(a) The difference between the internal diameter of the
drum measured at any cross section and the nominal internal
diameter of the drum should not exceed 1 per cent of
Any departure of profile measured on the outside of
the drum with a gauge of the designed form of the exterior
of the drum and of length equal to a quarter of the
internal diameter, shall not exceed the percentage given
in table below:-
|Nominal internal diameter of
||Percentage of nominal internal
|Up to and including 36"
|Over 36" up to and including
Flats at the welded seams shall not be permitted and
any local departure from circularity shall be gradual.
Tolerance – (i) The deviation from circularity in any
section shall, in the case of normalised drums, not
exceed 2% and in case of stress relieved drum 1%. The deviation from a straight line shall not exceed 0.3% of
the cylindrical length.
order to determine the deviation from circularity of the
drums the maximum and minimum internal diameter at one
cross section shall be measured.
From these measured values the percentage
deviation from circularity shall be calculated according
to the following formula:-
2(dmax – dmin)
C = ---------------------
(dmax + dmin)
= percentage deviation from circularity of the drums.
d = internal diameter at one cross section.
In order to determine the deviation from a
straight line, a stretched line should be placed
longitudinally against the sides and its largest
distance from the shell line concerned shall be
this distance, and from the cylindrical shell, the
deviation from the straight line shall be calculated