By Jeremy Goddard

Gibralter tank fire, May 31, 2011Two significant storage tank fires occurred in Europe the week of May 30, 2011—one in Gibraltar and one in southwest Wales. Tragically, the Wales explosion and fire resulted in four people dead and a fifth in critical condition. Coincidentally, last week I was working on a project reviewing hazards and risks associated with some new onshore oil and gas production facilities which had a number of oil storage tanks.

So I wondered just how common storage tank fires are, and I did some quick research on the Internet—I was a little surprised by what I found.

In the past three months at least 9 fires involved storage tanks. Many of them escalated to involve multiple tanks, some tragically resulted in serious injury and fatality, and all resulted in significant property damage and business interruption. In addition, whilst this bulletin was being prepared, another fire involving storage tanks occurred during maintenance at a Texas refinery June 7.The causes of storage tank fires vary; however, the following figure provides a breakdown based on approximately 250 fires (A study of storage tank accidents, Journal of Loss Prevention in the Process Industries 19 (2006) 51–59). 

A significant amount of literature relates to prevention, control, and mitigation of storage tank fires. A few stood out for me:

  •            Center for Chemical Process Safety (CCPS) Guidelines for Facility Siting and Layout (2003).
    Provides guidance on safe layout of facilities and separation distances. It interested me to note that the storage tank separation distances recommended by CCPS are significantly greater than those in National Fire Protection Agency (NFPA) 30 Flammable and Combustible Liquids Code (2008).     http://www.aiche.org/Publications/pubcat/listings/0816908990.aspx
  •            UK HSE safety and environmental standards for fuel storage sites (2009).
    Provides guidance applicable to storing gasoline or similar Reid vapor pressure (RVP) materials (such as condensate) and incorporates the findings from the B

    uncefield storage tank site explosion and fire. http://www.hse.gov.uk/comah/buncefield/fuel-storage-sites.pdf
  •       UK HSE HSG176: The storage of flammable liquids in tanks (1998).
    Whilst this is an older reference, it provides good information about storage tank layout and fire safety design. For recommended minimum tank separation distances the guidance states:     If a serious fire develops involving one tank in a group then it is unlikely that these between-tank separation distances will prevent damage or even destruction of the adjacent tanks. However, they should allow sufficient time for emergency procedures to be implemented and for people to be evacuated from areas threatened by the incident. http://www.hse.gov.uk/pubns/books/hsg176.htm 
  •        US Chemical Safety Board, Death in the Oilfield (2006).
    This short video depicts an incident wherein three workers were killed while performing maintenance on a storage tank. The video discusses the causes of the accident and recommended findings.     http://www.csb.gov/videoroom/detail.aspx?VID=6

Lessons Learned

When dealing with storage tank fires, unless workers are specially trained with the appropriate equipment it is especially important to remember that municipal fire departments are not equipped mentally or physically to put out tank fires.

Emergency responders should be aware that after being extinguished, tank fires often can re-ignite.

  • Since a significant number of tank fires are caused by maintenance and hot work, before conducting any tank maintenance activities, robust procedures should be in place that include:
    •  Risk assessment (job safety analysis) before conducting any work
    • Training and competence of personnel
    • Control hot work and eliminate flammable atmosphere, including isolation, purging, gas testing, and control of ignition sources
    • Adherence to minimum separation distances given in codes and standards (such as NFPA 30 is unlikely to prevent escalation from one tank to another in case of fire
    • Provide adequate separation from tanks to site boundary, process equipment, loading areas, and buildings
      In the absence of facility-specific risk assessment, CCPS Guidelines for Facility Siting and Layout (2003) provides the most conservative guidance.
    • The only effective means to extinguish a tank fire is foam, and even this may not work for large fires
    • The strategy to minimize potential for escalation between tanks should consider a combination of separation and fire suppression
    • Consider segregating groups of tanks if large separation distances between individual tanks in batteries is impractical, as in the figure below

    • For higher risk tanks (e.g., those containing highly flammable liquids), provide an automatic overfill prevention system that is physically and electrically separate and independent from the tank gauging system

    • Periodically test overfill protection systems; long periods of inactivity may render them ineffective

    • Locate fire-safe isolation valves close to the piping inlet and outlet of tanks

    • Remotely ope

      rated shut-off valves provide the safest means to isolate the large inventories in storage tanks

    • Shut-off valve closures should be initiated from a point remote from the valve itself and a sufficient distance from potential fires for which they are intended to safely isolate inventory

    • Provide tertiary containment measures to prevent escape of liquids from the site and threatening a major accident to the environment; also design site drainage and grading to assist in containing spills that may overflow secondary containment. 

    Three Months of Tank Fires 

    Click on pictures for source information

     
    June 7, 2011, Refinery in Beaumont, Texas.
    Cause: Maintenance      

     
    June 2, 2011, Fuel tank in Pembrokeshire, UK.
    Cause: Maintenance      

     
    May 19, 2011, Oil tank in Kansas, USA.
    Cause: Lightning strike

     
    April 22, 2011, Slop tank farm in Oklahoma, USA.
    Cause: Lightning strike

     
    April 4, 2011, Salt water disposal tank in Texas, USA.
    Cause: Lightning strike

     
    April 2, 2011, Oil storage tank in Central Java, Indonesia.
    Cause: Unknown

     


    March 31, 2011, Oil storage tank in Mississippi, USA.
    Cause: Unknown

     
    March 24, 2011, Aviation fuel tank in Miami, USA.
    Cause: Thought to be a faulty pump

    References

    1. Overfill Protection for Storage Tanks in Petroleum Facilities. API Recommended Practices 2350, Third Edition. January 2005

    2. R. Ritchie. "Preventing storage tank fires. Implementing these safety rules may reduce risk," Hydrocarbon Processing, Vol. 88, No. 11, Nov. 2009, p.35

    3. C. Breitweiser. "AST Lightning Protection. API 545 Update," American Petroleum Institute Tank Conference Proceedings, 2008

    4.  Lightning Protection: Floating-Roof Tank Shunts,” Industrial Fire World, Vol. 21, No. 6, 2006 www.fireworld.com/ifw_articles/lightning.php

    5. "NFPA 30 Flammable and Combustible Liquids Code," National Fire Protection Association, 2008

    6. UK HSE HSG176 The storage of flammable liquids in tanks, 1998 http://www.hse.gov.uk/pubns/books/hsg176.htm

    7. UK HSE Safety and environmental standards for fuel storage sites, Final Report, 2009 http://www.hse.gov.uk/comah/buncefield/fuel-storage-sites.pdf

    8. "CCPS Guidelines for Facility Siting and Layout," Center for Chemical Process Safety, 2003. http://www.knovel.com/web/portal/browse/display?_EXT_KNOVEL_DISPLAY_bookid=930

    9. J.I. Chang, C-C Lin. "A study of storage tank accidents," Journal of Loss Prevention in the Process Industries, Vol.19, 2006, pp. 51–59

    10. UK HSE Containment of Bulk Hazardous Liquids at COMAH Establishments – Containment Policy Supporting Guidance for Secondary and Tertiary Containment, April 2008

    11. S Mannan, Ed., Lees' Loss Prevention in the Process Industries, Third Edition, Burlington, MA: Elsevier, 2005

    12. D. Newell, G. Cammack, and P. Muniyapp. Tank Overfill Protection - API 2350 and IEC 1511 Safety Considerations, ISA Expo 2009. http://leadwise.mediadroit.com/files/10756WP3.pdf

    13. "OSHA Hot Work / Welding," United States Department of Labor.  http://www.osha.gov/SLTC/etools/oilandgas/general_safety/hot_work_welding.html

    14. UK HSE HSG 250 Guidance on permit-to-work systems: A guide for the petroleum, chemical and allied industries, 2005 http://books.hse.gov.uk/hse/public/saleproduct.jsf?catalogueCode=9780717629435

    15. US Chemical Safety Board, Death in the Oilfield, 2006.  http://www.csb.gov/videoroom/detail.aspx?VID=6

    Contact the ERM North America Risk Practice Group, a global leader in assessments of engineering design and operations safety for hazardous facilities. The Risk Practice conducts facility siting, consequence analysis, process hazard assessments, hazard identification, and a host of other safety and hazard analysis.

    Join our mailing list to receive monthly Bulletins (Practical Lessons Learned from Major Accidents) upcoming educational events, and other industry-related news.

    Visit our bulletin archives.