
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 onehalf 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. = 
C_{1}

{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,
C_{1}= 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 (t_{1}  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
C_{1}= 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. 

