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Reg. 227, Reg. 228, Reg. 229
FURNACES
Cross Tubes
The working pressure of the tubes shall be determined by the
following formula :-
| W. P. = |
200 (t - 7)
|
Eqn.(64) |
| D |
where
W. P. = working pressure in lbs. per sq. inch.
t = minimum thickness in 32nds of an inch.
D = the internal diameter in inches of the cross tube.
Reg. 228
FURNACES
Uptakes of Vertical Boilers
The working pressure for uptake tube of vertical boilers
shall be determined by Eqns. 57 and 58 but only half the least
pressure so found is to be allowed for uptake tubes.
Reg. 229
SUPPORTS FOR COMBUSTION CHAMBER AND FIREBOX CROWN
Girder stay for firebox crowns
| a) |
For girders supporting crown
plates of rectangular fireboxes, where the ends of the
girders are supported by the vertical end or side plates,
their proportions shall be calculated from the following
formula : -
| W. P. = |
CSTD2 |
Eqn.(65) |
| L2Y |
where
W. P. = working pressure in lb. per sq. inch,
S = Minimum tensile stress of the material in tons per
sq. inch,
T = Total thickness of the stay in thirty seconds of an
inch,
D = Depth of the girder stay in inches,
L = Length of girder stay in inches measured between the
inside of the tube plate and the firehole plate, or between
the inside of the side plates, according to the method
of support
Y = Pitch of girder stays in inches,
C = 22 for steel plates or steel forgings, 19 for steel
castings. |
| b) |
Where girders are supported
in any other way than by the end or side plates of the
firebox or combustion chamber the calculations for determining
the working pressure shall be made in accordance with
the actual conditions of support.
In such cases the length of the strip of firebox or
combustion chamber top plate to be supported by the
girder shall, subject to the limit imposed on the distance
of the nearest stay, be taken as equal to the product
of the number of bolts carried by the girder into the
pitch of the bolts. A maximum nominal stress of 14,000
lbs. per square inch on girder section shall be allowed
for steel.
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| c) |
Slings, links pins, rivets
and connections to shell of slung girders shall be sufficient
to carry the whole load that would otherwise be carried
by the girder, and each girder must be equally slug or
supported. For stresses allowed on the sections, see Regulation
203. |
| d) |
In the case of girders supported
at the ends only by angle bars riveted to casing crown,
the length L may, when the girder extends over the full
breadth of the angle face, be taken as the distance between
the centres of the angle faces. When this distance does
not exceed that of L in the formula, the pressure shall
be determined in the ordinary way. The supporting angles
and rivets shall be of sufficient section for the intended
purpose. For stresses allowed on the sections, see Regulation
203. |
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