Vibration and Oil analysis Flashcards
What cpm is displacement used?
Below 600 cpm or 1000 rpm
What cpm is velocity used?
600-60,000 cpm
What cpm is acceleration used?
Anything above 60,000 cpm
What is phase?
The time relationship between 2 related events
What is synchronous vibration?
A frequency that is a whole multiple of the rotating speed
Ex.
1 x RPM
2 x RPM
What is non-synchronous vibration?
Frequencies that are not whole multiples of the rotating speed of the machine
What are sub-synchronous vibrations?
Frequencies that occur at less then the rotating speed of the machine
What is natural frequency?
The frequency in which an object or system naturally vibrates when a forcing function has been introduced
At what percent should you keep a machine out of its resonant frequency?
20%
What is frequency?
How often an event happens in a unit of time or in one cycle
Ex.
Cycles per second (cps , Hz)
Cycles per minute (cpm)
Orders
1 cps = 1 Hz = 60 cpm
What is amplitude?
Indicates how much a machine is vibrating.
The distance from the at rest position and indicates the magnitude of a measure signal
What is displacement?
The motion from one extreme of the motion to the other (peak to peak)
What are the 4 ways to mount transducers from best to okay?
Stud- Best
Magnet- Good
Probe- Fair
Or
Adhesive bond to a flat surface
What are the 3 mounting positions of a transducer?
Horizontal, vertical, axial
The transducer is only capable of picking up a vibration that is in line with the transducer
What are the characteristics of imbalance?
Identified by a frequency that is 1 x rpm
Amplitude of the vibration increases with the shaft speed
If the problem is imbalance, the phase is stable
Characteristics of shaft misalignment on a vibration signature?
Frequency is usually 1 x rpm but severe misalignment can be 2 or 3 x rpm
Axial vibration component is usually about 1/2 or more of the radial amplitude
Phase readings can be erratic
Vibration characteristics of gear problems?
Usually several times higher then
1 x rpm unless only one tooth is bad
Is a multiple of the number of teeth times the rpm of the shaft
Inner race bearing frequency?
Frequency= 0.60 x (number of rollers) x rpm
Outer racing bearing frequency?
Frequency= 0.40 x (number of rollers) x rpm
Oil whirl vibration characteristics?
Usually occurs at 45% to 50% of the shaft rotation
Mechanical looseness vibration characteristics?
Dominant vibration frequency of
2 x rpm
Vibrations at other frequencies such as 1/2 and
4 x rpm
Belt drive problem vibration frequencies?
Are a multiple of the machine speed, which are 1, 2, 3 or 4 times rpm of the belts
What are the 4 products of oil oxidation?
Gum
Varnish
Sludge
Acids
What are the particle counts in the ISO cleanliness standard?
4 microns
6 microns
14 microns
When talking about thermal imaging, what is emissivity?
The materials ability to emit thermal radiation
Where should you not have oil sample collection points in a system?
At dead pipe legs, after filters or separators
A thermal imaging camera produces an image called?
A thermogram
What does critical speed refer too?
The speed at witch a rotor will near its natural frequency.
It create a large increase in vibration and can damage the machine.
You should keep the machine 20% - 30% outside of a rotors critical speed
What type of transducer does not generate its own power?
Displacement transducers
What type of transducers generate there own power?
Velocity transducers
Acceleration transducers
