Regarding the issue of heating the liquid oxygen pump
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After the liquid oxygen pump is shut down, is it better to heat it from the pump outlet pipeline and discharge from the pump inlet pipeline, or to heat it from the pump inlet pipeline and discharge from the outlet pipeline?
There’s actually not much difference. Relatively speaking, reverse defrosting from export to import is better, as it also allows for the cleaning of the pump’s inlet filter, whereas this cannot be done during forward defrosting
We can only heat in the direction of flow; there’s a check valve at the outlet. Besides, if we heat in the reverse direction, wouldn’t the pump operate in reverse?
Most designs go from import to export. It applies domestically as well as to foreign equipment. The reason might be to prevent the pump from reversing, and secondly, it could be due to high outlet pressure, with concerns about backflow (hypothetically). Again, considering the positions of the pump’s inlet and outlet, this helps to blow away debris inside the pump more effectively.
I think reverse heating is the best option, as it allows for a more thorough drying. Regarding the reversal issue, we can prevent it from occurring by controlling the pressure of the heating gas ； Additionally, reversing the direction should also be acceptable, right? (I remember that for some compressors, the rotation direction needs to be reversed during turning (the sealing mechanism is definitely different from that of cryopumps); I’m not entirely sure about this.) I really hope an authoritative source can provide an explanation! !
Export heating means heating before the check valve to discharge from the inlet
Thank you all. I’m just starting to learn *air separation, and there are many things I don’t quite understand.
Normally, heating is applied at the inlet and discharge occurs at the outlet. In our unit, the heating inlets for the oxygen and nitrogen pumps are located before the pumps; however, there is a discharge point also before the pumps and another one at the outlet. During heating, when there is no frost in the pre-pump drain, the flow rate is reduced significantly, and a large amount of gas is discharged from behind the pump. In my opinion, reversing the direction of airflow should allow control over the amount of heating gas used, but this issue is mainly related to the way the pumps are installed. Generally, the pump inlet is located at the top and the outlet at the bottom, with the pump installed vertically. If the heating inlet is placed on the pump’s outlet pipeline, that is, if air is blown from bottom to top, it will make it difficult for hydrocarbons to flow out during separation, and even very small particles cannot be expelled smoothly.
Whether the oxygen pump is heated with inlet air or outlet air makes a significant difference…