Case history: Corrosion of equipment in steam circuit of fertiliser plant

Abstract

A case history is presented relating to corrosion of boiler plant which provides clear examples of the problems that can arise with inadequate attention to water treatment. Failures were observed in various components of the steam circuit of a urea plant: superheater tubes; stainless steel pipelines; expansion bellows carrying steam at 3·5 MPa pressure; the plugs and seats of steam admission valves; bolts and studs and the heads of Allen screws in reversing segments of the turbine; and the turbine rotor disc. All the components that failed were using steam from the steam generation plant. Investigation revealed that carryover of boiler chemicals in the steam had resulted in buildups of alkalinity and chlorides, leading to stress corrosion cracking.