Regarding the large fluctuations in the liquid oxygen level in the air separation tower

1. Rule out the possibility that it is a problem with the transmitter. 2. Check whether there are any leaks in the pressure sensing pipelines outside the cryogenic box. 3. If all external factors have been ruled out and no problems are found, it is likely that there is an issue with the installation of the positive pressure pipeline inside the cryogenic box

1 Is the pressure guiding tube of the liquid oxygen differential pressure transmitter insulated? If it were me suggesting, it’s better not to wrap it, as this can easily lead to a mixture of gas and liquid and thus fluctuations. 2 Is there no on-site level gauge? Is the process itself highly volatile?

It is recommended to take the following measures to see if it works. 1. Disconnect the negative pressure tube of the transmitter sampling pipe behind the valve at the root of the cold box, and use an instrument valve to control the purging process to check whether liquid is being discharged from the tube. It is possible to determine whether liquid is entering through the negative pressure pipe, or whether the tower liquid level is too high, resulting in liquid suspension. 2. Disassemble the section behind the valve at the base of the positive pressure tube cryostat, and finally use an oxygen cylinder plus a pressure regulator to enable backflow. After clearing the airflow interference, restart the differential voltage measurement. It should be stable at this time. As time passes, any further fluctuations indicate that there is a leak in the pressurized pipeline. 3. Check whether the tracking scale of the on-site control valve matches that on the computer, and whether there is any cold flow at the valve stem; this issue should be addressed or the area should be heated. 4. If the problem that arises cannot be resolved, a temporary on-line pressure gauge (an oil-free pressure gauge specifically designed for oxygen) should be connected to the sampling point at the lower part of the liquid oxygen in the main cooler of the tower. The upper limit for operation is set at the highest liquid level when the oxygen purity drops suddenly, with the pressure reading also serving as a reference point. Relative to the normal liquid level (with the liquid level indication being relatively accurate after backwashing), the pressure indication is marked as the lowest operating value. The above approach is only used to maintain production, with a thorough investigation to address the issues carried out when an opportunity arises. For reference.

It is estimated that the pipeline layout inside the tower is not proper; check to see if the liquid discharge time is long or not. Also, examine the transmitter and the wiring, as interference could be the cause