Calculating Bearing Fault Frequency: A Guide Using CSI and Charlotte Formulas

Question:

Seeking information on the accuracy of bearing fault frequency calculation and the corresponding formula? Utilizing the formula from CSI and Charlotte, I aim to determine the frequency of faults in the Morgan NTM mill. Thank you for any insights or advice on this topic.

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Are you familiar with the type of bearing and its designation? I have discovered that the calculations provided by the CSI library can be helpful for diagnosing bearing issues, as most faults with bearings are asynchronous. For instance, if I am dealing with a 6300 series bearing, I know to inspect the area in the signature form between 3.3x and 7.5x for spikes in ball pass frequency. It becomes challenging when a calculated frequency or its multiple is close to a harmonic of the running speed. I have encountered instances where the frequency falls around 121 to 122Hz, appearing as 2x line frequency when resolution is not sufficient.

When accessing your CSI database, input a popular bearing number such as 6313, without specifying a manufacturer, and view the frequency results. You will find a comprehensive list of 6313 bearings from various OEMs in the database. By analyzing the BSF, FTF, BPFO, and BPFI values across different bearing OEMs, a consistent pattern emerges. Typically, BPFO is 3-5 times shaft speed, BPFI is 5-8 times shaft speed, FTF/cage is .4 times shaft speed, and BSF is slightly above 2 times shaft speed. However, outliers with different ball numbers do not adhere to this pattern. Repeat the process with a different bearing style like 22223, and you will observe similar multiplier trends among different OEMs. The sum of BPFO and BPFI multipliers should correspond to the number of balls/rollers in the bearing. Remember, this is a general rule of thumb to follow. - Dave

Bearing failure frequencies are typically determined based on the bearing's geometry, following established standards for bearing sizes. These frequencies, including inner race, outer race, cage, and ball frequencies, are crucial indicators of failure, especially in advanced stages. They are calculated using machine RPM (or CPM) values and the rotating shaft associated with the bearing. During the initial stages of failure, material tends to fracture and delaminate, leading to defects on the surfaces that can be detected by high frequency vibration equipment as 'metal to metal' contact. The progression of bearing failure often follows four stages, starting with increased metal to metal contact, followed by peaks surrounding bearing frequencies, a raised noise floor around the frequencies, and finally a drop in metal to metal contact value. In some cases, bearing issues manifest as harmonics of calculated values, such as in current signature analysis where it typically occurs at the 4th harmonic. If specific information is unavailable, bearings may exhibit non-integer multiples (or sub-multiples for cage frequencies) of the shaft RPM. Overall, bearing fault detection through vibration analysis is a highly reliable method. Howard W Penrose, Ph.D., CMRP at MotorDoc.com.

It sounds like you're on the right track using the CSI and Charlotte's formulas for bearing fault frequency calculation. However, keep in mind that the accuracy of your calculations will depend on several factors like the condition of the bearing, load, speed etc. If you haven't already, I would also suggest looking into ISO 15243 standard which outlines the process of failure mode identification in rolling bearings, fairly helpful in understanding bearing faults and their frequencies.

From my experience, bearing fault frequency calculations can be quite accurate if you're careful about considering all variables involved. The CSI and Charlotte formulas are generally reliable, but the real world is always a bit more complicated. Make sure you're accounting for factors like load on the bearing, lubrication condition, and even ambient temperature as these can impact the actual frequency of faults. Also, the type and brand of the bearing could alter the failure mode as well. It’s important to correlate your calculated data with actual physical conditions for the most accurate results. Good luck with your analyses on the Morgan NTM mill.

Bearing fault frequency calculations are indeed crucial for effective predictive maintenance. The generalized equation for bearing fault frequencies (BPFO, BPFI, FT) usually works well. However, you need to keep in mind that actual physical parameters like the contact angle and the bearing load can slightly tweak these frequencies. I suggest referring to bearing manufacturers' data or using specialized software from bearing manufacturers for a more accurate evaluation. CSI and Charlotte have a good reputation, but if you're focusing on the Morgan NTM mill, it may be beneficial to also consult directly with Morgan's technical resources. Hope that helps you along the path!

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Frequently Asked Questions (FAQ)

FAQ: FAQs:

Answer: 1. What is the significance of calculating bearing fault frequency in machinery maintenance? - Calculating bearing fault frequency helps in identifying potential issues in bearings and allows for timely maintenance to prevent costly breakdowns.

FAQ: 2. How accurate are the formulas provided by CSI and Charlotte for calculating bearing fault frequency?

Answer: - The formulas provided by CSI and Charlotte are widely used and trusted in the industry for accurately determining bearing fault frequencies.

FAQ: 3. Can calculating bearing fault frequency be beneficial for monitoring the health of bearings in the Morgan NTM mill?

Answer: - Yes, calculating bearing fault frequency in the Morgan NTM mill using the CSI and Charlotte formulas can provide valuable insights into the condition of the bearings and help in proactive maintenance planning.

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