SPM SC Presentation - Vibrationvibration.org/Presentation/Dec 2008/SPM_SC_Presentation.pdf51 dbm dbi...
Transcript of SPM SC Presentation - Vibrationvibration.org/Presentation/Dec 2008/SPM_SC_Presentation.pdf51 dbm dbi...
Shock Pulses
0 5000 1.104 1.5.104 2.104 2.5.104 3.104 3.5.104 4.104
0
0.05
Hz
UnbalancePeaks around the resonant frequency
Resonance Frequency
Shock Pulse Transducer
n
0 100 200 300 400 500 600 700 800 900 10000
0.2
0.4
0.6
0 0.005 0.01 0.015 0.02 0.025 0.03 0.0352
0
2
Bearing damage Unbalance
Unbalance
Bearing damage
Hz
Trancients Resonance
0 0.005 0.01 0.015 0.02 0.025 0.03 0.0352
0
2
UnbalancePeaks around the resonans frequency
Band pass filter
Enveloping at a Resonance Frequency
Peaks around the resonant frequency
0 5000 1 104
1.5 104
2 104
2.5 104
3 104
3.5 104
4 104
0
0.05
Hz
0.1
0
0.1
Signal after band pass filter
0.1 After rectifying
0
01. After enveloping
Peak detection
0 0.005 0.01 0.015 0.02 0.025 0.03 0.0352
0
2
Bearing damage
Bearing damage
0
0.1
II. Frequency domain
0
0.1
dBm
dBcHz
I. Time domain (SPM)
0
0.1
The dBc value is effected by the lubrication condition in a bearing. It is commonly referred to as the background noise or the carpet noise of a bearing. The dBc value is calculated by sampling the incoming signal about a 1000/sec an average of all the lower Shock Pulses.
dBc
dBc
Full film lubrication
Partial lubrication
Boundary lubrication
Viscosity
Lubricant type
Temperature
Lubricant supply
Static and dynamic load
Preload Alignment Properly sized shaft and housing fits
Geometric quality of bearing
Total load Rolling velocity
Contaminants in Lubricant film
Surface finish Cleanliness
Things that effect the Lubricant film
thickness
The dBm value indicates the bearing operating condition once a measurement is completed. The dBm is commonly referred to as the Max valueOn the Infinity, the LED s and the color coded dots to the left of the measuring results indicate the operating condition.
dBc
dBm
The dBm value is calculated by sampling the incoming signal approximately 50/ sec an average of all the stronger Shock Pulses.
dBm
dBc
SPM Evaluation Scale
The dBi value is calculated once
the RPM and Shaft Diameter
have been input into the instrument or
software.Normalized measuring scale: dBsv = dBn + dBi
-9
dBsv 100
33 dbc
51 dbm
dbi 15
36 dbm
18 dbc
dBn 60
0
This becomes the starting
point for the 0 60 Green -
Yellow - Red scale.
Time
SPM recommends changing thebearing when dBm reaches 55
Red - Bad (dBm 35 and more)Yellow - Caution (dBm 21 to 34)Green - Good (dBm up to 20)
Bearing Operating Condition:
1 2 3
Small delta with elevated dBm/dBc readings typically indicate lubrication problems
Large delta (15 or >) with elevated dBm/dBc readings indicate possible bearing damage or other mechanical problems
Low dBm/dBc readings with small delta indicates a good bearing
Bearing Lubricated because dbc reading increased it also drove up the dbm.
SPM dbm/ dbc trend graphBearing replaced
Signal Source?
Is the Red or Yellow SPM Reading from the bearing or outside source?
SPM Spectrum used to confirm bearing and lubrication concerns
Add bearing coefficients in software to
utilize Bearing Symptom feature
SPM Spectrum with Bearing Symptom in software
Bearing Symptom
matches up with FTF in
this example confirming
bearing damage.