|Reg. 223, Reg. 224, Reg. 225, Reg. 226
Hemispherical Furnaces of Vertical Boilers
When furnaces are hemispherical in form and subject to pressure
on the convex side and are without support from stays of any
kind, the maximum working pressure shall be : -
|W. P. =
||275 (t - 1)
t is the thickness of the top plate in 32nds of an inch,
R is the outer radius of curvature of the furnace in inches.
Corrugated Fireboxes of Vertical Boilers
For the semi-spirally corrugated fireboxes of "Sentinel"
standard motor wagon boilers the working pressure shall be determined
by the following formula :-
|W. P. =
||C (t - 1)
t is the thickness of the firebox plate in 32nds of an inch.
D is the mean of the external diameters of firebox measured
over the plain part at each end at commencement of curvature
C = 390
Foundations of Vertical Boiler Furnaces
Where circular furnaces, or fireboxes of vertical boilers
are not connected to the shell crown by uptake tube, smoke tube
or bolt stays and the whole load on the firebox vertically is
borne by the bottom part of the firebox where it is connected
to the shell the working pressure for the part, if firebox is
joggled out to meet the shell or if an ogee ring is fitted,
shall not exceed that found by the following formula ; -
|W. P. =
||140 (t - 1)2
|D (D - D1)
t is the thickness of the joggled firebox plate or ogee ring
in 32nds of an inch.
D is the inside diameter of the boiler shell in inches,
D1 is the outside diameter of the joggled firebox at the commencement
of curvature above joggled part or the outside diameter of the
firebox where it joins the ogee ring.
Foundations of Loco-type Boiler Fireboxes
Where the firebox roof in loco-type boilers is not stayed
direct to the external casing crown or to girders carried by
the casing or is not connected to the casing, by slings in accordance
with Regulations 229(c) and the whole load on the firebox vertically
is borne by the bottom parts of the firebox where connected
to the external casing, the working pressure for the parts,
if plates are joggled out to meet the casing or if an ogee ring
if fitted, shall not exceed that found by the following formula
|W. P. =
||70 (t - 1)2 x (L + W)
|L x W (W - W1)
t is the thickness of the joggled firebox side plates or fire
hole plate (whichever is less), or ogee ring in 32nds of an
L is the length of firebox casing in inches measured between
the water sides of front end plate and saddle plate at the foundation
W is the width of firebox casing in inches measured between
the water sides of casing side plates at the foundation seam.
W1 is the width of firebox in inches measured between the water
sides of firebox side plates at the commencement of curvature
above joggled part of where it joins the ogee ring.
Where only a comparatively narrow strip of the firebox roof
is stayed directly to the casing crown the area so stayed shall
be deducted from the area represented by L x W in the bottom-line
of the formula thus: (L x W - A) (W - W1) and so used in Equation
(63) in determining the working pressure for the parts, "A"
being the area in square inches of the part of roof supported
by the casing crown.