04 Unbalance Tolerances

7/28/2019 04 Unbalance Tolerances

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Unbalance Tolerances

Determination of permissible residual unbalance


contents

ISO 1940-1

Determination of balance quality

requirements

by three different methods

Allocation to each correct ion plane

is necessary when using

Determination of the residual unbalanceby

ISO 1940-1

chapter

6

balance quality gradeexperimental deter-mination

bearing forces

balance quality gradebearing forces

balancing machine

6.26.3

6.4

7

8

8.1


3/19


balance

quality

page 11-04-01-02


according ISO 1940-1

Formula Unit

G = e * mm/s

v = e * mm/s

the quality grade Gcorresponds to thevelocity vof the c.g.

around therotational axisin operation

e

v


4/19

page 11-04-02-01


balance

quality

Remarks in the table

1) =2 n / 60 approx. n / 10,if n is measured in revolutions per minuteand in radians per second

2) For allocating the permissible residualunbalance to correction planes,see clause 7

3) A crankshaft/drive is an assembly whichincludes a crankshaft, flywheel, clutch,pulley, vibration damper, rotating portionof connecting rod, etc. (see 3.5)

4) For purposes of this part of ISO 1940,slow diesel engines are those with apiston velocity of less than 9 m/s;fast diesel engines are those with apiston velocity of greater than 9 m/s.

5) In complete engines, the rotor masscomprises the sum of all massesbelonging to the crankshaft/drivedescribed in note 3 above.


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The numerical value ofG

is equal to the product ofe x

expressed inmillimeters per second

per T

r / min (rpm, revolutions per minute)

r / s (rps, revolutions per second,can use also Hz - Hertz)

Maximumof rotationservice speed

page 11-04-02-03


balance

quality

It is not T


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ISO 1940-1Calculation of permissible residual unbalance

Symmetrical rotor - permissible residual unbalance in 2 plane

Uper = permissible residual unbalance (total)

G = Quality Grade

eper = permissible specific unbalance (total)

Uper 1/2 = permissible residual unbalance (per plane 1/2)

Uper1/2 = permissible residual mass (per plane 1/2)

W = rotor weight

n = operational speed

Uper 1/2 =G * W * 1000 * 10

N * 2

(gmm)


7/19

page 11-04-03-01Veit Bleistein -27.Okt.1999


Unbalance TolerancesAl location to correct ion planes

Single plane

balancing

Symmetrical rotorpermissible residual unbalancein 1 plane

static balancing

1

Uper 1

Uper 1

= Uper

Uper

ISO 1940-1

chapter

3.3

6.37.2


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Symmetrical

set-up

Symmetrical rotorpermissible residual unbalancein 2 planesclose to bearing planes

Uper2 =U

2

per

ISO 1940-1

chapter

7.3.1

Uper 1 =

1 2

Uper1 Uper 2

Uper


9/19

page 11-04-ex.Veit Bleistein -27.Okt.1999


Unbalance TolerancesExercise

Exercise

ISO 1940-1

r1 r2

Example

rotor type armature

rotor mass m =100 kg

service speed n =3000 1/min

correction radius r =r =100 mm1 2

quality grade G

perm. unbalance mass per plane uper 1 =

uper 2 =

perm. res. unbalance per plane Uper 1 =

Uper 2 =

permissible specific unbalance (total) e =

perm. residual unbalance (total) Uper =


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Symmetrical

set-up

Symmetrical rotorc.g. In mid third of rotor lengthone each correction planein the outer thirdsrelated to the bearing distance L

Uper 2 =U

2

per

ISO 1940-1

chapter

7.3.2.1

Uper 1 =

L

L/3 L/3 L/3

1 2


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page 11-04-03-06Veit Bleistein -10.Aug.2000


Unbalance TolerancesAl location to correction planes

Non-

Symmetricalset-up

ISO 1940-1

chapter

7.3.2._

Uper1

U per

Uper2

L

b

h1 h2

Non-symmetrcal rotorc.g. in not symmetrical to thecorrection planes

permissible residual unbalance:

0.3 U = U = Uper per1 per

0.3 U = U = Uper per2 per

= 0.7 Uper

= 0.7 Uper

hb

2

hb

1


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b

b b

b

L

L L

L

Static Unbalance

U = UA,B 1,2

Couple Unbalance

U = UA,B 1,2 bL

U1

U1

U2

UA

UB

U2 UA UB


Unbalance TolerancesEffect of unbalances in the bearing planes

Effect inbearing planes



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Unbalance Vectors can be calculated precisely for other planes(on a rigid rotor)

Unbalance Tolerances are not vectors, but areas.Unbalance Tolerances are the maximum amount of unblance permissable.

The angular position is not normally considered.

Unbalance Tolerances cannot be calculated precisely for other planes.The worst case is always .

Therefore either the static unbalance or the couple unbalanceis usually corrected better than necessary.

considered


Unbalance TolerancesAllocation to correction planesBalancing planesvs.bearing planes

page 11-04-03-08Veit Bleistein - 28-Feb-2001


14/19

Symmetrcal Rotorpermissible residual unbalancein 2 correction planeswith wide distance betweencorrection planes

Both s ides overhanging (outboard) correction planes

L

b

1 2

U *per

Uper


Symmetricalset-up



U * = UL

b

U2 = 2U *per

U1 =

per per


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Non-symmetricalset-up, inboardnarrow planes

non-symmetrical rotornarrow correction planesc.g. between bearing planes

2 or 3 correction planes possible

ISO 1940-1

chapter

7.3.2.3

Permissib le static unbalance

Permissib le couple unbalance

U

2

perUper 3 =

L

2c

Uper2 =U

2

per

Uper 1 =3L

4 b

1 2

3L

c

b

Uper


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Non-symmetrical

set-up,narrow planes outboard

non-symmetrical rotornarrow correction planesc.g. not between bearing planes(outboard, overhanging rotor)

2 or 3 correction planes possible

ISO 1940-1

chapter

7.3.2.3

Permissiblestatic unbalance

Permissiblecouple unbalance

1 2

3

Uper

L

c

b

Uper2=Uper 1=3L

4b

U2per

Uper 3 =U2per L

2c


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exampleacc.ISO 1940-1

Permissiblestatic unbalance

Permissiblecouple unbalance

1 2

3

Uper

L = 86

c = 115

b = 26

Uper 3 =U2per L

2c

Uper 3 = U 0.19per

Uper2=Uper 1=

3L

4b

U

2per

Uper2=Uper 1=

U 1.24per


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Generalmethods

Permissible resid. Unbalancein plane 1is the smallest figureout o f these 4 equations

Uper 1

Uper

Uper 2

L

baReference-bearing

U = R Uper 2 per 1

U =Uper 1 per

U =Uper 1 per

U =Uper 1 per

U =Uper 1 per

k L[(L-a) +R(L-a-b)]

k L[(L-a) - R(L-a-b)]

(1 - k) L[a +R(a +b)]

(1 - k) L[a - R(a +b)]

(1)

(2)

(3)

(4)

Permissible resid. Unbalancein plane 2

Within these parameters

k = U /UR = U /U

per Refper

per 2 per 1

0.3 = k = 0.70.5 = R = 2.0


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General

methodsrel. example

Permissible resid. Unbalancein plane 1is the smallest figureout o f these 4 equations

L = 116

b =85a=15

Referenc

e-bearing

Permissible resid. Unbalance

in plane 2

With these parameters

U =Uper 1 per

U =Uper 1 per

U =Uper 1 per

U =Uper 1 per

k L

[(L-a) +R(L-a-b)]k L

[(L-a) - R(L-a-b)]

(1 - k) L[a +R(a +b)]

(1 - k) L[a - R(a +b)]

= U 0.51per

=U 0.64per

=U 0.68per

=U 1.05per

k = 0.5R = 0.7

k = U /UR = U /U

perRef per

per 2 per 1

Uper 1

Uper

Uper 2

= 0.7 Uper 1= 0.36 UperU = R Uper 2 per 1

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