A new method for determing the MST (maximum shutdown time) of a waxy crude oil pipeline is not only more accurate and flexible, but can also yield substantial savings in heating costs compared to the subjective methods employed before a pipeline enters service. Pipeline operators often heat waxy crude lines to ensure safe and economic transport. Shutdowns may occur regularly for operational reasons and occasionally for such emergencies as pipe ruptures. Shutdowns lower the temperature of the oil, increasing is viscocity and strengthening its thixotropic tendencies, the combination of which requires a large start-up pressure. Start-up pressure exceeding the capacity of the pipe could leap to pipe failure, resulting in potentially large economic losses. Increasing heating temperature before a planned shutdown can help ensure a successful restart. An accidental shutdown, however, requires that restart occur before a predetermined maximum shutdown time has elapsed. This time can be increased by heating the line after the shutdown has occured. The operator must, however, return the pipeline to service before reaching the MST, even if it means incurring such associated risks as soil contamination. For large-throughput hot oil pipeline, however, reducing the heating temperature even slightly may save a great amount of fuel, creating a potential conflict with the desire to maximize MST. How to save fuel while ensuring reliable and safe operations therefore becomes an important question.
Waxy crude shutdown method yields savings
Oil and Gas Journal ; 105 , 30 ; 65-69
2007
4 Seiten, 5 Tabellen, 10 Quellen
Article (Journal)
English
Pipeline , Schweröl , Erwärmung , Kosteneinsparung , Unterbrechung , Wachs
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