Quality Grades & Tolerances

Balance quality grade G
ew 1] 2] mm/s
 Rotor Types - General examples
G 40
40

- Car wheels, wheel rims, wheel sets, drive shafts.
- Crankshaft-drives of elastically mounted fast four-cycle engines (gasoline or diesel) with six or more cylinders4).
- Crankshaft-drives for engines of cars, trucks and locomotives.

G 16
16
 - Drive Shafts (propeller shafts, cardanshafts with special req
- Parts of crushing machinery.
- Parts of agricultural machinery.
- Individual components of engines (gasoline or diesel) for cars, trucks and locomotives.
- Crankshaft-drives of engines with six or more cylinders under special requirements.
G 6,3
6,3
 - Parts or process plant machines.
- Marine main turbine gears (merchant service).
- Centrifugal drums.
- Fans
- Assembled aircraft gas turbine rotors.
- Fly wheels.
- Pump impellers.
- Machine-tool and general machinery parts.
- Normal electrical armatures.
- Individual components of engines under special requirements.
G 2,5
2,5
 - Gas and steam turbines, including marine turbines (merchant service).
- Rigid turbo-generator rotors.
- Rotors.
- Turbo-compressors.
- Machine-tool drives.
- Medium and large electrical armatures with special requirements.
- Small electrical armatures.
- Turbine-driven pumps.
G 1
1
 - Tape recorder and phonographs (gramophone) drives.
- Grinding-machine drives.
- Small electrical armatures with special requirements
G 0,4
0,4
 - Spinles, disks and armatures of precision grinders.
- Gyroscopes.

1] w=2xn / 60-N / 0, if n is measured in revolutions per minute and w in radians per second. To simplify: Tolerance = Component Weight [kg] x Quality Grade x 9549 / Operational Speed [RPM]

2] In general, for rigid rotors with two correction planes, one-half of the recommended residual unbalance is to be taken for each plane.

Unbalance
The inertia axis in a rotor differs from its rotational axis and the dynamic forces from this increase with the speed. Equal mass distribution about the rotational axis is required (Balancing) to an acceptable tolerance as per above Two types of unbalance are STATIC (single plane) which is eccentricity of the centre of gravity and DYNAMIC (two plane) usually referred to as a ³wobble² effect.

 

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