The Technical Safety Authority of Saskatchewan (“TSASK”) has finalized its investigation into the December 24, 2013, explosion at the Co-op Refinery Complex (“CRC”) in Regina. The investigation has concluded that a bypass line of Polymerization Unit 27 froze following a maintenance procedure. The stress of the freezing process ruptured the bypass pipe. Once the air temperature warmed, the petroleum product was released through the line, resulting in an explosion and subsequent fire. The event was not related to a malfunction of pressure equipment.
On December 24, 2013, at approximately 3:25 pm local time, an explosion occurred in the Polymerization Unit 27 (PMU) at the Co‐op Refinery Complex (CRC) in Regina, Saskatchewan. The ensuing fire was extinguished at approximately 9:00 pm local time on December 24, 2013. The blast and fire destroyed the equipment and structure around reactors 1, 2 and 3 in the PMU. The remaining five reactors in the PMU suffered blast and post incident freezing damage, and were rendered unusable. Blast damage also occurred to CRC buildings and equipment outside of the PMU. Blast effects were also felt at locations outside the refinery complex. No personnel were injured in the incident or in the subsequent emergency response.
Unit Operation December 19, 2013 – December 24, 2013
There were no freezing issues that affected unit startup and operation during December 19 to 24, 2013. The PMU functioned within normal parameters for pressures, temperatures and flows during this period. Operators were not aware of any process problems that could lead to a component failure during this period.
Outdoor temperatures were very cold from December 19, 2013, to December 21, 2013. Beginning on December 22 and continuing into December 23 outdoor temperatures dropped dramatically to a static low of ‐35° C at 2:00 AM on December 23 and a wind chill low of ‐47° C at 6:00 AM on December 23. These were, in fact, the coldest temperatures since the water floating procedure of November 26, 2013.
The bypass line 123BPL dead leg contained water throughout the cold weather that occurred between November 26, 2013, and December 24, 2013. Water in the line froze and ruptured the line due to hydrostatic overstress at some point during this period. An ice plug existed within the line and created a seal which prevented the escape of highly volatile poly feed through the pipe rupture.
Beginning at 6:00 AM on December 23, 2013, the temperature began to rise dramatically, peaking at ‐2° C at 2:00 PM on December 24, 2013. On December 24, 2013, unit operations were within normal parameters. Due to the Christmas holiday, a number of operations staff had left early that day, resulting in much fewer than normal personnel around the PMU as the day progressed.
As outdoor temperatures warmed, combined with heat from unit operations, the ice plug in bypass line 123BPL thawed and eventually gave way to the high-pressure poly feed. At 3:25 PM this caused a sudden release of hydrocarbons into the PMU, followed by a large explosion and ensuing fire.
CLICK HERE for the full report and analysis.
PLEASE NOTE this is not the first time freezing in a dead leg gas lead to a catastrophic failure of piping!
http://www.csb.gov/videos/fire-from-ice/
http://www.csb.gov/assets/1/19/CSBFinalReportValeroSunray.pdf