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Reg. 580, Reg. 581
Pitch of tubes
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The spacing
of tube holes shall be such that the minimum width in
inches of any ligament between the tube holes shall be
not less than:-
alternatively,
the thickness and cross-section of the plate between
the tube holes shall be not less than
0.125D+0.2=minimum thickness in inches.
0.17D+0.025=minimum cross-section in square inches where
D is diameter of the tube holes in inches.
In no case shall the minimum thickness of any tube plate
in the tube area be less than the following limits:-
T=1/2 inch, Where the diameter of the tube holes does not exceed
2 inches.
T=9/16 inch, Where the diameter of the tube hole is greater than
2 inches.
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Reg. 581
Stay tubes
Stay
tubes shall be of steel seamless or electrically resistance
welded.
| a) |
Minimum thickness of
stay tubes – The minimum thickness of stay
tubes shall be as per regulation
148. |
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| b) |
The
maximum working pressure for screwed in stay tube shall
be calculated by the following formula:
| WP = |
5900 |
1.28
[(D---------------/N )² - D1²] |
Equation XII/16 |
| A |
D is diameter of the stay tube over threads in inches.
D1 is internal diameter of the tubes under the threads
in inches.
N is number of threads per inch.
A is the area in square inches supported by one Stay tube,
measured from centre to centre of stay tubes. When the
area contains tubes or parts of tubes their aggregate
area, calculated from their smallest external diameter
of body when in tension and smallest internal diameter
when in compression, shall be deducted from the area of
the containing figure and the remainder used as A in the
formula.
Where stay tubes have their thickness increased at the
screwed, ends to provide for plus threads the increased
thickness shall be obtained by up-setting and not by welding,
and the tubes shall be subsequently annealed.
Stay tubes may be attached to the tube plates either by
screwing or by metal arc welding.
Where stay tubes are screwed into the tube plates they
shall be screwed with a continuous thread not finer than
11 threads per inch at both ends and shall be expanded
into the tube plates, by roller expander and, if desired,
may be seal welded.
Welded attachment of stay tubes be as shown in Figure
XII/67,XII/67A,XII/68, ,XII/68A
and XII/69. |
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