Greetings, I am reaching out regarding a concern with one of our multi-stage boiler feed water pumps. During the assembly process, we noticed 3-4 scratch marks at the NDE seal seating area. While the runout at these points is within acceptable limits, I am concerned about the potential long-term effects on the pump's performance. I am wondering how quickly these scratches will deteriorate and if we will need to replace the shaft at the next available opportunity. Additionally, I am concerned about the possibility of premature seal failure due to these scratches. The NDE seal has a sleeve, but I am unsure if it can adequately protect the shaft surface from failure.
Jatan, providing more detailed descriptions, including photos and sketches, would greatly assist us. It is important to specify the location, depth, and number of scratches, as well as the seal face diameter and shaft speed. It would be beneficial to know the total runout at the seal face and the wear rings' runout and clearance. Additionally, clarity on the purpose of the sleeve in protecting the shaft is needed. Addressing the scratches promptly is crucial to prevent issues with other parts. Have you considered polishing and deburring the scratched area? Understanding the cause of the scratches is also important.
Hey Vee, this shaft is brand new, so scratches may have occurred during the assembly process of wear rings and impellers, or while taking run out measurements. The run out on the wear area measures 0.03 mm, well within design limits. The machine operates at a speed of 2970 rpm. These marks are not grooves, but rather scratch marks similar to those made by a scriber on a metal surface. The seal diameter is unknown to me, as this is a cartridge seal with an o-ring between the sleeve and shaft. All seals, bearings, and o-rings are new. I will update you with a photograph soon.
Thank you, Jatan. I have organized my questions in bullet points for clarity, and it would be greatly appreciated if you could address each question by its corresponding number. To reiterate the unanswered questions: 1. Can you specify the location and quantity of scratches on the surface? 2. What is the diameter of the seal face? Additionally, could you provide the sleeve diameter for reference? 4. What is the precise total runout measurement at the seal face? 5. I require further clarification regarding your inquiry about protecting the shaft - specifically, what potential threats are you looking to prevent?
If you possess the necessary skills, it would be beneficial to analyze the impact of scratches on the data collected. This can be done by examining the raw signal in the time domain at a slow roll speed, typically around 200 to 300 RPM. By using proximity probes and the right instrumentation, you can observe the effects of scratches on the signal. Additionally, utilizing an oscilloscope may help in interpreting the data if you have the expertise. It is important to note that attempting to remove scratches with a file wrapped in emery cloth could potentially create flat spots on the shaft, which are harder to detect in the data. Identifying scratches is relatively straightforward, while flat spots pose a greater challenge. - John from PA
After examining the mechanical seal area at the non-drive end (NDE), it was found that there are 3-4 scratches where the rotating face sits. These scratches do not come into contact with the O-rings of the seal. The seal diameter is 75mm while the sleeve diameter is 55mm. The actual runout on the seal face area is measured at 0.03mm. My concern is whether the sleeve will cover the scratch area and prevent friction on the shaft during normal operation. It is important to note that this pump does not have an online condition monitoring system and the shaft is new. The seal faces installed are also new and arranged in a cartridge setup. I hope this addresses your query. If you require further information or data, please feel free to reach out.
Hi there, the NDE seal scratches are definitely something to monitor closely. In my experience, while the runout may be within acceptable limits for now, these scratches could potentially lead to a drop in efficiency and even cause parts to fail prematurely, especially if they lead to uneven wear on your seal. The sleeve should provide some protection, but it's not infallible. I'd suggest running the pump under close inspection and documenting any changes. If there are signs of accelerated wear or damage, replacement may be necessary. In the meantime, it may be helpful to revisit your assembly process to prevent similar issues in the future.
That's definitely a valid concern you've raised. Although the scratches are within acceptable limits currently, you're correct to worry about potential long-term wear. Over time, these scratches could become breeding grounds for corrosion, increasing the rate of wear. This might lead to premature seal failure, as you mentioned. While the sleeve does provide protection, it may not be sufficient depending on the operating conditions and the severity of the scratches. If the pump is critical in your operation, I'd recommend considering a replacement at the next convenient opportunity to avoid future downtime. You might also want to inspect your assembly process to see if there's a way to prevent these scratches in the future.
While scratches on the NDE seal seating area seem concerning, they may not necessarily lead to immediate severe issues if the runout remains within specified limits. However, over time, these scratches could indeed increase the likelihood of wear and tear, potentially affecting the pump's overall performance. Continuous monitoring can help identify any degradation early on. Simultaneously, it might not be a bad idea to order a replacement shaft in advance to expedite repairs if necessary. The sleeve on your NDE seal should offer an additional layer of protection, but its effectiveness might depend on the severity and exact location of these scratches. You might want to consider consulting an expert in this particular area for a more accurate assessment of the situation.
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Answer: Answer: Scratches on the shaft can lead to concerns about the pump's performance and the possibility of premature seal failure. They may deteriorate over time, potentially requiring shaft replacement.
Answer: Answer: The rate of deterioration of scratches on the shaft can vary. Monitoring the performance of the pump and the severity of the scratches will help determine if and when the shaft needs to be replaced.
Answer: Answer: While the sleeve on the NDE seal provides some protection, concerns about potential seal failure due to scratches should be addressed through careful monitoring and potentially considering shaft replacement if necessary.
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