About Central Boilers Board •Contents Chapter Wise • Contents Regulation WiseIndian Boilers Act 1923
Reg. 230, Reg. 231, Reg. 232
PATENT FIREBOX ROOFS OF LOCOTYPE BOILERS

Marshall Type

For Messrs. Marshall Sons and Company's patent stayless roof for fireboxes of locotype boilers made of steel in which the centre lines of the corrugations meet the centre lines of the end riveted seams at points not farther distance from the side plates than one-half the inner radius of curvature of the corner formed by the roof and side plate, in order to ensure that the thickness and height of the pressed diagonal corrugations of the chamber are satisfactory, the working pressure shall not exceed the smaller of the values obtained from the following formulae:-
 W. P. = 25000 ( t - 1 ) x H2 Eqn.(66) W x L x ( W2 + L2)1/2

 W. P. = 55 ( t - 1 )2 x ( W +( ( W2 x L2 )2)1/2 Eqn.(67) W2 x L2

where
t is the thickness of the roof plate in 32nds of an inch,

H is the height of the corrugation at its highest part measured perpendicularly on one side of the plate in inches,

W is the width of the roof plate between the flat of side plate at top less the inner radius of curvature of corner of roof and side plate in inches, i.e. W + radius = internal width of firebox at top,

L is the length of the roof plate between centre lines rivets in inches.

Reg. 231
PATENT FIREBOX ROOFS OF LOCOTYPE BOILERS

Garrett Type

For Messrs. Richard Garrett and Son's corrugated stayless roof for fireboxes of locotype boilers made of steel in which the side corrugations are parts of true circles and the radius of the middle corrugation is not more than about 1/4th of the radius of the outer corrugations and the corrugations are cambered longitudinally, the working pressure shall not exceed the smaller of the values obtained from the following formulae :-
 W. P. = C X ( t - 1 )2 Eqn.(68) R L + 24

 W. P. = C1 {10 ( t - 1 ) - L } Eqn.(69) R

Where
t is the thickness of the corrugated plate in 32nds of an inch,

L is the length of the roof plate between centre lines of rivets in inches,

R is the external radius of the side corrugations at the middle of the length in inches,

C = 363 where the roof and side plates are in one piece and 325 when they are riveted,

C1= 12.5 where the roof and side plates are in one piece and 11.25 where they are riveted.

Reg. 232
PATENT FIREBOX ROOFS OF LOCO TYPE BOILERS

Fowler Type

a) For Messrs. John Fowler and Company's (Leeds) corrugated roof for fireboxes of locotype boilers made of steel in which the crown of the roof is transversely curved and corrugated in the style of Fox's corrugated furnace and the roof plate, if not solid with the side plates of the firebox, is securely riveted thereto and to the flanges of the tube plate and fire hole plate and there is a row of suitably sized and spaced screw stays below the commencement of corrugations on each side attaching the roof plate to the external casing, when the conditions hereunder are complied with, the working pressure shall not exceed the smaller of the values obtained from the following formulae ; -
 W. P. = C (t - 3) Eqn.(70) R

 W. P. = C1 (t1 - 1) Eqn.(71) W

where
t is the thickness of roof plate before corrugations are formed, in 32nds of an inch,

t1 is the thickness of side plates of firebox to which roof plate is attached, in 32nds of an inch,

R = the radius of transverse curvature or camber of middle part of corrugation measured from the bottom of corrugation on water side in inches,

W = the width of firebox in inches measured over water sides of side plates at the seams attaching them to roof plate,

C = 240

C1= 875
b) The corrugations measured from top to bottom on one side, shall not be less than three times the thickness of the finished plate in depth and not more than 12 times the thickness of the finished plate apart.
c) The inner radius of corner at sides where corrugations merge into the flat sides shall be not less than 4 times the thickness of the finished plate
d) the length of the plain parts at ends of roof between the centre lines of riveted seams and commencement of curvature of corrugations shall not exceed that allowed for flat plate margins under Regulation 200.

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