The socket welding flange is similar to a slip-on flange except it has a bore and a counterbore dimension. The counterbore is slightly larger than the O.D. of the matching pipe, allowing the pipe to be inserted into the flange similar to a slip-on flange. The diamter of the smaller bore is the same as the I.D. of the matchine pipe A restriction is built into the bottom of the bore which sets as a shoulder for the pipe to rest on. This is eliminates any restriction in flow when using a socket welding flange.
Specifications:

Socket Welding Flanges
Size: 1/2" to 60", DN 12mm to DN 1500mm view...
Pressure class: Class 150 to Class 2,500, PN 2.5 to PN 250
Facing: RF / RTJ
Material:view...
Cabon steel: A105, A350 LF2
Stainless steel: A182 F304/F304L/F316/F316L/F321
Alloy steel: F11, F12
Packing: plywood case and plywood pallet
Uses of socket weld flanges:
They are ideal for small diameter applications.
They are used for high pressure applications.
Socket weld flanges have an internal recess on the inside diameter which allow for a smoot flow of the process fluid.
They create a smooth bore with the proper welding and grinding.
Note:
Flange dimensions to ANSI B16.5.
Dimensions "B" & "D" includes raised face thickness.
Bore (SCH) "C" purchasess to Specity.
Larger outlet sizes are avilable on applications.
ANSI 150# / 300# 2mm Raised Face.
ANSI 600# / 2500# 7mm Raised Face.
Standards, Dimensions & Weight
ASME/ANSI B16.5 Class 150 SW
ASME/ANSI B16.5 Class 300 SW
ASME/ANSI B16.5 Class 600 SW
ASME/ANSI B16.5 Class 1500 SW