balancing requirement according to iso 1940
TRANSCRIPT
Balancing Requirement According to ISO 1940/1
1. Introduction
1.1 Known as International Standard Organization, ISO 1940/1 – Balance quality requirements for rigid rotors.
ISO 1940/1 – Balance quality requirements for rigid rotors.
ANSI S2.19-1975
BS 6861: Part 1
VDI 2060
1.2 Also adopted by:- ANSI (American National Standards Institute) S2.19-1975.- British Standards, BS 6861: Part 1- German Standards, VDI 2060.
1.3 Other standard- MIL-STD-167-1- API 610
2. Balance Quality Grade ISO 1940/1
2. Balance Quality Grade ISO 1940/1
What is mean by G 0.4, G 1.0, G 2.5, G 6.3 and so on?
G is the product of specific unbalance & the angular velocity of the rotor at maximum operating speed.
What is specific unbalance?
Specific unbalance - center of gravity displacement of rotor.- Symbol = eper
- Unit in g.mm/kg or um.
2. Balance Quality Grade ISO 1940/1What is angular velocity?
- Measure how fast rotor is turning.-The standard unit for angular velocity is "radians per second“.- One turn or one revolution:
- 2∏ radians- 360 degrees- 60 seconds- 1 minute
- Unit can be in rpm or Hz-Symbol is ω (omega)- Formula = ω = 2 ∏n/60
ω
Back to G 0.1, G 1.0, G 2.5, G 6.3 and so on
Is actually = eper x ω
Unit in mm/sMeaning G1.0 is the rotor unbalance shall create vibration of 1.0 mm/s at maximum operating speed at certain center of gravity displacement.
3. Maximum Permissible Specific Residual Unbalance, eper
Is the method to find center of gravity displacement by referring to:
1. Balance quality grade required
2. Operating or maximum rotor speed
Two ways how to find center of gravity displacement
2. Using ISO 1940/1 unbalance nomogram.1. Calculation by using formula.
Calculation by using formula.
eper = (10 x G) / (n x 1000)
WhereG = Balance quality graden = Rotor operating speed in RPM.
3. Maximum Permissible Specific Residual Unbalance, eper
Using ISO 1940/1 unbalance nomogram
Units in:
g.mm/kg
or
= g.mm/kg= 1/1000 x mm= 10-3 x 10-3 m= 10-6 m= um (microns)
4. Maximum Permissible Residual Unbalance, Uper
Is a function of:
Rotor’s center gravity of displacement (um)Rotor weight (kg),
Divided into four rules:
1st - General rules2nd – Rules for symmetrical rotor3rd – Rules for outboard rotor
4th – Rules for overhung & narrow rotor
Balancing radius (mm).
1st – General rules
Uper = (eper x m) / r
Whereeper = Rotor permissible specific unbalance (g.mm/kg or um)m = Weight of rotor (kg)r = Balancing radius (mm) i.e. balancing wieght location.
4. Maximum Permissible Residual Unbalance, Uper
2nd – Rules for symmetrical Rotor
Apply to dynamic balancing requirement for two planes.
Formula
Plane 1 , Uper = [(eper x m) / r] ÷ 2Plane 2 , Uper = [(eper x m) / r] ÷ 2
If HL = HR
Plane 1 , Uper = [(eper x m) / r] (HR ÷ B)Plane 2 , Uper = [(eper x m) / r] (HL ÷ B)
If HL ≠HR
4. Maximum Permissible Residual Unbalance, Uper
2nd – Rules for symmetrical Rotor (Cardan shaft example)
Apply to dynamic balancing requirement for two planes.
Calculate: eper
eper = (10 x G) / (n x 1000) = (10 x 16) / (1272 x 1000) = 125.7 um
Data:Balance quality grade = G 16Weight = 450 kgMax. speed = 1272 rpmBalancing radius = 190 mm
Plane 1 , Uper = [(eper x m) / r] ÷ 2Plane 2 , Uper = [(eper x m) / r] ÷ 2
If HL = HR
Uper = [(125.7 x 450)/190] ÷ 2 = 148.8 grams
Calculate: Uper
Permissible residual unbalance for each plane = 148.8 grams
4. Calculate Center of Gravity
L
DD
d/2
d/2e
CG= e = (1/3) x [(3D + 2d)÷(2D+d)] x L
D = 1500 2d + D = 2500 L = 3000
CG= e = 1625 mm
Plane 1 , Uper = [(eper x m) / r] (H2 ÷ B)Plane 2 , Uper = [(eper x m) / r] (H1 ÷ B)
If H1 ≠H2
5. Maximum Permissible Residual Unbalance, Uper
2nd – Rules for symmetrical Rotor (Pulper rotor example)
Apply to dynamic balancing requirement for two planes.
Calculate: eper
eper = (10 x G) / (n x 1000) = (10 x 6.3) / (160 x 1000) = 393.7 um
Data:Balance quality grade = G 6.3Weight = 5700 kgMax. speed = 160 rpmBalancing radius 1 = 725 mmBalancing radius 2 = 1200 mm
Calculate: Uper
Permissible residual unbalance for Plane 1 = 1416 gramsPlane 2 = 1013 grams
Plane 1 , Uper = [(eper x m) / r1] (H2 ÷ B) = [(393.7 x 5700)/725] (1375/3000) = 1416 grams
Plane 2 , Uper = [(eper x m) / r2] (H1 ÷ B) = [(393.7 x 5700)/1200)] (1625/3000) = 1013 grams
If HL ≠HR
6. Maximum Permissible Residual Unbalance, Uper
Apply to dynamic balancing requirement for one planes.
Formula
Static , Uper = [(eper x m)/r] x (2D/C)Dynamic, Uper = [(eper x m)/r] x (3D/4C)
4th – Rules for overhung/narrow Rotor
7. Maximum Permissible Residual Unbalance, Uper
4th – Rules for overhung/narrow Rotor (Trim pit blower example)
Apply to dynamic balancing requirement for one planes.
Calculate: eper
eper = (10 x G) / (n x 1000) = (10 x 6.3) / (2890 x 1000) = 21.7 um
Data:Balance quality grade = G 6.3Weight, m = 155 kgMax. speed = 2890 rpmBalancing radius, r = 400 mmC = 720 mmD = 490 mm
Calculate: Uper
Permissible residual unbalance for Dynamic = 4.20 grams
Dynamic, Uper = [(eper x m)/r] (3D/4C) = 4.20 gram