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本文叙述了管线在试压过程中出现的压力逆射现象,并用断裂力学观点加以解释。本文还探讨了影响压力逆射现象的诸因素并针对工程实际给出几点建议。我国目前已建成油、气长输管道一万五千多公里,油、气田集长输管线数十万公里。这些管线在试压和操作过程中曾发生过以下似乎难以解释的现象。在试压时,管道的某处曾经受了较高的压力,而在其它处发生断裂而不得不将管线减压,并对缺陷部位加以修补后再重新升压时,就在这曾经受了较高压力之处却在低于以前的压力下破裂。举例说,有一处曾经受过7.2MPa的压力,却在第三次试压时,在不足6MPa下断裂。我们通常的做法是先对管线进行分段试压,然后再连起来并进行整体试压,尤其是在后一种情况下,产生泄漏或断裂的概率大为增加了,往往多次修补,多次升压、降压,前述这种现象是屡见不鲜的。对于间断输送的管线,经常要升压和降压。这种管线也发生过前述现象,即在低于以前曾承受过的压力下,还会发生泄漏或断裂,而管线并无腐蚀现象。国外一些文献称这种现象为“Pressure Rerersal,”此处暂译为“承压能力逆转”或简称为“压力逆转。”从力学上如何解释压力逆转现象,影响压力逆转的因素以及在工程上如何尽量减少和控制这种现象,对于管道工业来说是一个重要的课题。
This article describes the pressure reversal phenomenon that occurs during pipeline pressure testing, and explains it from the perspective of fracture mechanics. This article also discusses the factors that affect the pressure reversal phenomenon and gives some suggestions for engineering practice. China has built more than 15,000 kilometers of oil and gas long-distance transmission pipelines, and oil and gas fields have set up long-distance transmission pipelines of several hundred thousand kilometers. The following seemingly inexplicable phenomena have occurred in these pipelines during pressure tests and operations. During the pressure test, some parts of the pipeline had been subjected to high pressure, but in other places there was a rupture and the pipeline had to be depressurized, and when the defective part was repaired and then re-pressurized, it was once suffered. At higher pressures it breaks below the previous pressure. For example, there was one place that had been under pressure of 7.2 MPa but fractured at less than 6 MPa during the third pressure test. Our common practice is to test the pipelines first, then connect them together and conduct overall pressure tests. Especially in the latter case, the probability of leakage or fracture is greatly increased, and it is often repaired many times. It is not uncommon for the aforementioned phenomenon to increase pressure and reduce pressure. For intermittently delivered pipelines, boosting and depressurization are often required. This phenomenon also occurred in the pipeline, ie, under the pressure lower than that previously experienced, leakage or fracture occurred, and the pipeline was not corroded. Some foreign literatures call this phenomenon “Pressure Rerersal,” which is temporarily translated as “reversal of pressure capacity” or simply “pressure reversal.” How to explain pressure reversal phenomenon from mechanics, factors that affect pressure reversal, and engineering How to minimize and control this phenomenon is an important issue for the pipeline industry.