Balancing

Question 1

_________ is the unequal distribution of weight of a rotating body about its centreline

Answer 1

imbalance

Question 2

What appears at a frequency of 1x rpm of the rotor. An eccentric armature also becomes apparent at 1x rpm.

Answer 2

Eccentricity

Question 3

The usual tolerance allowed for runout of the outside diameter in relation to its bore is ______ inch.

Answer 3

0.002

Question 4

Some sheaves, pulleys, hubs, gears, and shafts are balanced with _______

Answer 4

Keys or half keys

Question 5

______ weight distribution is the basic cause of imbalance.

Answer 5

Asymmetrical

Question 6

Liquid collecting (water, oil) within rolls causes imbalance. why is impossible to balance?

Answer 6

Because it moves to a different position each time the roll is spun to balancing speed

Question 7

___________ is a charateristic of all materials, regardless of how they are produced.

Answer 7

Non-homogeneity

Question 8

________ is caused when a shafts weight is evenly distributed along its length, but unevenly from side to side.

Answer 8

Static imbalance

Question 9

if the required balance correction is at a single point on the rotor, it is called _______

Answer 9

single plane balancing

Question 10

__________ means that there is extra end of the shaft. The extra weights are equal, but on opposite sides of the shaft 180degree apart

Answer 10

Couple imbalance

Question 11

_______ is a type of vibration caused by extra weight unevenly distributed along the length of the shaft, across the width of the shaft , and/or at different angles about the radius

Answer 11

dynamic imbalance

Question 12

A __________ in just one rotating component of an assembly may cause an entire assembly to vibrate. This induced vibration may in turns cause exessive wear in bearings, bushings, shafts, spindles or gears, substantially reducing their service life.

Answer 12

imbalance

Question 13

the amount of force caused by the lack of balance is proportional to the rpm squared. therefore doubling the rpm quadruples the force caused by the imbalance

Question 14

you can measure the vibration caused by the heavy spot with a _______

Answer 14

vibration probe

Question 15

Imbalance shows up at 1x rpm of the rotor, which means that the _______ passes the same spot each time the rotor makes one revolution

Answer 15

heavy side

Question 16

the angle of delay is called ________

Answer 16

flash angle

Question 17

the spot where the line remains is called the

Answer 17

phase angle

Question 18

A strobe lights primary purpose in balancing is to _________

Answer 18

check phase angle

Question 19

_________ is finding the heavy spot and removing it or adding a weight opposite, which balances the rotational forces.

Answer 19

balancing

Question 20

Calculate a trial weight sufficient to change the amplitude of the vibration by ____. In modern analyzers, this weight can be programmed into the balancing software.

Answer 20

30%

Question 21

Some analyzers still require ___________ and _______ to calculate the weights required. Their appropriate positions must be determined to correct the imbalance.

Answer 21

vector diagrams and charts

Question 22

attach vibration transducers in the direction of ______

Answer 22

highest amplitude

Question 23

if the vibration pickup is moved from horizontal to vertical (H to V) and you get 90degree phase shift 90% of the time, the shift is caused by ________

Answer 23

imbalance

Question 24

A _________ added to a rotor either shows a decrease in the vinration or an increase in the vibration.

Answer 24

Trial weight

Question 25

A common approach for selecting a trial weight is to use a weight that produces an imbalance force at the support bearing equal to ____ of the rotor weight supported by the bearing

Answer 25

10%

Question 26

to determine the trial weight size, you must know?

Answer 26

weight of rotor, rotor rpm, and radius at which you place the trial weight

Question 27

the greater the amount of imbalance, the greater the ________ caused by the imbalance

Answer 27

forces

Question 28

this balance procedure is performed manually using 7 things
a vibration analyzer set in displacement,
a strobe light,
a phase angle identifier,
a weight scale,
what is the last three?

Answer 28

weights
polar graph paper
a ruler and protractor

Question 29

The _______ stays the same and the phase reading moves in the opposite direction

Answer 29

magnitude

Question 30

______ are dynamically balanced, meaning that the _ is set on bearings or pedestals, and rotated at a specified rpm.

Answer 30

Rotors

Question 31

a ______ is a line whose lenght corresponds to the amount of vibration (imbalance) present and whose direction corresponds to the phase angle.

Answer 31

Vector

Question 32

1 mil vibration on vector = _____

Answer 32

7.75 mm

Question 33

Always install the __________ in the opposite direction to which the O+T vector moved from the original imbalance vector O trial weight position.

Answer 33

correction weight

Question 34

Measure the angle with a _______. the angle between O and T

Answer 34

protractor

Question 35

run the rotor and record the new imbalance. record it as O+T. add vector O+T to the graph. Use this when _________

Answer 35

verifying balance

Question 36

if a rotor is operating at a speed that is below ____ of its natural frequency, two-plane balancing may be all that is required

Answer 36

70%

Question 37

the vibration is usually ______ in the horizontal than the vertical position (in horizontally mounted machines)

Answer 37

larger

Question 38

the characteristics of a misalignment problem are

Answer 38

the phase readings are unstable

Question 39

what are the four types of unbalance?

Answer 39

static, couple, quasi-static, and dynamic

Question 40

what type of unbalance is the most usual and the hardest to analyze and correct.

Answer 40

Dynamic