Introduction to threaded pipe fittings (ASME B16.11)

Screw connection is probably the earliest method of pipe system connection. Similar to socket welded pipe fittings, threaded pipe fittings are usually used for small diameter pipes with a nominal diameter of DN50 and below.

The dimensions of taper pipe threads are specified in ASME B1.20.1. The standard specifies the number of threads per inch, pitch diameter and screw in length of pipe thread.

Threaded pipe fittings are usually used in low cost and non harsh working conditions. For example: domestic water, fire pipeline and industrial cooling system.

Stainless steel forged threaded elbow A182 F316 90 degree

Stainless steel forged threaded elbow A182 F316 90 degree

The materials of threaded pipe fittings usually include gray cast iron or malleable cast iron, cast brass or bronze, forged alloy or carbon steel.

There are three pressure grades of threaded pipe fittings specified in ASME B16.11: class2000, 3000 and 6000.

NPT thread

NPT thread is adopted for threaded pipe fittings in ASME B16.11 standard, i.e. taper pipe thread in ASME B1.20.1, which is the most commonly used mechanical connection and hydraulic seal thread. The internal and external threads of NPT are tapered and sealed with polytetrafluoroethylene tape or sealant.

ASME B16.11 threaded equal tees

ASME B16.11 threaded equal tees

DN-NPT OD 攻丝钻孔直径 mm 每英寸的牙数 TPI 螺距 Pitch
mm mm
1/16″ 7.895 6 27 0.941
1/8″ 10.242 8.25 27 0.941
1/4″ 13.616 10.7 18 1.411
3/8″ 17.055 14.1 18 1.411
1/2″ 21.223 17.4 14 1.814
3/4″ 26.568 22.6 14 1.814
1″ 33.228 28.5 11.5 2.209
1.1/4″ 41.985 37 11.5 2.209
1.1/2″ 48.054 43.5 11.5 2.209
2″ 60.092 55 11.5 2.209
2.1/2″ 72.699 65.5 8 3.175
3″ 88.608 81.5 8 3.175
3.1/2″ 101.316 94.3 8 3.175
4″ 113.973 107 8 3.175
5″ 141.3 134.384 8 3.175
6″ 168.275 161.191 8 3.175
8″ 219.075 211.673 8 3.175
10″ 273.05 265.311 8 3.175
12″ 323.85 315.793 8 3.175

 

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