NPT, PT, G threads are pipe threads

The abbreviation of NPT is National (American) Pipe Thread, which belongs to the American standard 60-degree tapered pipe thread and is mainly used in North America. National standard GB/T12716

The abbreviation of PT is Pipe Thread, a 55-degree sealing taper pipe thread, which belongs to the Whitworth thread family and is mainly used in Europe and the Commonwealth of Nations. It is more commonly used in the water and gas pipeline industry, and the taper is specified as 1:16. The national standard is GB/T7306.

G is a 55-degree threaded pipe thread seal, a family of Whitworth threads, marked G for straight threads. National standard GB/T7307. G is generally called pipe thread (guan), and the division of 55 and 60 degrees is functional, commonly known as round pipe. By cylindrical thread.

In addition, the markings of 1/4, 1/2, and 1/8 in the thread refer to the diameter of the thread size, and the unit is inches. Inline folks usually refer to thread sizes in terms of dots, one inch equals eight dots, 1/4 inch equals two dots, etc.

Since the threads of a Type G connection will bottom out at the wrench flats, no threads are exposed. Once the connector bottoms out to seal, the orientation of the instrument cannot be changed. To avoid problems with inconvenient gauge positioning, use "crush washers" and hand-tight connections. At the point of resistance, there are about 1½ turns remaining before the compression washer flattens out. This leeway allows the user to fine-tune the gauge's final position** with a wrench. If the position of the instrument is not critical, flat washers can be used instead.

Focus on the difference between NPT and G connections

The difference between the two connection types is clear when placed side by side. NPT threads are slightly tapered while G connections are straight. Another obvious visual: The G-connector has a small protrusion (nipple) on the end to center the gasket. A third method, if a caliper is handy, is to measure the angle between the threads: 60° for NPT threads and 55° for BSP threads.

But what about when the gauge is already inserted in the process? Is there an easy way to tell what connector type an instrument has without removing it? Yes. Because the G connection bottoms out, the threads are not visible. In NPT connections, some threads or exposed PTFE tape may be visible.

NPS connects with G

Tips

1. Although BSP is now based on metric measurements, the name of the system still reflects its imperial origins. That's why the G and R connection designations range from 1/8 to 6 (inches), not 6 to 150 (mm). As for the "A" or "B" in some designations, such as the common G ¼ B connection type, the letter designation lets the user know that 1) it is an external thread, as BSP internal threads do not have the last letter, and 2) its tolerance class .

2. To avoid damaging the gauge's threads, regardless of the connection type, use the correct wrench and use it only on the flat areas of the socket. Also, never hand-tighten the instrument through the case or case.

Both fittings have the same pitch of 1.814 and the same number of threads per inch of 14 but different angles, 60° for NPSM and 55° for G1/2B (BSP). To some extent it appears to work, but in general we don't recommend combining two different threads.

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