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Reg. 223, Reg. 224, Reg. 225, Reg. 226

FURNACES

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)
Eqn.(60)
R

Where
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.

Reg. 224

FURNACES

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) Eqn.(61)
D

Where
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 of flange,

C = 390


Reg. 225

FURNACES

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 Eqn.(62)
D (D - D1)

Where
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.


Reg. 226

FURNACES

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) Eqn.(63)
L x W (W - W1)

where
t is the thickness of the joggled firebox side plates or fire hole plate (whichever is less), or ogee ring in 32nds of an inch.

L is the length of firebox casing in inches measured between the water sides of front end plate and saddle plate at the foundation seam.

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.
 
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