I am seeking insights on the potential causes behind this issue. Through my initial investigation, I have ruled out excessive speed and significant heat as factors. Despite experiencing noticeable vibrations, it did not result in a catastrophic failure. The fan blades are substantial at nearly 3/8" thick, indicating a high-quality and durable construction. The fan's maximum speed is 1480 rpm, aligning with its intended design. This particular fan serves as the exhaust for a cooling chamber in a furnace, with the air being warm but not excessively hot to induce warping. Do you have any suggestions on what may have led to this outcome?
Please find the attached document which may provide assistance. The document is titled "Overhung Fans.pdf" and is 9.64 MB in size. Thank you.
Nick, I'm curious if this fan has hollow foil blades with weep holes towards the center like our RTO fans. If these weep holes get blocked, it can lead to increased vibration and potentially cause warping in the fan wheel. This could be a result of uneven heat dissipation and imbalance. To prevent issues, we conduct NDT testing annually on our larger fan wheels to check for cracked welds, which can also lead to warping if not fixed promptly. These are just some insights based on my experiences. I hope this information is helpful for you.
Thank you for your response, CDTuttle. These blades are sturdy and durable. Based on information gathered from reputable fan manufacturers, it is believed that the damage occurred due to the blades spinning at a speed beyond their intended design. While I lack concrete proof to confirm this theory, I also lack evidence to debunk it. Therefore, I will defer to the expertise of industry professionals in this matter.
Feedback from my network members: 1) I had a similar experience a few years ago where a rebuilt motor was installed without proper attention to detail. The motor was rewound to 1800 rpm instead of the required 1500 rpm, leading to restricted flow and excess back pressure. This, combined with product build-up on the discharge side and incorrect motor overload protection, ultimately caused issues with the fan itself. - Joseph B. Kenemore, Engineering and Maintenance Management Professional 2) Recognizing the indicators of a boiler backfire, especially when dealing with a Boiler Forced Draft fan, is crucial. - Mahesh Narwankar, FPSO Maintenance Superintendent
Thank you for the valuable feedback. I will promptly review the RPM levels to ensure we are within the optimal range for performance.
The vibration you're experiencing might have something to do with an imbalance in the fan. Even though the blades are thick, issues can still occur if one or more of them is slightly misaligned or weighted differently. This could happen due to manufacturing flaws, or perhaps even wear and tear over time. The vibration might not have caused a catastrophic failure yet, but it's certainly something that shouldn't be ignored as it could cause issues in the long run, like bearing failure. I'd recommend checking the balance of the blades. If you can't find anything visibly wrong, you might want to consider calling in a professional to inspect and balance it for you. It's always better to be safe than sorry!
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Answer: - Possible causes could include improper fan installation, misalignment, imbalance, foreign object damage, or material fatigue.
Answer: - Excessive speed can be ruled out by verifying that the fan's maximum speed aligns with its intended design. Heat may not be a factor if the air being exhausted is warm but not excessively hot to induce warping.
Answer: - Vibrations can lead to damage over time, even if catastrophic failure does not occur immediately. To mitigate vibrations, ensure proper fan mounting and alignment, and regularly inspect for any signs of imbalance.
Answer: - Regular maintenance and inspection of the fan, ensuring proper installation and alignment, addressing any vibration issues promptly, and monitoring for any signs of wear or fatigue in the fan blades can help prevent damage in the future.
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