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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(t-1)² Equation XII/31
D(D-D1)

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.
D1 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 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 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 (t-1) x (L+W)
Equation XII/32
L+W(W-W1)

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.
W1  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)(W-W1) 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.

 
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