(i)
For boiler as per clause (I) of sub-regulation
(ggg) of regulation
546:-
(a)
Arrangement of stays: Stays
shall be arranged to give sufficient breathing space around the furnace
connections and tube nests (see figures XII/75
and XII/77) and shall divide the
unstayed area equally
(b)
Multi-tubular boilers: For
both the front and near attachment of furnaces, the breathing spaces between
furnace and tube nests or between furnace and shell shall be a minimum of 50mm
or 5% of the shall inside diameter, whichever is larger, with a maximum
requirement of 100mm.
Clearances
between the furnace and wet-back wrapper plates shall not require consideration
as breathing spaces.
In
the case of reverse flame boilers, the breathing space at the front end
between furnace and tube nests shall be not less than 50mm and the breathing
space formed by the outer – annuler area of the furnace rear plate shall be
not less than 50mm or 5% of the shell inside diameter, whichever is larger,
with a maximum of 100mm.
Breathing
spaces between gusset or link stays and tube ends shall be not less than 100m.
Clearances between the tubes and wet-back wrapper plates shall not require
consideration as breathing spaces.
Breathing
spaces between tubes and shells shall be not less than 40mm.
Breathing
spaces between gusset or link stays and furnaces shall be not less than
200mm except that for shell outside diameters exceeding 1800mm and furnace
lengths exceeding 6000mm they shall be not less than 250mm and for shell
outside diameter less than 1400mm and furnace lengths less than 3000mm they
shall be not less than 150mm.
All other
breathing spaces shall be a minimum of 50mm or 3% of the shell inside diameter,
whichever is larger, with a maximum requirement of 100mm.
(c)
Cornish and Lancashire boilers.-
In
Cornish boilers, the circle defining the breathing spaces shall be as
shown in figure XII/73 i.e. the distance AB between the centre of the stay
circle and the centre of the flue shall be not less than 3e + 63, where e is the
thickness of the end plate in millimetres.
NOTE: For
Lancashire boilers, the proportions shown in table XII/6A given below are
recommended for the portion of the end plates above the furnaces and flues.
Table XII/6A
Breathing space
for Lancashire boilers
Thickness of
end plate (in mm) |
13 |
14 |
16 |
18 |
20 |
Over 20 |
Dimension L
(in mm) (see figure XII/70) |
255 |
280 |
305 |
330 |
330 |
340 |
It is
recommended that the breathing space below the flue be approximately one-half of
the dimensions given in table XII/6A.
(ii) For boilers as per clause (ii) of sub-regulation (ggg) of Regulation
546:-
Stays shall
given breathing space around the furnace connections and tube nests (see figures
XII/70,XII/71,XII,72,XII/73,XII/74,XII/75,XII/76,
XII/77,
XII/80, XII/80A, XII/80B, XII/80C and
XII/80D) and equally
divide the unsayed areas. Breathing
spaces between furnaces and tube nests shall be a minimum of 50mm or 5% of the
shell outside diameter, whichever is larger, but need not be more than 100mm.
Breathing
space between furnaces and shells shall be as given in Table XII/6B or XII/6C as
applicable, but shall be not less than 50mm or, for bowling hoop furnaces, not
less than 75mm as measured from the outside diameter of the bowling hoop.
For the
boilers having more than one furnace, breathing spaces between furnaces shall be
not less than 120 mm.
Breathing
spaces between gusset or link stays and furnaces shall be not less than 200 mm,
except for:
Shell outside
diameter >1800 mm)
or
furnace length >6000 mm) …
250 mm.
Shell outside
diameter <1400 mm)
or furnace
length <3000 mm)
.. 150 mm.
Breathing
spaces between gusset or link stays and tube nests shall be not less than 100mm.
When unflanged
flat end plates as used, the breathing spaces between gussets or link stays and
furnaces shall be increased as follows:
Increases 200
mm to 220 mm
Increases 250
mm to 275 mm
Increases 150
mm to 165 mm
Increases 100
mm to 110 mm
All other
breathing spaces shall be a minimum of 50 mm or 3% of the shall outside diameter
whichever is larger but need not be more than 100 mm.
Table
XII/6B
Breathing
spaces between furnaces and shells when
tube plate thickness does not exceed 25
mm.
(See Table XII/6C also)
Design |
Length between the boiler end plates
L in metres |
Breathing
space
% of outside
Maximum
diameter
mm
(NOTE)
|
Inserted flat ends |
£
5.5
|
5
|
100 |
|
5.5 <
L
£
6.0 |
5.5
|
110 |
|
6.0 <
L
£
6.5 |
6
|
120 |
Flanged ends |
Any length |
5 |
10 |
NOTE: But not less than 50 mm or,
for bowling hoop furnaces 75mm
When the actual thickness of the
end plate exceeds 25mm the breathing spaces in accordance with table XII/6B
shall be increased in accordance with Table XII/6C.
Table XII/6C
Breathing spaces between furnaces and shells
when thickness of the end plate exceeds 25 mm.
Length of furnace |
|
Breathing space |
|
% of
d |
Need not be more than mm |
Minimum
Mm
|
< 5.5 |
6.5 |
130 |
65 |
5.5 < L
< 6.0 |
7.0 |
140 |
70 |
6.0 < L
< 6.5 |
8.0 |
150 |
75 |
(iii) For boilers not covered
under the above clauses of this regulation:-
Gusset stays
shall be arranged to give sufficient bearing space around the furnace
connections and tube nests (see Figures XII/70,XII/71,XII/72,XII/73,XII/74,XII/75,XII/76,
XII/77, XII/80,
XII/80A to XII/80D.
The proportions shown in
Table XII/6D are recommended for the portion of the end plates above the
furnaces and the flues.
Table XII/6D
Breathing
Space
Thickness of end plate
(mm)
|
Dimension ‘L’
(mm)
|
<13
> 13 <
14
> 14 <
16
> 16 <
20
> 20
|
255
280
305
330
340
|
The breathing space below the flues shall be
approximately one-half the diamensions given in Table XII/6.
For gusset stays above the tube
nests, as fitted in multi-tubular waste heat boilers without internal furnaces,
a breathing space of 20.3mm from the centre line of the adjacent tubes to the
toe of the gusset angle or plate, may be maintained. For the back end stays below the furnaces of multi-tubular
dry-back boilers, a breathing space of 152 mm may be maintained where the flues
are constructed in accordance with regulation
546.
Where
the flues are constructed of corrugated sections welded together, a breathing
space of 114mm may be maintained.
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