After the direct tube heating reaches the temperature of the plastic deformation, the pipe is formed by the mechanical arm restriction, which is called the bending pipe.

There are two main systems for international flanges, namely the European tube flanges system represented by German DIN (including the former Soviet union) and the American tube flange system represented by the American ANSI tube flange. In addition, there are Japanese JIS tube flanges, but in petrochemical installations, they are generally used only for public works and have little international impact. Now the country's flanges are introduced:

1. European system tube flanges represented by Germany and the former Soviet union

2. Standard of American system tube flange, represented by ANSI B16.5 and ANSI B 16.47

3. British and French flanges standard, each of which has two pipe flange standards.

To sum up, the international standard of tube flanges can be summarized into two different and uninterchangeable pipe flanges system: a European tube flange system represented by Germany; The other is a system of American tube flanges represented by the United States.

Ios7005-1 is a standard adopted by the international organization for standardization in 1992, which effectively combines the two sets of pipe flanges in the United States and Germany.