The centrifugal pump leaks after stopping during long-period operation; however, there is no leakage when it starts running again. What’s the reason for this?
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The centrifugal pump leaks after stopping during long-period operation; however, there is no leakage when it starts running again. What’s the reason for this?
Is it because, during operation, a negative pressure area is created at the machine seal, which prevents leakage?
I’ve encountered this situation as well; could it be that the axial movement during operation fills in the gap in the seal, thereby compressing the sealing surfaces of the stationary and rotating rings?
There are several explanations: 1. It is the static ring that is leaking; sometimes, as the temperature rises during operation, the various components of the seal expand and thus achieve sealing. 2. Sometimes it’s the moving and stationary rings of the mechanical seal; there is slight wear on the sealing surfaces, which may cause leakage when the equipment is stopped. But once it starts operating, the motion generates a force that creates a liquid seal (I’m not familiar with this equipment, so I just came up with this name; it’s my personal interpretation). 3. When the equipment is stopped, the pressure ratio is low; as the temperature rises, the spring expands and the pressure ratio increases, allowing normal operation again.
Looking forward to the correct answer; experts, please step forward! ! ! ! ! ! ! ! My thought: The stationary ring cannot move axially; therefore, it must be the rotating ring that moves axially, which ensures proper sealing and eliminates leaks. But what axial movement occurred? Why does axial motion occur? Wait, I don’t understand. What the original poster is referring to is probably a high-flow double-suction single-stage centrifugal pump or a single-suction single-stage centrifugal pump? ~!
There are two reasons: 1. When at rest, minor impurities may get trapped on the sealing surfaces of the stationary and rotating rings, resulting in poor sealing. Compensate for the original issues such as spring warping, misalignment, and cold shrinkage of O-rings. 2. After the rotating and stationary rings start to move, relative friction is generated, resulting in the formation of a spiral-sealing air film (or liquid film) between the sealing surfaces.
What was said upstairs is absolutely correct. Additionally, the rotating ring of the mechanical seal is fixed to the shaft by a shaft sleeve, so it does not move axially. There is a spring inside the static ring, which allows the graphite ring that provides sealing to move axially.
Part of it is due to thermal expansion and contraction! When the pump is running, the seal expands due to heat; once the pump stops running, the seal contracts, which leads to leakage!
There’s also the reason of thermal expansion and contraction@
It should be a leakage in the friction pair. The part of a mechanical seal that is prone to leakage is the dynamic seal, which is the friction pair composed of the rotating ring and the stationary ring. In my opinion, 1. check whether the friction pair is damaged. 2. Check whether the pre-tension of the spring is sufficient. I would like to ask the original poster: What is the temperature of the material being transported?
I spent a long time looking at it but couldn’t figure out what it meant; the moderator should give some hints or correct the spelling mistakes in the question