Influences of insulation layer failure on safe shutdown time of heat tracing heavy oil pipeline

With respect to difficulty of safe shutdown after failure of thermal insulation layer for heat tracing heavy oil pipeline, a 2D non-steady-state analysis model is built for the heat tracing heavy oil pipeline based on the finite volume method. Effects caused by latent heat of heavy oil solidification are considered in the model and change law of temperature field in the heavy oil pipe in the case (I) of heavy oil pipe shutdown and in the case (II) of shutdown for the heavy oil pipe and tracing pipe before and after the thermal insulation layer failure is studied. On this basis, the curve of relation between shutdown time and average heavy oil temperature after shutdown is fitted by using SPSS software to further determine safe shutdown time of the tracing heavy oil pipeline before and after failure of the thermal insulation layer. Temperature drops of oil pipe before and after failure of the thermal insulation layer in case I and case II's results are similar in the law. With respect to safe shutdown time before failure of the thermal insulation layer, case I and case II receptively takes 58 h and 54 h, of which the former extends its safe shutdown time by 4 h due to impacts of the tracing pipe. After the thermal insulation layer fails, both cases reduce the safe shutdown time to 11 h, that is, the tracing pipe has no effect on the safe shutdown time.