Balancing Flashcards
_________ is the unequal distribution of weight of a rotating body about its centreline
imbalance
What appears at a frequency of 1x rpm of the rotor. An eccentric armature also becomes apparent at 1x rpm.
Eccentricity
The usual tolerance allowed for runout of the outside diameter in relation to its bore is ______ inch.
0.002
Some sheaves, pulleys, hubs, gears, and shafts are balanced with _______
Keys or half keys
______ weight distribution is the basic cause of imbalance.
Asymmetrical
Liquid collecting (water, oil) within rolls causes imbalance. why is impossible to balance?
Because it moves to a different position each time the roll is spun to balancing speed
___________ is a charateristic of all materials, regardless of how they are produced.
Non-homogeneity
________ is caused when a shafts weight is evenly distributed along its length, but unevenly from side to side.
Static imbalance
if the required balance correction is at a single point on the rotor, it is called _______
single plane balancing
__________ means that there is extra end of the shaft. The extra weights are equal, but on opposite sides of the shaft 180degree apart
Couple imbalance
_______ 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
dynamic imbalance
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.
imbalance
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
you can measure the vibration caused by the heavy spot with a _______
vibration probe
Imbalance shows up at 1x rpm of the rotor, which means that the _______ passes the same spot each time the rotor makes one revolution
heavy side
the angle of delay is called ________
flash angle
the spot where the line remains is called the
phase angle
A strobe lights primary purpose in balancing is to _________
check phase angle
_________ is finding the heavy spot and removing it or adding a weight opposite, which balances the rotational forces.
balancing
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.
30%
Some analyzers still require ___________ and _______ to calculate the weights required. Their appropriate positions must be determined to correct the imbalance.
vector diagrams and charts
attach vibration transducers in the direction of ______
highest amplitude
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 ________
imbalance
A _________ added to a rotor either shows a decrease in the vinration or an increase in the vibration.
Trial weight
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
10%
to determine the trial weight size, you must know?
weight of rotor, rotor rpm, and radius at which you place the trial weight
the greater the amount of imbalance, the greater the ________ caused by the imbalance
forces
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?
weights
polar graph paper
a ruler and protractor
The _______ stays the same and the phase reading moves in the opposite direction
magnitude
______ are dynamically balanced, meaning that the _ is set on bearings or pedestals, and rotated at a specified rpm.
Rotors
a ______ is a line whose lenght corresponds to the amount of vibration (imbalance) present and whose direction corresponds to the phase angle.
Vector
1 mil vibration on vector = _____
7.75 mm
Always install the __________ in the opposite direction to which the O+T vector moved from the original imbalance vector O trial weight position.
correction weight
Measure the angle with a _______. the angle between O and T
protractor
run the rotor and record the new imbalance. record it as O+T. add vector O+T to the graph. Use this when _________
verifying balance
if a rotor is operating at a speed that is below ____ of its natural frequency, two-plane balancing may be all that is required
70%
the vibration is usually ______ in the horizontal than the vertical position (in horizontally mounted machines)
larger
the characteristics of a misalignment problem are
the phase readings are unstable
what are the four types of unbalance?
static, couple, quasi-static, and dynamic
what type of unbalance is the most usual and the hardest to analyze and correct.
Dynamic
