Starting of the hot oil pump
Thread Content
After the hot oil pump is started and the outlet valve is opened, how can cavitation in the pump be prevented?
1. Slowly open the pump outlet valve by referring to the reading on the outlet pressure gauge.
Let me help you think about it. When the temperature is high, cavitation occurs, mainly because the pressure at the pump is too low. The equation p1+ρgh1+0.5ρu1^2=p2+ρgh2+0.5ρu2^2 applies here; we need to avoid having p1 too low. It seems that the only solution is to increase the value on the right side of the equation and reduce u1. Once the pressure reaches a certain level, we can slightly open the outlet valve, and then gradually increase it further?
This causes the liquid to rush towards the center of the bubble at high speed, generating impacts with very high frequencies and intense instantaneous pressures; this phenomenon is known as cavitation. Therefore, ① the outlet valve of the pump should be closed when starting up, and for pumps with high pressure, the outlet valve can be slightly opened to prevent difficulty in opening it later； ②The hot oil pump should be preheated before starting to prevent gas from accumulating inside the pump. ③The pump inlet valve must be fully open.
First, ensure proper preheating so that the moisture inside the pump is removed promptly. Next, open the outlet valve slowly based on the outlet pressure; close it again as soon as the vacuum is created. Repeating this process a few times will suffice. The last two pumps should be switched over without any disturbances; once the pressure of the standby pump is stable, the outlet valve of the operating pump should be gradually closed, while the outlet valve of the standby pump should be opened.
Pay close attention to the export pressure and open slowly