Machining allowance API 650 Table 5-3b Shell Manhole Covers / Flanges

[Quillion]

Do the thicknesses given in this table include a machining allowance for the gasketed face?
Are they the required finished thicknesses or the raw material thicknesses?
Where can this be verified?

 

[JStephen]

I was thinking in the tables, it showed the thickness as the thickness after machining.

 

[fegenbush]

Per Figure 5-7A Note 2, only the flange side need to be machine-finished. Per Table 5-3, the thicknesses of the flange provided are "Minimum Thickness of Bolting Flange After Finishing." So, if you require a specific machining allowance, that must be added to the values listed in the table.

Note: There is a typographical error in the 12th edition page 5-34. Figure 5.7a is incorrectly shown as "Table 5.7a - Shell Manhole."

 

[Quillion]

Thank you for your quick, clear response. It was very helpful.
I don't understand the logic in only machining the flange face. Do you not also require a good seal on the cover side?

 

[fegenbush]

The flange can warp due to welding. The cover is not welded, so it does not have this issue.

 

[Quillion]

Of course. That makes perfect sense. Thank you.