Tech Report #1
Technical Information Report  #FTI-041098-1

Howard L. Chesneau

Reference: 

Chesneau, H.L., “Fuel System Contaminants: An Introduction,” 

Distillate Fuel:  Contamination, Storage and Handling, ASTM STP 1005, H.L. Chesneau and Michele M. Doris, Eds., American Society for Testing and Materials, Philadelphia, 1988, pp. 1-5.

Fuel System Contaminants:  An Introduction
 
The relative decline of distillate fuel quality in the United States over the past several years has been discussed in many recent publications [1-6].  This decline has taken the form of lower cetane numbers, heavier fuels, poorer stability characteristics and poorer cold weather characteristics [7].  These factors combined with increasing demands made by economical realities, environmental concerns and equipment refinements have placed a heavy burden on both the suppliers and users of fuel.

Compounding this issue are new laws under Resource Conservation and Recovery Act (RCRA) signed by the President of the United States in 1984, which define the storage of liquids underground [8].  The law, in effect, has forced suppliers and users to look more closely at their fuel storage facilities.  This action was brought about because of estimates that in excess of 100,000 underground storage tanks are currently leaking in the United States [9,10].
 
The focus of this symposium is to provide awareness of fuel storage problems, some of the chemical solution alternatives and practical experiences with solutions.
 
Sources of Contaminants
 
There are three basic ways in which contamination is introduced into a fuel system:  air, water and the fuel itself.
 
Air

Air enters a system through venting pipes.  It may be clean or filtered, but can be contaminated by dust, microbiological spores, hydrocarbon utilizing bacteria or other gases.  It also may contain large amounts of moisture.

Air is generally used to displace the volume of fuel consumed in a storage system.  It is not practical to keep air from entering the storage tank; however, it may be practical to utilize filters designed to limit the amount of airborne debris and moisture that may enter through the vent system.

 Air itself may be considered a contaminant because of the oxygen present can increase the oxidation of the fuel.  This is especially important because of the general trend toward less stable fuel [2,11].

Water
 
The second major source of contamination is water.  It is the easiest contaminant to identify and one of the most destructive.  Free water in the fuel system can lead to corrosion and fuel degradation, and the presence of water can create a fertile growing place for microbiological contaminants [12,13].  Water is arguably one of the simpler contaminants to control although, in many systems, poor tank design has made complete removal of water impossible.  Also, systems lacking of positive filtration equipment will allow water to be passed downstream.
 
Water can enter the fuel system as condensation from the air in the tank.  Vents and seals that are poorly designed, improperly installed, or are faulty or damaged can allow water to enter.  Also, water is often used for tank cleaning and as ballast.
 
Contaminants that can enter with the water include dirt, rust and microbiologicals.  Preventing water from entering the system will reduce the amount of these contaminates;  however, removal of the water will not always guarantee removal of these other contaminants.
 
Fuel

 The third source of fuel system contamination is the fuel itself.  Fuel in storage may degrade to form insoluble materials.  These fuel insolubles can plug filters, foul injectors, form combustion system deposits and promote corrosion.  The stability of the fuel is a measure of its resistance to this chemical change.  Fuel stability is dependent on several factors including crude sources, refinery processes, base fuel components, base fuel blends and storage conditions [5,14].
 
As with air and water, fuel can bring in or pick up contaminants during the delivery process.  As the fuel cools, water will condense and create free water droplets.  When housekeeping practices are not strictly enforced, dirt, debris, water and bacteria can gather in tankers, fill lines, fill areas and storage tanks.
 
Storage Tank Problems
 
Throughout the distribution chain, large or small storage tanks, for the most part, have been poorly designed.  Improper placement of water drawoffs or a complete lack of an adequate  water drawoff system have left many storage systems seriously lacking in ability to perform proper housekeeping procedures.  This not only accentuates the problem of water contamination, but leaves the system without any viable means of controlling water and contamination.
           
Since water is a major contaminant, it is important to understand some of the problems associated with it in storage tanks.  With the increasing examination of tank interiors prompted by the RCRA laws, older steel tanks have become suspect of serious internal corrosion.  While the water itself can create internal corrosion, the more complex corrosive mechanism of microbial activity has to be addressed.
            
These organisms, both aerobic and anaerobic, produce sludge’s and slimes known commonly to cause filter plugging.  In addition, their activity creates corrosive by-products that can cause severe pitting of metal fuel tanks and can lead to leaks [15-17].  These bi-products can also cause fuel to become unstable [18].
 
The interlocking relationship between microorganisms, water, air, corrosion and unstable fuel needs to be understood so that by controlling them, one can minimize their effect on the storage of fuels.
            
This Special Technical Publication (STP) does not try to provide all the answers.  It does suggest, however, several ideas towards assisting the end user in dealing with fuel storage related problems. 
 
References

  1. Engines, Fuels and Lubricants - A Perspective on The Future SAE SP-471, Fuels and Lubricants, Baltimore,MD, 20-23 Oct. 1980.
  2. Distillate Fuel Stability and Cleanliness, STP 751, L.L. Stavinoha, C.P. Henry, Eds.,American Society for Testing and Materials, Philadelphia, 1981.
  3. Matching Diesel Fuel Quality to Diesel Engine Requirements, SAE SP-577, Fuels and Lubricants Meeting & Exposition, San Francisco, CA, 31 Oct.- 4 Nov, 1983.
  4. Diesel Fuel Quality and Trends, SAE SP-639, International Fuels and Lubricants Meeting and Exposition, Tulsa, OK, 21-24 Oct. 1985.
  5. 2nd International Conference on Long Term Storage Stabilities of Liquid Fuels, Conference -
    Proceedings, Vols. 1 and 2, San Antonio, TX, 29 July- 1 Aug. 1986.
  6. Diesel Fuels: Performance and Characteristics, SAE SP-675, International Fuels and Lubricants Meeting and Exposition, Philadelphia, 6-9 Oct. 1986.
  7. Diesel Fuel Quality and Performance Additives, T.R. Coley, F. Rossi and M.G. Taylor, Eds.
    PARAMINS Technology Division, Abingdon, England, J.E. Chandler, PARAMINS Technology Division, Linden, NJ, Diesel Fuels: Performance and Characteristics, SAE SP- 675, International Fuels and Lubricants Meeting and Exposition, Philadelphia, 6-9 Oct. 1986.
  8. Resource Conservation and Recovery Act (RCRA), 8 Nov.  1984 Amendments, Subtitle 1, 42
    U.S.C. 9001-9010, Superfund Legislation, CERCLA 101(14).
  9. What To Do About Leaking Underground Storage Tanks, Seminar Cosponsored by Inside
    EPA, Weekly Report and The Center for Energy and Environmental Management, Atlanta, GA, 14 Jan. 1985.
  10. The 1985 Washington Conference on Underground Tanks, Seminar Cosponsored by Inside EPA, Weekly Report and The Center for Energy and Environmental Management, Arlington, VA, 15-16 July, 1985.
  11. Middle Distillate Fuel Stability, Time for Reassessment, M.W. Schrepfer, C.A. Stansky and
    R.J. Arnold, Eds., UOP Process Division, UOP Inc., presented at the National Petroleum
    Refiners Association 1983 Fuels and Lubricants Meeting, Houston, TX, 3-4 Nov. 1983.
  12. Bugs, Surfactants and Woes, H.F. Hostetler and E.J. Powers, Eds., presented at the 28th
    Meeting of the American Petroleum Institute Session on Fuels, Philadelphia, 13 May 1963.
  13. Litman, E.S., “Microbiological Contamination of Fuels During Storage,” Distillate Fuel -
    Stability and Cleanliness, STP 751, American Society for Testing and Materials,   
    Philadelphia, 1981, pp. 136-144.
  14. LePera, M.E., Stavinoha, L.L., Westbrook, S.R., Lentz, S.J., “Army Diesel Fuel Stability and
    Cleanliness,” 1st Conference on Long-Term Storage Stability of Liquid Fuels, Tel Aviv,
    Israel, 11- 14 July 1983.
  15. DeGray, R.J. and Killian, L.N., “Life in Essentially Non Aqueous Hydrocarbons,”
    Developments in Industrial Microbiology, Vol. 3, Standard Oil Company, OH, p. 296.
  16. Miller, J.D.A., “Metals,” Economic Microbiology, Vol. 6 pp. 150-202.
  17. Lunden, K.C., Stastny, T.M., “Sulfate Reducing Bacteria in Oil and Gas Production,” Paper
    296, Amoco Production Company, Presented at the International Corrosion Forum NACE,
    Boston, MA, 25-29 March 1985.
  18. “2nd International Conference on Long-Term Storage Stabilities of Liquid Fuels,” Conference -
    Proceeding, Vol. 1-2, San Antonio, TX, 29 July - 1 Aug. 1986.