We have encountered numerous failures in a vacuum pump application involving a C-mount motor/pump alignment and a Woods #9 SureFlex Coupling with EPDM inserts. Out of 4 similar pumps, only one continuously experiences issues such as stripped teeth or torn inserts. Despite low vibration levels with all vibration at 1X, no laser alignment can be performed due to limited space. To simplify changes, we have started using a two-piece coupling insert. Strobing the coupling reveals distortion, with the metal center retaining ring beginning to bend. Evaluating the coupling size, it appears borderline between #9 and #10, potentially causing the repeated failures. Other pumps with #9 couplings do not exhibit similar problems. Any suggestions on measurements or further steps to identify the issue with this specific pump would be appreciated. Kindly share your thoughts with Rich Wurzbach at rwurzbach@mrgcorp.com.
I'm interested to know if this vacuum operates efficiently under heavy loads and if it has the ability to rotate in reverse. Can you confirm if it is a liquid ring vacuum? The image is unclear, but it seems like the vacuum may be starting under excessive load.
Thank you, Stan, for responding. I have addressed the pictures. The load was verified by checking the ammeter readings on the motor leads, all of which showed consistent values. - Rich Wurzbach
I can see the hubs now. Are they worn out? I can see that they do not match. Is there any room for movement in the couplings, or do the halves push the insert tightly? The image appears distorted, possibly due to misalignment. Can you insert an indicator to check for proper alignment?
It is important to check the alignment of the dial indicator, as it can be a more reliable option than a laser. A C-fit does not guarantee proper alignment, so it's crucial to verify. If the vibration is high in the 1X frequency, this could indicate significant misalignment, whereas the 2X and 3X frequencies will diminish with radial misalignment.
The image at the bottom shows a strobed view of the coupling while in operation. When stationary, no distortion is visible. It was initially thought that torque could be the culprit, but alignment is also being considered as a potential factor. Despite very low levels of vibration, concerns about alignment persist due to limited space for a dial indicator within the tight C-mount bracket opening. Options being weighed include removing the bracket to inspect the fits on the motor, pump, and C-mount bracket. There are additional hold-down bolts on the rear motor feet, raising suspicions of soft-foot induced misalignment contributing to coupling issues. It's possible that a combination of alignment problems and a slightly undersized coupling may be at play. Your input and comments are welcome. – Rich Wurzbach
Hi Rich, it's indeed peculiar that only one of these pumps is repeatedly experiencing issues. You mentioned that you've observed signs of distortion on the coupling, which could hint at an underlying misalignment problem beyond the capabilities of a standard laser alignment procedure. Even though space is limited, I suggest you try a dial indicators setup for better accuracy in your alignment. Additionally, you might want to re-evaluate the load conditions specifically for this troubled pump because, even though it's similar to the others, operating conditions could potentially be different enough to cause consistent issues. Lastly, given the borderline size of the coupling, you might want to consider upscaling to a #10 as a preventive measure.
It appears you've done a great job in troubleshooting so far, Rich. One possibility could be either motor or pump axis inclinations, differing from the other setups. Even minor inclinations can lead to accumulated stress over time, as the EPDM element likely has to compensate for it, resulting in possible fatigue of the tooth. Perhaps consider checking alignment with a specialized dial indicator, if feasible given your space constraints. Another suggestion is to evaluate the operational and system conditions such as temperature, pressure, torque requirement, etc., just to rule out whether these are within the coupling’s specification. Hope this helps!
It sounds like you're dealing with a tricky situation! Since you're experiencing distortion in the coupling, it could be worthwhile to double-check not only the alignment but also the mounting surfaces for any irregularities that might not be immediately visible. Given the bending of the center retaining ring, perhaps a more robust coupling or even considering a flexible coupling type that could accommodate minor misalignments might help. Additionally, if possible, try measuring the actual spacing and condition of the motor mounts and other connected components to rule out any underlying issues. It might also be useful to consult the manufacturer’s specs on the couplings to ensure you're operating within their recommended tolerances. Good luck!
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Answer: The repeated failures could be due to potential issues such as improper sizing of the coupling, misalignment between the motor and pump, or distortion in the coupling components.
Answer: To address these issues, it is recommended to check the alignment between the motor and pump, ensure proper sizing of the coupling, and consider using a two-piece coupling insert for easier maintenance.
Answer: The distortion in the coupling could be caused by factors such as improper sizing of the coupling, excessive torque or misalignment, leading to stress on the components.
Answer: To determine the correct coupling size for the pump, it is advisable to conduct accurate measurements and compare them with the specifications provided by the manufacturer. Additionally, consulting with a technical expert or engineer may help in identifying the correct size for optimal performance.
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