Basic Machinery Vibration

Question 1

The magnitude/quantity of vibrations is dependent of not only the _______ but also properties of the system. The physical properties are

Answer 1

Speed

Mass, stiffness, and damping.

Question 2

Amplitudes of Vibration are described using the following units:

Answer 2

Question 3

Frequencies are expressed in what 3 ways?

Answer 3

Cycles/Minute (CPM)
Cycles/Sec (CPS, or Hz)
Orders(Multiples of Operating speeds)

Question 4

Electrical signal is measured in ___ or ____. How do you make the conversion?

Answer 4

Electrical signal is measured in Volts or Mv.

To convert mV to Volts, moved the decimal place 3 times to left or divide by 1000.

Ex. 1000. Volts = 1. mV

Question 5

Proximity Probes do what? How many are mounted? How are they Mounted?

Answer 5

Measure shaft vibration relative to mounting position of the probe

Usually two

Horizontal is usually 90 Degrees to the right of the vertical.

Question 6

What does an Optical Sensor do?

Answer 6

Produces electronic pulse when a mark on the shaft circumference passes the sensor. This is called a Trigger Signal.

Question 7

Period is defined as

Answer 7

Time required to complete one cycle of vibration.
Ex:

Question 8

Units of Period are?
Units of Frequency are?
How do you convert?

Answer 8

Units of Period are? Sec/Cycle
Units of Frequency are? (Cycles/Sec AKA Hz -OR- CPM)

Period: is 1/Frequency
Frequency: 1/Period

Question 9

When vibration measures displacement, it’s measured in? And the Amplitude is measured in?
Time is in ___ direction, Amplitude is in ___ direction.

Answer 9

Mils( 1 mil = 1/1000in = .001in )
Peak to Peak

Question 10

The Amplitude of a Velocity Signal is measured in? It can be reported in?

Answer 10

Zero-Pk - considering the largest value plus or minus the zero line.

rms - root mean square

Question 11

If the data is in Harmonics(One Frequency), then the RMS value is
If it’s not harmonic?

Answer 11

If the data is in Harmonics(One Frequency), then the RMS value is .707 times the Peak Value.

In this case, it’s .424 IPS - RNS

There is no mathematical relationship between peak and RMS if it’s not Harmonic.

Question 12

Displacement
- Units
- Description
- Relates to
- Type of Vibration

Answer 12

Mils Pk-Pk
Motion of Machine
Stress
Low Frequency(<600 CPM)

Question 13

Velocity
-Units
- Description
- Relates to
- Frequency Range
- Amplitude Measured in

Answer 13

-In/Sec OR IPS
-Time Rate of Motion/Displacement
-Component Fatigue Severity
-600CPM(10Hz) to 60,000 CPM(1,000 Hz)
-Peak Units(positive or negative from 0)

Question 14

Acceleration
-Units
- Relates to
- Frequency
-Typically used on

Answer 14

gs**, 1g = 386.1 in/sec
Forces Present in Components
High Frequencies>1,000Hz(60,000 CPM)
Gears and Bearings

Question 15

The three basic vibrations are displacement, velocity, and acceleration.
The Raw Vibrational Data Frequencies are?
The Amplitude?

Answer 15

The Same
Are different values and units

Question 16

To calculate velocity, displacement must be change from _____ to ______? You do this by?

Answer 16

Mils Pk to Pk to inches- Pk

Division by two and by 1,000 mils

Example 5 mils- pk to pk becomes 5/2000, which equals .0025 inches-peak.

Then you plug in formula

Question 17

On a Spectrum Plot, the Frequency is measured in ____ and relates to the?

The other spectral components are?

Answer 17

Hz
Speed of the Machine.
Multiples of operating speed

Question 18

When does resonance occurs?
What is critical speed?

Answer 18

When forcing frequency is equal of close to a natural frequency l. Vibration amplifies at resonance.

A special resonance