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  • 1.  Short interval / high frequency vibration analysis

    Posted 20 days ago

    I need some help understanding the newer technology being utilized in condition monitoring.  I am talking about the wireless sensors that are measuring vibration and temperature.  I haven't been in the market for a long time and my pervious experience is with route based and wired sensors.  I am being told, by salespeople, that these short interval/high frequency sensors do just as good as the old school route based sensors due to the frequency of the readings outweigh the "full revolution" readings.  I am having a hard time wrapping my head around snippets of vibration readings giving me enough data to analyze and determine even proactive maintenance.  Can anyone explain how not seeing a full revolution or more helps me evaluate a bearing?



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    Brian Hutchings
    Maintenance and Reliability Mgr
    ICP Group
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  • 2.  RE: Short interval / high frequency vibration analysis

    Posted 20 days ago

    Hi Brian,

    Bearing tones' early warning occurs at high frequency ( Frequency that can only picked up by ultrasound or high frequency accelerometers). if a shaft full rotation is 3600 rpm and has 12 bearing. if any of the bearing is damaged or the raceway has a tiny defect , it will emit a signal that will propagate at a very short rates before a full revolution. the term like BPFI, BPFO , Ball Pass frequency Inner or outer occur at frequency less than a full rotation. when you notice a high peak you can suspect an early warning of a bearing defect.



    ------------------------------
    Cheick Rouamba
    BSME-MS-CMRP
    Maintenance Manager
    Richmond, Tx
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    Original Message


  • 3.  RE: Short interval / high frequency vibration analysis

    Posted 20 days ago

    Other than a few specific applications where route-based data isn't practical (like waste tank pumps, where it's difficult to know exactly when they will be running), I haven't bought into wireless vibe monitoring yet. The cheap sensors just don't provide enough data to be useful. When a salesman tries to show me his version, I ask to see the waveform and spectrum. When he responds with a puzzled look, I am done with the conversation. The truly good sensors are still expensive enough that it costs me less to pay someone to do manual routes. It would take around $6 million to instrument all of my rotating equipment with wireless sensors. For much less than that I pay a group of technicians to lubricate everything and do ultrasound checks, collect and analyze vibration data, and do visual inspections of the equipment and surrounding areas. (Recently they turned in notifications for a damaged catwalk and a leaking pump seal. Wireless sensors will never catch those types of problems.)

    To address your question specifically, I am not familiar with the short interval sensors. In my recent Cat III class the instructor said you need at least five shaft revolutions to get a good, representative spectrum. I don't see how you can even get useful information with less than one revolution. Especially if you are interested in subsynchronous frequencies like bearing cage or belt pass or oil whirl. If an asset is so critical that you need data every few minutes or even every few hours, it should be hard-wired. If it's not that critical, but you still want data more than once a week, sure, put a wireless sensor on it and collect a good, detailed waveform and spectrum once a day. If once a week or once a month is often enough, put it on a manual route.

    I will relent a little and mention that there are some RMS-only vibe sensors that also report crest factor. A high crest factor suggests there is impacting, so you can respond by sending someone out to collect some real data for analysis. This may be a good option for a plant that doesn't have their own vibe techs. Use the wireless sensors to detect any potential problems, and hire a contractor to come in and diagnose them. (But I still think the plant would get more mileage out of training one of their own people how to use an ultrasound tool to detect bearing faults, and bring in a contract vibe tech occasionally to catch any low-order problems like imbalance and misalignment.)

    These are just my personal thoughts. I realize there are many other good ways to approach these topics.



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    Dale Nicholson, PE, CMRP, CRL
    Reliability Engineering Mgr
    Evonik Corp
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    Original Message


  • 4.  RE: Short interval / high frequency vibration analysis

    Posted 20 days ago

    From a practical field perspective, especially in large industrial shutdown environments like pulp and paper, my experience is that wireless condition monitoring still has some limitations depending on the application.

    In Brazil, we don't see widespread adoption in critical equipment yet, mainly due to cost-benefit considerations and reliability concerns. In many cases, even wireless sensors still depend on local power availability, and the robustness of the communication network becomes a key factor.

    Another challenge we observe is vendor dependency. Different manufacturers often use proprietary systems that don't communicate well with each other, which can create operational risks, especially during shutdowns or emergency situations where flexibility and fast replacement are critical.

    Regarding vibration analysis, I still see challenges in relying on short-interval or high-frequency snapshots alone, particularly when compared to full-route or continuous monitoring approaches. Capturing only partial data may not always provide enough resolution to confidently assess bearing conditions or predict failures in a proactive way.

    That said, I do believe wireless solutions can add value in non-critical assets or where traditional monitoring is not feasible. But for critical equipment, I still see wired or continuous monitoring systems as more reliable, at least in current industrial conditions.



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    Adilan Bittar
    Financial Director
    RAL Manutenção e Montagens LTDA
    ARACRUZ
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    Original Message


  • 5.  RE: Short interval / high frequency vibration analysis

    Posted 19 days ago
    Edited by Adrian Messer 19 days ago

    Hi Brian.  

    Great question and observations, and it's a reflection as to where the wireless vibration sensor market is right now.  There's a lot of "salespeople" in that space who don't have much technical experience, and it even shows in their marketing material and presentations.  I heard someone refer to the wireless sensor market as it's kind of like the wild west right now. : )

    It ultimately comes down the failure mode that you're looking for.  If a short interval/high frequency sensor can detect the failure mode that you're most concerned about, then it's not an issue.  If it doesn't, then exploration of a technology or sensor that will detect that failure mode should be done and implemented.  

    There can also be a trade-off between sensor-based and traditional route-based monitoring.  In a conversation that I had years ago with a customer, what it came down to for them was simply this, "do we want to know that there's a problem or do we want to know what the problem is?"  In your case, will the short interval/high frequency sensor provide you with just an alarm or actual diagnostic data?  

    Traditionally, it has been all about looking for repetition.  For example, an asset rotating at 300rpm would only need a 5 second reading to capture 5 complete revolutions (in principal, and for the sake of this discussion and understanding that there may be other considerations).  One 5 second reading per day still gives you a better chance at seeing changes in the vibration data than one reading per month (like traditional route-based data collection).  

    You'd also want to take into account having enough of a sampling rate to capture quick event failure modes.  So, you want to make sure that you're getting the right kind of data (resolution, sampling rate, frequency range, averaging, etc.). Of course, all of this affects the battery life of the sensor.  

    In conclusion, you need data which has enough resolution and frequency range to capture the failure mode that is of most importance to you. 

    Just some thoughts regarding your question, with some personal input on the wireless vibration sensor space, but when it's all said and done, knowledge is a key differentiator.  



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    Adrian Messer, CMRP, CRL
    US Operations Manager
    SDT Ultrasound Solutions
    adrian.messer@sdtultrasound.com
    (864)314-9898
    ------------------------------

    Original Message


  • 6.  RE: Short interval / high frequency vibration analysis

    Posted 19 days ago

    I can say honestly that wireless sensors have reached a point where they exceed the abilities of the first route-based data collectors I used. Of course, that was in the 1990's and things were different back then. Wireless sensors and online systems both offer higher "data density" (data more often). Route-based was always just a snapshot of what the machine was doing when the technician was collecting readings, so data density was limited to one reading every month or so.

    As far as high frequency data, it really depends on how the vendor is processing it. Remember that proven processing methods like demod, PeakVue and Spike Energy are all based on high frequency vibration energy. The advantage of using high frequency data is that is does not require a long sample window to capture the data. The downside is that sometimes this data can have a wide variation in amplitude and content when compared to a "properly windowed and averaged FFT capture".

    If you are trending unbalance, misalignment or bearing fundamental frequencies. Then a data sample from 3-5 rotations is going to give you a good picture, especially if you keep a low max frequency and have decent lines of resolution.

    I often see wireless sensor successfully integrated with route-based programs as they complement each other. Using the wireless sensor as an indicator rather than a diagnostic tool is a helpful approach initially. Treat a sensor alert as you would an operator making a complaint about a weird noise. Let it act as a trigger to send a vibration person to investigate.

    The folks collecting route data are the best equipped to confirm readings, diagnose issues and collect information for Planners. The are also likely collecting vibration data on perfectly normal machines - in my experience close to 90% of the route machines were normal. Using wireless sensors as a trigger can save them time to focus on machines that do have problems. Additionally, the route technicians will often identify other concerns in the area like safety issues or process anomalies.



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    Christopher Olsen
    Sr. EMR Technician
    CHA Consulting, Inc
    Fence WI
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    Original Message


  • 7.  RE: Short interval / high frequency vibration analysis

    Posted 17 days ago
    Edited by FRANCOIS VIVIAN KINGUE NJANJO 17 days ago

    Hi Brian,

    I think, your concern is absolutely valid. To be direct, short and frequent measurements do not replace a long acquisition in vibration analysis.

    The quality of a reliable diagnosis fundamentally depends on two key physical factors:

    - the duration of the signal

    - the number of cycles captured during the measurement.

    In fact, frequency resolution is directly related to the acquisition time:

    Delta f = 1/T

    In practical terms, this means that shorter signals result in poorer resolution. Peaks become broader and less precise, and important phenomena-especially modulation effects associated with bearing defects-become difficult or even impossible to identify.

    When it comes to bearings, a defect typically generates periodic impacts that are modulated by shaft rotation. To properly identify these signatures, you need:

    - multiple repeated cycles

    - a stable envelope signal

    - sufficient resolution to clearly distinguish characteristic frequencies (BPFO, BPFI, etc.) along with their sidebands.

    With short "snapshot" signals, you may detect an increase in high-frequency energy, but this is generally not enough to accurately characterize the type of defect.

    In practice, wireless sensors do not truly compensate for this limitation by improving signal quality. Instead, they adopt a different approach based on:

    - high measurement frequency

    - global indicators such as RMS, ...

    - and in some cases, AI-driven analytics to detect deviations

    In other words, the philosophy shifts from:
    "measuring better"
    to:
    "measuring more often to detect when something changes".

    However, there is a fundamental limitation. Increasing the frequency of measurements does not compensate for:

    - insufficient frequency resolution

    - lack of usable modulation information

    - loss of low-frequency content.

             In summary, the Wireless technology is highly effective for early anomaly detection, but it remains limited for detailed diagnosis.
    You gain responsiveness, but you lose diagnostic depth.

    Thank you all   ...

    -----------------------------
    FRANCOIS VIVIAN KINGUE NJANJO
    Mechanical engineer, Vibration Analyst
    Cegelec Cameroon / Perenco Rio Del Rey / Offshore
    Douala
    ------------------------------

    Original Message


  • 8.  RE: Short interval / high frequency vibration analysis

    Posted 16 days ago

    This is a really good way to put it, Francois.



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    Dale Nicholson, PE, CMRP, CRL
    Reliability Engineering Mgr
    Evonik Corp
    ------------------------------

    Original Message


  • 9.  RE: Short interval / high frequency vibration analysis

    Posted 12 days ago
    Thanks Dale,
    I appreciate the feedback.
    I think this really highlights the importance of clearly defining the role of each technology within a reliability program.

    Wireless sensors are excellent for expanding coverage and enabling early detection, but they don’t eliminate the need for deeper analysis when it comes to decision-making.

    In my view, the real challenge is making sure organizations don’t confuse detection capability with diagnostic capability — especially when maintenance actions and risk decisions are involved.

    Curious to hear how others are addressing this balance in their programs.


    ---------------------------------
    FRANCOIS KINGUE NJANJO
    Mechanical engineer, vibration analyst. (Oil&gas field)
    Cegelec Cameroon/ Perenco
    Douala
    ---------------------------------



    Original Message


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