"Exfoliation corrosion in Cu-Ni HP feedwater heaters"
Question:
"We are a power plant, 1800# nat. gas fired boiler. We have significant exfoliation corrosion in our copper-nickel tubes (steam side). We are a cycling plant, and break vacuum in the condenser at night, and use morpholine/cyclohexylamine as a neutralizing amine, carbohydrazide as an oxygen scavenger. Any ideas why this corrosion is occurring and how we can reduce it. This plant is over 30 years old."
Answer:
This is specifically the type of failure that occurs with daily cycling of 30 year old power plants! These plants were originally designed to be baseloaded and run continuously, and the material selection and FW heater design was probably intended for baseloaded service. I'll bet your tubes are arsenical admiralty metal ( copper nickel is too broad of a term) Suggest that you check POWER and POER ENGINEERING websites for articles on similar problems from other utilities. Also, if you can track down a mister Carl Andreone, the godfather of feedwater heaters, (Stone & Webster Engineering) he might provide insight.