Unconventional Procedure for Purging a Crack-Weakened Pipeline

The Arauca´ria to Paranagua´ Pipeline (OLAPA) owned by PETROBRAS, was built in 1976 in Parana´ State, Brazil, connecting an oil refinery nearby the city of Curitiba to a marine terminal near Paranagua´ Seaport. The pipeline had been operating normally for 25 years, moving liquefied petroleum gas (LPG) and diesel fuel to the refinery as well as petrochemical Naphtha and light cycle oil (LCO) in the opposite direction. The second week of February 2001 came along with heavy and continuous summer rain on Parana´ State most of which on a hilly terrain portion crossed by the pipeline, currently regarded as an environment preservation area of the Atlantic Rain Forest. On 16th day, that same month, while the line was on shut in condition, a hardly noticeable landslide across the right-of-way led the pipeline to the complete rupture, succeeded by product spill. Further analysis on the rupture section pointed to circumferential cracks caused by axial stress induced by a slow and steady slide on the adjacent soil. Surveys on other regions possibly affected by similar soil movement on the right-of-way warned operations staff that there could be more weakened sections along the pipeline, therefore pipe failures and product spill might still happen due to the continuation of the rainy season. Product removal became required to avoid environmental threats. The purging procedure should meet two main constrains, i.e., minimize pressure and volume flow through the identified risky locations. This paper describes the planning and execution of such purging process, tailored for a weakened pipeline on an environmental sensitive area, adopting unconventional methods to move liquid products upward high steeps, considering restrains to operational pressures around one third of normal values.