Field Test Results of High Pressure Feedwater-Heater Tubing Materials of a Power Plant

Abstract

Studies were carried out on the corrosion of high pressure feed water-heater tubing materials of a power plant in peaking service and the material selection of a high pressure feedwater heater from May 1962 to June 1965. For this purpose, nine kinds of tubing materials were fitted in actual high pressure feedwater-heater of No.1 and No.2 units of Himeji No.1 Thermal Power Station, Kansai Electric Power Co., Inc. The results obtained are as follows: 1) Typical exfoliation type corrosion was formed on 70-30 cupro-nickel alloy. 2) 80-20, 90-10 cupro-nickel and 5% iron modified cupro-nickel did not form exfoliation type corrosion. 3) 70-30 nickel-copper alloy and the STC 52 A austenitic stainless steel formed a thin adherent oxide film and did not show measurable metal loss. 4) Three kinds of steel tubes were pitted in both drain and feedwater side, but not in the steam side. The pitting rates were about 0.3mm/yr. 5) From the above results, the material in actual units was replaced with 90-10 cupro-nickel tube to prevent exfoliation type corrosion.