Our single stage Centrifugal pump features a double mechanical seal back to back arrangement, with Seal Plan 53A and pressurized red oil. Recently, we encountered a mechanical seal leak issue which led to the pump getting jammed and unable to rotate freely after re-pressurizing with red oil. Upon releasing the pressure, the pump resumed free movement. Despite checking for axial movement when pressurized and finding none, the problem persisted upon re-pressurization. The seal vendor was consulted and seal assembly was redone in their presence, yet the jamming issue persisted. We welcome any suggestions or insights on resolving this recurring problem.
Are you monitoring your barrier fluid pressure to prevent issues? It's important to maintain the correct pressure to ensure proper face contact and loading. If you are using a cartridge type seal, be wary of excessively high seal face contact pressure that could lead to increased friction and pump jamming. Running the pump in such conditions can quickly wear out the seal face and even cause the hard face to break, leading to leaks. What did you discover with the old leaky seal? Make sure to address any issues to prevent further damage. Check out Vibmaster for more insights.
The pressure of the barrier fluid is maintained at 5.0 kg/cm2g in the seal pot, which is controlled by nitrogen. The mechanical seal in question is not a cartridge type, but rather a manually assembled back to back design. Face loading is adjusted by compressing the rotating component of the seal to specific dimensions outlined in the seal drawing. It is worth noting that this mechanical seal recently failed for the first time in the pump's 13-14 year history, with no previous maintenance records available. While there were no visible damages on the seal faces, the back plate holding the stationary component was found cracked, leading to fluid leakage. Your guidance and advice on this issue would be greatly appreciated.
Experiment with adjusting the hydrostatic pressure by slowly decreasing the nitrogen purge pressure while hand-rotating the pump. If the jamming eases as the pressure is reduced, it indicates that the issue is related to the 5 bar pressure. This pressure forces the rotating face against the stationary face, preventing manual rotation. It is advisable to rotate the pump manually before starting it to avoid excessive wear on the seal faces. If the seal pot level remains stable when the pump is off, the seal is suitable for use. If a slight reduction in hydrostatic pressure is needed before starting the pump, it is recommended to do so. The pressure can always be increased if the pot level rises. If the seal holds up well at the reduced pressure, you can continue operating with it.
Could it be possible that we overlooked a crucial step? Have you attempted to manually open the suction valve and rotate the pump while under a 5-bar hydrostatic pressure? This could potentially resolve the issue at hand.
The 5 bar pressure mentioned should be balanced against a suction pressure to prevent jamming of seal faces. Without a proper suction fluid, 5 bar may be too high and cause the pump to not rotate. Consider designing for an optimal intake suction pressure before attempting to rotate the pump for smooth operation.
It sounds like you've tried quite a few things already, but it's possible that the issue might be internal friction within the seal assembly. Considering it works fine until pressurized with the red oil, one potential issue could be thermal expansion of the seal components that's causing undue friction. However, it doesn't seem your seals are having any axial movement when pressurized. Alternatively, could there be contamination in the red oil causing increased friction? Maybe consider running an analysis of the oil for any impurities. Lastly, make sure the pressure you are using doesn't surpass the recommended value for the seal. Any one of these issues, or even a combination, may be the culprit behind the jamming issue.
It sounds like a tricky situation, but it could be bearing related, assuming the pump bearings are adequately lubricated. You might be dealing with an issue of misalignment or the seal face might be distorting under pressure. The seal-face distortion could be caused by excessive pressure from the red oil. Also, check the oil pressure in Plan 53A, maybe it's exceeding the seal balance ratio causing excessive heat or damage to components. Do ensure that the Plan 53A system is adequately cooled and your buffer/barrier fluid is compatible. Finally, consult with your seal vendor again to see if they have a higher-pressure alternative or suggest another Plan. Sometimes, you might need custom solutions for persistent problems.
From your description, it sounds like the issue may be the pressure itself rather than the seal. The fact that the pump operates fine when pressure is released suggests that the pump could be getting overloaded when pressurized. Maybe you could try operating with a less pressurized fluid or consider checking if your pump can handle the current pressure level. It's also possible that the seal isn't the issue but rather, unwanted foreign particles might have entered the pump, that can get lodged when the pressure increases. A thorough cleaning could potentially solve the problem.
It sounds like you've already tried a thorough troubleshooting process, which is great. One potential issue could be related to the pump bearings. Misalignment or wear and tear on the bearings could potentially lead to mechanical seal leakage and the jamming issue. Another possibility could be related to the pressurized red oil. It could be that the oil viscosity is either too high or has been compromised by contaminants, which could lead to increased friction and subsequent issues. Lastly, incorrect installation and torqueing of the seal can cause similar problems even with the vendor’s oversight. You might want to double-check these aspects.
It sounds like you're dealing with a frustrating situation! Have you considered checking the lubrication in the bearing housing and confirming that the oil supply is consistent and clean? Sometimes, contamination in the red oil or an improper fill level can contribute to the seals not functioning as they should. Additionally, make sure to inspect the alignment of the pump and its motor; misalignment can lead to additional strain on the seals. It might also be worth reviewing the operating parameters to see if anything has changed in the system that could be affecting seal performance. Hope you find a solution soon!
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Answer: Answer: The issue could be related to the seal assembly, pressurization process, or other operational factors affecting the pump's performance.
Answer: Answer: Axial movement can be checked by observing the movement of the pump shaft when pressurized and ensuring there is no excessive play or misalignment.
Answer: Answer: The seal assembly was redone in the presence of the seal vendor, but unfortunately, the jamming issue persisted despite this intervention.
Answer: Answer: Possible solutions could involve revisiting the seal assembly procedure, examining the pressurization system, or investigating other underlying issues affecting the pump's performance.
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