Contributing to the severity and duration of the fire was the lack of storage tank fail-safe control valves and internal fire valves and the location of the control building in the containment area where fuel leaks are likely to occur.
The National Transportation Safety Board determined that the probable cause of the fire at the fuel storage facility at Denver’s Stapleton International Airport was the failure of AHR Combs to detect loose motor bolts that permitted the motor of motor/pump unit 3 to become misaligned, resulting in damage to the pump and subsequent leakage and ignition of fuel.
Contributing to the accident was the failure of the contractor responsible for the fuel depot to properly train its employees to inspect and maintain the fuel pump equipment and the failure of the city and county of Denver to carry out its certificate-holder responstbtltty to oversee the fuel storage facility in accordance with its airport certification manual.
–to the National fire Protection Association: Revise National fire Protection Association Standard 30 to require internal fire valves and fail-safe control valves on all aboveground fuel storage tanks. (Class II, Priority Action) (I-91-02)
Location of Control Building -The motor/pump equipment was mounted ~n such a way as to allow for thr collection of small, accidental releases of fuel; it is located in the most likely area for fuel leaks to occur. The location of the control building in this same area causes the Safety Board concern. The investigation of the cause of this fire was hampered by the loss of records in the control building that was located in the same area as the motor/pump equipment. The Safety Board is unaware of any valid reason to locate a control building that houses electrical equipment, emergency shutoff switches, and records in an area that is designed to collect fuel leaks. [Facility Siting]
The Safety Board concludes that had the control building been located in an area separate from the motor/pump equipment and outside of the containment area , vital records that could have been helpful to the investigation would not have been lost, emergency response personnel could have accessed emergency shutoff switches and possibly could have remotely closed some of the control valves, thus reducing the amount of fuel that ultimately fed the fire. The placement of the control building adjacent to the motor/pump units in the fuel spill containment area, therefore, contributed to the severity of the accident. Consequently, the Safety Board urges the FAA to require certificate holders to ensure that :
- fuel operators locate fuel farm control systems,
- one or more emergency shutoff switches, and
- the recording equipment
in an area remote from the pumping equipment and outside a spill containment area.
Inspections of Equipment
The nature of the failure of motor/pump unit 3 over a period of time raises questions about the adequacy of daily inspections conducted by fuel farm employees and about the concern of management or adequate inspections. According to training manuals furnished by the contractor, the pumping equipment was to have been checked daily and at the beginning of each day. The entries on the daily inspection sheet for the month of November indicate that the pumps were checked daily and were recorded as being satisfactory. The daily inspection forms for the equipment were signed off by the night shift employee, and interviews confirmed that he was performing the inspections. The night shift was the time of lightest fuel demand at the ramp, and little, if any, fueling was done after 2200. Consequently, unless the night shift employee inspected the motor/pump units early in the shift, most of the pumps would have been inspected when they were not operating. Further, it is not likely that all six motor/pump units would be operating during the night shift. Because, according to maintenance staff, inspection of the equipment relied heavily on feeling vibrations and listening for unusual noises in the equipment, only very obvious discrepancies with these pumps could be noted when the equipment is not operating.
The night shift employee had worked at the fuel farm for less than 1 month. Further, his testimony indicates that he had been given no guidance or training by management regarding equipment inspect ions and that he might not have been able to detect a problem with the equipment if one existed. Inspection of the equipment during nighttime when the equipment was not operating and by an inexperienced and untrained employee could account for the fact that the deteriorating condition of motor/pump unit 3 went undetected. Moreover, the fact that the night shift employee had initialed before the fire the daily inspection sheet for November 26, 1990 (the day after the fire), indicates that the inspections were not conducted properly, if at all, and that the employee may have been merely satisfying paperwork requirements.
According to information received later during the investigation from the fuel farm manager, the equipment was to be inspected during each shift and the formal sign-off on the status of the pumping equipment was performed during the night shift. It is difficult to understand how the deteriorating condition of motor/pump unit ~J could have gone undetected if the equipment was inspected during each shift by more experienced personnel and when the equipment was likely to be operating. The Safety Board concludes that adequate inspect ions were not being performed, and the failure to conduct adequate inspect ions caused the accident.
Had tanks 3 and 4 been equipped with fail-safe control valves and internal fire valves with fusible links, the amount of fuel that fed the fire would have been significantly reduced, and, consequently, the duration and intensity of the fire would have been lessened.
Source: https://www.ntsb.gov/investigations/AccidentReports/Reports/AAR9107.pdf