Threaded Fittings

Definition and Details of Threaded Fittings ASME B16.11

Threaded Fittings general

Threaded joints probably represent the oldest method of joining piping systems. Like Socket Weld fittings, threaded fittings are mainly used for small pipe diameters (Small Bore Piping); generally for piping whose nominal diameter is NPS 2 or smaller. The dimensional standards for taper pipe threads are given in ASME B1.20.1. That document gives all required dimensions including number of threads per inch, pitch diameter, and normal engagement lengths for all pipe diameters.

NPT Thread

All fittings on this page are described, are provided with NPT thread, ASME B1.20.1. The American National Pipe Thread Tapered, is the best known and most widely used connection where the pipe thread provides both the mechanical joint and the hydraulic seal. NPT has a tapered male and female thread which seals with Teflon� tape or jointing compound.

Ball Long Pattern
TYPES OF THREADED FITTINGS BY CLASS AND SIZE
Description
Class Designation
3000
6000
9000
Elbows 45 and 90 degrees,
Tees, Crosses, Couplings,
Half-Couplings,
End or Pipe Caps
1/2 – 4
1/2 – 2
1/2 – 2
1/2 – 4
1/2 – 2
1/2 – 2
1/2 – 4
1/2 – 2
1/2 – 2
Pipe Size by Wall Thickness
SCH 80 / XS
SCH 160
XXS

Plugs and Bushings are not identified. They may be used up through Class 6000

DIMENSIONS OF AMERICAN TAPER PIPE THREAD, WITH SEALANT COMPOUND

Ball Long Pattern
DN-NPT
Major Diameter mm
Tapping Drill Size mm
TPI
Pitch mm
1/16″
7.895
6.00
27
0.941
1/8″
10.242
8.25
27
0.941
1/4″
13.616
10.70
18
1.411
3/8″
17.055
14.10
18
1.411
1/2″
21.223
17.40
14
1.814
3/4″
26.568
22.60
14
1.814
1″
33.228
28.50
11.5
2.209
1¼”
41.985
37.00
11.5
2.209
1½”
48.054
43.50
11.5
2.209
2″
60.092
55.00
11.5
2.209
2½”
72.699
65.50
8
3.175
3″
88.608
81.50
8
3.175
3½”
101.316
94.30
8
3.175
4″
113.973
107.00
8
3.175
5″
141.300
134.384
8
3.175
6″
168.275
161.191
8
3.175
8″
219.075
211.673
8
3.175
10″
273.050
265.311
8
3.175
12″
323.850
315.793
8
3.175

Fittings for Threaded Pipe systems

ELBOW 90°

This Elbows make 90° changes of direction in the run of pipe.

TEE

This Tee makes 90° branch from the main run of pipe.

CROSS

Crosses makes 90° branch from the main run of pipe.

ELBOW 45°

This Elbows make 45° changes of direction in the run of pipe.

FULL-COUPLING

A Full Coupling, joins pipe two pipe or to a nipple etc...

CAP (END CAP)

Seals the threaded end of pipe.

HALF-COUPLING

The Half Coupling can be directly welded to the run pipe, to make a branch connection.

SQUARE HEAD PLUG

Seals the threaded end of fitting.

HEX HEAD PLUG

Seals the threaded end of fitting.

ROUND HEAD PLUG

Seals the threaded end of fitting.

HEX HEAD BUSHING

Can be used to reduce a threaded fitting.

ROUND HEAD PLUG

Unions are primarily used for maintenance and installation purposes. It is a screwed joint design and it consists of three interconnected pieces. Two internally threads and a centerpiece that draws the ends together when rotated.

Advantages and Disadvantages of Threaded Fittings

ADVANTAGES

REMARK(S) OF THE AUTHOR...

At the smallest sizes, the amount of wall lost during threading actually equals approximately 55% of the original pipe wall.

DISADVANTAGES