||Stay tubes are tubes having
a weld depth equal to the nominal tubes thickness plus
3 millimetres. These stay tubes are not required within
tube nests except when the tube nests comprise tubes which
are expanded only.
||If tube nests comprise plain
tubes that are expanded and beaded, expanded and belled
or expanded and welded, welded stay tubes shall be used
in flat plate loadings outside the tube area.
||For plain tubes or stay tubes
exposed to flame or gas temperatures exceeding 600°C,
the ends of welded tubes shall be dressed flush with the
welds. If not so exposed, the ends of welded tubes shall
extend a maximum of 10 millimetres beyond the weld or,
in the case of expanded tubes the tubes shall project
beyond the tube plate upto a maximum of 15 millimetres.
||Each stay tube shall be designed
to carry its due proportion of the load on the plates
which it supports.
||The thickness of stay tubes
welded into tube plates shall be such that the axial stress
on the thinnest part of the tube does not exceed 70 N/mm2.
||The thickness of stay tube
at any part shall not be less than the values shown in
the Table below. Minus tolerances shall be taken into
account when ordering tubes.