|Tubes shall be connected to
the tube plates by one of the following methods:-
bell mounting or seal welding.
||Rolled expanded tubes shall project
through the neck or bearing part in the holes by at least
quarter of an inch and shall be secured from drawing out
by being bellmouthed to the extent of 1/32 for each
inch in diameter plus 2/32.
||Tubes expanded into headers
may be seal-welded inside or outside the header. Where
a seal weld is provided inside the header, the tube end
projection and bellmouthed specified in (b) is not required.
||In the case of roller expanded
tubes the tube holes in the headers shall be formed in
such a way that the tubes can be effectively tightened
in them, there shall be a neck or belt of parallel seating
of at least ½ inch.
||Where the tubes are strength
welded direct to the headers, the technique followed shall
be approved by the Inspecting Authority and all welds
shall be suitably heat treated.
||Bolted joints shall be designed
in accordance with Regulation
||Tube spacers supporting clips
and lugs may be welded to the tubes.
||The tubes shall be so arranged
that they are accessible for cleaning internally and externally.