Feed Water Heater is a device to pre-heat the water using extraction steam in steam and water heat exchanger system, usually used in power plant, this component reduce heat loss during heat transfer process resulting from cooling water, therefor improve transfer efficiency.
Performance of feed water heater impact the whole system economical efficiency and safety, tubes play a important role in feed water heater, resisting high temperate and corrosion, failed tubes cause leakage problem, that will increase maintenance cost by repairing.
ASTM A688, ASTM A803 Feed Water Heater Tube
There are two specifications specified feed water heater tube, ASTM A688 and ASTM A803, compared to ASTM A213, A249, A268, A269 standard, this two standards are special for heater tubes, requiring tight tolerances and more testing to ensure tubes to suitable in critical environment.
Common Stainless Steel Alloys
TP304. TP304L, TP316L, 439, 446 stainless steel is common grade to produce tubes, and derivatives, also duplex steels are available, like 2205, selecting which grade depend on applications, user should know single stainless steel grade has special properties.
TP304 is wide used 18 Chromium 8 Nickel stainless steel, its properties make it use in most applications.
The “L” grade has low carbon which provides significant extra resistance to corrosion, like TP304L, TP416L, which used in environment requiring tubes to enable to resist corrosion.
U Bend Tube
U bend tubes are designed common for feed water heater tube, both welded and seamless tube are for opting, max length to 30 meters, bending portion heat treated, maximum bend radius reach 1.5 meters, tolerances are controlled as ASTM A688.
Testing and Inspection
Non-destructive testing and pressure test should be conducted, in practice, eddy current testing and air under water testing are common methods to ensure tubes superior condition, optional tests can be made for feed water heater tube.