Solutions for the decrease in outlet pressure of the heat transfer medium circulation pump
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After adding additional pipelines to the original system, since a hydrostatic test was conducted initially, it’s possible that all the water was not completely removed before hot oil was introduced. Upon putting the pipelines into use, it was found that there was still some water remaining in the new pipelines, which caused significant fluctuations in the pressure at the pump outlet. The system currently in use features two circulation paths: one path involves the return oil flowing into the heat medium expansion tank and then being sent to the pump inlet, while the other path involves the return oil being drawn directly into the pump inlet and then discharged through the pump. At that time, another oil heating process was carried out over a period of one week; no significant amount of gas or water was observed to be released during this process. After that, the smaller circulation path was closed off, and the pump outlet pressure was able to be maintained between 0.4–0.45 Mpa. However, after about three weeks of operation, the pump outlet pressure has dropped back to around 0.2–0.25 Mpa. Apart from the solutions suggested below, are there any other methods that could be used? 1. Close the expansion tank vent valve and use nitrogen for gas sealing. 2. Clean the filter screen at the inlet of the circulation pump
The main reason is the presence of water in the oil; as this oil enters the pump, the water vaporizes inside the pump, turning into water vapor, which causes the pump to lose its vacuum. This can be addressed by finding a high point from which the water can be drained, or by lowering the oil temperature – once the water is removed at the lower point, the problem will be resolved
It’s caused by cavitation; efforts are being made to address this issue
The first option is not recommended, as an increase in pressure inside the expansion tank could lead to overpressure throughout the entire system. Since the pressure was within the required range before, it shouldn’t be a water content issue. Option 2 can be considered, and then we can see how it turns out.