海底管道正向预热时机分析

输送高凝点原油的海底管道在预热投产或停输再启动过程中，预热时机作为管道温度场预热充分的“显性”标志，具有重要意义。针对海底掩埋保温管道，建立了正向预热一投油计算模型，以某海底管道为对象，研究其在预热一投油过程中沿线温度的瞬变过程，并对预热时机的选取及影响因素进行探讨。结果表明：在管道投油一稳定瞬变过程中，最低油温出现在管道终点，故只要管道出口温度满足安全流动的需要，即可确保整条管道的油温处于流动安全允许范围内；预热时机取“终点水温=凝点”时，可以满足原油安全流动的温度要求，并且适用于不同热水流量和投油流量工况，推荐工程采用。（图6，参11）

Analysis of direct preheat timing of submarine pipeline

During the preheating commissioning and start-up after shutdown of submarine pipeline transporting high solidifying point oil, preheat timing as the ＂dominant＂ logo of adequate preheating pipeline temperature field is of great significance. According to the buried submarine insulated pipeline, direct preheat-flushing calculation model is established. Taking a pipeline as the study object, transient process of linear temperature in the process of preheat-flushing is studied. And then the selection of preheat timing and the influence factor are discussed. The results show that the minimum oil temperature appeared at the end of the pipe during the transient process of pipeline flushing-stabilization. Therefore, as long as the outlet temperature of the pipeline meets the needs of safe flow, the oil temperature of the whole pipe is certainly in the allowed range of flow security. The temperature requirement of crude oil safe flow is satisfied, when the preheat timing is taken at the moment of the finish temperature is equaled to the freezing point. And it is applied to different working conditions of hot water flow and flushing flow, and recommended for project. （6 Figures, 11 References）