Select flange size1


Weld Neck Flange steel type
and strength
Matching pipe size
schedule and strength


  I.D. O.A.L.
1 See important information and cautions below.
** When a double asterisk appears after the "Matching pipe size", it indicates that WOODCO USA recommends a heavier pipe schedule than that specified by API.

All API Specified 6B Weld Neck Flanges have restricted bores to match standard pipe sizes and schedules. API Spec 6A does not provide specifications for 6B Weld Neck Flanges in sizes above 11” nominal, WOODCO USA shows 6B “type” Weld Neck Flanges in sizes above 11” because operators request these flanges.

All Weld Necks shown have a minimum wall thickness of .200 inches, which in some cases exceeds API requirements.  See Weld Neck Flanges section of this Web Site for more information.  Click here to find Carbon Steel Pipe Dimensions to match Flange Weld Necks other than those shown.

Note: API Spec 6A does not specify Over All Length of 6BX Weld Neck Flanges, but instead provides dimensions of specific portions of the flange, with tolerance, that manufacturers must add together, along with an undefined weld bevel, to achieve a length. Consider any length for API 6BX Weld Neck Flanges shown on this website as an approximate length. When API Spec 6A provides no weld neck data for a specific 6BX flange, WOODCO USA has concluded that operators will not choose to make a field weld attachment of that flange and suggests no weld neck dimensions.

API Spec 6A Specified, 6 BX Weld Neck Flanges, have material and dimensions that conform to the requirements for full bore Integral flanges.

For information about full bore API 6B weld neck flanges, made to integral flange specifications, Click Here.

To view cautions about Series 2900 Weld Neck Flanges, Click Here.  

To view cautions about 6BX Weld Neck Flanges, Click Here.

To learn more about Weld Neck Flanges, Click Here.

To View Carbon Steel Pipe Dimensions and Weights, Click Here.

To Calculate Working Pressure for API 5L Line Pipe, Click Here.


Manufacturers may also make API 6B Weld Neck Flanges to Integral flange specifications for the purpose of attaching the flanges to bodies of equipment by welding, thus making them integral to that equipment. These flanges, made to integral flange specifications, may also be sold as “Full Bore Weld Neck Flanges” intended for attachment to equipment or tubular members by the purchaser. These “Loose” integral flanges require that the purchaser use the same Qualified Welding Procedures and Post Weld Heat Treatment as that used to manufacture any new equipment having integral flanges attached by welding. The “full bores” of these flanges may not match any commonly available pipe size, as the neck O.D.’s and weld preparations must satisfy API Spec 6A stress allowables. API Spec 6A requires that all integral flanges attached by welding shall have Full Penetration Welds.