The structural sizes of the branch pipe in accordance with State Standard 3262-75 are shown in fig. 4.26

PIPES AND BRANCH PIPES

PIPE JOINTS

Pipes are used to carry steam, water, gas, oil and many other fluids. The pipes for a particular use cannot be made of desired length. Therefore pipes of standard length are taken and joined together with the help of pipe joints of different types. Normally the pipes are made of cast iron, steel, copper and wrought iron, depending upon te pressure and temperature of the fluid to be conveyed.

A pipe cylinder or a conical thread is used for pipe joints. All parameters, including external diameter of a pipe thread, are determined according to conventional nominal sizes of thread in inches, which correspond the diameter of a pipe opening (in inches), if a thread is cut at the external surface of a pipe.

Thus, the external diameter of a pipe thread is always greater (fig. 4.5) than the conventional nominal size on two thickness of a wall pipe. Parameters of a pipe thread resulted in table 4.12.

It should be remembered, that an opening diameter in a pipe depends on the accuracy of its manufacturing and approximately corresponds the conventional nominal size of a thread in inches (1inch =25,4mm).

A basic parameter for pipes and connecting parts is a size of nominal bore Dy, that approximately equals the size of the internal nominal diameter of an opening pipe. Nominal bores are standardized. According to the State Standard 3262-75 the steel welded pipes for water- and gas pipelines, for the systems of heating are made galvanized and non-galvanized, normal accuracy of manufacturing and extra accuracy. These pipes are made from steel in accordance with State Standard 380-71 or State Standard 1050-74.

Figure 4.26 – The structural sizes of the branch pipe

The numerical values of parameters of a thread are resulted in table 4.12 according to the nominal bore Dy.

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