Signal processing as the best method of failure prevention in rotary machinery

If you’ve ever had a part break in your car you know how frustrating it is to be on the side of the road in the middle of nowhere waiting for help to come. When it comes to machinery, every component has its service life and that means sooner or later you have to replace parts to make everything run like it should. If your business is dependent on the smooth operation of rotary machinery, we have the thing for you. The new Vidisy platform is the only solution due to its ability to process the minutest changes in bearings. With Vidisy, your business will never suffer downtime, due to unexpected maintenance again. You have the parts, the proper repair personnel available when it’s convenient for you.

The Vidisy platform in a nutshell

Similar to the prevention of diseases and ailments in the medical world, Vidisy is a real innovation for engines dependent on rolling bearings. As opposed to hooking up a cable to see which part has failed, Vidisy can continuously monitor and diagnose faulty parts. The core of Vidisy is a powerful and precise signal processing unit which trumps all other systems, rendering them next to obsolete.


Every part in a machine has a certain vibration, because friction is impossible to avoid. With time, a part’s integrity can start to compromise the whole machine. Vidisy aims to detect macro and micro defects in a bearing, to warn operators, another part and the proper repair personnel needs to be scheduled.


In a nutshell, it’s a very sophisticated early warning system, and also a very precise diagnostic tool. It will give you the confidence and power to run your business the way you want it to be run. No more waiting on parts and proper repair personnel. Chaos will cost you cash.

Why choose Vidisy over others?

There are dozens of other defect detection systems on the market, but they simply fall short when compared with Vidisy. The new approach, meticulously developed by scientists and experts in the field, is unique because it can pinpoint the location of a future malfunction months in advance.

 

Related: A signal processing app Easy Sig Pro roundup

 

Why would this be helpful for a business owner or manager? When something breaks, you have to stop production, which means you lose money. Your workers have to stop too, which is frustrating and can affect morale, especially if they’re under strict time constraints. Not only that, but you may not have foreseen the need to replace a certain part, meaning you’ll have to special order it from who knows where, and settle for what you can get at the time. That takes time, and time is precious when halting the manufacturing process bites into your company’s profits. Save time, money, morale, and have peace of mind with Vidisy. Can you afford to wait another day?

 

 In the second part of our article we will show you a recent investigation that highlights just how well the Vidisy approach works on the example of vibrations from healthy and faulty bearings 

 

minion

Technical characteristics of the subject:

  • Electric power - 30 kW.
  • Frequency of rotation - 3630 rpm.
  • Mechanism class - II (see Appendix A).

Defective bearing assembly (outer ring defect)[1]
     Vibration parameters:

  • Root mean square values (RMS): 9.7 mm/s;
  • Signal-noise ratio: 4:1;
  • Dmin / Dmax ratio: 0.03.

Root mean square of vibration exceeds the normal figure for the observed mechanism (see Appendix A). The signal contains a powerful deterministic component.
Fragment of vibration signal realization is shown in Fig. 1. This figure clearly shows that the vibrational signal contains powerful impacts caused by the interaction of rolling elements with a defect present on the bearing race (Fig. 1).

 

Vibration diagnostic

Figure 1. Fragment of vibration signal realization

 

Correlation function of the vibration signal

Fig. 2. Correlation function of the vibration signal

 

Correlation function and power spectral density of the vibration signal are shown on Fig. 2 and Fig. 3, respectively. The tail of the correlation function contains strong impacts at a frequency corresponding to the speed of shaft rotation (Fig. 2). This indicates collision of moving parts and fixed parts in the mechanism (collision of rotary parts with defect).

 

Power spectral density of the vibration signal

Fig. 3. Power spectral density of the vibration signal

 

In the spectrum of the vibration signal, a main harmonic component corresponding to the frequency of shaft rotation and multiples of it are present (Fig. 3).
The stochastic component of the vibration signal contains a powerful modulation of the main harmonic component by stationary random processes. The variance of the vibration signal stochastic part is shown in Fig. 4.

The variance of the vibration signal stochastic part

Fig. 4. The variance of the vibration signal stochastic part

 

The variance graph clearly shows that there are powerful emissions during shaft rotation.

MinionConclusion: The bearing is in critical condition and needs to be replaced.

Working bearing assembly
      Vibration parameters:

  • Root mean square values (RMS): 2.4 mm/s;
  • Signal-noise ratio: 10:1;
  • Dmin / Dmax ratio: 0.92.

Root mean square value of vibration does not exceed the established normal figure for this mechanism (see Appendix A). The signal contains a powerful deterministic component.
Vibration signal realization is shown in Fig. 5. From the figure clearly shows that there are oscillations in the signal corresponding to the shaft rotation (Fig. 5). This figure clearly shows that the signal contains oscillations that correspond to shaft rotation (Fig. 5).
 

Fragment of vibration signal realization

Fig. 5. Fragment of vibration signal realization

 

Correlation function of the vibration signal

Fig. 6. Correlation function of the vibration signal

 

Correlation functions and power spectral density of the vibration signal are shown in Fig. 6 and Fig. 7, respectively. The tail of the correlation function of the vibration signal shows closed oscillations (Fig. 6) and has fluctuations characteristic of shaft rotation.


The spectrum of the vibration signal shows a powerful main harmonic component corresponding to the frequency of shaft rotation and multiple harmonics (Fig. 7).

 

The spectral power density of the vibration signa

Fig. 7. The spectral power density of the vibration signal

 

The stochastic component of the vibration signal did not contain modulations of main harmonic component by stationary random processes. Variance of the stochastic components of the vibration signals are shown in Fig. 8.

 

 Variance of the stochastic component of the vibration signal

Fig. 8. Variance of the stochastic component of the vibration signal

 

The dispersion graph is almost a perfect circle, meaning the stochastic component of the vibration signal is stationary.
 

minionConclusion: The condition of the bearing is satisfactory. 

 

Spectral and correlation analysis of vibration signals are somewhat informative if a strong stochastic component is present (noisy signal). For these cases a number of methods have been developed to separate deterministic and stochastic signal components and to analyze each of them. Analysis of the deterministic component allows one to detect such mechanism faults as defects in systems (imbalance, skewed rings, size problems, oil viscosity problems, etc.), and analysis of the stochastic component allows to detect local defects in rolling elements in the earliest stage.

[1] analysis of the vertical component of the vibration signal

Appendix A.
Mechanism classes and normal ranges for vibrations (ISO 10816)

 

Classification of mechanisms and norms of vibration.

Fig. A. Classification of mechanisms and norms of vibration.
 

Class I. Some of the motor parts and mechanisms are connected with the machine and work as they should (standard motors up to 15 kW are typical examples of this class).

Class II. Mechanisms with average power (typical motors with power ranging from 15 to 875 kW) without special foundations, rigid-mounted motors or mechanisms (300 kW) on special foundations.

Class III. Powerful primary motors and other mechanisms with rotating elements mounted on massive foundations with relative difficulty in measuring vibrations.

Class IV. Powerful primary motors and other mechanisms with rotary elements mounted on massive foundations with relative ease in measuring vibrations (turbogenerators, gas turbines with an output of over 10 MW).

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