The mechanical seal does not leak when the centrifugal pump is in operation, but it leaks when the pump is in standby mode. What is causing this?
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The mechanical seal does not leak when the centrifugal pump is in operation, but it leaks when the pump is in standby mode. What is causing this? PLAN52 plan
It is possible that the service life of the sealing ring is insufficient, resulting in slight deformation of the sealing surface; during operation this acts as a form of grinding of the sealing surface, which is why there is no leakage. This situation often occurs in inlaid sealing rings.
If the rubber ring is aging or the compression amount is not properly designed, it is recommended to consult a sealing manufacturer for an assessment.
1. In principle, a mechanical seal is a dynamic seal; it creates a liquid seal when in rotation, but not when at rest. So, compared to dynamic conditions, the static leakage will be somewhat higher. 2. From a theoretical perspective, if the leakage increases significantly, it’s most likely due to aging of the O-ring. 3. If the leakage is not severe, it can be ignored; but if it’s significant, it’s definitely worth checking the mechanical seal, as any issues in that area will be obvious
I fully agree with your explanation of this dynamic balance; in our case, generally, by adjusting the pump shaft to a certain specific angle, the leakage is reduced or eliminated as well.
It is indeed a dynamic seal. During tests a few days ago, as soon as the pipes were connected and the inlet and outlet valves were opened, the mechanical seal started leaking; however, no leakage occurred once the machine was in operation, and there was also no leakage after it stopped running. It seems that a seal is formed during operation, and it remains intact even when the machine stops working again
Simply put, this issue is related to axial force. When the pump is operating, external forces act on the mechanical seal; the spring force also plays a role in this process. When the pump stops operating, the compressive force of the spring remains active. The solution is to increase the degree of compression of the mechanical seal. This answer is provided for your reference.
Is the spring a single-spring structure?
Leakage-free rotation is achieved by ensuring that the dynamic and static sealing surfaces form a friction pair that prevents leakage; as the axial force generated during pump operation increases, the pre-tension of the spring is increased to avoid leakage. After the pump stops running, one can turn the shaft by hand to feel the level of spring pressure, thereby adjusting it as needed.
It is suspected that the friction pair at the medium side of the mechanical seal has been damaged; the absence of leakage is due to the pump drawing in sealing water into its chamber during operation, which creates an illusion of no external leakage. During shutdown, due to the lack of suction, leakage of the seal water can be observed. The pump can be disassembled to inspect the friction pair on the medium side of the mechanical seal for verification.
It’s simple: when the pump is running, there is negative pressure and no leakage; when it’s stopped, there is positive pressure and leakage occurs as expected. In short, there’s a problem with the sealing