Vibration Analysis Assignment 1-4 Flashcards
List 3 benefits of vibrations analysis?
- Down time reduced
- Machine destruction can be avoided
- Can be corrected
Identify 4 items of machine information needed to help with vibration analysis;
- Type of machine
- Machines location
- Machines speed (most critical)
- Bearing types and locations
- The date of data collection
- Coupling types and location
- The components (machines) with the line (turbines, generators, pumps, gearboxes)
- Equipment number
List 5 possible sources of vibration;
- Imbalance
- Misalignment
- Bearing damage
- Gear problems
- Cracked welds
- Resonance
What type of machine damage will oil analysis identify?
Contamination in the oil/lubricant, from metals in oil, water, oxidization, varnish, dirt, antifreeze, breakdown of oil.
True or False;
Temperature analysis requires direct contact with the machinery to be examined.
False - infrared thermometers can be used as its a non contact radiant energy detector. (Infrared Thermography)
What spectrum of light is detected when using thermography?
Infrared radiation
-detects the thermal radiation(emissivity) of an object.
Vibration is the movement of a body about its ___________ position,
Vibration is the movement of a body about its REFERENCE position.
A _____________ analysis is used to find the direct cause of the vibration.
A SIGNATURE analysis is used to find the direct cause of the vibration.
List 3 ways vibrations can transfer from one machine to an adjacent machine.
- Piping
- Floor
- Noise
By changing either the ______ or the __________ of an object, you change the vibration signature.
By changing either the MASS or the STIFFNESS of an object, you change the vibration signature.
List 3 terms used to describe the vibration sine wave;
- Frequency
- Amplitude
- Phase
FAP - haha
What vibration term identifies how often an event occurs in relation to a unit of time?
Frequency
If a cycle happens 60 times per minute, what is the CPS or Hertz?
1 CPS or 1 Hz
25Hz = ?
25 x 60 = 1500 CPM
1500 rpm = ?
1500/60 = 25 Hz
Orders are multiples of the __________ _________.
Orders are the multiples of the OPERATING SPEED.
*
True or False;
Displacement is the distance of movement from rest to the peak of travel.
False
- total movement above and below axis.
Displacement is measured in _______ for imperial and _________ for metric.
Displacement is measured in MILS(Peak to Peak for imperial and MICRONS (Peak to Peak) for metric.
Velocity is a unit of _________ over _________.
Velocity is a unit of DISPLACEMENT(how far it moves) over TIME.
When placed on a sine wave, the maximum velocity takes place on the _____________.
When placed on a sine wave, the maximum velocity takes place on the NEUTRAL AXIS.
Velocity readings are most consistent between _____ cpm and ___________ cpm.
Velocity readings are most consistent between 600 cpm and 60000(60K) cpm.
Acceleration is measured in _-_________.
Acceleration is measured in G-FORCES.
True or False;
Acceleration is best for slow frequencies.
False
- above 60K
Phase is a relationship between ______ related events and is measured in _________.
Phase is a relationship between TWO related events and is measured in DEGREES.
Define Natural Frequency;
Natural Frequency - The frequency at which an object or system naturally vibrates when a forcing function has been introduced.
True or False;
Resonant frequency is the desired frequency to run a machine at.
False
-destroys machines.
What is the safe distance from a natural frequency at which to run a machine?
20%
Define Harmonic;
A multiple or sub-multiple of the fundamental frequency.
Why is the baseline information important?
Used as a reference to the normal conditions of the machine.
Define Synchronous Vibration;
A frequency that is a whole multiple of the rotating speed(velocity) of the machine.
What is the purpose of severity charts?
A reference graph, indicates how smooth your vibration readings are.
Fast Fournier transform turns Amplitude versus time to Amplitude versus ____________.
Fast Fournier transform turns Amplitude versus time to Amplitude versus FREQUENCY.
What type of vibration measuring tool is permanently installed to watch a specific piece of equipment?
Vibration Monitors
What is the most important part of any vibration measurement system?
Transducer
What are the 3 basic categories of transducers?
- Displacement
- Velocity
- Acceleration
A non-contact eddy current displacement transducer is also called a _________ __________.
A non-contact eddy current displacement transducer is also called a PROXIMITY PROBE.
Why are proximity probes mounted permanently to the machine?
- missed this one in class, shoot me a message and I’ll fix.
For the eddy current transducer to work, the shaft must be a _____________.
For the eddy current transducer to work, the shaft must be a CONDUCTOR.
What type of transducer is made with a coil of wire and a permanent magnet?
Velocity transducer
*
What type of transducer is the most common?
Acceleration transducers
(Accelerometer)
What is produced when the piezoelectric material is squeezed?
- Electrical current proportional to force.
“a piezoelectric material, when strained or compressed by an external force, creates an electrical current proportional to force.
What are the 4 ways to mount the transducer?
- Stud (Best)
- Magnetic Pickup (Good)
- Hand held probe
- Shaft rider accessory
True or False
- A vertical mounted transducer can also be used to calculate data in the horizontal and axial plane?
False
“The transducer is only capable of picking up a vibration that is in line with the transducer. The transducer does not pickup vibrations at 90 degrees to the transducer.”
Strobe lights are used when the ________ _________ needs to be measured with the prominent frequency.
Strobe lights are used when the SHAFT SPEED(RPM OF MACHINE) needs to be measured with the prominent frequency.
What is a major concern when using a strobe light to determine rpm?
Errors, because the strobe can be at any multiple of shaft speed.
What does it mean to trend the data?
If readings are taken at the same locations, you can identify changes from previous data within the machine.
- a reference for changes in the machinery.
What is a very common source of vibration and is identified at 1X rpm?
Imbalance
When will imbalance produce a high axial reading?
Overhung rotor
True or false;
An increase in shaft speed will cause imbalance to produce a decrease in vibration amplitude.
False;
“The amplitude of the vibration also increases with the speed of the machine”
True or False;
Imbalance will have a large variation from a vertical to a horizontal reading.
False?
-not sure, if wrong, let me know, ill change.
List 5 possible causes of imbalance?
- Incorrect Machine assembly(loose parts)
-Material worn off one side of rotating parts(impeller)
-Material build up on rotating parts (fan blades)
-Sag in shaft or rotor - A hollow spot in rotor(porosity) or a spot has a different density than the rest of the material
- Part is made off centre(Eccentricity)
Frequency for misalignment is usually __ x rpm, but if misalignment is severe there can be frequencies at ___ x rpm or ____ x rpm.
Frequency for misalignment is usually 1x rpm, but if the misalignment is severe there can be frequencies at 2x rpm, or 3x rpm.
Angular misalignment will cause a high Vertical, Horizontal, or Axial reading?
Axial?
Parallel misalignment will cause a high Vertical, Horizontal or Axial reading?
Vertical?
How should you check to determine if a vibration problem is caused by an electrical problem?
Turn off power to motor, if immediate drop in the amplitude of vibration, there is an electrical problem.
Gear vibration is a multiple of the ___________ times the RPM.
Gear vibration is a multiple of the NUMBER OF TEETH times the RPM
What situation would a gear vibration cause a high vibration of 1x rpm?
If one tooth was bad
A ball bearing with 18 rolling elements is mounted on a shaft rotating at 1750 rpm and has a damaged inner race, what is the vibration frequency?
Frequency = 0.60 x 18 x 1750
Frequency = 18900 cpm?
A bearing with 15 rolling elements is mounted on a shaft rotating at 1750rpm and has a damaged outer race, what is the vibration frequency?
Frequency = 0.40 x 15 x 1750
Frequency = 10500 cpm?
True or False;
Oil whirl will cause vibration frequency below 1x rpm.
True
“Usually occurs at frequencies of about 45-50% of shaft rotation”
Mechanical looseness is identified by a dominant frequency of __ x rpm?
2 x rpm.
Looseness between machine foot and baseplate will cause the phase to be the same or different?
Different
Where is vibration from belts the greatest?
In the direction of belt tension
How does phase identify a shaft?
1x or 2x rpm, phase readings are different at opposite ends of the bearing housings.
How can resonance be identified as a problem?
Adding/removing weight, standing on a part, clamping or bracing it. If the vibration changes, the machine is resonating.
