

Reg. 596, Reg. 597
Foundations of Vertical Boilers Furnaces


When
circular furnaces of fireboxes of vertical boilers are
not connected to the shell crown by uptake tube, smoke
tubes 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 any ogee ring is fitted, shall not exceed that found
by the following formula:
W.P. = 
C(t1)² 
Equation XII/31 
D(DD_{1}) 
W.P. is working pressure in pounds per square inch.
t is thickness of the joggled firebox plate or ogee ring
in thirty seconds of an inch.
D is inside diameter of the boiler shell in inches.
D_{1} is 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.
C = 140 for Ogee rings (see Fig
XII/26 and XII/27.
C = 100 where ‘U’ ring section is used (see Fig.
XII/28) 
Reg. 597
Foundations of Locotype Boiler Fireboxes
Where
the firebox roof in locotype boilers is, not stayed direct
to the external casing crown or to girders carried by
the casing or if not connected to the casing by slings
the working pressure for the parts, if plates are joggled
out to meet the casing or if an ogee ring is fitted, shall
not exceed that found by the following formula:
W.P. = 70 
(t1) x (L+W)

Equation XII/32 
L+W(WW_{1}) 
WP is working pressure in pounds per square
inch. 
t is thickness of the joggled firebox side plates
or fire hole plate (whichever is less) or ogee ring
in thirty seconds of an inch. 
L is length of firebox casing in inches measured
between the water sides of front end plate and saddle
plate at the foundation seam. 
W is width of firebox casing in inches measured
between the water side of casing side plates at
the foundation seam. 
W_{1} is width of firebox in inches measured between
the water sides of firebox side plates at the commencement
of curvature above joggled part or 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
LXW in the bottom line of the formula thus:
(L X W – A)(WW_{1}) and so used in Equation XII/32
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.


