8.1.1 Pressure
vessels are to be so made that the internal surfaces may be examined.
Wherever practicable, the openings for this purpose are to be sufficiently
large for access and for cleaning the inner surfaces.
8.1.2 Manholes
in cylindrical shells should preferably have their shorter axes arranged
longitudinally.
8.1.3 Doors
for manholes and sightholes are to be formed from steel plate or of
other approved construction, and all jointing surfaces are to be machined.
8.1.4 Doors
of the internal type are to be provided with spigots which have a
clearance of not more than 1,5 mm all round, i.e. the axes of the
opening are not to exceed those of the door by more than 3 mm. The
width of the manhole gasket seat is not to be less than 16 mm.
8.1.5 Doors
of the internal type for openings not larger than 230 x 180 mm need
be fitted with only one stud, which may be forged integral with the
door. Doors for openings larger than 230 mm x 180 mm are to be fitted
with two studs or bolts. The strength of the attachment to the door
is not to be less than the strength of the stud or bolt.
8.1.6 The
crossbars or dogs for doors are to be of steel.
8.1.7 External
circular flat cover plates are to be in accordance with a recognised
standard.