1. An introduction
1.1 The definition of the flange
Flanges are spare parts between two shafts to connect tube ends. Flanges such as reducer flanges are also used for inlets and outlets of facilities to connect two facilities. The
flange connection or the flange joint refers to a set of detachable connection with the sealed structure composed of the flange, the gasket and the bolt. Pipe flanges are applied to pipe fittings in pipelines, and also can be used for inlets and outlets of facilities. Holes and bolts on flanges can make two flanges closely connected. Flanges are sealed through gaskets.
1.2 Categories of flanges
The
flange manufacturing industry can provide their users with about 19 categories of flanges. According to the production materials, flanges can be divided into WCB (carbon steel), LCB (low temperature carbon steel), LC3 (3.5% nickel steel), WC5 (1.25% chromium and 12% chromium steel), CF8M (316 stainless steel), CF8 (304 stainless steel), CF3 (304L stainless steel), CF3M (316L stainless steel), etc.
1.3 Detection methods of flanges
The conventional detection methods of
flanges can be divided into chemical composition detection method, mechanical property detection method, size detection and nondestructive testing method. Selective detection method of
flanges can be further classified into metallographic detection method, low-acid etching detection method, coating thickness detection method, stainless steel grain-boundary corrosion detection method, pressure detection method and HIC detection method. China's enterprises or test centers, most of them have purchased advanced test equipment, but the number of inspectors and quality of inspection are still not up to the requirements. The actual test specifications are relatively far from those of the first well-known international testing institutions such as the SGS. Professional, accurate and rapid test data can give timely feedback to the production process, trade and use.
1.4 Export of China's flanges to the world
In the conventional detection of steel flange, the HS code is 7307.9100. China's steel
flanges have been exported to the United States and Europe. In 2016, the total amount of exported steel products to the United States and the EU fell by 63.5% and 13.2%, respectively. However, the export volume of steel flanges was not much affected. The export volume of steel flanges exported to the EU even had an year-on-year increase of 3.0% in 2016. The export value of China's steel flanges exported to the world was USD490,000,000 and the export weight was 406,000 tons. The export situation of China's steel
flanges to the world is shown in Figure 1.