Numerical Prediction of Inner Pipe Temperature in Pipeline Hot Work Repair by In-Service Buttering Layers Welding of Pipeline Sleeves

In-service welding is a type of hot work repair process using pipeline sleeves. It is hazardous and necessitates thorough planning and procedures. The inside pipe surface and fluid temperature are all unknown and unpredictable. Therefore, the risk resulting from burn-through where the welding arc causes pipe wall breaching, hydrogen cracking, and the likelihood of occupational health risks are high. Hence, this work aimed to predict the pipe’s inner surface temperature and fluid temperature in contact with the pipe’s inner surface during the buttering layers welding of the pipeline sleeve to determine if it is safe to carry out welding of the buttering layers in a no-flow condition. This analysis was achieved through 2-dimensional Steady-State Thermal Analysis in Ansys APDL (Ansys Parametric Design Language). The Ansys simulation results showed that the fluid temperature was high, almost getting to the fluid autoignition temperature, and in some instances, even higher than the fluid autoignition temperature. The implication is that, in-service buttering layers welding of pipeline sleeves must not be performed in a no-flow condition during pipeline repair. Also, hot work repair welding for pipeline sleeves by the in-service method could be safely done following all necessary precautions and preventive measures where in-service welding for pipeline sleeves during the buttering layers might cause a severe hazard and dangerous incidents such as explosion. The temperature prediction helps to assure safety in in-service welding for pipeline sleeves to avoid pipeline explosion due to extremely high temperature or decrease in the toughness of the Heat-affected-zone (HAZ) in the welded joint because of the high cooling rate of the weldment, which reduces the pipe mechanical strength.