Procedure 6-7 Local Thin Area LTA

Occasionally a vessel shell will sustain damage or be overground in a local area such that the thickness in the damaged area is below the minimum wall thickness. This is known as a Local Thin Area or LTA . ASME VIII-1 has allowance for such a case as long as certain proportions and guidelines are followed. These guidelines are taken from ASME Section VIII, Division 1, Mandatory Appendix 32 and are presented here. 

Maximum design temperature is less than shown in Table 6-16 for a given material. 

These rules do not apply to corrosion resistant lining or weld overlay. 

A pair of LTA with finished axial length, Li and L2, providing all of the conditions for a single LTA are met and all of the following  

When 6 45 , the minimum axial separation shall be the greater of the following  

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