This document discusses machine balancing and provides definitions and explanations of key terms. It describes the different types of unbalance including static, couple, and dynamic unbalance. It explains the causes of unbalance such as uneven mass distribution, wear, corrosion, and assembly issues. The document also outlines the methods used for static and dynamic balancing of rigid and flexible rotors. It provides standards and formulas for determining acceptable balance tolerances.

2. MACHINE BALANCING
Presented by: M. Asif(SO-PM III) ARL
00923012544942
Dated: 30/5/2018

3. IMPORTANT TERM
 Rotating centerline:
The rotating centerline being defined as the axis about
which the rotor would rotate if not constrained by its
bearing.(Also called the principle inertia axis or PIA)
 Geometric centerline :
The geometric centerline being the physical centerline of
the rotor.

4. MASS & WEIGHT
 MASS:
 A measure of how much matter is in an object.
 Mass is commonly measured by how much something
weighs. But weight can change for different locations (such as
on the moon) while the mass stays the same.
 The standard unit of mass in the (SI) is the kilogram (kg). ...
The mass of an object can be calculated if the force and the
acceleration are known.
 WEIGHT:
 The most common definition of weight as the,
 force exerted on a body by gravity.
 This is often expressed in the formula:
 W = mg,
 where W is the weight, m the mass of the object, and g
gravitational acceleration.

5. UNBALANCE
 Unbalance
“ is uneven distribution of mass about a rotor’s rotating
centerline.
 The condition which exists in a rotor when vibratory
force or motion is imparted to its bearings as a result of
centrifugal forces is called unbalance.

6. TYPES OF UNBALANCE
 STATIC UNBALANCE:
A static unbalance (sometimes called a force unbalance)
 A body is said to be in static unbalance,
when its center of gravity is out from the axis of rotation.
 Static unbalances can occur more frequently in disk-shaped
rotors because the thin geometric profile of the disk allows for
an uneven distribution of mass.

7. COUPLE UNBALANCE
 A couple unbalance occurs when a rotating mass has two
equal unbalance forces that are situated 180° opposite each
other.
 Couple unbalance exists when two unbalances exist 180
degrees apart, but in different planes
 A system/rotor that is statically balanced may still have a
couple unbalance. Couple unbalance occurs frequently in
elongated cylindrical rotors.

8. DYNAMIC UNBALANCE
 Combination of static and couple unbalance is dynamic
unbalance.
 Dynamic unbalance is the most common type of unbalance and
is defined simply as
 unbalance where the central principal axis and the rotating
centerline do no touch.
 To correct dynamic unbalance, it is necessary to make vibration
measurements while the machine is running and to add
balancing masses in two planes.

9. WHAT IS BALANCING?
 Balancing:
 Balancing is equal distribution of mass about a rotor’s rotating centerline.
 Balancing:“ is the technique/process of attempting to improve the mass
distribution of a body/rotor so that it rotates in its bearings without
unbalanced centrifugal forces that caused the high vibration.
 There are several methods of testing the balancing of a rotating part. A
simple method that is sometimes used for flywheels, etc., An accurate shaft is
inserted through the bore of the finished wheel, which is then mounted on
carefully leveled “parallels” A. If the wheel is in an unbalanced state, it will
turn until the heavy side is downward.

10. BALANCING METHOD
 Mass balancing is routine for rotating machines, and some
reciprocating machines.
There are two common method for balancing
 (1) BY ADDING OF MASSES(Bolting/welding)
 (2) BY REMOVAL OF MASSES(Grinding/Drilling)

11. TYPES OF BALANCING
 STATIC BALANCING.
Static balancing known as single plane balancing.
 DYNAMIC BALANCING.
Dynamic balancing known as dual plane balancing.

12. TYPES OF BALANCING
 STATIC BALANCING or SINGLE PLANE BALANCING
Static balancing is a balance of forces due to action of gravity.
 A body is said to be in static balance,
when its center of gravity is on the axis of rotation.
The condition which exists in a body which has an absolutely
even distribution of the mass around the axis of rotation.

13. STATIC BALANCING OR SINGLE PLANE BALANCING
 Single plane balancing is the placement of a weight in one plane
to achieve an acceptable level of balance.
 All balancing that is done without spinning the component up to
operating speed is said to be single plane balancing.
 Static balancing on rollers or knife-edges or other gravity
balancing methods use single plane balancing.
 This method is always applicable to thin disk or rotors where the
unbalance is mainly in one plane.

14. TYPES OF BALANCING
 DYNAMIC BALANCING.
 Dynamic balance is a balance due to the action of inertia forces. It require that
two criteria to be met.
 The sum of forces must be zero. ∑ F=0
 The sum of moments must also be zero. ∑ M=0
 Dynamic balancing is the practice of spinning an object/rotor at a high rate of
speed/operating speed, and adjusting the balance or removing the vibration by
Balancing while subtracting or adding weight.
Dynamic balancing is normally requires on wide rotors like:
 Pumps, Compressors & Turbine rotors.
 Fans & Blowers with longer distance between ends.
 Electric motors & Generators.
 Centrifuge drums, Paper machine rolls, Machine tool spindles etc.
A rotor being completely dynamically balanced will also be in completely statically
balanced.
Inertial force is a force that resists a change in velocity
of an object

15. SINGLE AND DUAL PLANE BALANCING
 Depending on the machinery, single or dual plane balancing is used. Selecting
one plane or two plane balancing generally depends on two factors.
 One of the factors is the ratio of the length of the rotor (L) to the diameter of
the rotor (D).
 The other factor is the operating speed of the rotor. As a general rule of thumb,
we can refer to the table shown below.

16. REASONS OF UNBALANCE
 Loss of mass from rotor system(gradual or sudden)
 Thermal bow- caused by a ‘rubbing’ between stationary and
rotating components of rotor system.
 The shape of rotor is unsymmetrical.
 Un symmetrical exists due to a machine error.
 The material is not uniform, especially in casting.
 A deformation is exists due to a distortion.
 Manufacturing :(Blow Holes in Castings )
 Fabrication problems:(casting, eccentric machining and poor
assembly.
 Distortion problems: rotational stresses, aerodynamics and
temperature changes

17. REASONS OF UNBALANCE
 Assembly- causes/Casting causes
 The addition of keys and keyways adds to the problem
 in practice, different manufacturers follow their own
procedures. Some use a full key, some a half key and some
no key at all. Thus, when a unit is assembled and the
permanent key is added, unbalance will often be the result.
 Casting (Blow Holes in Casting)
 Occasionally, cast rotors such as pump impellers or large
sheaves have blow holes or sand traps which result from
the casting process. While undetectable through normal
visual inspection, blow holes may be present within the
material and create a significant source of unbalance.

18. REASONS OF UNBALANCE
 Installed Machines – Causes
 When a rotor has been in service for some time, various other
factors can contribute to the balance condition.
 These factors are also contribute for unbalancing of rotor
corrosion, wear, distortion, and deposit build up.
 This particularly applies to fans, blowers, compressors and
other rotating devices handling process variables.
 Routine inspection and cleaning can minimize the effect,
but eventually the machines will have to be removed from
service for balancing.

19. REASONS OF UNBALANCE
 Corrosion or Wear & Deposit Build-Up :
 Many rotors, particularly fan, blower, compressor, pump rotors, or any
other rotors involved in the material handling processes, are subject to
corrosion, abrasion, or wear. If the corrosion or wear does not occur
uniformly, unbalance will result.
 Rotors used in material handling may become unbalanced due to the
unequal build-up of deposits (dirt, lime, etc.) on the rotor.
 Hydraulically Unbalance :
 Oil trapped in oil galleries, oil trapped in grinding wheels and
cavitations or turbulence in flow can sometimes produce unbalance
forces.
 Distortion :
Thermal distortion occurs with a change in temperature.
Most metals expand when heated.
 Thermal distortion is common on machines that operate at elevated
temperatures including electric motors, fans, blowers, compressors,
expanders, turbines, etc. Thermal distortion can sometimes require the
rotor to be balanced at its normal operating temperature.

20. REASONS OF UNBALANCE
 Other Causes:
Another cause of unbalance that is not readily apparent, is the difference between
types of rotors.
 There are two types of rotors:
1 Rigid rotors
2 flexible rotors
 Rotors that operate above 70% of their critical speed
 it can be considered to be a flexible rotor . Rotors that operate above 70% of
their critical speed will actually bend or flex due to the forces of unbalance
and, thus are called flexible rotors.
 If it is operating below 70% of their critical speed it is considered rigid.
 Critical speed of the turbine is the rotor speed, at which natural frequency of
the assembled rotor (rotor shaft with discs, blades, etc in assembled condition)
becomes equal to the operating speed. or some other exciting frequency of
vibration, there is a condition of resonance.
 The rotating speed at which the rotor itself goes into bending resonance is
called a "critical speed.

21. REASONS OF UNBALANCE
 BALANCING RIGID ROTORS:
Because unbalance exists in a component even when stationary, rigid rotors
can be balanced at a low speed, just enough to produce a centrifugal force to
register the unbalance.
A rigid rotor can be balanced at the two end planes and will stay in balance
when in service.
 BALANCING FLEXIBLE ROTORS:
This type of rotor is balanced at a low speed where the rotor does not flex.
Correction for unbalance is made, then the speed is gradually increased, and
the unbalance is corrected in stages until the rotor’s operating speed is
reached.
A flexible rotor will require multi-plane balancing.
 Typical machines which contain flexible rotors are steam and gas
turbines, multistage centrifugal pumps, compressors, and paper rolls.

22. EFFECTS OF UNBALANCING
 Rotating a rotor which has unbalance causes the
following problems.
 Major cause of vibration in a machine.
 The whole machine vibrates.
 Noise, occurs due to vibration of the whole machine.
 Abrasion of bearings may shorten the life of the
machine.
 Decreased life of bearings.
 Decreased life of sealing element
 Reduce machine life.
 Increased maintenance

23. NEED FOR BALANCING
 Mass balancing is routine for rotating machines,
some reciprocating machines and vehicle.
 Mass balancing is necessary for quiet operation,
 high speeds.
 long bearings life.
 Long life for sealing element.
 Decrease maintenance.
 Increase machine life.
 operator comfort.
 controls free of malfunctioning, or a quality feel

24. ROTATING COMPONENTS FOR
BALANCING
 PULLEY AND GEAR SHAFT ASSEMBLIES
 IMPELLERS.
 FLYWHEELS
 FAN AND BLOWERS
 CRANK SHAFT
 STEAM AND GAS TURBINE ROTORS
 COMPRESSORS ROTORS
 CENTRIFUGE ROTORS
 ELECTRIC MOTORS ROTORS
 PRECISION SHAFTS
 GRINDING WHEELS
 TURBO CHARGERS
 HIGH SPEED MACHINE SPINDLES

25. BALANCING MACHINE (WORKSHOP BALANCING)
 A balance machine is used to detect the amount and location of the
unbalanced masses on a rotor.
 To identify the position and amount of unbalance, balancing machines are
used to correct any unbalance that exists.
 These machines are available in different versions With the use of modern
electronics, accuracy that balance the rotor in either the horizontal or
vertical axis.
Nomenclature: Dynamic Balancing
Model : ZE 2000
Version : TC GV
Calibrated speed: 700
 The set-up of the machine is very simple by just typing measurements into a
computer.
 length of rotor.
 Dia of rotor.
 type of rotor
 Method of balancing(add or removal of weight)

26. BALANCING MACHINE

27. TYPES OF BALANCING MACHINES
 Horizontal Balancers:
 Horizontal balancing machines with, horizontal spindle, and table balancing
machines that are designed to balance rotors, roots rotors, impellers, crank
shaft, armatures, and many more types of component.
 Vertical Balancers:
 Vertical balancing machines are are designed to balance disc type rotors and
components.

28. BALANCING MACHINE
 Rotor can be balanced by aligning the rotor mass with the bearing
centers .
 We measure the initial state, then we add a trial weight of known mass,
calculate the position and mass of a counterweight, remove the trial
weight and put the calculated weight on the opposite side, to cancel out
the imbalance. By grinding, drill/by weight
 Appropriate corrections can then be made by the operator

29. UNITS OF UNBALANCING
 The amount of unbalance in a rotating work piece is expressed as the product
of the unbalance
 mass (ounces, grams, etc.)
 And its distance from the rotating centerline (inches, centimeters, etc.).
 U=m*e
 Where U is the unbalance, m is the magnitude of the mass, and e is the
eccentricity in the disc (or the distance from the center point of the mass to the
axis of rotation).
 Imperial Units:
 gram inches (g in)
 ounce inches (oz in)
 Metric Units:
 gram millimeters (g mm)
 gram centimeters (g cm)

30. BALANCING STANDARD
 ISO Standards based on the measurement of machinery
vibration velocity. The (ISO) publishes standards & Tolerance
which are the global benchmark for industrial balancing.
 ISO 1940: For rigid rotor
 ISO 21940: For flexible rotors
 There are balance limits, just like machining limits, where the
unbalance is acceptable.
 International standards are quoted for rotors,
 for example: A car wheels are balanced to a limit of grade 40
and small electrical armatures are balanced to grade 2.5.

31. BALANCING STANDARDS
 ISO 1940 is famous for its classification of vibration in terms
of G codes although many people don’t know what they mean,
 it is easy to figure out that G2.5 is a tighter tolerance than
G6.3.
 G2.5 means a vibration velocity of 2.5 mm/s under specified
conditions. it is the theoretical value assuming the rotor was
spinning in free space .
 The standard has issued guidelines with regard to a number of
different kinds of devices. For example
 A balance quality grade of G6.3 is appropriate to most fans.
 A grade of less than G2.5 is usually only achievable on very
special equipment.

32. BALANCING TOLERANCE FORMULA
 Uper = balance tolerance
g is referred to as the acceleration of gravity. Its value is 9.8 m/s2 on Earth.
BALANCING FORMULA: Wx10x G numberx1000
RPM
For Static: Ans
r1
For Dynamics: Ans
2
225x10x2.5x1000= 1504.01
3740
S=1504/145=10.37 gram
D= 10.37/2 =5.18 gram
G number can be obtained from the table below (ISO 1940)
:

33. BALANCING FORMULA
 API 610
 API 610 is based on the following formula (using SI units):
T = 6350W/N
 W = rotor weight in kg
 n = speed in RPM
 T = tolerance in kg

34. BALANCE QUALITY GRADE
 Tabled below is an example of standard guidelines with regard to different devices (Indicative example
only).
 B.quality grade : Magnitude: General Examples
G 100 :100 :Complete engines for cars, trucks and locomotives
G40 :40 :Car wheels, wheel rims, wheel sets, Drive shafts, Crankshaft
G16 :16 : Parts of crushing machines , agricultural machinery ,
: Drive shafts, Cardan shafts, Propeller shafts, Crankshaft/drives
rigidly mounted
G6.3 :6.3 : Fans. Fly wheels, Pump impellers, Paper
machinery rolls, printing rollers , Parts of process
plant machines, Marine main turbine gears, Machine tools
Aircraft gas turbines, General machinery parts, Medium
and large electric armatures (of electric motors having
at least 80 mm shaft height and max speed of 950RPM)
Small electric armatures, Turbo Chargers
G2.5 :2.5 : Gas and steam turbines, Compressors/multi s pumps,
Parts of textile Machines, Medium and large electric motor and generator armatures
G 1 : 1 : Video, Audio and Tape recorder and phonograph drives
G0.4 : 0.4 : Spindles, discs, and armatures of precision systems.

35. BENEFITS OF BALANCING
 Increase quality of operation.
 Increase machine life.
 Minimize vibration.
 Minimize noise.
 Minimize structural fatigue stresses.
 Minimize operator annoyance and fatigue.
 Increase bearings life.
 Increase sealing element life
 Minimize power loss.
 Decrease maintenance
 Smooth operation of machine.
 Cast saving in sense of spares, time, labor etc

36. VIDEO
 SEE VIDEO FOR MACHINE BALANCING

37. FINISH