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Reg. 148
STAY TUBES

 

Stay Tubes

a) 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.
b) 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.
c) 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.
d) Each stay tube shall be designed to carry its due proportion of the load on the plates which it supports.
e) 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.
f) 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.
 

TABLE

Nominal outside diameter in millimetres Minimum thickness in millimetres
Not exceeding 38 2.28
Exceeding 38 but not exceeding 51
2.81
Exceeding 51 but not exceeding 70 3.12
Exceeding 70 but not exceeding 76.2 3.38
Exceeding 76.2 but not exceeding 88.9 3.96
Exceeding 88.9 but not exceeding 101.6 4.26
Exceeding 101.6 but not exceeding 127 4.55
 
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