High pressure heater and low pressure feed wate heater of large-scale thermal power is assembled by different radius to complete”U”type tube.The pipe diameter of “U”type tube is small,the tube wall is thin but the length is long.

ND steel is a new type of low alloy structural steel, compared with other steel, like low-carbon steel, Corten, CRIA, ND steel has the advantage of excellent corrosion resistance and mechanical property. The experimertal results showed that the corrosion resisteance of ND steel in aqueous solutionlike sulfuric acid, hydrochloric acid and sodium chloride is higher than carbon steel.The most prominent feature is the ability of sulfuric acid dew poinrcorrosion resitance,the mechanical property is acid dew poinrcorrosion resitance from room temperature to 500℃, and the welding performance is nice. ND steel always used for manufacturing economizer, heat exchanger, air pre-heater, Since, ND steel has widely been used in the industry of petrifaction and electricity.

Mainly used in the petrochemical industry, heat exchanger tube bundle. Including the heat exchanger, air cooler, reboiler, paraffin hydrogenation unit ,hydrogen cooler, water cooler, wax oil steam generator, hydrogen compressor intercooler, the first top condenser, often top coole, softened water heat exchanger and other devices. At the same time, electricity, fertilizer, transportation , oil and other industries can also apply.