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4.5.5.1 PIPES AND BRANCH PIPES

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

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.

Table 4.12
Nominal Thread External Internal Thickness of a wall pipe, L 1, L 2, L,
bore, Dy, G, diameter, mm diameter, s, mm mm mm mm
mm inch mm Thin- Normal Thick-
walled walled
10 3/8 16.663 14.951 2 2.2 2.8 8.5 46 105
15 1/2 20.956 18.532 2.5 2.8 3.2 9 58 120
20 3/4 26.442 24.119 2.5 2.8 3.2 10.5 64 135
25 1 33.250 30.292 2.8 3.2 4 11.0 75 150
32 1 41.912 38.954 2.8 3.2 4 13.0 85 160
40 1 47.805 44.847 3 3.5 4 15.0 85 160
50 2 59.616 56.659 3 3.5 4.5 17.0 85 160
The example of the conventional denotation of a steel non-galvanized pipe with the nominal
bore 20 mm:
Pipe 20 State Standard 3262-75.

Pipe fittings are used for joining pipe different lengths and to provide changes of direction,
branch connection at different angles or to effect a change in size. The fittings are made for
screwed, flanged or welded connection.
A drawings and structural sizes of the pipe fittings is pointed below.

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