recommended to try the following steps: reinstall the process diagram related to that level. If the problem persists, delete the program associated with that level’s display module, which means removing that level’s programming, and then reinstall it again. Be sure to make backups of the programs during this process.
This is a magnetic flap level gauge, fromABB
Ignore it; it will be fine in a day. There is only 6 floors upstairs, that’s correct. Weren’t you the one who emptied all the water from the vapor side? If so, please follow the steps below from now on. Close the vapor side root valve, open the liquid side root valve, and slightly open the vent screw on the vapor side of the transmitter. Wait a few minutes, and the condensate in the central cylinder will fill the tank. Just restore it to its original state.