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Reg. 590

Breathing Space-
Breathing spaces as provided in clause (i), (ii) or (iii) shall provided depending on the design of the boiler with special attention to the provisions of sub- regulation (ggg) of regulation 546 regarding furnances.

 

(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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