Heat tracing could cause cracking in carbon steel piping in which service?

Heat tracing could cause cracking in carbon steel piping in which service?

• A. Hydrocarbon Service
• B. Acid Service
• C. Caustic Service
• D. Hydrogen Service

Answer: (C)

Hot caustic solutions can cause a specific cracking failure in carbon steel when the pipe is heated. Heat tracing raises the temperature of the contents, and in caustic (alkaline) service carbon steel is susceptible to caustic stress corrosion cracking. The combination of tensile stress (from fabrication, operations, or residual stresses) and elevated temperatures in a concentrated caustic environment makes grain boundaries vulnerable to cracking, often along welds or heat-affected zones. This is why heat tracing is avoided or carefully managed on lines carrying caustic solutions. In other services, the cracking mechanisms differ. Hydrogen service involves hydrogen embrittlement or sulfide-related cracking, and hydrocarbon or acid service concerns are driven more by general corrosion or acid attack rather than the caustic cracking mechanism described above.

Hot caustic solutions can cause a specific cracking failure in carbon steel when the pipe is heated. Heat tracing raises the temperature of the contents, and in caustic (alkaline) service carbon steel is susceptible to caustic stress corrosion cracking. The combination of tensile stress (from fabrication, operations, or residual stresses) and elevated temperatures in a concentrated caustic environment makes grain boundaries vulnerable to cracking, often along welds or heat-affected zones. This is why heat tracing is avoided or carefully managed on lines carrying caustic solutions.

In other services, the cracking mechanisms differ. Hydrogen service involves hydrogen embrittlement or sulfide-related cracking, and hydrocarbon or acid service concerns are driven more by general corrosion or acid attack rather than the caustic cracking mechanism described above.