CEMB USA N300 - Manual (Page 81)

HOW TO USE THE BALANCING TOLERANCE GRAPH
The balancing quality grade G is determined according to the
characteristics of the rotor and the machine on which the rotor
is mounted under normal service conditions (see table).
The residual permissible eccentricity may then be deduced from
the graph, as a function of the rotational speed, in
correspondence with the G grade.
The residual eccentricity is not a fixed value: it may vary for a
given G grade between a minimum and a maximum,
corresponding to the two fine lines above and below the line of
the G grade, according to the rotor type and purpose and to the
construction characteristic of the machine on which the rotor
will be mounted.
The balancing tolerance in gr·mm may be obtained from the
residual eccentricity e (micrometers) multiplied by the rotor
weight P (kg).
The tolerance values obtained are generally a good guide and
sufficient to ensure satisfactory service conditions to a great
extent. Some corrections may, however, be opportune and
sometimes necessary, particularly when the machine has
construction characteristics substantially different from those
of traditional machines of the same category.