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Inner Ring Dimensions For ASME B16.20
NPS Class Class Class Class Class Class Class
Nominal Pipe Size 150 300 400 600 900 1500 2500
1/2" 0.56 0.56 NOTE 1 0.56 NOTE 1 0.56 0.56
3/4" 0.81 0.81 NOTE 1 0.81 NOTE 1 0.81 0.81
1" 1.06 1.06 NOTE 1 1.06 NOTE 1 1.06 1.06
1-1/4" 1.5 1.5 NOTE 1 1.5 NOTE 1 1.31 1.31
1-1/2" 1.75 1.75 NOTE 1 1.75 NOTE 1 1.63 1.63
2" 2.19 2.19 NOTE 1 2.19 NOTE 1 2.06 2.06
2-1/2" 2.63 2.63 NOTE 1 2.63 NOTE 1 2.5 2.5
3" 3.19 3.19 NOTE 1 3.19 NOTE 1 3.19 3.19
4" 4.19 4.19 4.19 4.19 4.19 4.19 4.19
5" 5.19 5.19 5.19 5.19 5.19 5.19 5.19
6" 6.19 6.19 6.19 6.19 6.19 6.19 6.19
8" 8.5 8.5 8.25 8.25 8.25 8.12 7.88
10" 10.56 10.56 10.25 10.25 10.25 10.15 9.75
12" 12.5 12.5 12.5 12.5 12.38 12.38 11.5
14" 13.75 13.75 13.75 13.75 13.5 13.38 NOTE 1
16" 15.75 15.75 15.75 15.75 15.5 15.25 NOTE 1
18" 17.69 17.69 17.69 17.69 17.5 17.25 NOTE 1
20" 19.69 19.69 19.69 19.69 19.5 19.25 NOTE 1
24" 23.75 23.75 23.75 23.75 23.75 22.75 NOTE 1
NOTE 1 There are no class 400 flanges in NPS 1/2” throug 3” (use class 600); nor class 900
  Flanges in NPS 1/2” through 2-1/2” (use class 1500); nor class 2500 flanges NPS 14” and larger.
** The Inner Ring Thickness shall be .118 to .128 inch

 

 

 

 

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