Damage Law of SL-I Pyrolysis Furnace Radiant Section Pipes

The field carburizing test, low acid corrosion test, room temperature tensile test and high temperature endurance test were carried out on the SL-I pyrolysis furnace radiant section pipes with naphtha as raw material, which was put into use in a refinery company in June 2018. The carburizing status and damage law of furnace pipes during service were analyzed, and the residual life of furnace pipes with different carburizing degrees were evaluated. The results show that the degree of carburizing varied greatly in different furnace pipes and in different directions around the same furnace pipe. The severe carburized positions were mainly located at 1.5–7.5 m away from the furnace bottom in the inlet and outlet pipes on the west side and middle of the furnace. The chemical composition and strength of the mild carburized inlet pipe met the order technical requirement. The carbon and niobium content of the severe carburized inlet pipe was relatively high. The severe carburized inlet pipe fractured before reaching the yield point during tension, and the strength and plasticity were far lower than the order technical requirement. Under the conditions of maximum wall temperature of 1 100 ℃ and stress of 0.22 MPa, main damage mechanisms of the mild and severe carburized inlet pipes were high temperature creep and carburizing, respectively; the residual life of mild carburized inlet pipe was 5.0 a, while the severe carburized inlet pipe needed to be replaced in time.