Plymon Flashcards
How are predictive programs justtfied?
Cost savings due to machine uptime and reduced secondary failures.
What is considered a measure of vibration severity?
Amplitude: Displacement (mils)
Velocity (ips)
Acceleration (g’s)
How are faults identified when viewing vibration data?
Frequency:
Hz-Cycles per second
CPM- cycles per minute
Orders- normalized to 1xRPM
What is a Time Waveform?
A plot of amplitude verses time.
What is a spectrum?
A plot of amplitude verses frequency.
What is a trend plot?
A plot of vibration amplitude over time (commonly the overall value)
How could motions in a time wave form be described?
Periodic, Impacting, Harmonic, Random, Pulsating (beat frequency), Ring down (impact test), Modulation,etc.
In most predictive maintenance programs on industrial machines. What measure is most often used to evaluate vibration?
Velocity, as it is more sensitive to vibration amplitudes across the frequency range of common machines.
How are the Period of vibration and the frequency of vibration related?
They are reciprocals of each other.
1/Period in seconds is equal to the frequency in cycles per second.
1/ frequency in cycles per second equals the period in seconds.
“Ten cycles per second” is equal to what frequency unit.
10 Hertz (Hz)
Convert 10 Hz (cycles per second) to CPM (cycles per minute)
10Hz x 60 (seconds/ minute)=600CPM
If the machine speed is 3600 rpm and the vibration is occurring at 7200 CPM, What order would the vibration be considered.
2 Orders- 7200(vibration) /3,600(1x RPM)=2
What components are required to acquire phase data on a machine?
Vibration transducer and a trigger (speed reference) or 2 vibration transducers acquiring data simultaneously.
Rank the transducer mounting methods from lowest to highest.
Hand probe, 2-rail magnet, flat magnet, epoxy mount, stud mount.
What transducer mounting method is accepted as the most convenient for normal vibration data collection.
Magnet mount.
What transducer mounting method is best for high frequency analysis.
Stud mount.
How many degrees are in one complete cycle of vibration?
360°
Which plot of data would best provide evidence that the period of vibration were changing.
The time waveform.
What is the most important frequency for diagnosing machine vibration?
Machine operating speed.
What parameters allow for the calculation of gear meshing frequency?
Operating speed and the number of gear teeth.
What parameters allow for the calculation of blade passing frequency?
Operating speed and the number of blades on the wheel.
What parameters allow for the calculation of Vane passing frequency?
Operating speed and the number of vanes on the impeller.
What parameters allow for the calculation of rolling element bearing frequencies.
•Operating speed,
•Pitch diameter,
•ball diameter
•contact angle,
•# Of rolling elements.
Note: There are 3 rotating components. Inner race(BPFI), rolling elements(BSF) cage (FTF)
What parameters allow for the calculation of natural frequency.
Stiffness
mass
What parameters allow for the calculation of belt frequency?
Pulley Diameter
Pulley RPM
Belt length
Where should vibration data be collected on the machine?
As close to the bearing as possible in the horizontal, vertical, and axial locations.
A velocity transducer collects signals in units of?
mV/ips, Native Velocity Units
An Eddy current or proximity probe collects signals in units of?
mV/Mil, Native Units of Displacement (mils)
Utilizing phase analysis is very useful in vibration testing when?
Machines with very similar vibrations spectral responses are observed at 1x rpm.
This would be the most logical next step in the analysis process when elevated vibration is occurring at 1x rpm.
What type of faults generate vibration considered “non synchronous”?
Rolling element bearings
Belts
Electrical in Nature (2x line frequency)
Natural Frequencies
What type of faults generate vibration considered “synchronous”
Unbalanced
Eccentricity
Mechanical looseness (type A)
What type of faults generate vibration at integer multiples of 1X operating speed?
Gear mesh
Blade pass
Rotor bar
What type of fault generates vibration considered “sub synchronous”?
Rub
Belt Frequency
Fundamental Train Frequency (cage)
Gear Assembly Phase.
What type of faults generate vibration in the “radial direction”?
Unbalance
Offset (parallel) misalignment
Eccentricity
Looseness (type A)
What type of faults generate vibration in the axial direction?
•Bent shaft
•Angular shaft misalinement
•Cocked Bearing
•Sheave Misalignment
•Overhung fan unbalance
•Bearing faults from bearings with contact angle.
What does ISO stand for?
International Organization for Standardization.
What does ASNT stand for?
American Society for Non-Destructive Testing.
When conducting phase analysis, what is considered “In-phase”?
Signals have a “0 degree” phase shift between measures.
When conducting vibration analysis, What type of fault would generate 1x RPM with several multiples (harmonics) of that frequency?
Mechanical looseness (Type C)
When conducting vibration analysis on an electric motor, what type of fault would generate 2x line frequency (120Hz or 7,200 CPM)?
Electrical faults such as an Air Gap Vibration.
When conducting vibration analysis on a gearbox, what unique frequencies are of interest related to the gear sets?
Gear Mesh
2x gear mesh
3x gear mesh
What is a predictive maintenance program?
Making decisions related to maintenance based on data and alarms acquired with technologies such as: Vibration Analysis, Infrared Thermography, Motor Circuit Evaluation, Motor Current Signature Analysis, Ultrasonics, and/or Oil Analysis.
What does Predictive mean in a Predictive Maintenance Program?
The ability to identify failures and make decisions in advance, such as procure parts, schedule labor, and perform repairs or replacements during scheduled equipment downtime.
