Limit of Reinforcement UG-40

Can any one give clear example or exact meaning of UG-40 or limit of reinforcement,

b.The limits of reinforcement, measured parallel to

the vessel wall, shall be at a distance, on each side of the

axis of the opening, equal to the greater of the following1.the diameter d of the finished opening;

2.the radius Rn of the finished opening plus the

vessel wall thickness

t, plus the nozzle wall thickness tn.

: this means RF OD should be with in 2 time diameter of the nozzle at corroded condition or it is more then 2d

QES: in some customer standards they will provide as RF as 2 inch or 50mm min.