Dear Forum Members, Good afternoon. I am seeking information on how to calculate the blade passing frequency for NASH Vacuum Pumps, which have two rotors with different numbers of blades (12 and 16). Your assistance on this matter would be greatly appreciated. Best regards, Jorge Luis
Hello Jorge, when analyzing your spectrum, you should observe peaks at 12x and 16x when displayed in orders with the correct shaft speed settings. The software will assist you in making these calculations. Additionally, you may notice rotational sidebands at 1x, indicating that the spectral speed aligns with the actual shaft speed. Most monitoring software can display in orders, allowing us to normalize speed by looking at multiples of the shaft speed. This is important because many issues in condition monitoring are related to multiples of shaft speed. Kind regards, Vibe Rater Dear Forum Members, I have a question regarding the vibrational monitoring of NASH Vacuum Pumps. These pumps have two rotors on the drive shaft, one with 12 blades and the other with 16 blades. How would the blade passing frequency be calculated in this case? Best wishes for success, Jorge Luis
Jorge, The Nash vacuum pump likely features a dual rotor scroll design, with one drive rotor containing 12 vanes and the other driven rotor containing 16 vanes that mesh together. In this configuration, there will be a single vane mesh frequency at 12xDriveRotorRPM = 16xDrivenRotorRPM. High vibration levels at the mesh frequency and its harmonics are common in these machines. Additionally, vibration at each rotor RPM may also be present. For a visual representation, refer to the Nash dual rotor vacuum pump parts diagram. Vibration analysis tools can help identify peaks at 12x and 16x orders in the spectrum, with software assisting in calculating these values accurately. Monitoring vibration in orders helps normalize speed and detect faults related to shaft speed multiples. Understanding and analyzing these frequencies is key to effective condition monitoring practices. Best regards, Gene ------------------------------ Eugene Vogel ------------------------------
Hello Eugene, I've primarily worked in an industry where Nash vacuum pumps utilize a single shaft. I tried to imagine how one end of a shaft could have 16 vanes while another part had 12 vanes. Therefore, I concur that the design likely involves 2 shafts, with the vane pass frequency in (Hz) being the same. When normalized to their respective shaft speeds, it would be 16x and 12x. I always make sure to set some points at each bearing with speeds corresponding to the respective shaft speeds. Regards. Vibration Monitoring of NASH Vacuum Pumps by Eugene Vogel: It is probable that the Nash vacuum pump features a dual rotor scroll design, with one drive rotor having 12 vanes and the other driven rotor with 16 vanes that mesh together. This design results in a single vane mesh frequency at 12x Drive Rotor RPM = 16x Driven Rotor RPM. Elevated vibration at mesh frequency and harmonics, as well as vibration at each of the rotor RPM, may be observed. Images of the Nash dual rotor vacuum pump parts diagram can be found through online search engines. When displayed in orders and with the correct shaft speed set or measured, you would see a 12x and 16x peak in the spectrum, with rotational sidebands at 1x indicating the spectral speed matches the actual shaft speed. Software can help in normalizing speed to multiples of shaft speed for analysis. The majority of faults and normal behaviors encountered in condition monitoring activities are typically related to integer or non-integer multiples of shaft speed. Regards.
Enhanced attention to design intricacies from Jorge would be beneficial. Regards. --- Vibrational Monitoring of NASH Vacuum Pumps Thank you, Eugene, for your insights. In my experience with Nash vacuum pumps, I have primarily dealt with models featuring a single shaft. Upon consideration, I pondered the possibility of one end of a shaft having 16 vanes while another part has 12 vanes. Consequently, I concur that the design likely involves two shafts, resulting in a uniform vane pass frequency (in Hz) for both shafts. Each point should be strategically placed at each bearing with point speeds aligned with the respective shaft speeds. Regards, Vibe Rater --- Vibrational Monitoring of NASH Vacuum Pumps Hello Jorge, When analyzing the spectrum in orders and accurately setting/measuring the shaft speed, peaks at 12x and 16x would be observable. The software simplifies these calculations for your convenience. These peaks may also exhibit rotational sidebands at 1x, serving as an additional check to ensure spectral speed matches the actual shaft speed. Many monitoring software tools offer the option to display in orders, facilitating the normalization of speed to multiples of shaft speed. It is crucial to note that a significant portion of abnormalities and typical behavior detected in regular condition monitoring activities often align with integer or non-integer multiples of shaft speed. Regards, Vibe Rater
Hello, I have included a diagram of a Vacuum Pump with a single shaft that houses two rotors. The first rotor (Pos. 3.1) features 16 blades, while the second rotor (Pos. 3.2) has 12 blades. If you have any questions, feel free to reach out. Best regards, Jorge Luis.
Hi Jorge Luis, To determine the blade passing frequency (BPF) for a NASH vacuum pump with two differently bladed rotors, you need to consider each rotor independently. The BPF is generally calculated as the rotational speed of the rotor (in revolutions per minute, or RPM) multiplied by the number of blades. So, for the 12-bladed rotor, you multiply its RPM by 12. Similarly for the 16-bladed one, multiply its RPM by 16. Remember to convert RPM to revolutions per second if necessary. The frequencies will likely differ, but both will contribute to the overall noise and performance of your pump. Best, [Your Name]
Hi Jorge, to calculate the blade passing frequency for your NASH Vacuum Pumps, you'll want to start with the formula: Blade Passing Frequency (BPF) = (RPM × Number of Blades) / 60. Since you have two rotors, you'll calculate the BPF for each one separately. Just make sure to convert RPM to revolutions per minute when plugging in your values. If you're unsure about the RPM, check the pump's specifications or operating manual, as that’s crucial for accuracy. Hope this helps!
Hi Jorge, calculating the blade passing frequency for your NASH vacuum pump is pretty straightforward! You can use the formula: BPF = (RPM * Number of Blades) / 60, where RPM is the speed at which your pump operates. Since you have two different rotors, you would calculate the BPF separately for both the 12-blade and 16-blade rotors. Just make sure your RPM is in a consistent unit, and you'll get the frequency in Hertz. Let me know if you need any more help!
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Answer: - The blade passing frequency is the rate at which the blades of a rotor pass a fixed point in a given time period. It is an important parameter in understanding the operation and performance of vacuum pumps.
Answer: - To calculate the blade passing frequency for NASH Vacuum Pumps with different rotors, you need to know the number of blades on each rotor. The formula is: Blade Passing Frequency = (Rotor Speed Number of Blades) / 60.
Answer: - To calculate the blade passing frequency, you will need to know the rotational speed of the rotors and the number of blades on each rotor. This information is essential for determining the frequency at which the blades pass a fixed point.
Answer: - Blade passing frequency is important because it affects the overall performance and efficiency of the vacuum pump. Understanding the blade passing frequency helps in optimizing the pump's operation and diagnosing any potential issues that may arise.
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