ISO21940

 
BALANCE QUALITY 
GRADE G		 MAGNITUDE e per Ω
mm/s		 MACHINERY TYPES – GENERAL EXAMPLES                                 
   G  4000 ≤4000
  • Crankshaft drives for large, slow marine diesel engines (piston speed below 9 m/s), inherently unbalanced
   G  1600 ≤1600
  • Crankshaft drives for large, slow marine diesel engines (piston speed below 9 m/s), inherently unbalanced
   G  630 ≤630
  • Crankshaft drives, inherently unbalanced, elastically mounted
   G  250 ≤250
  • Crankshaft drives, inherently unbalanced, rigidly mounted
   G  100 ≤100
  • Complete reciprocating engines for cars, trucks and locomotives
   G  40 ≤40
  • Cars: wheels, wheel rims, wheel sets, drive shafts
  • Crankshaft drives, inherently balanced, elastically mounted
   G  16 ≤16
  • Agricultural machinery
  • Crankshaft drive, inherently balanced, rigidly mounted
  • Crushing machines
  • Drive shafts (cardan shafts, propeller shafts)
   G  6.3 ≤6.3
  • Aircraft gas turbines
  • Centrifuges (separators, decanters)
  • Electric motors and generators (of at least 80 mm shaft height), of maximum rated speeds up to 950 r/min
  • Electric motors of shaft heights smaller than 80 mm
  • Fans
  • Gears
  • Machinery, general
  • Machine tools
  • Paper machines
  • Process plant machines
  • Pumps
  • Turbo chargers
  • Water turbines
   G  2.5 ≤2.5
  • Compressors
  • Computer drives
  • Electric motors and generators (of at least 80 mm shaft height), of maximum rated speeds up 950 r/min
  • Gas turbines and steam turbines
  • Machine-tool drives
  • Textile machines
   G   1 ≤1
  • Audio and video drives
  • Grinding machine drives
   G  0.4 ≤0.4
  • Gyroscopes
  • Spindles and drives of high-precision systems
NOTE 1    Typically, completely assembled rotors are classified here. Depending on the particular application, the next higher or lower grade may be used instead. For components, see clause 9.

NOTE 2   All items are rotating if not otherwise mentioned (reciprocating) or self-evident (e.g. crankshaft drives).

NOTE 3   For some additional information on the chosen balance quality grade, see Figure 2 which contains generally used areas (service speed and balance quality grade G) based on common experience.

NOTE 4    For some machines, specific International Standards stating unbalance tolerances exist.

NOTE 5   The selection of a balance quality grade G for a machine type requires due consideration of the expected duty of the rotor when installed in situ which typically reduces the grade to a lower level if lower vibration magnitudes are required in service.

NOTE 6   The shaft height of a machine without feet, or a machine with raised feet, or any vertical machine, is to be taken as the shaft height of a machine in the same basic frame, but of the horizontal shaft foot-mounting type. When the frame is unknown, half of the machine diameter should be used.

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