Reg. 555, Reg. 555 a, Reg. 555 b,
Reg. 555 c
Seatings for mountings
For pressures not exceeding 125 pounds per square inch
mountings with screwed ends not exceeding 1 inch may
be used; the screwed portion of any such mounting being
an integral part thereof and the thickness at the bottom
of the thread being not less than 3/16 inch.
The mountings may be screwed:-
Directly into the boiler shell plate, nuts being fitted
on the waterside, or into steel distance pieces the
length of thread engaged being in no case less than
the bore of the mounting plus ¼ inch.
The distance pieces shall be made from solid mild steel.
They shall be screwed into the plate and fitted with
nuts on the water side. The walls of the distance pieces
shall be not less than ¼ inch thick at the bottom
of the thread.
Mountings may be attached directly to any shell or end
plate where the plate is of sufficient thickness to
allow a suitable surface to be obtained for the attachment
of the boiler mounting.
The minimum thickness at the hole in the shell or end
plate shall be not less than the thickness required
for the maximum permissible working pressure considering
the plate as being unpierced.
Where the boiler mountings are secured by studs the
studs shall have a full thread holdings in the plate
for at least one diameter. If the stud holes penetrate
the whole thickness of the plate, the stud shall be
screwed right through the plate and be fitted with a
nut inside having a thickness equal to the diameter
of the stud. Where bolts are used for securing mounting
they shall be screwed right through the plate with their
heads inside the shell or end plate.
Reg. 555 a
Where standpipes are used, the flanges shall be machined
or flame-cut by machine on the edges. The bolting flanges
shall be machined on the jointing and bolting surfaces.
Reg. 555 b
Where saddles are used, the edges of the flanges shall
be machined or flame-cut by machine. The jointing surfaces
shall be machined. The studs for the attachment of the
mountings, if screwed through the saddle, shall be fitted
on the inside with nuts of full thickness.
Where the stud holes do not penetrate through the saddles
the length of the screwed portion of the stud in the
plate shall be not less than the diameter of the stud.
Reg. 555 c
Where pads are used, the joining surfaces shall be
machined. The pads shall have sufficient thickness to
allow the drilling of the stud holes for mountings without
the inner surface being pierced and the length of the
screwed portion of the stud in the pad shall be not
less than the diameter of the stud.