A Technical Research On The Safty Shutdown And Restart Of Qingha Oil Pipeline

Qingha long distance pipeline has been used to transport crude oil from Daqing toHarbin refineries since1999. Due to the long distance of pipeline and complex terrain, someshutdown problems are hard to avoid such as artificial or natural problems and which arecaused by power cut or pipeline maintenance. If shutdown time is too long, the liquid inpipeline could be concretionary which will cause restart failure. Therefore, to ensure thesafety of pipeline operation, it is necessary to determine the restart pressure and safetyshutdown time.Firstly, this paper built hydraulic and thermodynamic calculation model to modifyhydraulic friction coefficient and built modified model according to actual operation conditionof Qingha oil pipeline. After developing a pipeline hydraulic friction coefficient correctionsoftware established on the C++programming platform, temperature and pressure distributionrule of Qingha oil pipeline were calculated in different conditions and the results werecompared with actual to verify the accuracy of the model.Secondly, under normal operating conditions and with the limitation of the maximumoutlet temperature and minimum inlet temperature, thermodynamic minimum safetythroughput was calculated in different seasons. With the standard that the pipeline must be insteady operation, hydraulic minimum safety throughput was also calculated according to thecrude oil rheological property and hydraulic characteristics. Then the minimum safetythroughput of Qingha oil pipeline was determined under overall consideration of hydraulicand thermodynamic minimum safety throughput.Finally, using OLGA software, shutdown and restart model of Qingha oil pipeline wasbuilt. When the end temperature of pipeline shutdown was3℃higher than condensationpoint, safety shutdown time was determined. When the start-up pressure was less than6.0Mpa,safety shutdown time which was limited by pipeline shutdown conditions and could ensurethe end flow recovered to normal level was determined. At last, the final safety shutdown timeof Qingha oil pipeline in different seasons throughout the year was determined which couldguarantee safty and efficient operation of Qingha oil pipeline.