ASME B16.11 Socket Weld and Threaded Fitting Dimensions

ASME B16.11 governs forged socket-welding and threaded fittings.
It is the dimensional standard behind every nickel alloy socket weld elbow,
tee, reducer, cap and stub end we supply in forged form, and it is the
reference a purchaser uses to check a fitting before it is welded into a
line. This page reproduces the dimension table from the standard itself,
sizes NPS 1/8 through NPS 4, in millimetres.

The dimensional letters used below are the standard’s own:

• B – socket bore diameter, the recess the pipe seats into.
• D – bore diameter of the fitting, the passage through it.
• C – socket wall thickness, the wall of the socket itself.
• G – body wall thickness, the wall of the fitting body.
• J – socket depth, how far the pipe enters the socket.
• A – centre-to-bottom of socket, from the fitting centreline to
  the bottom of the socket recess. It is the dimension a piping layout needs
  to set the take-out from the pipe centreline.

Socket bore and bore diameter

The socket bore B is bored larger than the pipe outside diameter so that
the pipe seats on the bottom of the socket and the fillet weld is made
outside the pipe wall. The bore diameter D is the passage through the
fitting.

Socket wall thickness and body wall thickness

Socket wall thickness C is given as an average and a minimum because the
socket is machined with a slight taper; the body wall G is the minimum
wall of the fitting body at each class.

Socket depth and centre-to-bottom of socket

Dimension A is the take-out dimension for a piping layout, given
separately for a 90 degree elbow, tee or cross and for a 45 degree elbow,
at each of the three classes.

What the numbers mean for a purchase order

Three points decide whether a socket weld fitting can actually be
matched to the pipe it will be welded to, and all three are visible in
the tables above.

First, B must be at or above the pipe outside diameter for the
nominal size. A 1/2 inch nominal pipe has an outside diameter of 21.34 mm
under ANSI B36.19, and the B16.11 socket bore for that size runs from
21.8 mm to 22.2 mm. A fitting whose socket bore is below the pipe
diameter will not take the pipe.

Second, G, the body wall, must be compared against the minimum
wall the piping code requires for the service, and the class chosen must
correspond to the pressure rating, not merely to the nominal size. Class
3000, 6000 and 9000 in this table are the fitting classes; the pressure
rating follows from the pipe schedule used with the fitting, which is why
ASME B16.11 Table 8 pairs each class with the pipe schedule used to
calculate the rating.

Third, A fixes the take-out. A 90 degree elbow in NPS 1 gives
A = 22.5 mm at Class 3000 and 32.0 mm at Class 9000, so the take-out
changes with the class and cannot be assumed constant for a given size.

Where this fits with the rest of the range

Socket weld and threaded fittings are the forged half of our fitting
range. The wrought butt weld fittings are dimensioned to ASME B16.9 and
are covered in our
nickel
alloy butt weld fittings range, and the forged socket weld and threaded
forms are in
nickel
alloy forged socket weld fittings and
nickel
alloy forged threaded fittings. Material grades, stock programme and
inspection requirements are set out on our
nickel alloy
fittings page.

The dimensional data in this table is reproduced from ASME B16.11-2016.
Where a purchase order specifies a different edition of the standard, the
dimensions of that edition govern the manufacture.