Due to improper adjustment of seal gas pressure during operation, liquid oxygen pump can not pump liquid or leak.
From the quality point of view, when the sealing pressure is too high, there will be gas leakage into the pump through the labyrinth seal, resulting in the impeller with gas or even idling, resulting in liquid injection or pressure drop; when the air pressure before sealing is too low, there will be liquid oxygen leakage.
From the quantity point of view, when (p1-p3) > 0.005 ~ 0.01Mpa, the sealing gas will enter the pump shell and air will appear. When p3 > p1, it will leak.
The purpose of using seal gas (dry nitrogen) is to prevent or reduce the leakage of liquid oxygen, but it is not allowed to carry air. Therefore, the principle of adjusting the sealing pressure is to allow the pump to operate with a small amount of liquid oxygen leakage and vaporization. The pressure level is related to many factors, such as the sealing structure, the position of the vent hole, the clearance of the pump, etc. It is difficult to set data strictly, so it is necessary to explore in practice to find a suitable method.
In general, the pressure difference (p1-p3) before and after the seal gas is preferably in the range of 0.005 to 0.01Mpa. For example, some factories initially stipulated that the pressure of seal gas should be higher than the discharge pressure of liquid oxygen pump, but it is not suitable in practice, which usually leads to pressure drop. After that, when the seal gas pressure is reduced to 0.02MPa lower than the pump outlet pressure, the normal operation can be ensured.
