Ansi b16.5 tabela 3

[firsan64]

What does it means the Table 3 in ANSI B16.5 ?
How can I undestand the table 3 of the norm ansi b16.5 (pag. 61)? What kind of defects is described in?

 

[grandnobi]

Table 3 of ASME B16.5 is not a stand-alone document. You first have to fully understand the pertaining paragraph ("Flange Facing Finish Imperfections") of ASME B16.5 before you can successfully use Table 3.

The paragraph reads as follows:
"Imperfections in the flange facing finish shall not exceed
the dimensions shown in Table 3.
Adjacent imperfections shall be separated by a distance of at least four
times the maximum radial projection.
A radial projection shall be measured by the difference between an outer
radius and an inner radius encompassing the imperfection
where the radii are struck from the centerline of
the bore.
Imperfections less than half the depth of the
serrations shall not be considered cause for rejection.
Protrusions above the serrations are not permitted."

When evaluating flange surfaces for imperfections I recommend the following sequence:
1.) Check the depth of the imperfection. This will tell you whether you can ignore the imperfection or which column of Table 3 applies.
2.) Determine the permissible radial projection, based on the NPS of the flange. The shape of the imperfection does not matter. It may be a scratch, a circular spot of corrosion or any foreign particle having been pressed into the flange facing. The value of the maximum permissible radial projection is the same for all tyes of imperfections.
3.) Check the distance between the imperfections.

One more comment: When evaluating flange surfaces, show some common sense and also take into account the service conditions of the flange. If the fluid is not critical and you are far away from the full rating of the flange you may also allow flanges with imperfections exceeding the limits of ASME B16.5.