ANSI B16.5 Flanges – Dimensional Tolerances

ASME B16.5 FLANGES DIMENSIONAL TOLERANCES:

WELDING NECK FLANGES
0 Outside Diameter When 0 is 24″ or less ±0.06″ ±1.6 mm
When O is over 24” ±0.12″ ±3.2 mm
R Diameter of Contact Face 0.06” (1.6 mm) raised face ±0.03″ ±0.8 mm
0.25″ (6.4 mm) raised face ±0.02″ ±0.5 mm
A Diameter of Hub at Point of Welding NPS 5 and smaller +0.09″, -0.03″ +2.4 mm, -0.8 mm
NPS 6 and larger +0.16″, -0.03″ +4.0 mm, -0.8 mm
B Inside Diameter NPS 10 and smaller ±0.03″ ±0.8 mm
NPS 12 to 18, inclusive ±0.06″ ±1.6 mm
NPS 20 and larger +0.12″, -0.06” +3.2 mm, -1.6 mm
X Diameter of Hub at Base When Hub Base is 24″ or less ±0.06″ ±1.6 mm
When Hub Base is over 24″ ±0.12″ ±3.2 mm
c Thickness NPS 18 and smaller +0.12″, -0.00″ +3.2 mm, -0.0 mm
NPS 20 and larger +0.19″, -0.00″ +4.8 mm, -0.0 mm
Drilling Bolt Circle Diameter ±0.06″ ±1.6 mm
Bolt Hole Spacing ±0.03″ ±0.8 mm
Eccentricity of Bolt Circle and Facing with Respect to Bore NPS 21/2 and smaller ±0.03″ ±0.8 mm
NPS 3 and larger ±0.06″ ±1.6 mm
Length Through Hub NPS 10 and smaller ±0.06″ ±1.6 mm
NPS 12 and larger ±0.12″ ±3.2 mm
SLIP-ON, LAP JOINT, SOCKET WELDING, THREADED and BLIND FLANGES
O Outside Diameter When O is 24″ or less
When O is over 24″		 ±0.06″ ±0.12″ ±1.6 mm
±3.2 mm
R Diameter of Contact Face 0.06″ (1.6 mm) raised face 0.25″ (6.4 mm) raised face ±0.03″ ±0.02″ ±0.8 mm
±0.5 mm
B Inside Diameter at Face of Socket Welding Flanges

Inside Diameter of Slip-On, Lap Joint, and Socket Welding

 NPS 10 and smaller
NPS 12 through 18, inclusive NPS 20 and larger		 ±0.03″ ±0.06″ +0.12″, -0.06″ ±0.8 mm
±1.6 mm
+3.2 mm, -1.6 mm
NPS 10 and smaller
NPS 12 and larger		 +0.03″, -0.00″ +0.06″, -0.00″ +0.8 mm, -0.0
+1.6 mm, -0.0 mm
Q Counterbore, Threaded Flanges NPS 10 and smaller
NPS 12 and larger		 +0.03″, -0.00″ +0.06″, -0.00″ +0.8 mm, -0.0
+ 1.6 mm, -0.0 mm
X Diameter of Hub at Base NPS 12 and smaller
NPS 14 and larger		 +0.09″, -0.06″ ±0.12″ +2.4 mm, -1.6
±3.2 mm
c Thickness NPS 18 and smaller
NPS 20 and larger		 +0.12″, -0.00″ +0.19″, -0.00″ +3.2 mm, -0.0
+4.8 mm, -0.0 mm
Drilling Bolt Circle Diameter Bolt Hole Spacing ±0.06″ ±0.03″ ±1.6 mm
±0.8 mm
Eccentricity of Bolt Circle and Facing with Respect to Bore NPS 2V2 and smaller
NPS 3 and larger		 ±0.03″ ±0.06″ ±0.8 mm
±1.6 mm
Overall Length Through Hub NPS 18 and smaller
NPS 20 and larger		 +0.12”, -0.03”
+0.19”, -0.03”		 +3.2 mm, -0.8 mm
+4.8 mm, -1.6 mm

Industrial Flanges Available Materials and Grades

Ample Alloys

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