In order to decrease the loss of heat which are left away by cooling water in condensers, water needs to be heated. That is to say, after high pressure water pump, heat water by increasing the high-pressure heater. Improve economic efficiency and save coal source. Heart ex-changer tubes are the important and core devices, including the form of U, n(flat-ended tube) and straight.
U-tube heat ex-changer, each ex-changer tube in the U forming, two ends of the U-tube are fixed to the same tube plate up and down. Partition inside divides it into two exporting and importing rooms. This kind heart ex-changer tube totally eliminates thermal stress and its structure is more simple than floating head heat ex-changer, but is not easy to clean.
Main steel grades
ASME SA-556M: Seamless cold-drawn carbon steel feedwater heater tubes
GB/T 24591-2009: High pressure feedwater heater tubes
Length: the longest is over 35 meters, slender: length-diameter ratio>1000. Because of high production and environment, it has high requirements for straightness, that is the whole length can undergo the ring gauge inspection of max OD plus 0.02mm. Demand on surface roughness is high, and corrosion is not allowed.
Product operating environment
It is required that U bended tubes’ working temperature is above 350℃. According to different units, the working pressure should be above 30MPa. The tubes inside also need to tolerate the water speed of 3m/s and vibration. It has high reliability and requirements for this kind of tubes, which are used for over 15 years.