1
Glenpool South Tank Farm Glenpool , Oklahoma April 7, 2003
Storage Tank Explosion and Fire ConocoPhillips
Investigation Team and Support Staff
• Rick Flint • Dr. Joseph Kolly, Nancy McAtee & Dr. Merritt Birky • Leslee Shumway • Frank Zakar • Robert Moore & Meg Athey Investigator-in-Charge Explosion and Fire
SCADA and Control Systems Materials Laboratory Editors
Estimated man hours for the investigation: 4,500
Parties to the Investigation
• ConocoPhillips • Explorer Pipeline • Office of Pipeline Safety • Glenpool Fire Department
North
9
8 7 12 Tank 11
Highway 75
eet t Str 131s
North
TT
Tank 12 TT TT 7 T T 11 TT TT TT TT
8
TT TT
9
TT
TT
138,00 volt power lines
TT
TT
T
N
Explorer Pipeline Glenpool Tank Farm
Explorer 24” line to ConocoPhillips 12” crude oil pipeline
30” line to tank 11 28” Explorer mainline from Texas
9 7 12
8
11
power lines
ConocoPhillips Glenpool South Tank Farm
Explorer and ConocoPhillips Tank Farms
Location of 138,000 volt power lines
Tank 11
Dike wall
Pipeline overpressure protection equipment
Fire picture here
dike wall
power poles
Power lines
Tank 11 Tank 7
Pipeline overpressure protection equipment
Tank 7 Tank 11
Tank 8: damage from internal fire
North
9
8 7 12 Tank 11
16
Safety Issues
• Tank operations, including switch loading • The adequacy of emergency planning and emergency response by ConocoPhillips and American Electric Power • The adequacy of Federal regulations and industry standards for emergency planning
Safety Issue #1
Tank operations, including switch loading, at the ConocoPhillips tank farm
Switch Loading
• Empty tank that previously contained gasoline was being filled with diesel • Hazards of switch loading
pressure/vacuum vents in floating roof
vent openings in fixed roof and shell
bond wires
internal floating roof roof support legs 10" diameter pontoons gasoline
Flow
sump 30” fill & drain pipe
Tank 11 with the floating roof landed
Tank Operations
• Fill velocity and turbulence increase static charge • Diesel is a static charge accumulator • Increased risk of a static discharge inside tank 11
Tank Operations - Flammability
• Tank operations with gasoline on April 4 to 7 created a flammable mixture inside the tank
Gasoline in storage
mechanical pressure/ vacuum vents in floating roof (closed) vent openings in tank roof and shell (always open) tank shell roof: floating roof support legs
gasoline
no flow
23
Gasoline removed (roof floating)
closed
gasoline roof: floating
Flow
24
Gasoline removed (roof landed)
open roof: landed
gasoline gasoline
Flow
25
Gasoline added (roof landed)
roof: landed
gasoline
Flow
26
Gasoline added (roof floating)
closed after roof floats
roof: floating
gasoline
Flow
27
Gasoline removed (roof landed)
roof: landed
gasoline Flow
28
Tank empty
closed roof: landed
No flow
29
Diesel added (switch load)
roof: landed
diesel
Flow
30
Conclusion
All the conditions necessary for fuel vapor ignition were present in the storage tank at the time of the accident, and the explosion most likely occurred when a static discharge ignited a flammable fuelair mixture in the space between the surface of the diesel and the floating roof. The extensive damage to the tank is consistent with the flammable fuelair mixture above the floating roof contributing to the force of the explosion.
32
Safety Issue # 2
Emergency Response and Emergency Planning
Emergency Response
• Emergency response by American Electric Power • Failure of energized power lines and additional fire • Unsuccessful management of the electrical hazard
Emergency Planning
No coordinated emergency planning between facility operators
Conclusions
The American Electric Power responder did not coordinate his actions with the incident command staff, and American Electric Power did not take effective emergency action.
Conclusions (Continued)
Because ConocoPhillips Company and American Electric Power did not preplan their response to emergencies near the Glenpool South Tank Farm, the emergency response was unsuccessful in managing the electrical hazard caused by the tank explosion and fire.
38
Safety Issue #3
Federal Regulations and Industry Standards for Emergency Planning
Federal Pipeline Regulations
• Require operators to prepare an emergency plan • Emergency plan must include procedures for notifying appropriate fire, police and other public officials • No requirements to coordinate with electric utilities
Industry Standards
• American Society of Mechanical Engineers (ASME) pipeline codes do not require pipeline operators to coordinate with electric utilities • Institute of Electrical and Electronic Engineers (IEEE) electrical safety code has no requirements for emergency response planning
Conclusion
Comprehensive, practical industry guidance for the preparation of emergency plans would help operators of electric systems respond effectively to emergencies involving their utilities.
43