Reg. 551, Reg. 552, Reg. 553
Girder stays for Firebox and Combustion Chamber Crowns
Where girder stays are attached with stay bolts and
nuts, they shall be bedded to the corners or ends of
The attachment of girder stays welded directly to the
crown plates shall comply with Figures XII/47, XII/48,
XII/49, XII/50 or XII/51. Such girders shall be welded
to the crown plate prior to stress-relieving.
Each girder shall be of sufficient strength to support
its due proportion of the load on the crown plate independently
of the crown plate, and the bolts or weld attachments
shall have sufficient cross-sectional area to carry
the applied load.
The waterways between the underside of the girder and
the crown plate shall be as large as practicable, but
in no case less than 1 ½ inches deep.
Gusset stays shall be flat and perpendicular to the
end plates. Gusset plates shall not be subjected to
cranking or setting.
At least one manhole or sight hole shall be provided
in the upper part of the boiler, the dimensions being
not less than those in Table XII/2 for the given size
Dimensions of Manholes or Sight Holes
|Diameter of boiler
||Minimum size of hole
|Boilers not exceeding
2 feet and 6 inches
||9 x 7
|Boiler over 2 feet and
6 inches diameter and not exceeding 3 feet
||12 x 9
|Boiler over 3 feet diameter
and not exceeding 3 feet and 6 inches
||14 x 10
|Boiler over 3 feet and
6 inches diameter and not exceeding 4 feet
||15 x 11
|Boiler over 4 feet
||16 x 12
Where the size of construction of the boiler does not
permit of entry for cleaning or inspection of all internal
surfaces, cleaning holes sufficiently large and numerous
shall be provided for this purpose. The cleaning holes
shall be not less than 3 ½ inches x 2 ½
inches in size.
One cleaning hole shall be provided opposite at least
one end of each crosstube in a vertical crosstube boiler.
Where the water tubes are arranged in banks, an opening
of sufficient size to permit of their replacement shall
to be provided.
At the bottom of the narrow water space in vertical boilers
where internal access is not possible, mud holes shall
be arranged at equal distances round the circumference
of the boiler not less in number than as given in Table
Number of Lower Cleaning Holes of Mud Holes
|Diameter of boiler
||No. of holes
|2 Feet and over but not
exceeding 3 feet
|Over 3 feet and not exceeding
|Over 5 feet and not exceeding
|Over 6 feet and not exceeding
7 feet and 6 inches
|Over 7 feet and 6 inches
and not exceeding 8 feet and 6 inches
|Over 8 feet and 6 inches
and not exceeding 9 feet
Cleaning holes or mud holes in loco-type boilers shall
be provided at each bottom corner or as nearly as possible
in the corners of the outer firebox casing and at the
top corners above firehole opening and also at each corner
of the saddle plate in line with the bottom of barrel.
Smoke box tube plate shall be provided with a mud hole.
A manhole shall be provided in the lower part of front
end plates of Lancashire boilers and in similar boilers
with internal flues wherever practicable.