What are some good solutions for evacuating the bottom of a negative pressure tower using a pump?

1 It is best to first check the airtightness of the pump inlet pipeline to ensure there are no leaks. Check the pump’s shaft seal system to ensure there is no air leakage. 2 Increase the bottom temperature of the tower to reduce the viscosity of the material. 3 Appropriately reduce the vacuum level of the tower (if possible). 4 Expand the diameter of the pump inlet pipe.

The inlet of the bottom pump in a negative-pressure tower should be under positive pressure. In our installation, we have also encountered situations where insufficient pressure at the pump inlet led to vacuum formation; the cause was found to be the leakage of steam or water. First and foremost, it is necessary to ensure that the temperature of the steam introduced into the tower is appropriate, so as to prevent water from entering the oil and thereby vaporizing inside the pump and causing vacuum. It is also important to check whether there is any possibility of water leaking into the pump chamber. Additionally, when switching to a backup pump, it is essential to verify that the temperature is sufficient! Under normal operating conditions, pump evacuation is caused either by insufficient liquid level, blockages, or the intrusion of water vapor. The possibility of excessive vacuum levels leading to pump evacuation is not very high!

It depends on whether the pump is constantly evacuating or only does so occasionally. If it’s constantly evacuating, it means the height difference between the tower base and the pump is too small, resulting in insufficient inlet head pressure at the pump to enable evacuation； When selecting a mechanical pump, choosing an overly low allowable suction vacuum level can result in the pump being prone to cavitation ； If you have some free time from time to time, first check whether the operation of the tower is normal, and whether any light components are entering the pump inlet; vaporization due to low pressure at the pump inlet can cause the pump to become vacuumed ； For the rest, just check above ；

It depends on whether the pump is constantly evacuating or only does so occasionally. If it’s constantly evacuating, it means the height difference between the tower base and the pump is too small, resulting in insufficient inlet head pressure at the pump to enable evacuation； When selecting a mechanical pump, choosing an overly low allowable suction vacuum level can result in the pump being prone to cavitation ； If you have some free time from time to time, first check whether the operation of the tower is normal, and whether any light components are entering the pump inlet; vaporization due to low pressure at the pump inlet can cause the pump to become vacuumed ； For the rest, just check above ；

A pipe is run from the pump outlet to the inlet; adjusting the opening degree can solve the issue.

Thank you to all the teachers for their replies; it really got much better after the water evaporated

1. First, raise the liquid level at the bottom of the tower to a level close to the maximum allowable value. Fully open the valve on the pump’s inlet pipeline, start the pump, and observe its operation: check whether the pressure during low-flow operation remains stable, and whether the pressure fluctuates significantly when a higher flow rate is used. Under normal conditions, it is possible to further increase the liquid level or lower the position of the pump inlet ； If the above method doesn’t work, proceed as follows: check whether the valves on the inlet pipeline are fully open; determine if there is high resistance in such cases, check the pressure difference across the filters, see by how much the diameter of the inlet pipe exceeds that of the pump’s inlet, examine whether there are too many elbows, and consider whether concentric reducer sleeves are used at the pump inlet to prevent liquid from evaporating – identify which device or fitting causes the greatest resistance. Generally speaking, the resistance of the filter is the highest, and this resistance increases over time. Solutions include connecting another filter in parallel to reduce the resistance, or moving the filter to the pump outlet. 3 Adopt two or more of the comprehensive measures, such as raising the liquid level, lowering the pump inlet position, enlarging the pipes, replacing valves with lower resistance, adding filters or relocating them, or even replacing the pump with one that has a higher net positive suction head.