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Reg. 166
MANHOLES, MUDHOLES, ETC.
Doors and Cross Bars
| a) |
All internally fitted doors
of manholes, mudholes and sightholes shall be of wrought
steel built up or pressed to shape and annealed or made
from one thickness of plate with a machined recess for
the jointing material or may be a steel casting. Their
spigot part or the recess shall not have a greater clearance
than 1/16th inch all round i.e. the axis shall not be
less than 1/8th inch smaller than the holes in which they
are fitted. |
| b) |
The studs or bolts of large
doors may be screwed through the plates and riveted over
when the working pressure of the boilers does not exceed
200 lbs. per square inch. When such pressure exceeds 200
lbs. per square inch, the studs or bolts need not be screwed
through the full thickness of the plate, provided that
the depth of screwing is not less than the diameter of
the stud and the stud is locked against turning by welding
or other means approved by the Inspecting Authority. Lugs
may be satisfactorily welded to manhole doors for the
attachment of bolts. All welds shall be made to the satisfaction
of the Inspecting Authority. |
| c) |
Internal doors for opening
not larger than 9 inches x 7 inches size need only be
fitted with one stud, which shall be provided with an
integral colar and screwed through the plate with a nut
on the inside of the door. Internal doors of opening not
larger than 5 inches x 3½ inches may have the stud
forged solid with the door or screwed, be efficiently
riveted to the doors. Where the door of a mudhole cleaning
hole or sight hole is fabricated by welding for boilers
not exceeding a working pressure of 8.8 kg./cm.2 (125
lbs. per sq. inch), the stud shall pass through the plate
and be secured to it by strength-welding on the inside
and fillet-welding on the outside to the satisfaction
of the Inspecting Authority. The door shall be stress
relieved by heat-treatment after welding. |
| d) |
The cross bars shall be of
substantial proportions and of mild or wrought steel. |
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