MEC&F Expert Engineers : CO-OP REFINERY EXPLOSION AND FIRE ON 12-24-2013: A BYPASS LINE FROZE AND RUPTURED. ONCE THE AIR TEMPERATURE WARMED, THE PETROLEUM PRODUCT WAS RELEASED THROUGH THE LINE, RESULTING IN AN EXPLOSION AND SUBSEQUENT FIRE.

Saturday, December 13, 2014

CO-OP REFINERY EXPLOSION AND FIRE ON 12-24-2013: A BYPASS LINE FROZE AND RUPTURED. ONCE THE AIR TEMPERATURE WARMED, THE PETROLEUM PRODUCT WAS RELEASED THROUGH THE LINE, RESULTING IN AN EXPLOSION AND SUBSEQUENT FIRE.





CO-OP REFINERY EXPLOSION AND FIRE ON 12-24-2013: a bypass line froze AND RUPTURED.  Once the air temperature warmed, the petroleum product was released through the line, resulting in an explosion and subsequent fire.

Regina, Saskatchewan – 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.

INCIDENT SUMMARY
On December 24, 2013 at approximately 3:25 pm local time, an explosion occurred in the Polymerization Unit 27 (PMU) at the Coop 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. Figure 1 shows a partial view of the explosion from a CRC surveillance camera. In Figure 1, the PMU is not within the view of the surveillance camera, but is located outside the upper left of the image.

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. TSASK’s report from the investigation has been provided to CRC for action. A copy of the report is available on the TSASK website at www.tsask.ca.



FINDINGS AND RECOMMENDATIONS
1.   Procedures for cold weather shutdown should be revised to improve decision making and the identification of conditions when cold weather shutdown is permissible and conditions when it is not.
·         Procedures for cold weather shutdown were inadequate, as they did not consider the high risks posed by extreme cold.

2.   Procedures for incident investigation should be revised to ensure that corrective actions are implemented so that incidents do not repeat.
·         A similar pipe rupture due to freezing occurred in December, 2008, where the resulting vapour cloud did not ignite. Eective corrective actions were not implemented.

3.   CRC should establish a written freeze protection program that includes the identification, mitigation, management of change and audit requirements for equipment at risk due to freezing.

4.   Procedures for water floating should be revised to ensure that instrumentation and process controls are eective and maintained. Additional redundancy in instrumentation, controls and verification methods should be developed.
·         The primary electronic instrument for water level measurement at the combined feed drum water boot was a Fisher 2500 pneumatic level transmitter. This instrument was found to be defective when tested during the investigation. Historical data from the instrument was reviewed and confirmed that the instrument was defective on November 26, 2013.
·         A sight glass served as a secondary instrument for the water level measurement in the combined feed drum water boot. This sight glass was operational, but was dicult to read because the appearance of water and poly feed are nearly identical.

5.   Thawing procedures should be revised to ensure all areas are addressed systematically, especially dead legs.
·         Thawing procedures were inadequate in that they did not systematically thaw all vulnerable locations. Thawing relied upon operator knowledge and memory of vulnerable locations as opposed to a documented and systematic approach.


6.   CRC should adopt the deadleg definition set out in the American Petroleum Institute standard 570 and ensure this definition is understood across the organization.
·         In the course of the investigation differing interpretations of what constitutes a deadleg were apparent at CRC.


7.   Deadlegs in piping should be systematically identified, documented and eliminated or otherwise mitigated wherever possible. Deadlegs that must remain should be highlighted and given special attention throughout operations and maintenance activities.
·         The deadleg on bypass line 123BPL allowed water to become trapped. This water subsequently froze and ruptured the line, causing the hydrocarbon leak and explosion of December 24, 2013.

8.   Maintenance procedures should be revised to ensure that critical sensing and monitoring equipment remains functional.
·         The Fischer 2500 pneumatic level transmitter at the combined feed drum water boot was found to be defective.

9.   CRC should systematically identify where installed piping differs from the design specifications. The dierences should be analyzed and suitably addressed as necessary. CRC should investigate whether corrosion survey data could be used to identify where piping does not conform to design specifications.
·         Although not a cause of this incident, in the course of the investigation bypass line 123BPL was found to be 2” Schedule 80, while design documents specified this line to be 2” Schedule 160. 2” Schedule 80 has a wall thickness when new of 0.218”, whereas 2” Schedule 160 has a wall thickness when new of 0.344”.
·         Thickness monitoring locations (TML) on bypass line 123BPL were located at the top elbow and the bottom elbow, both locations being well away from the ruptured area. CRC thickness monitoring data of October 29, 2013 shows a wall thickness of 0.220” at the top elbow and a wall thickness of 0.200” at the bottom elbow.

10.                CRC should revise its corrosion survey procedures to assess corrosion under insulation (CUI) on jacketed and insulated components. The corrosion survey procedures should utilize methods to identify and assess areas where corrosion is the greatest.
·         Although not a cause of this incident, significant exterior corrosion was found on bypass line 123BPL. Bypass line 123BPL was jacketed and insulated.
·         Data from thickness monitoring locations (TML) on bypass line 123BPL did not detect the exterior corrosion that was found. The TML’s were not located at the area where the CUI was found.
·         CUI on bypass line 123BPL resulted in a wall thickness loss of up to 27%.
·         The placement of steam lances inside insulation jackets for the purpose of thawing frozen lines is a common practice at CRC, and this may play a role in CUI.



GLOSSARY OF TERMS AND ABBREVIATIONS
BPD barrels per day

Bypass Line 123BPL The 2” poly feed bypass line located near the north side of polymerization reactor
#2. This bypass line diverts poly feed flow around polymerization reactors #1, 2 and 3. This bypass line is designated on CRC drawings as 27P1070FA5A2IH.
CRC Coop Refinery Complex CUI Corrosion Under Insulation
Deadlegs Components of a piping system that normally have no significant flow. Some examples include blanked branches, lines with normally closed block valves, lines with one end blanked, pressurized dummy support legs, stagnant control valve bypass piping, spare pump piping, level bridles, relief valve inlet and outlet header piping, pump trim bypass lines, highpoint vents, sample points, drains, bleeders, and instrument connections.
FCCU Fluid Catalytic Cracking Unit PMU Polymerization Unit 27
PSIG Pounds per square inch, gage. A measure of pressure.
RFPS Regina Fire and Protective Services TML Thickness Monitoring Location
TSASK Technical Safety Authority of Saskatchewan