# Bearing Severity Fault Evaluation Using Contour Maps--Case Study
## 3 Results
### Diagnosis of Failure Levels for 500 rpm at Different Filter Bands  
As previously stated, given the inconvenience in the diagnosis of level 1 and 2 failures, a study was carried out to analyse the influence of the filtering band on the diagnosis using contour maps. Three filtering bands are studied in the following sections.  
3.3.1 Diagnosis for a Level 2 Fault in the Frequency Band of 0.2-1.8 \(\times\) 10\({}^{3}\) Hz  
As Figure 20 shows, lowering the filter band is not an option when diagnosing a fault using contour maps. This is due to the presence of a large amount of noise, which distorts the analysis frequencies.  
Figure 20: Diagnosis of a level 2 fault record (at 500 rpm) in the analysis band 0.2–1.8 \(\times\) 10\({}^{3}\) Hz: (**a**) Spectrum envelope of record; and (**b**) representation of significant points of the spectrum on the contour map.  
3.3.2. Diagnosis for a Level 2 Fault in the Frequency Band of 6.1-9.2 \(\times\) 10\({}^{3}\) Hz  
Figure 21a shows an obvious improvement in noise, where the amplitude of the fault-associated frequency (BPFO) is clearly significant, while the BSF frequency is overshadowed by the noise. This results in a higher concentration of the analysis data in the case study in the contour diagram, as can be seen in Figure 21b.  
Figure 21: Diagnosis of a level 2 fault record (at 500 rpm) in the analysis band 6.1–9.2 \(\times\) 10\({}^{3}\) Hz: **(a)** Recording envelope spectrum; and **(b)** representation of significant points of the spectrum on the contour map.  
3.3.3. Diagnosis for a Level 2 Fault in the Frequency Band of 9.2-12.8 \(\times\) 10\({}^{3}\) Hz  
In this case, the noise increased as the filter frequency band increased, as shown in Figure 22a. This caused problems in the diagnosis of the registry, which can be seen from Figure 22b. However, this increase in noise was associated with the characteristics of the accelerometer used, as it has a response frequency of up to 10 kHz.  
Figure 22: Diagnostic level 2 fault record (at 500 rpm) in the 9.2-12.8 \(\times\) 10\({}^{3}\) Hz analysis band: (**a**) Record envelope spectrum; and (**b**) representation of significant points of the spectrum on the contour map.  
Diagnosis for a Level 2 Fault at 200 and 350 rpm (Frequency Band of 1.8-6.1 \(\times\) 10\({}^{3}\) Hz)  
This section analyses the influence of the rotation speed in the fault diagnosis, specifically for fault level 2, given the inconveniences observed in the analysis at 500 rpm. In both cases, the concentration of the analysis points was associated with the level of failure under study. However, at 200 rpm, there was a higher concentration of points in the fundamental fault frequency; see Figure 23a. On the other hand, the record at 350 rpm--as shown in Figure 23b--presented a behaviour similar to that at 500 rpm, where there was dispersion in the analysis points; however, for this case, although dispersed, they were closer to the studied failure level.  
Figure 23: Diagnosis of a level 2 fault record, band filtered at 1.8–6.1 \(\times\) 10\({}^{3}\) Hz. Contour maps for diagnosis at: (**a**) 200 rpm; and (**b**) 350 rpm.